Red Hat CERTIFICATE SYSTEM 8 - DEPLOYMENT, Certificate System 8 Deployment Manual

Red Hat Certificate

System 8

Deployment Guide

Ella Deon Lackey

Publication date: July 22, 2009, updated on September 24, 2009

Deployment Guide

Red Hat Certificate System 8 Deployment Guide

Author Ella Deon Lackey
Copyright © 2009 Red Hat, Inc.

Copyright © 2009 Red Hat, Inc.

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iii

About This Guide vii

1. Examples and Formatting .............................................................................................. vii

1.1. Formatting for Examples and Commands ............................................................. vii

1.2. Tool Locations .................................................................................................... viii

1.3. Guide Formatting ............................................................................................... viii

2. Additional Reading ........................................................................................................ viii

3. Giving Feedback ............................................................................................................ ix

4. Document History ............................................................................................................ x

1. Introduction to Public-Key Cryptography 1

1.1. Encryption and Decryption ............................................................................................ 1

1.1.1. Symmetric-Key Encryption ................................................................................. 2

1.1.2. Public-Key Encryption ........................................................................................ 2

1.1.3. Key Length and Encryption Strength ................................................................... 3

1.2. Digital Signatures ......................................................................................................... 4

1.3. Certificates and Authentication ...................................................................................... 5

1.3.1. A Certificate Identifies Someone or Something .................................................... 5

1.3.2. Authentication Confirms an Identity ..................................................................... 5

1.3.3. How Certificates Are Used ................................................................................. 9

1.3.4. Contents of a Certificate .................................................................................. 13

1.3.5. How CA Certificates Establish Trust .................................................................. 16

1.4. Managing Certificates ................................................................................................. 21

1.4.1. Issuing Certificates .......................................................................................... 21

1.4.2. Key Management ............................................................................................ 22

1.4.3. Renewing and Revoking Certificates ................................................................. 22

2. Overview of Red Hat Certificate System Subsystems 23

2.1. A Review of Certificate System Subsystems ................................................................ 23

2.1.1. About the Certificate Manager (CA) .................................................................. 24

2.1.2. About the Registration Manager (RA) ............................................................... 26

2.1.3. About OCSP Services ...................................................................................... 27

2.1.4. About the Data Recovery Manager (DRM) ........................................................ 29

2.1.5. About the Token Processing System (TPS) ....................................................... 32

2.1.6. About the Token Key Service (TKS) .................................................................. 33

2.2. Red Hat Certificate System Services ........................................................................... 33

2.2.1. Interfaces for Administrators ............................................................................. 33

2.2.2. Agent Interfaces .............................................................................................. 36

2.2.3. End User Pages .............................................................................................. 37

2.2.4. Enterprise Security Client ................................................................................. 38

3. Supported Standards and Protocols 41

3.1. PKCS #11 .................................................................................................................. 41

3.2. SSL/TLS, ECC, and RSA ........................................................................................... 42

3.2.1. Supported Cipher Suites for RSA ..................................................................... 43

3.2.2. Using ECC ...................................................................................................... 43

3.3. IPv4 and IPv6 Addresses ........................................................................................... 44

3.4. Supported PKIX Formats and Protocols ....................................................................... 45

3.5. Supported Security and Directory Protocols ................................................................. 46

4. Major Features in Certificate System 49

4.1. Certificate Issuance .................................................................................................... 49

4.2. Authentication for Certificate Enrollment ....................................................................... 49

4.3. Certificate Profiles ...................................................................................................... 49

Deployment Guide

iv

4.4. CRLs ......................................................................................................................... 50

4.5. Publishing .................................................................................................................. 50

4.6. Notifications ............................................................................................................... 50

4.7. Jobs .......................................................................................................................... 50

4.8. Dual Key Pairs ........................................................................................................... 50

4.9. Cross-Pair Certificates ................................................................................................ 50

4.10. Logging .................................................................................................................... 50

4.11. Auditing .................................................................................................................... 51

4.12. Self-Tests ................................................................................................................. 51

4.13. Access Controls ....................................................................................................... 51

4.14. Security-Enhanced Linux Support .............................................................................. 51

5. Planning the Certificate System 55

5.1. Deciding on the Required Subsystems ........................................................................ 55

5.1.1. Single Certificate Manager ............................................................................... 55

5.1.2. Planning for Lost Keys: Key Archival and Recovery ........................................... 57

5.1.3. Balancing Certificate Request Processing ......................................................... 57

5.1.4. Balancing Client OCSP Requests ..................................................................... 58

5.1.5. Planning for Smart Cards ................................................................................. 59

5.2. Defining the Certificate Authority Hierarchy .................................................................. 61

5.2.1. Subordination to a Public CA ........................................................................... 62

5.2.2. Subordination to a Certificate System CA .......................................................... 62

5.2.3. Linked CA ....................................................................................................... 62

5.2.4. CA Cloning ...................................................................................................... 62

5.3. Planning Security Domains and Trust Relationships ..................................................... 63

5.3.1. Understanding Security Domains ...................................................................... 63

5.3.2. Using Trusted Managers .................................................................................. 65

5.4. Determining the Requirements for Subsystem Certificates ............................................. 65

5.4.1. Determining Which Certificates to Install ........................................................... 65

5.4.2. CA Distinguished Name ................................................................................... 67

5.4.3. CA Signing Certificate Validity Period ................................................................ 67

5.4.4. Signing Key Type and Length .......................................................................... 67

5.4.5. Using Certificate Extensions ............................................................................. 68

5.4.6. Using and Customizing Certificate Profiles ........................................................ 70

5.4.7. Planning Authentication Methods ...................................................................... 72

5.4.8. Publishing Certificates and CRLs ...................................................................... 73

5.4.9. Renewing or Reissuing CA Signing Certificates ................................................. 74

5.5. Planning for Network and Physical Security ................................................................. 74

5.5.1. Considering Firewalls ....................................................................................... 74

5.5.2. Considering Physical Security and Location ...................................................... 75

5.5.3. Port Considerations ......................................................................................... 75

5.6. Tokens for Storing Certificate System Subsystem Keys and Certificates ......................... 76

5.7. Questions for Planning the Certificate System .............................................................. 78

6. Setting up a Common Criteria Environment 79

6.1. About Common Criteria .............................................................................................. 79

6.2. Required Configuration for the Server or Network ......................................................... 79

6.3. Required Features and Configurations for the Certificate System Subsystems ................ 80

6.4. Users, Roles, and Access Control for Common Criteria ................................................ 81

6.4.1. Certificate System User Types .......................................................................... 82

6.4.2. Access Controls for Common Criteria ............................................................... 83

6.5. Security Objectives for the Common Criteria Environment for Certificate System ............. 83

v

6.5.1. Usage Assumptions ......................................................................................... 83

6.5.2. Organizational Policies ..................................................................................... 84

6.5.3. Potential Threats ............................................................................................. 84

6.5.4. Security Objectives .......................................................................................... 85

6.6. Features Not Covered by Common Criteria Evaluation` ................................................ 87

Glossary 89

Index 103

vi

vii

About This Guide

This guide explains how to install and configure Red Hat Certificate System subsystems.

This guide is intended for experienced system administrators planning to deploy the Certificate
System. Certificate System agents should refer to the Certificate System Agent's Guide for information
on how to perform agent tasks, such as handling certificate requests and revoking certificates. For
information on using Certificate System to manage smart cards and security tokens, see Managing
Smart Cards with the Enterprise Security Client.

Before using Certificate System, become familiar with the following concepts:

• Intranet, extranet, and Internet security and the role of digital certificates in a secure enterprise,
including the following topics:

• Encryption and decryption

• Public keys, private keys, and symmetric keys

• Significance of key lengths

• Digital signatures

• Digital certificates, including different types of digital certificates

• The role of digital certificates in a public-key infrastructure (PKI)

• Certificate hierarchies

• LDAP and Red Hat Directory Server

• Public-key cryptography and the Secure Sockets Layer (SSL) protocol, including the following:

• SSL cipher suites

• The purpose of and major steps in the SSL handshake

1. Examples and Formatting

1.1. Formatting for Examples and Commands

All of the examples for Red Hat Certificate System commands, file locations, and other usage are
given for Red Hat Enterprise Linux 5 (32-bit) systems. Be certain to use the appropriate commands
and files for your platform.

To start the Red Hat Certificate System:

service pki-ca start

Example 1. Example Command

About This Guide

viii

1.2. Tool Locations

All of the tools for Red Hat Certificate System are located in the /usr/bin directory. These tools can
be run from any location without specifying the tool location.

1.3. Guide Formatting

Certain words are represented in different fonts, styles, and weights. Different character formatting is
used to indicate the function or purpose of the phrase being highlighted.

Formatting Style Purpose

Monospace font Monospace is used for commands, package names, files and

Monospace
with a
background

Italicized text Any text which is italicized is a variable, such as

Bolded text Most phrases which are in bold are application names, such as

Other formatting styles draw attention to important text.

NOTE

A note provides additional information that can help illustrate the behavior of the system or
provide more detail for a specific issue.

IMPORTANT

Important information is necessary, but possibly unexpected, such as a configuration
change that will not persist after a reboot.

WARNING

A warning indicates potential data loss, as may happen when tuning hardware for
maximum performance.

2. Additional Reading

The documentation for Certificate System includes the following guides:

• Certificate System Deployment Guide1 describes basic PKI concepts and gives an overview of the
planning process for setting up Certificate System.

This manual is intended for Certificate System administrators.

Giving Feedback

ix

• Certificate System Installation Guide2 covers the installation process for all Certificate System
subsystems.

This manual is intended for Certificate System administrators.

• Certificate System Administrator's Guide3 explains all administrative functions for the Certificate
System. Administrators maintain the subsystems themselves, so this manual details backend
configuration for certificate profiles, publishing, and issuing certificates and CRLs. It also covers
managing subsystem settings like port numbers, users, and subsystem certificates.

This manual is intended for Certificate System administrators.

• Certificate System Agent's Guide4 describes how agents — users responsible for processing
certificate requests and managing other aspects of certificate management — can use the
Certificate System subsystems web services pages to process certificate requests, key recovery,
OCSP requests and CRLs, and other functions.

This manual is intended for Certificate System agents.

• Managing Smart Cards with the Enterprise Security Client5 explains how to install, configure,
and use the Enterprise Security Client, the user client application for managing smart cards, user
certificates, and user keys.

This manual is intended for Certificate System administrators, agents, privileged users (such as
security officers), and regular end users.

• Using End User Services6 is a quick overview of the end-user services in Certificate System, a
simple way for users to learn how to access Certificate System services.

This manual is intended for regular end users.

• Certificate System Command-Line Tools Guide7 covers the command-line scripts supplied with Red
Hat Certificate System.

This manual is intended for Certificate System administrators.

• Certificate System Migration Guide8 covers version-specific procedures for migrating from older
versions of Certificate System to Red Hat Certificate System 8.0.

This manual is intended for Certificate System administrators.

• Release Notes9 contains important information on new features, fixed bugs, known issues and
workarounds, and other important deployment information for Red Hat Certificate System 8.0.

All of the latest information about Red Hat Certificate System and both current and archived
documentation is available at http://www.redhat.com/docs/manuals/cert-system/.

3. Giving Feedback

If there is any error in this Deployment Guide or there is any way to improve the documentation,
please let us know. Bugs can be filed against the documentation for Red Hat Certificate System
through Bugzilla, http://bugzilla.redhat.com/bugzilla. Make the bug report as specific as possible, so
we can be more effective in correcting any issues:

• Select the Red Hat Certificate System product.

About This Guide

x

• Set the component to Doc - deployment-guide.

• Set the version number to 8.0.

• For errors, give the page number (for the PDF) or URL (for the HTML), and give a succinct
description of the problem, such as incorrect procedure or typo.

For enhancements, put in what information needs to be added and why.

• Give a clear title for the bug. For example, "Incorrect command example for setup
script options" is better than "Bad example".

We appreciate receiving any feedback — requests for new sections, corrections, improvements,
enhancements, even new ways of delivering the documentation or new styles of docs. You are
welcome to contact Red Hat Content Services directly at [e-mail].

4. Document History

Revision 8.0.4 September 24, 2009 Ella Deon Lackey

Tech edits to the subsystems overview chapter, per Bugzilla #510596. This completes the tech
reviews for this guide.

Revision 8.0.3 September 19, 2009 Ella Deon Lackey

Further edits to the key length and strength section in chapter 1, per feedback from Bob Relyea.

Revision 8.0.2 September 9, 2009 Ella Deon Lackey

Tech edits to chapter 1, per Bugzilla #510594.

Revision 8.0.1 August 5, 2009 Ella Deon Lackey [e-mail]

Tech edits to chapters 3, 4, and 5, per Bugzilla #510598, #510599, #510597. The biggest changes
were to the SELinux feature overview.

Revision 8.0.0 July 22, 2009 Ella Deon Lackey [e-mail]

Initial draft for Certificate System 8.0 Deployment Guide.

Chapter 1.

1

Introduction to Public-Key
Cryptography

Public-key cryptography and related standards underlie the security features of many products such
as signed and encrypted email, single sign-on, and Secure Sockets Layer (SSL) communications. This
chapter covers the basic concepts of public-key cryptography.

Internet traffic, which passes information through intermediate computers, can be intercepted by a
third party:

• Eavesdropping. Information remains intact, but its privacy is compromised. For example,
someone could gather credit card numbers, record a sensitive conversation, or intercept classified
information.

• Tampering. Information in transit is changed or replaced and then sent to the recipient. For example,
someone could alter an order for goods or change a person's resume.

• Impersonation. Information passes to a person who poses as the intended recipient. Impersonation
can take two forms:

• Spoofing. A person can pretend to be someone else. For example, a person can pretend to have

the email address [e-mail] or a computer can falsely identify itself as a site called
www.example.net.

• Misrepresentation. A person or organization can misrepresent itself. For example, a site called

www.example.net can purport to be an on-line furniture store when it really receives credit-card
payments but never sends any goods.

Public-key cryptography provides protection against Internet-based attacks through:

• Encryption and decryption allow two communicating parties to disguise information they send to
each other. The sender encrypts, or scrambles, information before sending it. The receiver decrypts,
or unscrambles, the information after receiving it. While in transit, the encrypted information is
unintelligible to an intruder.

• Tamper detection allows the recipient of information to verify that it has not been modified in transit.
Any attempts to modify or substitute data are detected.

• Authentication allows the recipient of information to determine its origin by confirming the sender's
identity.

• Nonrepudiation prevents the sender of information from claiming at a later date that the information
was never sent.

1.1. Encryption and Decryption

Encryption is the process of transforming information so it is unintelligible to anyone but the intended
recipient. Decryption is the process of decoding encrypted information. A cryptographic algorithm,
also called a cipher, is a mathematical function used for encryption or decryption. Usually, two related
functions are used, one for encryption and the other for decryption.

With most modern cryptography, the ability to keep encrypted information secret is based not on
the cryptographic algorithm, which is widely known, but on a number called a key that must be used

Chapter 1. Introduction to Public-Key Cryptography

2

with the algorithm to produce an encrypted result or to decrypt previously encrypted information.
Decryption with the correct key is simple. Decryption without the correct key is very difficult, if not
impossible.

1.1.1. Symmetric-Key Encryption

With symmetric-key encryption, the encryption key can be calculated from the decryption key and vice
versa. With most symmetric algorithms, the same key is used for both encryption and decryption, as
shown in Figure 1.1, “Symmetric-Key Encryption”.

Figure 1.1. Symmetric-Key Encryption

Implementations of symmetric-key encryption can be highly efficient, so that users do not experience
any significant time delay as a result of the encryption and decryption. Symmetric-key encryption also
provides a degree of authentication, since information encrypted with one symmetric key cannot be
decrypted with any other symmetric key. Thus, as long as the symmetric key is kept secret by the two
parties using it to encrypt communications, each party can be sure that it is communicating with the
other as long as the decrypted messages continue to make sense.

Symmetric-key encryption is effective only if the symmetric key is kept secret by the two parties
involved. If anyone else discovers the key, it affects both confidentiality and authentication. A person
with an unauthorized symmetric key not only can decrypt messages sent with that key, but can encrypt
new messages and send them as if they came from one of the legitimate parties using the key.

Symmetric-key encryption plays an important role in SSL communication, which is widely used for
authentication, tamper detection, and encryption over TCP/IP networks. SSL also uses techniques of
public-key encryption, which is described in the next section.

1.1.2. Public-Key Encryption

Public-key encryption (also called asymmetric encryption) involves a pair of keys, a public key and
a private key, associated with an entity. Each public key is published, and the corresponding private
key is kept secret. (For more information about the way public keys are published, see Section 1.3,

“Certificates and Authentication”.) Data encrypted with a public key can be decrypted only with the

corresponding private key. Figure 1.2, “Public-Key Encryption” shows a simplified view of the way
public-key encryption works.

Figure 1.2. Public-Key Encryption

Key Length and Encryption Strength

3

The scheme shown in Figure 1.2, “Public-Key Encryption” allows public keys to be freely distributed,
while only authorized people are able to read data encrypted using this key. In general, to send
encrypted data, the data is encrypted with that person's public key, and the person receiving the
encrypted data decrypts it with the corresponding private key.

Compared with symmetric-key encryption, public-key encryption requires more processing and may
not be feasible for encrypting and decrypting large amounts of data. However, it is possible to use
public-key encryption to send a symmetric key, which can then be used to encrypt additional data. This
is the approach used by the SSL/TLS protocols.

The reverse of the scheme shown in Figure 1.2, “Public-Key Encryption” also works: data
encrypted with a private key can be decrypted only with the corresponding public key. This is not
a recommended practice to encrypt sensitive data, however, because it means that anyone with
the public key, which is by definition published, could decrypt the data. Nevertheless, private-key
encryption is useful because it means the private key can be used to sign data with a digital signature,
an important requirement for electronic commerce and other commercial applications of cryptography.
Client software such as Mozilla Firefox can then use the public key to confirm that the message was
signed with the appropriate private key and that it has not been tampered with since being signed.

Section 1.2, “Digital Signatures” illustrates how this confirmation process works.

1.1.3. Key Length and Encryption Strength

Breaking an encryption algorithm is basically finding the key to the access the encrypted data in plain
text. For symmetric algorithms, breaking the algorithm usually means trying to determine the key used
to encrypt the text. For a public key algorithm, breaking the algorithm usually means acquiring the
shared secret information between two recipients.

One method of breaking a symmetric algorithm is to simply try every key within the full algorithm
until the right key is found. For public key algorithms, since half of the key pair is publicly known, the
other half (private key) can be derived using published, though complex, mathematical calculations.
Manually finding the key to break an algorithm is called a brute force attack.

Breaking an algorithm introduces the risk of intercepting, or even impersonating and fraudulently
verifying, private information.

The key strength of an algorithm is determined by finding the fastest method to break the algorithm
and comparing it to a brute force attack.

For symmetric keys, encryption strength is often described in terms of the size or length of the keys
used to perform the encryption: longer keys generally provide stronger encryption. Key length is
measured in bits. For example, 128-bit keys with the RC4 symmetric-key cipher supported by SSL
provide significantly better cryptographic protection than 40-bit keys used with the same cipher. The
128-bit RC4 encryption is 3 x 1026 times stronger than 40-bit RC4 encryption.

An encryption key is considered full strength if the best known attack to break the key is no faster than
a brute force attempt to test every key possibility.

Different types of algorithms — particularly public key algorithms — may require different key lengths
to achieve the same level of encryption strength as a symmetric-key cipher. The RSA cipher can use
only a subset of all possible values for a key of a given length, due to the nature of the mathematical
problem on which it is based. Other ciphers, such as those used for symmetric-key encryption, can
use all possible values for a key of a given length. More possible matching options means more
security.

Chapter 1. Introduction to Public-Key Cryptography

4

Because it is relatively trivial to break an RSA key, an RSA public-key encryption cipher must have a
very long key — at least 1024 bits — to be considered cryptographically strong. On the other hand,
symmetric-key ciphers are reckoned to be equivalently strong using a much shorter key length, as little
as 80 bits for most algorithms.

1.2. Digital Signatures

Tamper detection relies on a mathematical function called a one-way hash (also called a message
digest). A one-way hash is a number of fixed length with the following characteristics:

• The value of the hash is unique for the hashed data. Any change in the data, even deleting or
altering a single character, results in a different value.

• The content of the hashed data cannot be deduced from the hash.

As mentioned in Section 1.1.2, “Public-Key Encryption”, it is possible to use a private key for
encryption and the corresponding public key for decryption. Although not recommended when
encrypting sensitive information, it is a crucial part of digitally signing any data. Instead of encrypting
the data itself, the signing software creates a one-way hash of the data, then uses the private key to
encrypt the hash. The encrypted hash, along with other information such as the hashing algorithm, is
known as a digital signature.

Figure 1.3, “Using a Digital Signature to Validate Data Integrity” illustrates the way a digital signature

can be used to validate the integrity of signed data.

Figure 1.3. Using a Digital Signature to Validate Data Integrity

Figure 1.3, “Using a Digital Signature to Validate Data Integrity” shows two items transferred to

the recipient of some signed data: the original data and the digital signature, which is a one-way
hash of the original data encrypted with the signer's private key. To validate the integrity of the data,
the receiving software first uses the public key to decrypt the hash. It then uses the same hashing
algorithm that generated the original hash to generate a new one-way hash of the same data.
(Information about the hashing algorithm used is sent with the digital signature.) Finally, the receiving
software compares the new hash against the original hash. If the two hashes match, the data has not
changed since it was signed. If they do not match, the data may have been tampered with since it was
signed, or the signature may have been created with a private key that does not correspond to the
public key presented by the signer.

If the two hashes match, the recipient can be certain that the public key used to decrypt the digital
signature corresponds to the private key used to create the digital signature. Confirming the identity of
the signer also requires some way of confirming that the public key belongs to a particular entity. For
more information on authenticating users, see Section 1.3, “Certificates and Authentication”.

Certificates and Authentication

5

A digital signature is similar to a handwritten signature. Once data have been signed, it is difficult
to deny doing so later, assuming the private key has not been compromised. This quality of digital
signatures provides a high degree of nonrepudiation; digital signatures make it difficult for the signer
to deny having signed the data. In some situations, a digital signature is as legally binding as a
handwritten signature.

1.3. Certificates and Authentication

• Section 1.3.1, “A Certificate Identifies Someone or Something”

• Section 1.3.2, “Authentication Confirms an Identity”

• Section 1.3.3, “How Certificates Are Used”

• Section 1.3.4, “Contents of a Certificate”

• Section 1.3.5, “How CA Certificates Establish Trust”

1.3.1. A Certificate Identifies Someone or Something

A certificate is an electronic document used to identify an individual, a server, a company, or other
entity and to associate that identity with a public key. Like a driver's license or passport, a certificate
provides generally recognized proof of a person's identity. Public-key cryptography uses certificates to
address the problem of impersonation.

To get personal ID such as a driver's license, a person has to present some other form of identification
which confirms that the person is who he claims to be. Certificates work much the same way.
Certificate authorities (CAs) validate identities and issue certificates. CAs can be either independent
third parties or organizations running their own certificate-issuing server software, such as Certificate
System. The methods used to validate an identity vary depending on the policies of a given CA for the
type of certificate being requested. Before issuing a certificate, a CA must confirm the user's identity
with its standard verification procedures.

The certificate issued by the CA binds a particular public key to the name of the entity the certificate
identifies, such as the name of an employee or a server. Certificates help prevent the use of fake
public keys for impersonation. Only the public key certified by the certificate will work with the
corresponding private key possessed by the entity identified by the certificate.

In addition to a public key, a certificate always includes the name of the entity it identifies, an expiration
date, the name of the CA that issued the certificate, and a serial number. Most importantly, a certificate
always includes the digital signature of the issuing CA. The CA's digital signature allows the certificate
to serve as a valid credential for users who know and trust the CA but do not know the entity identified
by the certificate.

For more information about the role of CAs, see Section 1.3.5, “How CA Certificates Establish Trust”.

1.3.2. Authentication Confirms an Identity

Authentication is the process of confirming an identity. For network interactions, authentication
involves the identification of one party by another party. There are many ways to use authentication
over networks. Certificates are one of those way.

Network interactions typically take place between a client, such as a web browser, and a server. Client
authentication refers to the identification of a client (the person assumed to be using the software) by

Chapter 1. Introduction to Public-Key Cryptography

6

a server. Server authentication refers to the identification of a server (the organization assumed to be
running the server at the network address) by a client.

Client and server authentication are not the only forms of authentication that certificates support. For
example, the digital signature on an email message, combined with the certificate that identifies the
sender, can authenticate the sender of the message. Similarly, a digital signature on an HTML form,
combined with a certificate that identifies the signer, can provide evidence that the person identified by
that certificate agreed to the contents of the form. In addition to authentication, the digital signature in
both cases ensures a degree of nonrepudiation; a digital signature makes it difficult for the signer to
claim later not to have sent the email or the form.

Client authentication is an essential element of network security within most intranets or extranets.
There are two main forms of client authentication:

• Password-based authentication . Almost all server software permits client authentication by
requiring a recognized name and password before granting access to the server.

• Certificate-based authentication . Client authentication based on certificates is part of the SSL
protocol. The client digitally signs a randomly generated piece of data and sends both the certificate
and the signed data across the network. The server validates the signature and confirms the validity
of the certificate.

1.3.2.1. Password-Based Authentication

Figure 1.4, “Using a Password to Authenticate a Client to a Server” shows the process of

authenticating a user using a username and password. This example assumes the following:

• The user has already trusted the server, either without authentication or on the basis of server
authentication over SSL.

• The user has requested a resource controlled by the server.

• The server requires client authentication before permitting access to the requested resource.

Figure 1.4. Using a Password to Authenticate a Client to a Server

These are the steps in this authentication process:

1. When the server requests authentication from the client, the client displays a dialog box requesting

the username and password for that server.

Authentication Confirms an Identity

7

2. The client sends the name and password across the network, either in plain text or over an
encrypted SSL connection.

3. The server looks up the name and password in its local password database and, if they match,
accepts them as evidence authenticating the user's identity.

4. The server determines whether the identified user is permitted to access the requested resource
and, if so, allows the client to access it.

With this arrangement, the user must supply a new password for each server accessed, and the
administrator must keep track of the name and password for each user.

1.3.2.2. Certificate-Based Authentication

One of the advantages of certificate-based authentication is that it can be used to replace the first
three steps in authentication with a mechanism that allows the user to supply one password, which is
not sent across the network, and allows the administrator to control user authentication centrally. This
is called single sign-on.

Figure 1.5, “Using a Certificate to Authenticate a Client to a Server” shows how client authentication

works using certificates and SSL. To authenticate a user to a server, a client digitally signs a randomly
generated piece of data and sends both the certificate and the signed data across the network. The
server authenticates the user's identity based on the data in the certificate and signed data.

Like Figure 1.4, “Using a Password to Authenticate a Client to a Server”, Figure 1.5, “Using a

Certificate to Authenticate a Client to a Server” assumes that the user has already trusted the server

and requested a resource and that the server has requested client authentication before granting
access to the requested resource.

Figure 1.5. Using a Certificate to Authenticate a Client to a Server

Unlike the authentication process in Figure 1.4, “Using a Password to Authenticate a Client to a

Server”, the authentication process in Figure 1.5, “Using a Certificate to Authenticate a Client to

Chapter 1. Introduction to Public-Key Cryptography

8

a Server” requires SSL. Figure 1.5, “Using a Certificate to Authenticate a Client to a Server” also

assumes that the client has a valid certificate that can be used to identify the client to the server.
Certificate-based authentication is preferred to password-based authentication because it is based on
the user both possessing the private key and knowing the password. However, these two assumptions
are true only if unauthorized personnel have not gained access to the user's machine or password,
the password for the client software's private key database has been set, and the software is set up to
request the password at reasonably frequent intervals.

NOTE

Neither password-based authentication nor certificate-based authentication address
security issues related to physical access to individual machines or passwords. Public­key cryptography can only verify that a private key used to sign some data corresponds to
the public key in a certificate. It is the user's responsibility to protect a machine's physical
security and to keep the private-key password secret.

These are the authentication steps shown in Figure 1.5, “Using a Certificate to Authenticate a Client to

a Server”:

1. The client software maintains a database of the private keys that correspond to the public
keys published in any certificates issued for that client. The client asks for the password to this
database the first time the client needs to access it during a given session, such as the first
time the user attempts to access an SSL-enabled server that requires certificate-based client
authentication.

After entering this password once, the user does not need to enter it again for the rest of the
session, even when accessing other SSL-enabled servers.

2. The client unlocks the private-key database, retrieves the private key for the user's certificate,
and uses that private key to sign data randomly-generated from input from both the client and the
server. This data and the digital signature are evidence of the private key's validity. The digital
signature can be created only with that private key and can be validated with the corresponding
public key against the signed data, which is unique to the SSL session.

3. The client sends both the user's certificate and the randomly-generated data across the network.

4. The server uses the certificate and the signed data to authenticate the user's identity.

5. The server may perform other authentication tasks, such as checking that the certificate presented
by the client is stored in the user's entry in an LDAP directory. The server then evaluates whether
the identified user is permitted to access the requested resource. This evaluation process can
employ a variety of standard authorization mechanisms, potentially using additional information
in an LDAP directory or company databases. If the result of the evaluation is positive, the server
allows the client to access the requested resource.

Certificates replace the authentication portion of the interaction between the client and the server.
Instead of requiring a user to send passwords across the network continually, single sign-on requires
the user to enter the private-key database password once, without sending it across the network. For
the rest of the session, the client presents the user's certificate to authenticate the user to each new
server it encounters. Existing authorization mechanisms based on the authenticated user identity are
not affected.

How Certificates Are Used

9

1.3.3. How Certificates Are Used

Certificates have a purpose: to establish trust. Their usage varies depending on the kind of trust they
are used to ensure. Some kinds of certificates are used to verify the identity of the presenter; others
are used to verify that an object or item has not been tampered with.

1.3.3.1. Uses for Certificates

• Section 1.3.3.1.1, “SSL”

• Section 1.3.3.1.2, “Signed and Encrypted Email”

• Section 1.3.3.1.3, “Single Sign-on”

• Section 1.3.3.1.4, “Object Signing”

1.3.3.1.1. SSL

The Secure Sockets Layer (SSL) protocol governs server authentication, client authentication, and
encrypted communication between servers and clients. SSL is widely used on the Internet, especially
for interactions that involve exchanging confidential information such as credit card numbers.

SSL requires an SSL server certificate. As part of the initial SSL handshake, the server presents
its certificate to the client to authenticate the server's identity. The authentication uses public-key
encryption and digital signatures to confirm that the server is the server it claims to be. Once the
server has been authenticated, the client and server use symmetric-key encryption, which is very fast,
to encrypt all the information exchanged for the remainder of the session and to detect any tampering.

Servers may be configured to require client authentication as well as server authentication. In this
case, after server authentication is successfully completed, the client must also present its certificate
to the server to authenticate the client's identity before the encrypted SSL session can be established.

For an overview of client authentication over SSL and how it differs from password-based
authentication, see Section 1.3.2, “Authentication Confirms an Identity”.

1.3.3.1.2. Signed and Encrypted Email

Some email programs support digitally signed and encrypted email using a widely accepted protocol
known as Secure Multipurpose Internet Mail Extension (S/MIME). Using S/MIME to sign or encrypt
email messages requires the sender of the message to have an S/MIME certificate.

An email message that includes a digital signature provides some assurance that it was sent by the
person whose name appears in the message header, thus authenticating the sender. If the digital
signature cannot be validated by the email software, the user is alerted.

The digital signature is unique to the message it accompanies. If the message received differs in
any way from the message that was sent, even by adding or deleting a single character, the digital
signature cannot be validated. Therefore, signed email also provides assurance that the email has
not been tampered with. This kind of assurance is known as nonrepudiation, which makes it difficult
for the sender to deny having sent the message. This is important for business communication. For
information about the way digital signatures work, see Section 1.2, “Digital Signatures”.

S/MIME also makes it possible to encrypt email messages, which is important for some business
users. However, using encryption for email requires careful planning. If the recipient of encrypted email

Chapter 1. Introduction to Public-Key Cryptography

10

messages loses the private key and does not have access to a backup copy of the key, the encrypted
messages can never be decrypted.

1.3.3.1.3. Single Sign-on

Network users are frequently required to remember multiple passwords for the various services they
use. For example, a user might have to type a different password to log into the network, collect email,
use directory services, use the corporate calendar program, and access various servers. Multiple
passwords are an ongoing headache for both users and system administrators. Users have difficulty
keeping track of different passwords, tend to choose poor ones, and tend to write them down in
obvious places. Administrators must keep track of a separate password database on each server
and deal with potential security problems related to the fact that passwords are sent over the network
routinely and frequently.

Solving this problem requires some way for a user to log in once, using a single password, and get
authenticated access to all network resources that user is authorized to use-without sending any
passwords over the network. This capability is known as single sign-on.

Both client SSL certificates and S/MIME certificates can play a significant role in a comprehensive
single sign-on solution. For example, one form of single sign-on supported by Red Hat products
relies on SSL client authentication. A user can log in once, using a single password to the local
client's private-key database, and get authenticated access to all SSL-enabled servers that user is
authorized to use-without sending any passwords over the network. This approach simplifies access
for users, because they don't need to enter passwords for each new server. It also simplifies network
management, since administrators can control access by controlling lists of certificate authorities
(CAs) rather than much longer lists of users and passwords.

In addition to using certificates, a complete single-sign on solution must address the need to
interoperate with enterprise systems, such as the underlying operating system, that rely on passwords
or other forms of authentication.

1.3.3.1.4. Object Signing

Many software technologies support a set of tools called object signing. Object signing uses standard
techniques of public-key cryptography to let users get reliable information about code they download in
much the same way they can get reliable information about shrink-wrapped software.

Most important, object signing helps users and network administrators implement decisions about
software distributed over intranets or the Internet-for example, whether to allow Java applets signed by
a given entity to use specific computer capabilities on specific users' machines.

The objects signed with object signing technology can be applets or other Java code, JavaScript
scripts, plug-ins, or any kind of file. The signature is a digital signature. Signed objects and their
signatures are typically stored in a special file called a JAR file.

Software developers and others who wish to sign files using object-signing technology must first obtain
an object-signing certificate.

1.3.3.2. Types of Certificates

The Certificate System is capable of generating different types of certificates for different uses and in
different formats. Planning which certificates are required and planning how to manage them, including
determining what formats are needed and how to plan for renewal, are important to manage both the
PKI and the Certificate System instances.

How Certificates Are Used

11

This list is not exhaustive; there are certificate enrollment forms for dual-use certificates for LDAP
directories, file-signing certificates, and other subsystem certificates. These forms are available
through the Certificate Manager's end-entities page, at https://server.example.com:9444/
ca/ee/ca. For more detailed information about the different certificates that can be created, see the
Certificate System Agent's Guide.

When the different Certificate System subsystems are installed, the basic required certificates and
keys are generated; for example, configuring the Certificate Manager generates the CA signing
certificate for the self-signed root CA and the internal OCSP signing, audit signing, SSL server, and
agent user certificates. During the DRM configuration, the Certificate Manager generates the storage,
transport, audit signing, and agent certificates. Additional certificates can be created and installed
separately.

Certificate Type Use Example

Client SSL certificates Used for client authentication

Server SSL certificates Used for server authentication

S/MIME certificates Used for signed and

Chapter 1. Introduction to Public-Key Cryptography

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Certificate Type Use Example

CA certificates Used to identify CAs. Client

Object-signing certificates Used to identify signers of

Table 1.1. Common Certificates

• Section 1.3.3.2.1, “CA Signing Certificates”

• Section 1.3.3.2.2, “Other Signing Certificates”

• Section 1.3.3.2.3, “SSL Server and Client Certificates”

• Section 1.3.3.2.4, “User Certificates”

• Section 1.3.3.2.5, “Dual-Key Pairs”

• Section 1.3.3.2.6, “Cross-Pair Certificates”

1.3.3.2.1. CA Signing Certificates

Every Certificate Manager has a CA signing certificate with a public/private key pair it uses to sign the
certificates and CRLs it issues. This certificate is created and installed when the Certificate Manager is
installed.

The Certificate Manager's status as a root or subordinate CA is determined by whether its CA signing
certificate is self-signed or is signed by another CA. Self-signed root CAs set the policies they use to
issue certificates, such as the subject names, types of certificates that can be issued, and to whom
certificates can be issued. A subordinate CA has a CA signing certificate signed by another CA,
usually the one that is a level above in the CA hierarchy (which may or may not be a root CA). If the
Certificate Manager is a subordinate CA in a CA hierarchy, the root CA's signing certificate must
be imported into individual clients and servers before the Certificate Manager can be used to issue
certificates to them.

The CA certificate must be installed in a client if a server or user certificate issued by that CA is
installed on that client. The CA certificate confirms that the server certificate can be trusted. Ideally, the
certificate chain is installed.

Contents of a Certificate

13

1.3.3.2.2. Other Signing Certificates

Other services, such as the OCSP responder service and CRL publishing, can use signing certificates
other than the CA certificate. For example, a separate CRL signing certificate can be used to sign the
revocation lists that are published by a CA instead of using the CA signing certificate.

1.3.3.2.3. SSL Server and Client Certificates

Server certificates are used for secure communications, such as SSL, and other secure functions.
Server certificates are used to authenticate themselves during operations and to encrypt data; client
certificates authenticate the client to the server.

NOTE

CAs which have a signing certificate issued by a third-party may not be able to issue
server certificates. The third-party CA may have rules in place which prohibit its
subordinates from issuing server certificates.

1.3.3.2.4. User Certificates

End user certificates are a subset of client certificates that are used to identify users to a server or
system. Users can be assigned certificates to use for secure communications, such as SSL, and other
functions such as encrypting email or for single sign-on. Special users, such as Certificate System
agents, can be given client certificates to access special services.

1.3.3.2.5. Dual-Key Pairs

Dual-key pairs are a set of two private and public keys, where one set is used for signing and one for
encryption. These dual keys are used to create dual certificates. The dual certificate enrollment form is
one of the standard forms listed in the end-entities page of the Certificate Manager.

When generating dual-key pairs, set the certificate profiles to work correctly when generating separate
certificates for signing and encryption.

1.3.3.2.6. Cross-Pair Certificates

The Certificate System can issue, import, and publish cross-pair CA certificates. With cross-pair
certificates, one CA signs and issues a cross-pair certificate to a second CA, and the second CA signs
and issues a cross-pair certificate to the first CA. Both CAs then store or publish both certificates as a
crossCertificatePair entry.

Bridging certificates can be done to honor certificates issued by a CA that is not chained to the root
CA. By establishing a trust between the Certificate System CA and another CA through a cross-pair
CA certificate, the cross-pair certificate can be downloaded and used to trust the certificates issued by
the other CA.

1.3.4. Contents of a Certificate

The contents of certificates are organized according to the X.509 v3 certificate specification, which has
been recommended by the International Telecommunications Union (ITU), an international standards
body.

Chapter 1. Introduction to Public-Key Cryptography

14

Users do not usually need to be concerned about the exact contents of a certificate. However, system
administrators working with certificates may need some familiarity with the information contained in
them.

1.3.4.1. Certificate Data Formats

Certificate requests and certificates can be created, stored, and installed in several different formats.
All of these formats conform to X.509 standards.

1.3.4.1.1. Binary

The following binary formats are recognized:

• DER-encoded certificate. This is a single binary DER-encoded certificate.

• PKCS #7 certificate chain. This is a PKCS #7 SignedData object. The only significant field in the

SignedData object is the certificates; the signature and the contents, for example, are ignored. The
PKCS #7 format allows multiple certificates to be downloaded at a single time.

• Netscape Certificate Sequence. This is a simpler format for downloading certificate chains in

a PKCS #7 ContentInfo structure, wrapping a sequence of certificates. The value of the
contentType field should be netscape-cert-sequence, while the content field has the
following structure:

CertificateSequence ::= SEQUENCE OF Certificate

This format allows multiple certificates to be downloaded at the same time.

1.3.4.1.2. Text

Any of the binary formats can be imported in text form. The text form begins with the following line:

-----BEGIN CERTIFICATE-----

Following this line is the certificate data, which can be in any of the binary formats described. This data
should be base-64 encoded, as described by RFC 1113. The certificate information is followed by this
line:

-----END CERTIFICATE-----

1.3.4.2. Distinguished Names

An X.509 v3 certificate binds a distinguished name (DN) to a public key. A DN is a series of name­value pairs, such as uid=doe, that uniquely identify an entity. This is also called the certificate subject
name.

This is an example DN of an employee for Example Corp.:

uid=doe, cn=John Doe,o=Example Corp.,c=US

In this DN, uid is the username, cn is the user's common name, o is the organization or company
name, and c is the country.

Contents of a Certificate

15

DNs may include a variety of other name-value pairs. They are used to identify both certificate
subjects and entries in directories that support the Lightweight Directory Access Protocol (LDAP).

The rules governing the construction of DNs can be complex; for comprehensive information about
DNs, see A String Representation of Distinguished Names at http://www.ietf.org/rfc/rfc4514.txt.

1.3.4.3. A Typical Certificate

Every X.509 certificate consists of two sections:

• The data section includes the following information:

• The version number of the X.509 standard supported by the certificate.

• The certificate's serial number. Every certificate issued by a CA has a serial number that is unique
among the certificates issued by that CA.

• Information about the user's public key, including the algorithm used and a representation of the
key itself.

• The DN of the CA that issued the certificate.

• The period during which the certificate is valid; for example, between 1:00 p.m. on November 15,
2004, and 1:00 p.m. November 15, 2009.

• The DN of the certificate subject, which is also called the subject name; for example, in an SSL
client certificate, this is the user's DN.

• Optional certificate extensions, which may provide additional data used by the client or server. For
example, the Netscape Certificate Type extension indicates the type of certificate, such as an SSL
client certificate, an SSL server certificate, or a certificate for signing email. Certificate extensions
can also be used for other purposes.

• The signature section includes the following information:

• The cryptographic algorithm, or cipher, used by the issuing CA to create its own digital signature.

• The CA's digital signature, obtained by hashing all of the data in the certificate together and
encrypting it with the CA's private key.

Here are the data and signature sections of a certificate shown in the readable pretty-print format:

Certificate:
Data:
Version: v3 (0x2)
Serial Number: 3 (0x3)
Signature Algorithm: PKCS #1 MD5 With RSA Encryption
Issuer: OU=Example Certificate Authority, O=Example Corp, C=US
Validity:
Not Before: Fri Oct 17 18:36:25 1997
Not After: Sun Oct 17 18:36:25 1999
Subject: CN=Jane Doe, OU=Finance, O=Example Corp, C=US
Subject Public Key Info:
Algorithm: PKCS #1 RSA Encryption
Public Key:
Modulus:
00:ca:fa:79:98:8f:19:f8:d7:de:e4:49:80:48:e6:2a:2a:86:

Chapter 1. Introduction to Public-Key Cryptography

16

ed:27:40:4d:86:b3:05:c0:01:bb:50:15:c9:de:dc:85:19:22:
43:7d:45:6d:71:4e:17:3d:f0:36:4b:5b:7f:a8:51:a3:a1:00:
98:ce:7f:47:50:2c:93:36:7c:01:6e:cb:89:06:41:72:b5:e9:
73:49:38:76:ef:b6:8f:ac:49:bb:63:0f:9b:ff:16:2a:e3:0e:
9d:3b:af:ce:9a:3e:48:65:de:96:61:d5:0a:11:2a:a2:80:b0:
7d:d8:99:cb:0c:99:34:c9:ab:25:06:a8:31:ad:8c:4b:aa:54:
91:f4:15
Public Exponent: 65537 (0x10001)
Extensions:
Identifier: Certificate Type
Critical: no
Certified Usage:
SSL Client
Identifier: Authority Key Identifier
Critical: no
Key Identifier:
f2:f2:06:59:90:18:47:51:f5:89:33:5a:31:7a:e6:5c:fb:36:
26:c9
Signature:
Algorithm: PKCS #1 MD5 With RSA Encryption
Signature:
6d:23:af:f3:d3:b6:7a:df:90:df:cd:7e:18:6c:01:69:8e:54:65:fc:06:
30:43:34:d1:63:1f:06:7d:c3:40:a8:2a:82:c1:a4:83:2a:fb:2e:8f:fb:
f0:6d:ff:75:a3:78:f7:52:47:46:62:97:1d:d9:c6:11:0a:02:a2:e0:cc:
2a:75:6c:8b:b6:9b:87:00:7d:7c:84:76:79:ba:f8:b4:d2:62:58:c3:c5:
b6:c1:43:ac:63:44:42:fd:af:c8:0f:2f:38:85:6d:d6:59:e8:41:42:a5:
4a:e5:26:38:ff:32:78:a1:38:f1:ed:dc:0d:31:d1:b0:6d:67:e9:46:a8:
d:c4

Here is the same certificate in the base-64 encoded format:

-----BEGIN CERTIFICATE----­MIICKzCCAZSgAwIBAgIBAzANBgkqhkiG9w0BAQQFADA3MQswCQYDVQQGEwJVUzER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-----END CERTIFICATE-----

1.3.5. How CA Certificates Establish Trust

CAs validate identities and issue certificates. They can be either independent third parties or
organizations running their own certificate-issuing server software, such as the Certificate System.

Any client or server software that supports certificates maintains a collection of trusted CA certificates.
These CA certificates determine which issuers of certificates the software can trust, or validate. In the
simplest case, the software can validate only certificates issued by one of the CAs for which it has a
certificate. It is also possible for a trusted CA certificate to be part of a chain of CA certificates, each
issued by the CA above it in a certificate hierarchy.

The sections that follow explains how certificate hierarchies and certificate chains determine what
certificates software can trust.

How CA Certificates Establish Trust

17

• Section 1.3.5.1, “CA Hierarchies”

• Section 1.3.5.2, “Certificate Chains”

• Section 1.3.5.3, “Verifying a Certificate Chain”

1.3.5.1. CA Hierarchies

In large organizations, responsibility for issuing certificates can be delegated to several different CAs.
For example, the number of certificates required may be too large for a single CA to maintain; different
organizational units may have different policy requirements; or a CA may need to be physically located
in the same geographic area as the people to whom it is issuing certificates.

These certificate-issuing responsibilities can be divided among subordinate CAs. The X.509 standard
includes a model for setting up a hierarchy of CAs, shown in Figure 1.6, “Example of a Hierarchy of

Certificate Authorities”.

Figure 1.6. Example of a Hierarchy of Certificate Authorities

The root CA is at the top of the hierarchy. The root CA's certificate is a self-signed certificate; that
is, the certificate is digitally signed by the same entity that the certificate identifies. The CAs that
are directly subordinate to the root CA have CA certificates signed by the root CA. CAs under the
subordinate CAs in the hierarchy have their CA certificates signed by the higher-level subordinate
CAs.

Organizations have a great deal of flexibility in how CA hierarchies are set up; Figure 1.6, “Example of

a Hierarchy of Certificate Authorities” shows just one example.

1.3.5.2. Certificate Chains

CA hierarchies are reflected in certificate chains. A certificate chain is series of certificates issued by
successive CAs. Figure 1.7, “Example of a Certificate Chain” shows a certificate chain leading from
a certificate that identifies an entity through two subordinate CA certificates to the CA certificate for

Chapter 1. Introduction to Public-Key Cryptography

18

the root CA, based on the CA hierarchy shown in Figure 1.6, “Example of a Hierarchy of Certificate

Authorities”.

Figure 1.7. Example of a Certificate Chain

A certificate chain traces a path of certificates from a branch in the hierarchy to the root of the
hierarchy. In a certificate chain, the following occur:

• Each certificate is followed by the certificate of its issuer.

• Each certificate contains the name (DN) of that certificate's issuer, which is the same as the subject
name of the next certificate in the chain.

In Figure 1.7, “Example of a Certificate Chain”, the Engineering CA certificate contains the DN
of the CA, USA CA, that issued that certificate. USA CA's DN is also the subject name of the next
certificate in the chain.

• Each certificate is signed with the private key of its issuer. The signature can be verified with the
public key in the issuer's certificate, which is the next certificate in the chain.

In Figure 1.7, “Example of a Certificate Chain”, the public key in the certificate for the USA CA can
be used to verify the USA CA's digital signature on the certificate for the Engineering CA.

1.3.5.3. Verifying a Certificate Chain

Certificate chain verification makes sure a given certificate chain is well-formed, valid, properly signed,
and trustworthy. The following procedure is used to form and verify a certificate chain, starting with the
certificate being presented for authentication:

How CA Certificates Establish Trust

19

1. The certificate validity period is checked against the current time provided by the verifier's system
clock.

2. The issuer's certificate is located. The source can be either the verifier's local certificate database
on that client or server or the certificate chain provided by the subject, as with an SSL connection.

3. The certificate signature is verified using the public key in the issuer's certificate.

4. If the issuer's certificate is trusted by the verifier in the verifier's certificate database, verification
stops successfully here. Otherwise, the issuer's certificate is checked to make sure it contains the
appropriate subordinate CA indication in the certificate type extension, and chain verification starts
over with this new certificate. Figure 1.8, “Verifying a Certificate Chain to the Root CA” presents an
example of this process.

Figure 1.8. Verifying a Certificate Chain to the Root CA

Figure 1.8, “Verifying a Certificate Chain to the Root CA” illustrates what happens when only the root

CA is included in the verifier's local database. If a certificate for one of the intermediate CAs, such as
Engineering CA, is found in the verifier's local database, verification stops with that certificate, as
shown in Figure 1.9, “Verifying a Certificate Chain to an Intermediate CA”.

Chapter 1. Introduction to Public-Key Cryptography

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Figure 1.9. Verifying a Certificate Chain to an Intermediate CA

Expired validity dates, an invalid signature, or the absence of a certificate for the issuing CA at any
point in the certificate chain causes authentication to fail. Figure 1.10, “A Certificate Chain That Cannot

Be Verified” shows how verification fails if neither the root CA certificate nor any of the intermediate CA

certificates are included in the verifier's local database.

Managing Certificates

21

Figure 1.10. A Certificate Chain That Cannot Be Verified

1.4. Managing Certificates

Certificates are used in many applications, from encrypting email to accessing websites. There are
two major stages in the lifecycle of the certificate: the point when it is issued (issuance and enrollment)
and the period when the certificates are no longer valid (renewal or revocation). There are also ways
to manage the certificate during its cycle. Making information about the certificate available to other
applications is publishing the certificate and then backing up the key pairs so that the certificate can be
recovered if it is lost.

• Section 1.4.1, “Issuing Certificates”

• Section 1.4.2, “Key Management”

• Section 1.4.3, “Renewing and Revoking Certificates”

1.4.1. Issuing Certificates

The process for issuing a certificate depends on the CA that issues it and the purpose for which it will
be used. Issuing non-digital forms of identification varies in similar ways. The requirements to get a

Chapter 1. Introduction to Public-Key Cryptography

22

library card are different than the ones to get a driver's license. Similarly, different CAs have different
procedures for issuing different kinds of certificates. Requirements for receiving a certificate can be as
simple as an email address or username and password to notarized documents, a background check,
and a personal interview.

Depending on an organization's policies, the process of issuing certificates can range from being
completely transparent for the user to requiring significant user participation and complex procedures.
In general, processes for issuing certificates should be flexible, so organizations can tailor them to
their changing needs.

1.4.2. Key Management

Before a certificate can be issued, the public key it contains and the corresponding private key must
be generated. Sometimes it may be useful to issue a single person one certificate and key pair for
signing operations and another certificate and key pair for encryption operations. Separate signing
and encryption certificates keep the private signing key only on the local machine, providing maximum
nonrepudiation. This also aids in backing up the private encryption key in some central location where
it can be retrieved in case the user loses the original key or leaves the company.

Keys can be generated by client software or generated centrally by the CA and distributed to users
through an LDAP directory. There are costs associated with either method. Local key generation
provides maximum nonrepudiation but may involve more participation by the user in the issuing
process. Flexible key management capabilities are essential for most organizations.

Key recovery , or the ability to retrieve backups of encryption keys under carefully defined conditions,
can be a crucial part of certificate management, depending on how an organization uses certificates.
In some PKI setups, several authorized personnel must agree before an encryption key can be
recovered to ensure that the key is only recovered to the legitimate owner in authorized circumstance.
It can be necessary to recover a key when information is encrypted and can only be decrypted by the
lost key.

1.4.3. Renewing and Revoking Certificates

Like a driver's license, a certificate specifies a period of time during which it is valid. Attempts to
use a certificate for authentication before or after its validity period will fail. Managing certificate
expirations and renewals are an essential part of the certificate management strategy. For example,
an administrator may wish to be notified automatically when a certificate is about to expire so that an
appropriate renewal process can be completed without disrupting the system operation. The renewal
process may involve reusing the same public-private key pair or issuing a new one.

Additionally, it may be necessary to revoke a certificate before it has expired, such as when an
employee leaves a company or moves to a new job in a different unit within the company.

Certificate revocation can be handled in several different ways. Servers can be configured so that the
authentication process checks the directory for the presence of the certificate being presented. When
an administrator revokes a certificate, the certificate can be automatically removed from the directory,
and subsequent authentication attempts with that certificate will fail, even though the certificate
remains valid in every other respect. Alternatively, a list of revoked certificates, a certificate revocation
list (CRL), can be published to the directory at regular intervals. The CRL can be checked as part of
the authentication process. The issuing CA can also be checked directly each time a certificate is
presented for authentication. This procedure is sometimes called real-time status checking.

Chapter 2.

23

Overview of Red Hat Certificate System
Subsystems

Every common PKI operation — issuing, renewing and revoking certificates; archiving and recovering
keys; publishing CRLs and verifying certificate status — are carried out by interoperating subsystems
within Red Hat Certificate System. The functions of each individual subsystem and the way that they
work together to establish a robust and local PKI is described in this chapter.

2.1. A Review of Certificate System Subsystems

Red Hat Certificate System provides six different subsystems, each focusing on different aspects of a
PKI deployment:

• A certificate authority called a Certificate Manager. The CA is the core of the PKI; it issues and

revokes all certificates. The Certificate Manager is also the core of the Certificate System. By
establishing a security domain of trusted subsystems, it establishes and manages relationships
between the other subsystems.

• A key recovery authority called a data recovery manager (DRM). Certificates are created based on

a specific and unique key pair. If a private key is ever lost, then the data which that key was used
to access (such as encrypted emails) is also lost because it is inaccessible. The DRM stores key
pairs, so that a new, identical certificate can be generated based on recovered keys, and all of the
encrypted data can be accessed even after a private key is lost or damaged.

• An online certificate status responder (OCSP). The OCSP verifies whether a certificate is valid and

not expired. This function can also be done by the CA, which has an internal OCSP service, but
using an external OCSP eases the load off of the issuing CA.

• A registration authority (RA). An RA accepts certificate requests and verifies, independently,

whether that request should be approved. It then forwards approved requests to the CA to issue the
certificate. Like the OCSP, this is a function that can be performed by the CA, but using a separate
subsystem reduces the load on the CA.

• A token key service (TKS). The TKS derives keys based on the token CCID, private information,

and a defined algorithm. These derived keys are used by the TPS to format tokens and enroll, or
process, certificates on the token.

• A token processing system (TPS). The TPS interacts directly with external tokens, like smart

cards, and manages the keys and certificates on those tokens through a local client, the Enterprise
Security Client. The Enterprise Security Client contacts the TPS when there is a token operation,
and the TPS interacts with the CA, DRM, or TKS, as required, then send the information back to the
token by way of the Enterprise Security Client.

Even with all possible subsystems installed, the core of the Certificate System is still the CA (or CAs),
since they ultimately process all certificate-related requests. The other subsystems connect to the CA
or CAs likes spokes in a wheel.

Chapter 2. Overview of Red Hat Certificate System Subsystems

24

2.1.1. About the Certificate Manager (CA)

As stated, the Certificate Manager is the heart of the Certificate System. It manages certificates
at every stage, from requests through enrollment (issuing), renewal, and revocation. The CA also
publishes certificates and lists of revoked certificates for use by clients like the OCSP or web servers.

2.1.1.1. Issuing Certificates (Enrollment)

An end entity enrolls in the PKI by submitting an enrollment request through the end-entity interface.
There can be many kinds of enrollment that use different enrollment methods or require different
authentication methods. For each enrollment, there is a separate enrollment page created that is
specific to the type of enrollment, type of authentication, and the certificate profiles associated with
the type of certificate. The forms associated with enrollment can be customized for both appearance
and content. Alternatively, the enrollment process can be customized by creating certificate profiles
for each enrollment type. Certificate profiles dynamically-generate forms which are customized by
configuring the inputs associated with the certificate profile.

About the Certificate Manager (CA)

25

When an end entity enrolls in a PKI by requesting a certificate, the following events can occur,
depending on the configuration of the PKI and the subsystems installed:

1. The end entity provides the information in one of the enrollment forms and submits a request.

The information gathered from the end entity is customizable in the form depending on the
information collected to store in the certificate or to authenticate against the authentication method
associated with the form. The form creates a request that is then submitted to the Certificate
Manager.

2. The enrollment form triggers the creation of the public and private keys or for dual-key pairs for the
request.

3. The end entity provides authentication credentials before submitting the request, depending on
the authentication type. This can be LDAP authentication, PIN-based authentication, or certificate­based authentication.

4. The request is submitted either to an agent-approved enrollment process or an automated
process.

• The agent-approved process, which involves no end-entity authentication, sends the request to

the request queue in the agent services interface, where an agent must processes the request.
An agent can then modify parts of the request, change the status of the request, reject the
request, or approve the request.

Automatic notification can be set up so an email is sent to an agent any time a request appears
in the queue. Also, an automated job can be set to send a list of the contents of the queue to
agents on a pre configured schedule.

• The automated process, which involves end-entity authentication, processes the certificate

request as soon as the end entity successfully authenticates.

5. The form collects information about the end entity from an LDAP directory when the form is
submitted. For certificate profile-based enrollment, the defaults for the form can be used to collect
the user LDAP ID and password.

6. The certificate profile associated with the form determine aspects of the certificate that is issued.
Depending on the certificate profile, the request is evaluated to determine if the request meets the
constraints set, if the required information is provided, and the contents of the new certificate.

7. The form can also request that the user export the private encryption key. If the DRM subsystem is
set up with this CA, the end entity's key is requested, and an archival request is sent to the DRM.
This process generally requires no interaction from the end entity.

8. The certificate request is either rejected because it did not meet the certificate profile or
authentication requirements, or a certificate is issued.

9. The certificate is delivered to the end entity.

• In automated enrollment, the certificate is delivered to the user immediately. Since the

enrollment is normally through an HTML page, the certificate is returned as a response on
another HTML page.

• In agent-approved enrollment, the certificate can be retrieved by serial number or request Id in

the end-entity interface.

Chapter 2. Overview of Red Hat Certificate System Subsystems

26

• If the notification feature is set up, the link where the certificate can be obtained is sent to the
end user.

10. An automatic notice can be sent to the end entity when the certificate is issued or rejected.

11. The new certificate is stored in the Certificate Manager's internal database.

12. If publishing is set up for the Certificate Manager, the certificate is published to a file or an LDAP
directory.

13. The internal OCSP service checks the status of certificates in the internal database when a
certificate status request is received.

The end-entity interface has a search form for certificates that have been issued and for the CA
certificate chain.

2.1.1.2. Renewal

When certificates reach their expiration date, they can either be allowed to lapse, or they can be
renewed.

Renewal regenerates a certificate request using the existing key pairs for that certificate, and then
resubmits the request to Certificate Manager. The renewed certificate is identical to the original (since
it was created from the same profile using the same key material) with one exception — it has a
different, later expiration date.

Renewal can make managing certificates and relationships between users and servers much
smoother, because the renewed certificate functions precisely as the old one. For user certificates,
renewal allows encrypted data to be accessed without any loss.

2.1.1.3. Revocation

End entities can request that their own certificates be revoked. When an end entity makes the request,
the certificate has to be presented to the CA. If the certificate and the keys are available, the request is
processed and sent to the Certificate Manager, and the certificate is revoked. The Certificate Manager
marks the certificate as revoked in its database and adds it to any applicable CRLs.

An agent can revoke any certificate issued by the Certificate Manager by searching for the certificate
in the agent services interface and then marking it revoked. Once a certificate is revoked, it is marked
revoked in the database and in the publishing directory, if the Certificate is set up for publishing.

If the internal OCSP service has been configured, the service determines the status of certificates by
looking them up in the internal database.

Automated notifications can be set to send email messages to end entities when their certificates are
revoked by enabling and configuring the certificate revoked notification message.

2.1.2. About the Registration Manager (RA)

A registration authority (RA) is an intermediary between a user and a CA. It accepts enrollment
requests and then authenticates them locally. If the request is approved, the RA sends the request to
the CA to issue the certificate and, once the certificate is issued, sends the certificate back to the user.

About OCSP Services

27

RAs remove some of the load from CAs by handling the validation part of a certificate request.
For example, offices or organizations can validate requests locally, according to their predefined
standards, using RA agents. This requires fewer CAs and allows the organization to group all of the
CAs in a separate, secure location.

The kinds of certificates that can generated in the Certificate System RA are limited to the most
common types of certificates: user certificates, SSL client certificates, RA agent certificates, and SCEP
certificates for local routers. Users can check the RA services pages to view their certificate request
status, retrieve their issued certificates, and renew their certificates.

Certificate System RAs can perform either automatic approval and manual approval, depending on
the configuration in the enrollment profiles. Like the CA, the RA can also be configured to send a
notification when the certificate request is processed.

The RA is normally set up outside of the firewall, and the CA is set up behind the firewall. This enables
requests to be made from outside the protected environment (for example, the Internet), while the CA
remains under the protection of the site's security measures.

2.1.3. About OCSP Services

The Certificate System CA supports the Online Certificate Status Protocol (OCSP) as defined in PKIX
standard RFC 25601. The OCSP protocol enables OCSP-compliant applications to determine the state
of a certificate, including the revocation status, without having to directly check a CRL published by
a CA to the validation authority. The validation authority, which is also called an OCSP responder,
checks for the application.

1. A CA is set up to issue certificates that include the Authority Information Access extension, which
identifies an OCSP responder that can be queried for the status of the certificate.

2. The CA periodically publishes CRLs to an OCSP responder.

3. The OCSP responder maintains the CRL it receives from the CA.

4. An OCSP-compliant client sends requests containing all the information required to identify the
certificate to the OCSP responder for verification. The applications determine the location of the
OCSP responder from the value of the Authority Information Access extension in the certificate
being validated.

5. The OCSP responder determines if the request contains all the information required to process
it. If it does not or if it is not enabled for the requested service, a rejection notice is sent. If it does
have enough information, it processes the request and sends back a report stating the status of
the certificate.

2.1.3.1. OCSP Response Signing

Every response that the client receives, including a rejection notification, is digitally signed by the
responder; the client is expected to verify the signature to ensure that the response came from
the responder to which it submitted the request. The key the responder uses to sign the message
depends on how the OCSP responder is deployed in a PKI setup. RFC 2560 recommends that the key
used to sign the response belong to one of the following:

• The CA that issued the certificate that's status is being checked.

1

http://www.ietf.org/rfc/rfc2560.txt

Chapter 2. Overview of Red Hat Certificate System Subsystems

28

• A responder with a public key trusted by the client. Such a responder is called a trusted responder.

• A responder that holds a specially marked certificate issued to it directly by the CA that revokes the
certificates and publishes the CRL. Possession of this certificate by a responder indicates that the
CA has authorized the responder to issue OCSP responses for certificates revoked by the CA. Such
a responder is called a CA-designated responder or a CA-authorized responder.

The end-entities page of a Certificate Manager includes a form for manually requesting a certificate for
the OCSP responder. The default enrollment form includes all the attributes that identify the certificate
as an OCSP responder certificate. The required certificate extensions, such as OCSPNoCheck and
Extended Key Usage, can be added to the certificate when the certificate request is submitted.

2.1.3.2. OCSP Responses

The OCSP response that the client receives indicates the current status of the certificate as
determined by the OCSP responder. The response could be any of the following:

• Good or Verified . Specifies a positive response to the status inquiry, meaning the certificate has
not been revoked. It does not necessarily mean that the certificate was issued or that it is within the
certificate's validity interval. Response extensions may be used to convey additional information on
assertions made by the responder regarding the status of the certificate.

• Revoked . Specifies that the certificate has been revoked, either permanently or temporarily.

Based on the status, the client decides whether to validate the certificate.

NOTE

The OCSP responder will never return a response of Unknown. The response will always
be either Good or Revoked.

2.1.3.3. OCSP Services

There are two ways to set up OCSP services:

• The OCSP built into the Certificate Manager

• The Online Certificate Status Manager subsystem

In addition to the built-in OCSP service, the Certificate Manager can publish CRLs to an OCSP­compliant validation authority. CAs can be configured to publish CRLs to the Certificate System
Online Certificate Status Manager. The Online Certificate Status Manager stores each Certificate
Manager's CRL in its internal database and uses the appropriate CRL to verify the revocation status of
a certificate when queried by an OCSP-compliant client.

The Certificate Manager can generate and publish CRLs whenever a certificate is revoked and at
specified intervals. Because the purpose of an OCSP responder is to facilitate immediate verification
of certificates, the Certificate Manager should publish the CRL to the Online Certificate Status
Manager every time a certificate is revoked. Publishing only at intervals means that the OCSP service
is checking an outdated CRL.

About the Data Recovery Manager (DRM)

29

NOTE

If the CRL is large, the Certificate Manager can take a considerable amount of time to
publish the CRL.

The Online Certificate Status Manager stores each Certificate Manager's CRL in its internal database
and uses it as the CRL to verify certificates. The Online Certificate Status Manager can also use the
CRL published to an LDAP directory, meaning the Certificate Manager does not have to update the
CRLs directly to the Online Certificate Status Manager.

2.1.4. About the Data Recovery Manager (DRM)

To archive private encryption keys and recover them later, the PKI configuration must include the
following elements:

• Clients that can generate dual keys and that support the key archival option (using the CRMF/
CMMF protocol).

• An installed and configured DRM.

• HTML forms with which end entities can request dual certificates (based on dual keys) and key
recovery agents can request key recovery.

Only keys that are used exclusively for encrypting data should be archived; signing keys in particular
should never be archived. Having two copies of a signing key makes it impossible to identify with
certainty who used the key; a second archived copy could be used to impersonate the digital identity
of the original key owner.

Clients that generate single key pairs use the same private key for both signing and encrypting data,
so a private key derived from a single key pair cannot be archived and recovered. Clients that can
generate dual key pairs use one private key for encrypting data and the other for signing data. Since
the private encryption key is separate, it can be archived.

In addition to generating dual key pairs, the clients must also support archiving the encryption key in
certificate requests. This option archives keys at the time the private encryption keys are generated as
a part of issuing the certificate.

2.1.4.1. Archiving Keys

The DRM automatically archives private encryption keys if archiving is configured.

If an end entity loses a private encryption key or is unavailable to use the private key, the key must
be recovered before any data that was encrypted with the corresponding public key can be read.
Recovery is possible if the private key was archived when the key was generated.

There are some common situations when it is necessary to recover encryption keys:

• An employee loses the private encryption key and cannot read encrypted mail messages.

• An employee is on an extended leave, and someone needs to access an encrypted document.

• An employee leaves the company, and company officials need to perform an audit that requires
gaining access to the employee's encrypted mail.

Chapter 2. Overview of Red Hat Certificate System Subsystems

30

The DRM stores private encryption keys in a secure key repository in its internal database; each key is
encrypted and stored as a key record and is given a unique key identifier.

The archived copy of the key remains wrapped with the DRM's storage key. It can be decrypted, or
unwrapped, only by using the corresponding private key pair of the storage certificate. A combination
of one or more key recovery (or DRM) agents' certificates authorizes the DRM to complete the key
recovery to retrieve its private storage key and use it to decrypt/recover an archived private key.

The DRM indexes stored keys by key number, owner name, and a hash of the public key, allowing for
highly efficient searching. The key recovery agents have the privilege to insert, delete, and search for
key records.

• When the key recovery agents search by the key ID, only the key that corresponds to that ID is
returned.

• When the agents search by user name, all stored keys belonging to that owner are returned.

• When the agents search by the public key in a certificate, only the corresponding private key is
returned.

When a Certificate Manager receives a certificate request that contains the key archival option,
it automatically forwards the request to the DRM to archive the encryption key. The private key is
encrypted by the transport key, and the DRM receives the encrypted copy and stores the key in its key
repository. To archive the key, the DRM uses two special key pairs:

• A transport key pair and corresponding certificate.

• A storage key pair.

Figure 2.1, “How the Key Archival Process Works” illustrates how the key archival process occurs

when an end entity requests a certificate.

Figure 2.1. How the Key Archival Process Works

1. The client requests and generates a dual key pair.

About the Data Recovery Manager (DRM)

31

a. The end entity, using a client which can generate dual key pairs, submits a request through

the Certificate Manager enrollment form.

b. The client detects the JavaScript in the enrollment form and exports only the private

encryption key, not the private signing key.

c. The Certificate Manager detects the key archival option in the request and asks the client for

the private encryption key.

d. The client encrypts the private encryption key with the public key from the DRM's transport

certificate embedded in the enrollment form.

2. After approving the certificate request and issuing the certificate, the Certificate Manager sends
it to the DRM for storage, along with the public key. The Certificate Manager waits for verification
from the DRM that the private key has been received and stored and that it corresponds to the
public encryption key.

3. The DRM decrypts it with the private key. After confirming that the private encryption key
corresponds to the public encryption key, the DRM encrypts it again with its public key pair of the
storage key before storing it in its internal database.

4. Once the private encryption key has been successfully stored, the DRM uses the private key of its
transport key pair to sign a token confirming that the key has been successfully stored; the DRM
then sends the token to the Certificate Manager.

5. The Certificate Manager issues two certificates for the signing and encryption key pairs and
returns them to the end entity.

Both subsystems subject the request to configured certificate profile constraints at appropriate stages.
If the request fails to meet any of the profile constraints, the subsystem rejects the request.

2.1.4.2. Key Recovery

The DRM supports agent-initiated key recovery. Agent-initiated recovery is when designated recovery
agents use the key recovery form on the DRM agent services page to process and approve key
recovery requests. With the approval of a specified number of agents, an organization can recover
keys when the key's owner is unavailable or when keys have been lost.

Through the DRM agent services page, key recovery agents can collectively authorize and retrieve
private encryption keys and associated certificates in a PKCS #12 package, which can then be
imported into the client. (This is explained in more detail in the Certificate System Agent's Guide.) To
authorize key recovery, the required number of recovery agents access the DRM agent services page
and use the Authorize Recovery button to enter each authorization separately.

In key recovery authorization, one of the key recovery agents informs all required recovery agents
about an impending key recovery. All recovery agents access the DRM key recovery page. One of
the agents initiates the key recovery process. The DRM returns a notification to the agent includes
a recovery authorization reference number identifying the particular key recovery request that the
agent is required to authorize. Each agent uses the reference number and authorizes key recovery
separately.

The DRM informs the agent who initiated the key recovery process of the status of the authorizations.

Chapter 2. Overview of Red Hat Certificate System Subsystems

32

NOTE

The page that the first agent used to initiate the key recovery request keeps refreshing
until all agents required to authorize have performed the authorization. It is important that
the first agent does not close this browser session until the authorization is complete.
Otherwise, the key recovery request needs to be started again.

When all of the authorizations are entered, the DRM checks the information. If the information
presented is correct, it retrieves the requested key and returns it along with the corresponding
certificate in the form of a PKCS #12 package to the agent who initiated the key recovery process.

WARNING

The PKCS #12 package contains the private key. To minimize the risk of key compromise,
the recovery agent must use a secure method to deliver the PKCS #12 package and
password to the key recipient. The agent should use a good password to encrypt the
PKCS #12 package and set up an appropriate delivery mechanism.

The key recovery agent scheme configures the DRM to recognize to which group the key recovery
agents belong and specifies how many of these agents are required to authorize a key recovery
request before the archived key is restored.

2.1.5. About the Token Processing System (TPS)

The Token Processing System (TPS) serves as the conduit between the Enterprise Security Client and
the other subsystems (CA, TKS, DRM) in the Certificate System and is the only means for the client
to communicate with the other subsystems. It provides the following functionalities for users managing
their smart cards through the Enterprise Security Client:

• Working with multiple instances of a subsystem

• Formatting smart cards

• Resetting the PIN on smart card tokens

• Upgrading the applet for smart card tokens

• Enrolling smart cards through the Enterprise Security Client

• Performing LDAP authentication

• Managing the token database

• Logging token events

The TPS must be configured to work with two Certificate System subsystems: the CA, which will
process all of the certificate enrollment and revocation requests initiated through the Enterprise
Security Client, and the Token Key Service, which generates a master key which is used to derive
secret keys specific to each smart card, which are used to wrap (encrypt) the certificates and
commands transmitted between the TPS and the client. The TPS can be optionally configured to work
with a DRM instance, which will perform server-side key generation and key archival and recovery for
the keys and certificates stored on the smart cards.

About the Token Key Service (TKS)

33

2.1.6. About the Token Key Service (TKS)

The Certificate System Token Management System consists of three components, the Token
Processing System (TPS), the Token Key Service (TKS), and the Enterprise Security Client. This
section explains the TKS, which manages the master keys required set up a secure communication
channel between the TPS and the client.

A TKS manages the master and transport keys required to generate and distribute keys for smart
cards or tokens. A master key is a Triple DES symmetric key stored either in software or hardware
token. When supplied with the token CUID, a TKS can derive the corresponding three symmetric keys
� authentication key, Mac key, and key encryption key (KEK) � on each token. This effectively shares
secrets between the Certificate System and the token without having to store these symmetric keys on
the server.

The Certificate System TPS subsystem uses the TKS subsystem to generate the token keys the TPS
uses to communicate with the Enterprise Security Client. The TPS communicates with the TKS over
SSL. The TKS provides the security between tokens and the TPS since the security relies on the
relationship between the master key and the token keys.

The functions provided by the TKS include the following:

• Helps establish a secure channel (signed and encrypted) between the token and TPS.

• Provides proof of presence for the security token during enrollment.

• Supports key changeover when the master key changes on the TKS. Tokens with older keys get

new token keys.

• Helps generate a symmetric session key for the DRM to wrap (encrypt) the entity's private key for

(optional) server-side key generation, where the entity's encryption keys are generated on the DRM

NOTE

Because of the sensitivity of the data that the TKS manages, the TKS should be set
behind the firewall with restricted access.

2.2. Red Hat Certificate System Services

There are three different interfaces for managing certificates and subsystems, depending on the user
type: administrators, agents, and end users.

2.2.1. Interfaces for Administrators

The administrative interface is used to manage the subsystem itself. This includes adding users,
configuring logs, managing profiles and plug-ins, and the internal database, among many other
functions. This interface is also the only interface that does not directly deal with certificates, tokens, or
keys, meaning it is not used for managing the PKI, only the servers.

There are two types of administrative consoles, Java-based and HTML-based. Although the interface
is different, both are accessed using a server URL and the administrative port number.

Chapter 2. Overview of Red Hat Certificate System Subsystems

34

2.2.1.1. The Java Administrative Console for CA, OCSP, DRM, and TKS
Subsystems

The Java console is used by four subsystems: the CA, OCSP, DRM, and TKS. The console is
accessed using a locally-installed pkiconsole utility. It can access any subsystem because
the command requires the hostname, the subsystem's administrative SSL port, and the specific
subsystem type.

pkiconsole https://server.example.com:admin_port/subsystem_type

This opens a console, as in Figure 2.2, “Certificate System Console”.

Figure 2.2. Certificate System Console

The Configuration tab controls all of the setup for the subsystem, as the name implies. The choices
available in this tab are different depending on which subsystem type the instance is; the CA has
the most options since it has additional configuration for jobs, notifications, and certificate enrollment
authentication.

All subsystems have four basic options:

• Users and groups

• Access control lists

• Log configuration

• Subsystem certificates (meaning the certificates issued to the subsystem for use, for example, in the
security domain or audit signing)

The Status tab shows the logs maintained by the subsystem.

2.2.1.2. The Administrative Interface for the RA and TPS

The RA and TPS subsystems use HTML-based administrative interfaces. These are accessed by
entering the hostname and secure port as the URL, authenticating with the administrator's certificate,
and clicking the appropriate Administrators link.

NOTE

There is a single SSL port for RA and TPS subsystems which is used for both
administrator and agent services. Access to those services is restricted by certificate-

Interfaces for Administrators

35

based authentication. The other subsystems used separate SSL ports for the agent and
administrative services, along with certificate-based authentication.

The HTML admin interface is much more limited than the Java console; the primary administrative
function is managing the subsystem users; all other administrative tasks are done by manually editing
the CS.cfg file.

The RA allows administrators to create and edit users and groups for the subsystem.

Figure 2.3. RA Admin Page

The TPS only allows operations to manage users for the TPS subsystem. However, the TPS admin
page can also list tokens and display all activities (including normally-hidden administrative actions)
performed on the TPS.

Chapter 2. Overview of Red Hat Certificate System Subsystems

36

Figure 2.4. TPS Admin Page

2.2.2. Agent Interfaces

The agent services pages are where almost all of the certificate and token management tasks are
performed. These services are HTML-based, and agents authenticate to the site using a special agent
certificate.

End User Pages

37

Figure 2.5. Certificate Manager's Agent Services Page

The operations vary depending on the subsystem:

• The Certificate Manager agent services include approving certificate requests (which issues the
certificates), revoking certificates, and publishing certificates and CRLs. All certificates issued by the
CA can be managed through its agent services page.

• The TPS agent services, like the CA agent services, manages all of the tokens which have been
formatted and have had certificates issued to them through the TPS. Tokens can be enrolled,
suspended, and deleted by agents. Two other roles (operator and admin) can view tokens in web
services pages, but cannot perform any actions on the tokens.

• DRM agent services pages process key recovery requests, which set whether to allow a certificate
to be issued reusing an existing key pair if the certificate is lost.

• The OCSP agent services page allows agents to configure CAs which publish CRLs to the OCSP, to
load CRLs to the OCSP manually, and to view the state of client OCSP requests.

• The RA agent services allows agents to list and approve certificate requests and to check the status
of requests and certificates processed through the RA.

The TKS is the only subsystem without an agent services page.

2.2.3. End User Pages

The CA, RA, and TPS all process direct user requests in some way. That means that end users have
to have a way to connect with those subsystems. The CA and RA both have end-user, or end-entities,
HTML services. The TPS uses the Enterprise Security Client.

Chapter 2. Overview of Red Hat Certificate System Subsystems

38

The end-user services are accessed over standard HTTP using the server's hostname and the
standard port number; they can also be accessed over HTTPS using the server's hostname and the
specific end-entities SSL port.

For CAs, each type of SSL certificate is processed through a specific online submission form, called
a profile. There are about two dozen certificate profiles for the CA, covering all sorts of certificates —
user SSL certificates, server SSL certificates, log and file signing certificates, email certificates, and
every kind of subsystem certificate. There can also be custom profiles.

Figure 2.6. Certificate Manager's End-Entities Page

End users retrieve their certificates through the CA pages when the certificates are issued. They can
also download CA chains and CRLs and can revoke or renew their certificates through those pages.

The RA is a more lightweight subsystem, so it only processes four common certificate profiles.
Like the CA, the enrollment forms are accessed through the End Entities URL. Users can submit
certificate requests and retrieve their certificates through the RA.

2.2.4. Enterprise Security Client

The Enterprise Security Client is a tool for Red Hat Certificate System which simplifies managing
smart cards. End users can use security tokens (smart cards) to store user certificates used for
applications such as single sign-on access and client authentication. End users are issued the tokens
containing certificates and keys required for signing, encryption, and other cryptographic functions.

The Enterprise Security Client is the third part of Certificate System's complete token management
system. Two subsystems — the Token Key Service (TKS) and Token Processing System (TPS) —
are used to process token-related operations. The Enterprise Security Client is the interface which
allows the smart card and user to access the token management system.

After a token is enrolled, applications such as Mozilla Firefox and Thunderbird can be configured to
recognize the token and use it for security operations, like client authentication and S/MIME mail.
Enterprise Security Client provides the following capabilities:

Enterprise Security Client

39

• Supports JavaCard 2.1 or higher cards and Global Platform 2.01-compliant smart cards like
Safenet's 330J smart card

• Supports Global Platform 2.01-compliant smart cards like Gemalto e-gate 32K and Gemalto TOP IM
FIPS CY2 tokens, both the smart card and GemPCKey USB form factor key.

• Enrolls security tokens so they are recognized by TPS.

• Maintains the security token, such as re-enrolling a token with TPS.

• Provides information about the current status of the token or tokens being managed.

• Supports server-side key generation so that keys can be archived and recovered on a separate
token if a token is lost.

The Enterprise Security Client is a cross-platform client for end users to register and manage keys
and certificates on smart cards or tokens. This is the final component in the Certificate System token
management system, with the Token Processing System (TPS) and Token Key Service (TKS).

NOTE

For more information on using the Enterprise Security Client, see the Certificate System
Enterprise Security Client Guide.

The Enterprise Security Client provides the user interface of the token management system. The end
user can be issued security tokens containing certificates and keys required for signing, encryption,
and other cryptographic functions. To use the tokens, the TPS must be able to recognize and
communicate with them. Enterprise Security Client is the method for the tokens to be enrolled.

Enterprise Security Client communicates over an SSL HTTP channel to the backend of the TPS. It is
based on an extensible Mozilla XULRunner framework for the user interface, while retaining a legacy
web browser container for a simple HTML-based UI.

After a token is properly enrolled, web browsers can be configured to recognize the token and use it
for security operations. Enterprise Security Client provides the following capabilities:

• Allows the user to enroll security tokens so they are recognized by the TPS.

• Allows the user to maintain the security token. For example, Enterprise Security Client makes it
possible to re-enroll a token with the TPS.

• Provides support for several different kinds of tokens through default and custom token profiles. By
default, the TPS can automatically enroll user keys, device keys, and security officer keys; additional
profiles can be added so that tokens for different uses (recognized by attributes such as the token
CUID) can automatically be enrolled according to the appropriate profile.

• Provides information about the current status of the tokens being managed.

40

Chapter 3.

41

Supported Standards and Protocols

Red Hat Certificate System is based on many public and standard protocols and RFCs, to ensure the
best possible performance and interoperability. The major standards and protocols used or supported
by Certificate System 8.0 are outlined in this chapter, to help administrators plan their client services
effectively.

3.1. PKCS #11

Public-Key Cryptography Standard (PKCS) #11 specifies an API used to communicate with devices
that hold cryptographic information and perform cryptographic operations. Because it supports PKCS
#11, Certificate System is compatible with a wide range of hardware and software devices.

At least one PKCS #11 module must be available to any Certificate System subsystem instance. A
PKCS #11 module (also called a cryptographic module or cryptographic service provider) manages
cryptographic services such as encryption and decryption. PKCS #11 modules are analogous to
drivers for cryptographic devices that can be implemented in either hardware or software. Certificate
System contains a built-in PKCS #11 module and can support third-party modules.

A PKCS #11 module always has one or more slots which can be implemented as physical hardware
slots in a physical reader such as smart cards or as conceptual slots in software. Each slot for a
PKCS #11 module can in turn contain a token, which is the hardware or software device that actually
provides cryptographic services and optionally stores certificates and keys.

Two cryptographic modules are included in the Certificate System:

Chapter 3. Supported Standards and Protocols

42

• The default internal PKCS #11 module, which comes with two tokens:

• The internal crypto services token, which performs all cryptographic operations such as
encryption, decryption, and hashing.

• The internal key storage token ("Certificate DB token"), which handles all communication with the
certificate and key database files that store certificates and keys.

• The FIPS 140-1 module. This module complies with the FIPS 140-1 government standard for
cryptographic module implementations. The FIPS 140-1 module includes a single, built-in FIPS
140-1 certificate database token, which handles both cryptographic operations and communication
with the certificate and key database files.

Any PKCS #11 module can be used with the Certificate System. To use an external hardware token
with a subsystem, load its PKCS #11 module before the subsystem is configured, and the new token is
available to the subsystem.

Available PKCS #11 modules are tracked in the secmod.db database for the subsystem. This file can
be modified using the modutil tool, and it should be modified when there are changes to the system
like installing hardware accelerators to use for signing operations. For more information on modutil,
see http://www.mozilla.org/projects/security/pki/nss/tools/.

PKCS #11 hardware devices also provide key backup and recovery features for the information stored
on the hardware token. Refer to the PKCS #11 vendor documentation for information on retrieving
keys from the tokens.

3.2. SSL/TLS, ECC, and RSA

Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols are universally accepted
standards for authenticated and encrypted communication between clients and servers. Both client
and server authentication occur over SSL/TLS.

SSL/TLS uses a combination of public key and symmetric-key encryption. Symmetric-key encryption
is much faster than public-key encryption, but public-key encryption provides better authentication
techniques. An SSL/TLS session always begins with an exchange of messages called the SSL
handshake, initial communication between the server and client. The handshake allows the server
to authenticate itself to the client using public-key techniques, then allows the client and the server
to cooperate in the creation of symmetric keys used for rapid encryption, decryption, and tamper
detection during the session that follows.

Both of these protocols support using a variety of different cryptographic algorithms, or ciphers, for
operations such as authenticating the server and client, transmitting certificates, and establishing
session keys. Clients and servers may support different cipher suites, or sets of ciphers. Among other
functions, the SSL handshake determines how the server and client negotiate which cipher suite they
will use to authenticate each other, to transmit certificates, and to establish session keys.

Key-exchange algorithms like RSA and Elliptic Curve Cryptography (ECC) govern the way the server
and client determine the symmetric keys to use during an SSL session. The most common SSL cipher
suites use RSA key exchange, while TLS supports ECC cipher suites as well as RSA. The Certificate
System1 supports both RSA and ECC public-key cryptographic systems.

Only RSA is supported natively. External PKCS#11 modules with ECC support must be loaded for subsystems to use ECC.

Supported Cipher Suites for RSA

43

NOTE

Longer RSA keys are required to provide security as computing capabilities increase.
The recommended RSA key-length is 2048 bits. Though many web servers continue to
use 1024-bit keys, web servers should migrate to at least 2048 bits. For 64-bit machines,
consider using stronger keys. All CAs should use at least 2048-bit keys, and stronger keys
(such as 3072 or 4096 bits) if possible.

As PKIs using RSA keys and certificates transition to other cryptographic systems like ECC, servers
should continue to support RSA. Certificate System supports using both RSA- and ECC-based
certificates in the same subsystem.

3.2.1. Supported Cipher Suites for RSA

Certificate System supports several different cipher suites with the RSA key exchange:

• AES and SHA-1 Message Authentication. Advanced Encryption Standard (AES) ciphers have a
fixed block size of 128-bits, and the keys can be either 128-bit or 256-bit. There are 3.4 x 10

38

possible 128-bit keys and 1.1 x 1077 possible 256-bit keys. There are more possible keys than any
other cipher, making AES the strongest cipher supported by SSL. These cipher suites are FIPS­compliant.

• Triple DES and SHA-1 Message Authentication. Triple DES (Data Encryption Standard) is the
second-strongest cipher supported by SSL, but it is not as fast as RC4. Triple DES uses a key
three times as long as the key for standard DES. Because the key size is so large, there are
approximately 3.7 * 1050 possible keys. This cipher suite is FIPS-compliant.

• RC4 and RC2 and MD5 Message Authentication. The RC4 and RC2 ciphers have 128-bit
encryption, which permits approximately 3.4 * 1038 possible keys. This makes RC4 or RC2 keys
very difficult to crack. RC4 ciphers are faster than RC2 ciphers.

RC4 can use SHA-1 message authentication as well as MD5 message authentication.

• DES and SHA-1 Message Authentication. DES 56-bit encryption permits approximately 7.2
* 1016 possible keys. This cipher suite is no longer FIPS-compliant because it is too weak
cryptographically.

3.2.2. Using ECC

Elliptic Curve Cryptography (ECC) is a cryptographic system that uses elliptic curves to create keys
for encrypting data. ECC creates cryptographically-stronger keys with shorter key lengths than RSA,
which makes it faster and more efficient to implement.

ECC has several advantages over RSA, since it is faster and requires shorter key lengths for stronger
keys. The drawback to using ECC is that it is not as widely supported as RSA.

Bits of Security

1

RSA Key Length ECC Key Length

80 1024 160-223

112 2048 224-255

128 3072 256-383

192 7860 384-511

Chapter 3. Supported Standards and Protocols

44

Bits of Security

1

RSA Key Length ECC Key Length

256 15360 512+

The information in this table is from the National Institute of Standards and Technology (NIST). For more information, see http://

csrc.nist.gov/publications/nistpubs/800-57/SP800-57-Part1.pdf.

Table 3.1. Comparison of RSA and ECC Cipher Strength

Certificate System supports using ECC with all of its subsystems, so ECC certificate requests can be
submitted to CAs through any of the enrollment profiles and ECC keys can be archived and restored in
the DRM. However, Certificate System does not include ECC support natively, so using ECC is slightly
different than using RSA:

• An external PKCS#11 module must be loaded before any subsystems are installed so that they can
be configured with ECC subsystem certificates.

• The CA profile pages can process ECC certificate requests, but they cannot generate ECC keys.
Some of the profile forms, like manual user certificates, then cannot be used for ECC certificates.
In those cases, a different or custom profile needs to be used, and certificate requests have to be
generated using certutil.

For a CA to issue ECC certificates, the CA must be configured with an ECC CA signing certificate.
This is best done by loading an ECC PKCS#11 module before the CA is installed, and then configuring
the CA using ECC keys.

NOTE

A CA with an ECC CA signing certificate can issue both ECC and RSA certificates. A CA
with an RSA CA signing certificate can only issue RSA certificates.

Only the CA signing certificate is required; if for support purposes it is better to use RSA client
certificates with the CA, simply delete the ECC subsystem certificates (except for the signing
certificate) and replace them with RSA certificates.

For more information on ECC, see RFC 44922, Section 5.6.1, Table 2.

3.3. IPv4 and IPv6 Addresses

Certificate System supports both IPv4 addresses and IPv6 addresses. In a very wide variety of
circumstances, Certificate System subsystems or operations references a hostname or IP address;
supporting both IPv4- and IPv6-style addresses ensures forward compatibility with network protocols.
The operations that support IPv6 connections include the following:

• Communications between subsystems, including between the RA and CA and between the TPS,
TKS, and CA and for joining security domains

• Token operations between the TPS and Enterprise Security Client

• Subsystem logging

• Access control instructions

2

http://ietf.org/rfc/rfc4492.txt

Supported PKIX Formats and Protocols

45

• Operations performed with Certificate System tools, including the Subject Alt Name Extension tool,
HttpClient, and the Bulk Issuance Tool

• Client communications, including both the pkiconsole and IPv6-enabled browsers for web
services

• Certificate request names and certificate subject names, including user, server, and router
certificates

• Publishing

• Connecting to LDAP databases for internal databases and authentication directories

Any time a hostname or URL is referenced, an IP address can be used:

• An IPv4 address must be in the format n.n.n.n or n.n.n.n,m.m.m.m. For example, 128.21.39.40 or

128.21.39.40,255.255.255.00.

• An IPv6 address uses a 128-bit namespace, with the IPv6 address separated by
colons and the netmask separated by periods. For example, 0:0:0:0:0:0:13.1.68.3,

FF01::43, 0:0:0:0:0:0:13.1.68.3,FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:255.255.255.0, and
FF01::43,FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FF00:0000.

If DNS is properly configured, then an IPv4 or IPv6 address can be used to connect to the web
services pages and to the subsystem Java consoles. The most common method is to use fully­qualified domain names:

https://ipv6host.example.com:9445/ca/services
pkiconsole https://ipv6host.example.com:9445/ca

To use IPv6 numeric addresses, then replace the fully-qualified domain name in the URL with the IPv6
address, enclosed in brackets ([]). For example:

https://[00:00:00:00:123:456:789:00:]:9445/ca/services

pkiconsole https://[00:00:00:00:123:456:789:00:]:9445/ca

3.4. Supported PKIX Formats and Protocols

The Certificate System supports many of the protocols and formats defined in Public-Key
Infrastructure (X.509) by the IETF. Along with the PKIX standards listed here, other PKIX-listed
standards are available at http://www.ietf.org/html.charters/pkix-charter.html3 under the Internet

Drafts section.

Format or Protocol RFC or Draft Description

X.509 version 1 and version 3 Digital certificate

formats recommended
by the International
Telecommunications Union
(ITU).

3

http://www.ietf.org/html.charters/pkix-charter.html

Chapter 3. Supported Standards and Protocols

46

Format or Protocol RFC or Draft Description

Certificate Request Message
Format (CRMF)

RFC 4211 A message format to send a

certificate request to a CA.

Certificate Management
Message Formats (CMMF)

Message formats to send
certificate requests and
revocation requests from end
entities to a CA and to return
information to end entities.
CMMF has been subsumed by
another standard, CMC.

Certificate Management
Messages over CS (CMC)

RFC 5274 A general interface to public-

key certification products
based on CS and PKCS
#10, including a certificate
enrollment protocol for RSA­signed certificates with Diffie­Hellman public-keys. CMC
incorporates CRMF and CMMF.

Cryptographic Message Syntax
(CMS)

RFC 2630 A superset of PKCS #7 syntax

used for digital signatures and
encryption.

PKIX Certificate and CRL
Profile

RFC 5280 A standard developed by

the IETF for a public-key
infrastructure for the Internet.
It specifies profiles for
certificates and CRLs. For more
information about certificate
and CRL profiles, see http://

www.ietf.org/rfc/rfc5280.txt.

Table 3.2. PKIX Standards Supported in Certificate System 8.0

3.5. Supported Security and Directory Protocols

The Certificate System supports several common Internet and network protocols.

Protocol Description

FIPS PUBS 140-1 Federal Information Standards Publications

(FIPS PUBS) 140-1 is a US government
standard for implementing cryptographic
modules such as hardware or software that
encrypts and decrypts data, creates and verifies
digital signatures, and other cryptographic
functions.

Hypertext Transport Protocol (HTTP) and
Hypertext Transport Protocol Secure (HTTPS)

Protocols used to communicate with web
servers.

KEYGEN tag An HTML tag that generates a key pair for use

with a certificate.

Supported Security and Directory Protocols

47

Protocol Description

Lightweight Directory Access Protocol (LDAP)
v2, v3

A directory service protocol designed to run over
TCP/IP and across multiple platforms. LDAP is
a simplified version of Directory Access Protocol
(DAP), used to access X.500 directories. LDAP
is under IETF change control and has evolved to
meet Internet requirements.

Public-Key Cryptography Standard (PKCS) #7 An encrypted data and message format

developed by RSA Data Security to represent
digital signatures, certificate chains, and
encrypted data. This format is used to deliver
certificates to end entities.

Public-Key Cryptography Standard (PKCS) #10 A message format developed by RSA Data

Security for certificate requests. This format is
supported by many server products.

Public-Key Cryptography Standard (PKCS) #11 Specifies an API used to communicate

with devices such as hardware tokens that
hold cryptographic information and perform
cryptographic operations.

Secure Sockets Layer (SSL) 2.0 and 3.0 and
Transport Layer Security (TLS)

A set of rules governing server authentication,
client authentication, and encrypted
communication between servers and clients.

Security-Enhanced Linux Security-enhanced Linux, or SELinux, is a set of

security protocols enforcing mandatory access
control on Linux system kernels. This was
developed by the United States National Security
Agency to keep applications from accessing
confidential or protected files through lenient or
flawed access controls.

Simple Certificate Enrollment Protocol (SCEP) A protocol designed by Cisco to specify a way

for a router to communicate with an RA or CA
for router certificate enrollment. SCEP defines
two modes of operation: RA mode and CA mode.
Certificate System supports CA mode, where
the the request is encrypted with the CA signing
certificate.

UTF-8 The certificate enrollment pages support all

UTF-8 characters for specific fields (common
name, organizational unit, requester name,
and additional notes). The certificates will be
generated with the UTF-8 strings correctly used
in the subject names and other fields, and the
UTF-8 strings are searchable and correctly
display in the CA, OCSP, and DRM end user and
agents services pages.

This UTF-8 support does not extended to
internationalized domain names, like in email
addresses.

Chapter 3. Supported Standards and Protocols

48

Protocol Description

IPv4 and IPv6 Certificate System supports both IPv4 and IPv6

address namespaces for communications and
operations with all subsystems and tools, as well
as for clients, subsystem creation, and token and
certificate enrollment,

Table 3.3. Supported Security and Directory Protocols

Chapter 4.

49

Major Features in Certificate System

This chapter covers some of the major features of Red Hat Certificate System, giving a brief
rundown of the major functionality of the product. These summaries are meant to help administrators
understand the capabilities of the Certificate System so they can effectively plan their subsystem
deployments.

4.1. Certificate Issuance

The Certificate System supports enrolling and issuing certificates and processing certificate requests
from a variety of end entities, such as web browsers, servers, and virtual private network (VPN)
clients. Issued certificates conform to X.509 version 3 standards.

The Certificate Manager can issue certificates with the following characteristics:

• Certificates that are X.509 version 3-compliant

• Unicode support for the certificate subject name and issuer name

• Support for empty certificate subject names

• Support for customized subject name components

• Support for customized extensions

Additionally, smart cards can have certificates enrolled and maintained through the Enterprise Security
Client. The Enterprise Security Client communicates directly with the TPS system, which, in turn,
processes requests through the CA and DRM subsystems. Certificates are generated automatically
when the token is first formatted, and all additional certificates belonging to the user can be imported
onto the token.

4.2. Authentication for Certificate Enrollment

Certificate System provides authentication options for certificate enrollment. These include agent­approved enrollment, in which an agent processes the request, and automated enrollment, in which
an authentication method is used to authenticate the end entity and then the CA automatically issues
a certificate. CMC enrollment is also supported, which automatically processes a request approved by
an agent.

4.3. Certificate Profiles

The Certificate System uses certificate profiles to configure the content of the certificate, the
constraints for issuing the certificate, the enrollment method used, and the input and output forms for
that enrollment. A single certificate profile is associated with issuing a particular type of certificate.

A set of certificate profiles is included for the most common certificate types; the profile settings
can be modified. Certificate profiles are configured by an administrator, and then sent to the agent
services page for agent approval. Once a certificate profile is approved, it is enabled for use. A
dynamically-generated HTML form for the certificate profile is used in the end-entities page for
certificate enrollment, which calls on the certificate profile. The server verifies that the defaults and
constraints set in the certificate profile are met before acting on the request and uses the certificate
profile to determine the content of the issued certificate.

Chapter 4. Major Features in Certificate System

50

4.4. CRLs

The Certificate System can create certificate revocation lists (CRLs) from a configurable framework
which allows user-defined issuing points so a CRL can be created for each issuing point. Delta
CRLs can also be created for any issuing point that is defined. CRLs can be issued for each type
of certificate, for a specific subset of a type of certificate, or for certificates generated according to
a profile or list of profiles. The extensions used and the frequency and intervals when CRLs are
published can all be configured.

The Certificate Manager issues X.509-standard CRLs. A CRL can be automatically updated whenever
a certificate is revoked or at specified intervals.

4.5. Publishing

Certificates can be published to files and an LDAP directory, and CRLs to files, an LDAP directory, and
an OCSP responder. The publishing framework provides a robust set of tools to publish to all three
places and to set rules to define with more detail which types of certificates or CRLs are published
where.

4.6. Notifications

The notification feature sets up automated messages when a particular event occurs, such as when
a certificate is issued or revoked. The notification framework comes with default modules that can be
enabled and configured.

4.7. Jobs

The jobs feature sets up automated jobs that run at defined intervals.

4.8. Dual Key Pairs

The Certificate System supports generating dual key pairs, separate key pairs for signing and
encrypting email messages and other data. To support separate key pairs for signing and encrypting
data, dual certificates are generated for end entities, and the encryption keys are archived. If a client
makes a certificate request for dual key pairs, the server issues two separate certificates.

4.9. Cross-Pair Certificates

It is possible to create a trusted relationship between two separate CAs by issuing and storing cross­signed certificates between these two CAs. By using cross-signed certificate pairs, certificates issued
outside the organization's PKI can be trusted within the system.

4.10. Logging

The Certificate System and each subsystem produce extensive system and error logs that record
system events so that the systems can be monitored and debugged. All log records are stored in the
local file system for quick retrieval. Logs are configurable, so logs can be created for specific types of
events and at the desired logging level.

Certificate System allows logs to be signed digitally before archiving them or distributing them for
auditing. This feature enables log files to be checked for tampering after being signed.

Auditing

51

4.11. Auditing

The Certificate System maintains audit logs for all events, such as requesting, issuing and revoking
certificates and publishing CRLs. These logs are then signed. This allows authorized access or activity
to be detected. An outside auditor can then audit the system if required. The assigned auditor user
account is the only account which can view the signed audit logs. This user's certificate is used to sign
and encrypt the logs. Audit logging is configured to specify the events that are logged.

4.12. Self-Tests

The Certificate System provides the framework for system self-tests that are automatically run at
startup and can be run on demand. A set of configurable self-tests are already included with the
Certificate System.

4.13. Access Controls

Certificate System users can be assigned to groups, and they then have the privileges of whichever
group they are members. A user only has privileges for the instance of the subsystem in which the
user is created and the privileges of the group to which the user is a member.

The Certificate System provides an authorization framework for creating groups and assigning access
control to those groups. The default access control on preexisting groups can be modified, and access
control can be assigned to individual users and IP addresses. Access points for authorization have
been created for the major portions of the system, and access control rules can be set for each point.

The Certificate System is configured by default with four user types with different access levels to the
system:

• Administrators, who can perform any administrative or configuration task for a subsystem.

• Agents, who perform PKI management tasks, like approving certificate requests, managing token
enrollments, or recovering keys.

• Auditors, who can view and configure audit logs.

• Trusted managers, which are subsystems with trusted relationship with another subsystem.

Additionally, when a security domain is created, the CA subsystem which hosts the domain is
automatically granted the role of Security Domain Administrator, which gives the subsystem the
ability to manage the security domain and the subsystem instances within it. Other security domain
administrator roles can be created for the different subsystem instances.

4.14. Security-Enhanced Linux Support

SELinux is a collection of mandatory access control rules which are enforced across a system to
restrict unauthorized access and tampering. SELinux is described in more detail in the Red Hat
Enterprise Linux documentation, such as "Introduction to SELinux"1 in the Red Hat Enterprise Linux
Deployment Guide.

Basically, SELinux identifies objects on a system, which can be files, directories, users, processes,
sockets, or any other resource on a Linux host. These objects correspond to the Linux API objects.

1

http://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/Deployment_Guide-en-US/ch-selinux.html

Chapter 4. Major Features in Certificate System

52

Each object is then mapped to a security context, which defines the type of object and how it is
allowed to function on the Linux server.

Objects can be grouped into domains, and then each domain is assigned the proper rules. Each
security context has rules which set restrictions on what operations it can perform, what resources it
can access, and what permissions it has.

The Certificate System has a separate RPM of SELinux policies installed by default. These SELinux
policies apply to every subsystem and service used by Certificate System. By running Certificate
System with SELinux in enforcing mode, the security of the information created and maintained by
Certificate System is enhanced.

Figure 4.1. CA SELinux Port Policy

The Certificate System SELinux policies define the SELinux configuration for every subsystem
instance:

• Files and directories for each subsystem instance are labeled with a specific SELinux context.

• The ports for each subsystem instance are labeled with a specific SELinux context.

• All Certificate System processes are constrained within a subsystem-specific domain.

• Each domain has specific rules that define what actions that are authorized for the domain.

Security-Enhanced Linux Support

53

• Any access not specified in the SELinux policy is denied to the Certificate System instance.

For Certificate System, each subsystem is treated as an SELinux object, and each subsystem has
unique rules assigned to it. The defined SELinux policies allow Certificate System objects run with
SELinux set in enforcing mode.

Every time pkicreate is run, new SELinux policies are automatically configured for the instance.
All SELinux policies are updated every time a subsystem is added with pkicreate or removed with
pkiremove.

The central definition for each instance is its SELinux domain. Each Certificate System subsystem
runs in a single subsystem-specific SELinux domain, no matter how many subsystems are installed
on a host. For example, if there are three CAs installed on a server, all three belong to the pki_ca_t
SELinux domain.

Each SELinux policy sets rules on what actions the instance is allowed to perform on the system,
based on the domain to which the instance belongs. For example, instances in the CA domain
(pki_ca_t) are limited to write access for files with the CA context (pki_ca_var_log_t) and
to access ports that match the CA type (pki_ca_port). When each Certificate System process
is started, it initially runs in an unconfined domain (unconfined_t) and then transitions into the
appropriate subsystem-specific domain.

The SELinux mode can be changed from enforcing to permissive, or even off, though this is not
recommended.

54

Chapter 5.

55

Planning the Certificate System

Each Red Hat Certificate System subsystem is installed and configured separately. They can all be
installed on the same machine, installed on separate servers, or have multiple instances installed
across an organization. Before installing any subsystem, it is important to plan the deployment out:
what kind of PKI services do you need? What are the network requirements? What people need to
access the Certificate System, what are their roles, and what are their physical locations? What kinds
of certificates do you want to issue and what constraints or rules need to be set for them?

This chapter covers some basic questions for planning a Certificate System deployment. Many of
these decisions are interrelated; one choice impacts another, like deciding whether to use smart cards
determines whether to install the TPS and TKS subsystems.

5.1. Deciding on the Required Subsystems

The Certificate System subsystems cover different aspects of managing certificates. Planning which
subsystems to install is one way of defining what PKI operations the deployment needs to perform.

Certificates, like software or equipment, have a lifecycle with defined stages. At its most basic, there
are three steps:

• It is requested and issued.

• It is valid.

• It expires.

However, this simplified scenario does not cover a lot of common issues with certificates:

• What if an employee leaves the company before the certificate expires?

• When a CA signing certificate expires, all of the certificates issued and signed using that certificate
also expire. So will the CA signing certificate be renewed, allowing its issued certificates to remain
valid, or will it be reissued?

• What if an employee loses a smart card or leaves it at home. Will a replacement certificate be
issued using the original certificates keys? Will the other certificates be suspended or revoked? Are
temporary certificates allowed?

• When a certificate expires, will a new certificate be issued or will the original certificate be renewed?

This introduces three other considerations for managing certificates: revocation, renewal, and
replacements.

Other considerations are the loads on the certificate authority. Are there a lot of issuance or renewal
requests? Is there a lot of traffic from clients trying to validate whether certificates are valid? How are
people requesting certificates supposed to authenticate their identity, and does that process slow
down the issuance process?

5.1.1. Single Certificate Manager

The core of the Certificate System PKI is the Certificate Manager, a certificate authority. The CA
receives certificate requests and issues all certificates.

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Figure 5.1. CA Only Certificate System

All of the basic processing for requests and issuing certificates can handled by the Certificate
Manager, and it is the only required subsystem. There can be a single Certificate Manager or many
Certificate managers, arranged in many different relationships, depending on the demands of the
organization.

Along with issuing certificates, a Certificate Manager can also revoke certificates. One question for
administrators is how to handle certificates if they are lost, compromised, or if the person or equipment
for which they are issued leaves the company. Revoking a certificate invalidates it before its expiration
date, and a list of revoked certificates is compiled and published by the issuing CA so that clients can
verify the certificate status.

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57

5.1.2. Planning for Lost Keys: Key Archival and Recovery

One operation the CA cannot perform, though, is key archival and recovery. A very real scenario is
that a user is going to lose his private key — for instance, the keys could be deleted from a browser
database or a smart card could be left at home. Many common business operations use encrypted
data, like encrypted email, and losing the keys which unlock that data means the data itself is lost.
Depending on the policies in the company, there probably has to be a way to recover the keys in order
to regenerate or reimport a replacement certificate, and both operations require the private key.

That requires a DRM, the subsystem which specially archives and retrieves keys.

Figure 5.2. CA and DRM

The Data Recovery Manager stores encryption keys (key archival) and can retrieve those keys so that
the CA can reissue a certificate (key recovery). A DRM can store keys for any certificate generated by
Certificate System, whether it is done for a regular certificate or when enrolling a smart card.

The key archival and recovery process is explained in more detail in Section 2.1.4, “About the Data

Recovery Manager (DRM)”.

NOTE

The DRM is intended for archival and recovery of private encryption keys only. Therefore,
end users must use a browser that supports dual-key generation to store their public­private key pairs.

5.1.3. Balancing Certificate Request Processing

Another aspect of how the subsystems work together is load balancing. If a site has high traffic, then it
is possible to simply install a lot of CAs, as clones of each other or in a flat hierarchy (where each CA
is independent) or in a tree hierarchy (where some CAs are subordinate to other CAs); this is covered
more in Section 5.2, “Defining the Certificate Authority Hierarchy”.

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Another option, though is to distribute some of the tasks of a single CA to another subsystem. For
example, Example Corp. has a manageable number of people requesting certificates for a single
CA to issue. However, because of their security policies, each certificate request has to be verified
in person by an agent, with supporting documentation. This creates a bottleneck for the CA agents
to approve requests. A registration authority (RA) is installed at each local office; the requests are
processed and approved locally, and then a central CA issues all of the certificates.

Figure 5.3. CA and RA

The Registration Manager takes the load of processing certificate requests; the CA then only has to
issue the requests. For network environments where there are strict, and possibly time-consuming,
rules for issuing certificates, an RA can speed the process while also give control to local managers
and administrators.

RA managers are also good for certain network demands. CAs require a very high degree of both
physical security and network security because of the sensitive nature of the information they contain.
RAs can be placed outside of a firewall so that regular users can connect to them and can be stored in
less secure locations because they do not process or contain sensitive data.

5.1.4. Balancing Client OCSP Requests

If a certificate is within its validity period but needs be invalidated, it can be revoked. A Certificate
Manager can publish lists of revoked certificates, so that when a client needs to verify that a certificate
is still valid, it can check the list. These requests are online certificate status protocol requests,
meaning that they have a specific request and response format. The Certificate Manager has a built-in
OCSP responder so that it can verify OCSP requests by itself.

However, as with certificate request traffic, a site may have a significant number of client requests to
verify certificate status. Example Corp. has a large web store, and each customer's browser tries to
verify the validity of their SSL certificates. Again, the CA can handle issuing the number of certificates,
but the high request traffic affects its performance. In this case, Example Corp. uses the external
OCSP Manager subsystem to verify certificate statuses, and the Certificate Manager only has to
publish updated CRLs every so often.

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59

Figure 5.4. CA and OCSP

5.1.5. Planning for Smart Cards

Most certificates are enrolled through the CA. This is useful for certificates enrolled through an
application such as a web browser or web server. For managing smart cards, or tokens, Certificate
System uses interlocking subsystems to create a token management system which handles
operations for certificates and keys stored on smart cards.

Four Certificate System subsystems are involved with managing tokens:

• The Token Processing System (TPS) interacts with smart cards to help them generate and store
keys and certificates for a specific entity, such as a user or device. Smart card operations go
through the TPS and are forwarded to the appropriate subsystem for action, such as the Certificate
Authority to generate certificates or the Data Recovery Manager to archive and recover keys.

• The Token Key Service (TKS) generates, or derives, symmetric keys used for communication
between the TPS and smart card. Each set of keys generated by the TKS is unique because they
are based on the card's unique ID. The keys are formatted on the smart card and are used to
encrypt communications, or provide authentication, between the smart card and TPS.

• The Certificate Authority (CA) creates and revokes user certificates stored on the smart card.

• Optionally, the Data Recovery Manager (DRM) archives and recovers keys for the smart card.

The Enterprise Security Client is the conduit through which TPS communicates with each token over
a secure HTTP channel (HTTPS), and, through the TPS, with the Certificate System.

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Figure 5.5. How Certificate System Manages Smart Cards

To use the tokens, the Token Processing System must be able to recognize and communicate with
them. The tokens must first be enrolled to format the tokens with required keys and certificates and
add the tokens to the Certificate System. The Enterprise Security Client provides the user interface
for end entities to enroll tokens.

The token management system is very scalable. Multiple TPSs can be configured to work with a single
CA, TKS, or DRM instance, while multiple Enterprise Security Clients can communicate with a single
TPS. As additional clients are installed, they can point back to the TPS instance without having to
reconfigure the TPS; likewise, as TPSs are added, they can point to the same CA, TKS, and DRM
instances without having to reconfigure those subsystems.

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61

After installation, the TPS configuration can be edited to use additional CA, DRM, and TKS instances
for failover support, so if the primary subsystem is unavailable, the TPS can switch to the next
available system without interrupting its token services.

5.2. Defining the Certificate Authority Hierarchy

The CA is the center of the PKI, so the relationship of CA systems, both to each other (CA hierarchy)
and to other subsystems (security domain) is vital to planning a Certificate System PKI.

When there are multiple CAs in a PKI, the CAs are structured in a hierarchy or chain. The CA above
another CA in a chain is called an root CA; a CA below another CA in the chain is called a subordinate
CA. A CA can also be subordinate to a root outside of the Certificate System deployment; for example,
a CA which functions as a root CA within the Certificate System deployment can be subordinate to a
third-party CA.

A Certificate Manager (or CA) is subordinate to another CA because its CA signing certificate,
the certificate that allows it to issue certificates, is issued by another CA. The CA that issued the
subordinate CA signing certificate controls the CA through the contents of the CA signing certificate.
The CA can constrain the subordinate CA through the kinds of certificates that it can issue, the
extensions that it is allowed to include in certificates, the number of levels of subordinate CAs the
subordinate CA can create, and the validity period of certificates it can issue, as well as the validity
period of the subordinate CAs signing certificate.

NOTE

Although a subordinate CA can create certificates that violate these constraints, a client
authenticating a certificate that violates those constraints will not accept that certificate.

A self-signed root CA signs its own CA signing certificate and sets its own constraints as well as
setting constraints on the subordinate CA signing certificates it issues.

A Certificate Manager can be configured as either a root CA or a subordinate CA. It is easiest to make
the first CA installed a self-signed root, so that it is not necessary to apply to a third party and wait for

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the certificate to be issued. Before deploying the full PKI, however, consider whether to have a root
CA, how many to have, and where both root and subordinate CAs will be located.

5.2.1. Subordination to a Public CA

Chaining the Certificate System CA to a third-party public CA introduces the restrictions that public
CAs place on the kinds of certificates the subordinate CA can issue and the nature of the certificate
chain. For example, a CA that chains to a third-party CA might be restricted to issuing only Secure
Multipurpose Internet Mail Extensions (S/MIME) and SSL client authentication certificates, but not
SSL server certificates. There are other possible restrictions with using a public CA. This may not be
acceptable for some PKI deployments.

One benefit of chaining to a public CA is that the third party is responsible for submitting the root CA
certificate to a web browser or other client software. This can be a major advantage for an extranet
with certificates that are accessed by different companies with browsers that cannot be controlled by
the administrator. Creating a root CA in the CA hierarchy means that the local organization must get
the root certificate into all the browsers which will use the certificates issued by the Certificate System.
There are tools to do this within an intranet, but it can be difficult to accomplish with an extranet.

5.2.2. Subordination to a Certificate System CA

The Certificate System CA can function as a root CA, meaning that the server signs its own CA
signing certificate as well as other CA signing certificates, creating an organization-specific CA
hierarchy. The server can alternatively be configured as a subordinate CA, meaning the server's CA
signing key is signed by another CA in an existing CA hierarchy.

Setting up a Certificate System CA as the root CA means that the Certificate System administrator
has control over all subordinate CAs by setting policies that control the contents of the CA signing
certificates issued. A subordinate CA issues certificates by evaluating its own authentication and
certificate profile configuration, without regard for the root CA's configuration.

5.2.3. Linked CA

The Certificate System Certificate Manager can function as a linked CA, chaining up to many third­party or public CAs for validation; this provides cross-company trust, so applications can verify
certificate chains outside the company certificate hierarchy. A Certificate Manager is chained to a third­party CA by requesting the Certificate Manager's CA signing certificate from the third-party CA.

Related to this, the Certificate Manager also can issue cross-pair or cross-signed certificates. Cross­pair certificates create a trusted relationship between two separate CAs by issuing and storing cross­signed certificates between these two CAs. By using cross-signed certificate pairs, certificates issued
outside the organization's PKI can be trusted within the system.

These are also called bridge certificates, related to the Federal Bridge Certification Authority (FBCA)
definition.

5.2.4. CA Cloning

Instead of creating a hierarchy of root and subordinate CAs, it is possible to create multiple clones of a
Certificate Manager and configure each clone to issue certificates within a range of serial numbers.

A cloned Certificate Manager uses the same CA signing key and certificate as another Certificate
Manager, the master Certificate Manager.

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63

Because clone CAs and original CAs use the same CA signing key and certificate to sign the
certificates they issue, the issuer name in all the certificates is the same. Clone CAs and the original
Certificate Managers issue certificates as if they are a single CA. These servers can be placed on
different hosts for high availability failover support.

The advantage of cloning is that it distributes the Certificate Manager's load across several processes
or even several physical machines. For a CA with a high enrollment demand, the distribution gained
from cloning allows more certificates to be signed and issued in a given time interval.

A cloned Certificate Manager has the same features, such as agent and end-entity gateway functions,
of a regular Certificate Manager.

The serial numbers for clones are distributed dynamically. All of the cloned servers share a common
entry which defines the next available range; when a server needs another range of numbers, it
claims the range in the shared entry, and the entry increments so that a new range is available. Serial
number ranges do not have to be manually assigned to the cloned Certificate Managers. This makes
managing serial numbers for certificates is easy to administrate.

TIP

If there is a chance that a subsystem will be cloned, then it is easiest to export its key
pairs during the configuration process and save them to a secure location. The key
pairs for the original Certificate Manager have to be available when the clone instance
is configured, so that the clone can generate its certificates from the original Certificate
Manager's keys.

It is also possible to export the keys from the security databases at a later time, using the
pk12util or the PKCS12Export commands.

5.3. Planning Security Domains and Trust Relationships

5.3.1. Understanding Security Domains

A security domain is a registry of PKI services. PKI services, such as CAs, register information about
themselves in these domains so users of PKI services can find other services by inspecting the
registry. The security domain service in Certificate System manages both the registration of PKI
services for Certificate System subsystems and a set of shared trust policies.

The registry provides a complete view of all PKI services provided by the subsystems within that
domain. Each Certificate System subsystem must be either a host or a member of a security domain.

A CA subsystem is the only subsystem which can host a security domain. The security domain shares
the CA internal database for privileged user and group information to determine which users can
update the security domain, register new PKI services, and issue certificates.

A security domain is created during CA configuration, which automatically creates an entry in the
security domain CA's LDAP directory. Each entry contains all the important information about the
domain. Every subsystem within the domain, including the CA registering the security domain, is
recorded under the security domain container entry.

The URL to the CA uniquely identifies the security domain. The security domain is also given a friendly
name, such as Example Corp Intranet PKI. All other subsystems — RA, DRM, TPS, TKS,

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64

OCSP, and other CAs — must become members of the security domain by supplying the security
domain URL when configuring the subsystem.

Each subsystem within the security domain shares the same trust policies and trusted roots which can
be retrieved from different servers and browsers. The information available in the security domain is
used during configuration of a new subsystem, which makes the configuration process streamlined
and automated. For example, when a TPS needs to connect to a CA, it can consult the security
domain to get a list of available CAs.

Each CA has its own LDAP entry. The security domain is an organizational group underneath that CA
entry:

ou=Security Domain,dc=server.example.com-pki-ca

Then there is a list of each subsystem type beneath the security domain organizational group, with a
special object class (pkiSecurityGroup) to identify the group type:

cn=KRAList,ou=Security Domain,dc=server.example.com-pki-ca
objectClass: top
objectClass: pkiSecurityGroup
cn: KRAList

Each subsystem instance is then stored as a member of that group, with a special pkiSubsystem
object class to identify the entry type:

dn: cn=drm.example.com:10444,cn=KRAList,ou=Security Domain,dc=server.example.com-pki-ca
objectClass: top
objectClass: pkiSubsystem
cn: drm.example.com:10444
host: server.example.com
SecurePort: 10444
DomainManager: false
Clone: false
SubsystemName: Data Recovery Manager

If a subsystem needs to contact another subsystem to perform an operation, it contacts the CA which
hosts the security domain (by invoking a servlet which connects over the administrative port of the
CA). The security domain CA then retrieves the information about the subsystem from its LDAP
database, and returns that information to the requesting subsystem.

The subsystem authenticates to the security domain using a subsystem certificate.

Consider the following when planning the security domain:

• The CA hosting the security domain can be signed by an external authority.

• Multiple security domains can be set up within an organization. However, each subsystem can
belong to only one security domain.

• Subsystems within a domain can be cloned. Cloning subsystem instances distributes the system
load and provides failover points.

• The security domain streamlines configuration between the CA and DRM; the DRM can push
its KRA connector information and transport certificates automatically to the CA instead of
administrators having to manually copy the certificates over to the CA.

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65

• The Certificate System security domain allows an offline CA to be set up. In this scenario, the offline
root has its own security domain. All online subordinate CAs belong to a different security domain.

• The security domain streamlines configuration between the CA and OCSP. The OCSP can push
its information to the CA for the CA to set up OCSP publishing and also retrieve the CA certificate
chain from the CA and store it in the internal database.

5.3.2. Using Trusted Managers

Trust relationships can be configured between subsystems in different security domains by using
special trusted managers. Basically, a trusted manager is a member of a special group in the
subsystem's user configuration. Another subsystem can be added as a member of that group and all
of its certificates — SSL server certificate, signing certificates, storage and transport certificates (for
DRMs) — can be added to establish trusted relationships.

5.4. Determining the Requirements for Subsystem

Certificates

The CA configuration determines many of the characteristics of the certificates which it issues,
regardless of the actual type of certificate being issued. Constraints on the CA's own validity period,
distinguished name, and allowed encryption algorithms impact the same characteristics in their issued
certificates. Additionally, the Certificate Managers have predefined profiles that set rules for different
kinds of certificates that they issue, and additional profiles can be added or modified. These profile
configurations also impact issued certificates.

5.4.1. Determining Which Certificates to Install

When a Certificate System subsystem is first installed and configured, the certificates necessary
to access and administer it are automatically created. These include an agent's certificate, server
certificate, and subsystem-specific certificates. These initial certificates are shown in Table 5.1, “Initial

Subsystem Certificates”.

Subsystem Certificates

Certificate Manager • CA signing certificate

RA • SSL server certificate

OCSP • OCSP signing certificate

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Subsystem Certificates

DRM • Transport certificate

TKS • SSL server certificate

TPS • SSL server certificate

Table 5.1. Initial Subsystem Certificates

There are some cautionary considerations about replacing existing subsystem certificates.

• Generating new key pairs when creating a new self-signed CA certificate for a root CA will invalidate
all certificates issued under the previous CA certificate.

This means none of the certificates issued or signed by the CA using its old key will work;
subordinate Certificate Managers, DRMs, OCSPs, TKSs, and TPSs will no longer function, and
agents can no longer to access agent interfaces.

This same situation occurs if a subordinate CA's CA certificate is replaced by one with a new key
pair; all certificates issued by that CA are invalidated and will no longer work.

Instead of creating new certificates from new key pairs, consider renewing the existing CA signing
certificate.

• If the CA is configured to publish to the OCSP and it has a new CA signing certificate or a new CRL
signing certificate, the CA must be identified again to the OCSP.

• If a new transport certificate is created for the DRM, the DRM information must be updated in the
CA's configuration file, CS.cfg. The existing transport certificate must be replaced with the new one
in the ca.connector.KRA.transportCert parameter.

• If a CA is cloned, then when creating a new SSL server certificate for the master Certificate
Manager, the clone CAs' certificate databases all need updated with the new SSL server certificate.

• If the Certificate Manager is configured to publish certificates and CRLs to an LDAP directory and
uses the SSL server certificate for SSL client authentication, then the new SSL server certificate

CA Distinguished Name

67

must be requested with the appropriate extensions. After installing the certificate, the publishing
directory must be configured to use the new server certificate.

• Any number of SSL server certificates can be issued for a subsystem instance, but it really only
needs one SSL certificate. This certificate can be renewed or replaced as many times as necessary.

5.4.2. CA Distinguished Name

The core elements of a CA are a signing unit and the Certificate Manager identity. The signing
unit digitally signs certificates requested by end entities. A Certificate Manager must have its own
distinguished name (DN), which is listed in every certificate it issues.

Like any other certificate, a CA certificate binds a DN to a public key. A DN is a series of name­value pairs that in combination uniquely identify an entity. For example, the following DN identifies a
Certificate Manager for the Engineering department of a corporation named Example Corporation:

cn=demoCA, o=Example Corporation, ou=Engineering, c=US

Many combinations of name-value pairs are possible for the Certificate Manager's DN. The DN must
be unique and readily identifiable, since any end entity can examine it.

5.4.3. CA Signing Certificate Validity Period

Every certificate, including a Certificate Manager signing certificate, must have a validity period. The
Certificate System does not restrict the validity period that can be specified. Set as long a validity
period as possible, depending on the requirements for certificate renewal, the place of the CA in the
certificate hierarchy, and the requirements of any public CAs that are included in the PKI.

A Certificate Manager cannot issue a certificate that has a validity period longer than the validity period
of its CA signing certificate. If a request is made for a period longer than the CA certificate's validity
period, the requested validity date is ignored and the CA signing certificate validity period is used.

5.4.4. Signing Key Type and Length

A signing key is used by a subsystem to verify and "seal" something. CAs use a CA signing certificate
to sign certificates or CRLs that it issues; OCSPs use signing certificates to verify their responses to
certificate status requests; all subsystems use log file signing certificates to sign their audit logs.

The signing key must be cryptographically strong to provide protection and security for its signing
operations. Certificate System supports six signing algorithms, by default, two in the MD family, four in
the SHA family, and one for ECC encryption:

• MD2withRSA

• MD5withRSA

• SHA1withRSA

• SHA256withRSA

• SHA512withRSA

• SHA1withEC

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SHA1withRSA is the default signing algorithm for CAs for RSA certificates. SHA1withEC is the default
signing algorithm for CAs for ECC certificates.

Along with a key type, each key has a specific bit length. Longer keys are considered cryptographically
stronger than shorter keys. However, longer keys require more time for signing operations.

The default RSA key length in the configuration wizard is 2048 bits; for certificates that provide access
to highly sensitive data or services, consider increasing the length to 4096 bits. ECC keys are much
stronger than RSA keys, so the recommended length for ECC keys is 256 bits, which is equivalent in
strength to a 2048-bit RSA key.

5.4.5. Using Certificate Extensions

An X.509 v3 certificate contains an extension field that permits any number of additional fields to be
added to the certificate. Certificate extensions provide a way of adding information such as alternative
subject names and usage restrictions to certificates. Older Netscape servers, such as Red Hat
Directory Server and Red Hat Certificate System, require Netscape-specific extensions because they
were developed before PKIX part 1 standards were defined.

The X.509 v1 certificate specification was originally designed to bind public keys to names in an X.500
directory. As certificates began to be used on the Internet and extranets and directory lookups could
not always be performed, problem areas emerged that were not covered by the original specification.

• Trust. The X.500 specification establishes trust by means of a strict directory hierarchy. By contrast,
Internet and extranet deployments frequently involve distributed trust models that do not conform to
the hierarchical X.500 approach.

• Certificate use. Some organizations restrict how certificates are used. For example, some
certificates may be restricted to client authentication only.

• Multiple certificates. It is not uncommon for certificate users to possess multiple certificates with
identical subject names but different key material. In this case, it is necessary to identify which key
and certificate should be used for what purpose.

• Alternate names. For some purposes, it is useful to have alternative subject names that are also
bound to the public key in the certificate.

• Additional attributes. Some organizations store additional information in certificates, such as when it
is not possible to look up information in a directory.

• Relationship with CA. When certificate chaining involves intermediate CAs, it is useful to have
information about the relationships among CAs embedded in their certificates.

• CRL checking. Since it is not always possible to check a certificate's revocation status against a
directory or with the original certificate authority, it is useful for certificates to include information
about where to check CRLs.

The X.509 v3 specification addressed these issues by altering the certificate format to include
additional information within a certificate by defining a general format for certificate extensions and
specifying extensions that can be included in the certificate. The extensions defined for X.509 v3
certificates enable additional attributes to be associated with users or public keys and manage
the certification hierarchy. The Internet X.509 Public Key Infrastructure Certificate and CRL Profile
recommends a set of extensions to use for Internet certificates and standard locations for certificate or
CA information. These extensions are called standard extensions.

Using Certificate Extensions

69

NOTE

For more information on standard extensions, see RFC 24591, RFC 32802, and RFC

32793.

The X.509 v3 standard for certificates allows organizations to define custom extensions and include
them in certificates. These extensions are called private, proprietary, or custom extensions, and
they carry information unique to an organization or business. Applications may not able to validate
certificates that contain private critical extensions, so it not recommended that these be used in wide­spread situations.

Before the X.509 v3 standard was finalized, Netscape and other companies had to address some
of the most pressing issues with their own extension definitions. For example, applications such as
Netscape Navigator and Enterprise Server supported an extension known as the Netscape Certificate
Type Extension that specifies the type of certificate issued, such as client, server, or email. To maintain
compatibility with older versions of browsers that were released before the X.509 v3 specification was
finalized, certain kinds of certificates should include some of these Netscape extensions.

The X.500 and X.509 specifications are controlled by the International Telecommunication Union
(ITU), an international organization that primarily serves large telecommunication companies,
government organizations, and other entities concerned with the international telecommunications
network. The Internet Engineering Task Force (IETF), which controls many of the standards that
underlie the Internet, is currently developing public-key infrastructure X.509 (PKIX) standards. These
proposed standards further refine the X.509 v3 approach to extensions for use on the Internet. The
recommendations for certificates and CRLs have reached proposed standard status and are in a
document referred to as PKIX Part 1.

Two other standards, Abstract Syntax Notation One (ASN.1) and Distinguished Encoding Rules
(DER), are used with Certificate System and certificates in general. These are specified in the CCITT
Recommendations X.208 and X.209. For a quick summary of ASN.1 and DER, see A Layman's

Guide to a Subset of ASN.1, BER, and DER, which is available at RSA Laboratories' web site, http://

www.rsa.com.

5.4.5.1. Structure of Certificate Extensions

In RFC 3280, an X.509 certificate extension is defined as follows:

Extension ::= SEQUENCE {

extnID OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING }

The means a certificate extension consists of the following:

• The object identifier (OID) for the extension. This identifier uniquely identifies the extension. It also
determines the ASN.1 type of value in the value field and how the value is interpreted. When an
extension appears in a certificate, the OID appears as the extension ID field (extnID) and the
corresponding ASN.1 encoded structure appears as the value of the octet string (extnValue).

• A flag or Boolean field called critical.

The value, which can be either true or false, assigned to this field indicates whether the
extension is critical or noncritical to the certificate.

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• If the extension is critical and the certificate is sent to an application that does not understand the
extension based on the extension's ID, the application must reject the certificate.

• If the extension is not critical and the certificate is sent to an application that does not understand
the extension based on the extension's ID, the application can ignore the extension and accept
the certificate.

• An octet string containing the DER encoding of the value of the extension.

Typically, the application receiving the certificate checks the extension ID to determine if it can
recognize the ID. If it can, it uses the extension ID to determine the type of value used.

Some of the standard extensions defined in the X.509 v3 standard include the following:

• Authority Key Identifier extension, which identifies the CA's public key, the key used to sign the
certificate.

• Subject Key Identifier extension, which identifies the subject's public key, the key being certified.

NOTE

Not all applications support certificates with version 3 extensions. Applications that
do support these extensions may not be able to interpret some or all of these specific
extensions.

5.4.6. Using and Customizing Certificate Profiles

Certificates have different types and different applications. They can be used to establish a single
sign-on environment for a corporate network, to set up VPNs, to encrypt email, or to authenticate to
a website. The requirements for all of these certificates can be different, just as there may also be
different requirements for the same type of certificate for different kinds of users. These certificate
characteristics are set in certificate profiles. The Certificate Manager defines a set of certificate profiles
that it uses as enrollment forms when users or machines request certificates.

A certificate profile defines everything associated with issuing a particular type of certificate, including
the authentication method, the certificate content (defaults), constraints for the values of the content,
and the contents of the input and output for the certificate profile. Enrollment requests are submitted
to a certificate profile and are then subject to the defaults and constraints set in that certificate profile.
These constraints are in place whether the request is submitted through the input form associated with
the certificate profile or through other means. The certificate that is issued from a certificate profile
request contains the content required by the defaults with the information required by the default
parameters. The constraints provide rules for what content is allowed in the certificate.

For example, a certificate profile for user certificates defines all aspects of that certificate, including the
validity period of the certificate. The default validity period can be set to two years, and a constraint
can be set on the profile that the validity period for certificates requested through this certificate profile
cannot exceed two years. When a user requests a certificate using the input form associated with this
certificate profile, the issued certificate contains the information specified in the defaults and will be
valid for two years. If the user submits a pre-formatted request for a certificate with a validity period of
four years, the request is rejected since the constraints allow a maximum of two years validity period
for this type of certificate.

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71

A set of certificate profiles have been predefined for the most common certificates issued. These
certificate profiles define defaults and constraints, associate the authentication method, and define the
needed inputs and outputs for the certificate profile.

The parameters of the default certificate profiles � the authentication method, the defaults, the
constraints used in each profile, the values assigned to any of the parameters in a profile, the input,
and the output � can be modified. It is also possible to create new certificate profiles for other types of
certificates or for creating more than one certificate profile for a certificate type. There can be multiple
certificate profiles for a particular type of certificate to issue the same type of certificate with a different
authentication method or different definitions for the defaults and constraints. For example, there can
be two certificate profiles for enrollment of SSL server certificates where one certificate profile issues
certificates with a validity period of six months and another certificate profile issues certificates with a
validity period of two years.

An input sets a text field in the enrollment form and what kind of information needs gathered from
the end entity; this includes setting the text area for a certificate request to be pasted, which allows
a request to be created outside the input form with any of the request information desired. The input
values are set as values in the certificate. The default inputs are not configurable in the Certificate
System.

An output specifies how the response page to a successful enrollment is presented. It usually displays
the certificate in a user-readable format. The default output shows a printable version of the resultant
certificate; other outputs set the type of information generated at the end of the enrollment, such as
PKCS #7.

Policy sets are sets of constraints and default extensions attached to every certificate processed
through the profile. The extensions define certificate content such as validity periods and subject name
requirements. A profile handles one certificate request, but a single request can contain information
for multiple certificates. A PKCS#10 request contains a single public key. One CRMF request can
contain multiple public keys, meaning multiple certificate requests. A profile may contain multiple sets
of policies, with each set specifying how to handle one certificate request within a CRMF request.

An administrator sets up a certificate profile by associating an existing authentication plug-in, or
method, with the certificate profile; enabling and configuring defaults and constraints; and defining
inputs and outputs. The administrator can use the existing certificate profiles, modify the existing
certificate profiles, create new certificate profiles, and delete any certificate profile that will not be used
in this PKI.

Once a certificate profile is set up, it appears on the Manage Certificate Profiles page of the agent
services page where an agent can approve, and thus enable, a certificate profile. Once the certificate
profile is enabled, it appears on the Certificate Profile tab of the end-entities page where end entities
can enroll for a certificate using the certificate profile.

The certificate profile enrollment page in the end-entities interface contains links to each certificate
profile that has been enabled by the agents. When an end entity selects one of those links, an
enrollment page appears containing an enrollment form specific to that certificate profile. The
enrollment page is dynamically generated from the inputs defined for the profile. If an authentication
plug-in is configured, additional fields may be added to authenticate the user.

When an end entity submits a certificate profile request that is associated with an agent-approved
(manual) enrollment, an enrollment where no authentication plug-in is configured, the certificate
request is queued in the agent services interface. The agent can change some aspects of the
enrollment, request, validate it, cancel it, reject it, update it, or approve it. The agent is able to update
the request without submitting it or validate that the request adheres to the profile's defaults and

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constraints. This validation procedure is only for verification and does not result in the request being
submitted. The agent is bound by the constraints set; they cannot change the request in such a way
that a constraint is violated. The signed approval is immediately processed, and a certificate is issued.

When a certificate profile is associated with an authentication method, the request is approved
immediately and generates a certificate automatically if the user successfully authenticates, all the
information required is provided, and the request does not violate any of the constraints set up for the
certificate profile. There are profile policies which allow user-supplied settings like subject names or
validity periods. The certificate profile framework can also preserve user-defined content set in the
original certificate request in the issued certificate.

The issued certificate contains the content defined in the defaults for this certificate profile, such as
the extensions and validity period for the certificate. The content of the certificate is constrained by
the constraints set for each default. Multiple policies (defaults and constraints) can be set for one
profile, distinguishing each set by using the same value in the policy set ID. This is particularly useful
for dealing with dual keys enrollment where encryption keys and signing keys are submitted to the
same profile. The server evaluates each set with each request it receives. When a single certificate
is issued, one set is evaluated, and any other sets are ignored. When dual-key pairs are issued, the
first set is evaluated with the first certificate request, and the second set is evaluated with the second
certificate request. There is no need for more than one set for issuing a single certificate or more than
two sets for issuing dual-key pairs.

Tailor the profiles for the organization to the real needs and anticipated certificate types used by the
organization:

• Decide which certificate profiles are needed in the PKI. There should be at least one profile for each
type of certificate issued. There can be more than one certificate profile for each type of certificate
to set different authentication methods or different defaults and constraints for a particular type of
certificate type. Any certificate profile available in the administrative interface can be approved by an
agent and then used by an end entity to enroll.

• Delete any certificate profiles that will not be used.

• Modify the existing certificate profiles for specific characteristics for the company's certificates.

• Change the defaults set up in the certificate profile, the values of the parameters set in the

defaults, or the constraints that control the certificate content.

• Change the constraints set up by changing the value of the parameters.

• Change the authentication method.

• Change the inputs by adding or deleting inputs in the certificate profile, which control the fields on

the input page.

• Add or delete the output.

5.4.7. Planning Authentication Methods

As implied in Section 5.4.6, “Using and Customizing Certificate Profiles”, authentication for the
certificate process means the way that a user or entity requesting a certificate proves that they are
who they say they are. There are three ways that the Certificate System can authenticate an entity:

• In agent-approved enrollment, end-entity requests are sent to an agent for approval. The agent
approves the certificate request.

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73

• In automatic enrollment, end-entity requests are authenticated using a plug-in, and then the
certificate request is processed; an agent is not involved in the enrollment process.

• In CMC enrollment, a third party application can create a request that is signed by an agent and
then automatically processed.

A Certificate Manager is initially configured for agent-approved enrollment and for CMC authentication.
Automated enrollment is enabled by configuring one of the authentication plug-in modules. More
than one authentication method can be configured in a single instance of a subsystem. The HTML
registration pages contain hidden values specifying the method used. With certificate profiles, the
end-entity enrollment pages are dynamically-generated for each enabled profile. The authentication
method associated with this certificate profile is specified in the dynamically-generated enrollment
page.

The authentication process is simple.

1. An end entity submits a request for enrollment. The form used to submit the request identifies

the method of authentication and enrollment. All HTML forms are dynamically-generated by the
profiles, which automatically associate the appropriate authentication method with the form.

2. If the authentication method is an agent-approved enrollment, the request is sent to the request

queue of the CA agent. If the automated notification for a request in queue is set, an email is sent
to the appropriate agent that a new request has been received. The agent can modify the request
as allowed for that form and the profile constraints. Once approved, the request must pass the
certificate profiles set for the Certificate Manager, and then the certificate is issued. When the
certificate is issued, it is stored in the internal database and can be retrieved by the end entity from
the end-entities page by serial number or by request ID.

3. If the authentication method is automated, the end entity submits the request along with required

information to authenticate the user, such as an LDAP username and password. When the user
is successfully authenticated, the request is processed without being sent to an agent's queue. If
the request passes the certificate profile configuration of the Certificate Manager, the certificate is
issued and stored in the internal database. It is delivered to the end entity immediately through the
HTML forms.

The requirements for how a certificate request is authenticated can have a direct impact on the
necessary subsystems and profile settings. For example, if an agent-approved enrollment requires
that an agent meet the requester in person and verify their identity through supported documentation,
the authentication process can be time-intensive, as well as constrained by the physical availability
of both the agent and the requester. In that case, having numerous local RAs may be preferable to
centralized CAs.

5.4.8. Publishing Certificates and CRLs

A CA can publish both certificates and CRLs. Certificates can be published to a plain file or to
an LDAP directory; CRLs can be published to file or an LDAP directory, as well, and can also be
published to an OCSP responder to handle certificate verification.

Configuring publishing is fairly straightforward and is easily adjusted. For continuity and accessibility,
though, it is good to plan out where certificates and CRLs need to be published and what clients need
to be able to access them.

Publishing to an LDAP directory requires special configuration in the directory for publishing to work:

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• If certificates are published to the directory, than every user or server to which a certificate is issued
must have a corresponding entry in the LDAP directory.

• If CRLs are published to the directory, than they must be published to an entry for the CA which
issued them.

• For SSL, the directory service has to be configured in SSL and, optionally, be configured to allow the
Certificate Manager to use certificate-based authentication.

• The directory administrator should configure appropriate access control rules to control DN (entry
name) and password based authentication to the LDAP directory.

5.4.9. Renewing or Reissuing CA Signing Certificates

When a CA signing certificate expires, all certificates signed with the CA's corresponding signing key
become invalid. End entities use information in the CA certificate to verify the certificate's authenticity.
If the CA certificate itself has expired, applications cannot chain the certificate to a trusted CA.

There are two ways of resolving CA certificate expiration:

• Renewing a CA certificate involves issuing a new CA certificate with the same subject name and
public and private key material as the old CA certificate, but with an extended validity period.
As long as the new CA certificate is distributed to all users before the old CA certificate expires,
renewing the certificate allows certificates issued under the old CA certificate to continue working for
the full duration of their validity periods.

• Reissuing a CA certificate involves issuing a new CA certificate with a new name, public and
private key material, and validity period. This avoids some problems associated with renewing a CA
certificate, but it requires more work for both administrators and users to implement. All certificates
issued by the old CA, including those that have not yet expired, must be renewed by the new CA.

There are problems and advantages with either renewing or reissuing a CA certificate. Begin planning
the CA certificate renewal or re-issuance before installing any Certificate Managers, and consider the
ramifications the planned procedures may have for extensions, policies, and other aspects of the PKI
deployment.

NOTE

Correct use of extensions, for example the authorityKeyIdentifier extension, can
affect the transition from an old CA certificate to a new one.

5.5. Planning for Network and Physical Security

When deploying any Certificate System subsystem, the physical and network security of the
subsystem instance has to be considered because of the sensitivity of the data generated and stored
by the subsystems.

5.5.1. Considering Firewalls

There are two considerations about using firewalls with Certificate System subsystems:

• Protecting sensitive subsystems from unauthorized access

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75

• Allowing appropriate access to other subsystems and clients outside of the firewall

The CA, DRM, and TKS are always placed inside a firewall because they contain critical information
that can cause devastating security consequences if they are compromised.

The RA is frequently placed outside the firewall and the TPS and OCSP can be. Likewise, other
services and clients used by the Certificate System can be on a different machine outside the firewall.
In that case, the local networks have to be configured to allow access between the subsystems behind
the firewall and the services outside it.

The LDAP database can be on a different server, even on a different network, than the subsystem
which uses it. In this case, all LDAP ports (389 for LDAP and 636 for LDAPS, by default) need to be
open in the firewall to allow traffic to the directory service. Without access to the LDAP database, all
subsystem operations can fail.

As part of configuring the firewalls, if iptables is enabled, then it must have configured policies to allow
communication over the appropriate Certificate System ports. Configuring iptables is described in the
Red Hat Enterprise Linux Deployment Guide, such as "Using iptables."

4

5.5.2. Considering Physical Security and Location

Because of the sensitive data they hold, consider keeping the CA, DRM, and TKS in a secure facility
with adequate physical access restrictions. Just as network access to the systems needs to be
restricted, the physical access also needs to be restricted.

Along with finding a secure location, consider the proximity to the subsystem agents and
administrators. Key recovery, for example, can require multiple agents to give approval; if these agents
are spread out over a large geographical area, then the time differences may negatively impact the
ability to retrieve keys. Plan the physical locations of the subsystems, then according to the locations
of the agents and administrators who will manage the subsystem.

5.5.3. Port Considerations

The default subsystems are installed and configured with a separate TCP/IP port for each service,
called port separation. Each Certificate System subsystem uses up to five ports:

• A standard port

• An SSL port for end users services

• An SSL port for agent services

• An SSL port for the administrative console or admin services

• A web server port (Tomcat for CA, DRM, OCSP, and TKS subsystems, Apache for the TPS and RA
subsystems)

All of the service pages and interfaces described in Section 2.2, “Red Hat Certificate System Services”
are connected to using the instance's URL and the corresponding port number. For example:

https://server.example.com:9444/ca/ee/ca

To access the admin console, the URL specifies the admin port:

4

http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.2/html/Deployment_Guide/s1-fireall-ipt-act.html

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pkiconsole https://server.example.com:9445/ca

All agent and admin functions require SSL client authentication. For requests from end entities, the
Certificate System listens on both the SSL (encrypted) port and non-SSL ports.

The ports for the different services to use are defined in the server.xml file for the CA, OCSP, DRM,
and TKS and in the httpd.conf and nss.conf files for the RA and TPS. If a port is not used, it can
be disabled in that file. For example:

<Service name="Catalina">
<!--Connector port="9180" ... /--> unused standard port
<Connector port="9443" ... />

The default ports for the first instance installed on a machine are already defined, but it is possible
to choose ports different ports for additional instances. Whenever a new instance in installed, it can
be configured to have a single SSL port or to use three separate SSL ports for the different interface.
Whichever way you choose, make sure that the new ports are unique on the host system.

To verify that a port is available for use, check the appropriate file for the operating system. Port
numbers for network-accessible services are usually maintained in a file named services. On Red
Hat Enterprise Linux, it is also helpful to confirm that a port is not assigned by SELinux, by running the
command semanage port -l to list all ports which currently have an SELinux context.

When a new subsystem instance is created, any number between 1 and 65535 can be specified as
the secure port number.

For additional instances, created with the pkicreate utility, it is possible to configure the instance
with port separation or using a single, consolidated SSL port for all services. Port separation is more
secure, but it depends on the maintenance costs, users, and network which is preferable.

Subsystem Standard End-Entity

SSL

Agent SSL Admin SSL Tomcat

CA 9180 9444 9443 9445 9701

RA 12888 12889 12889

OCSP 11180 11444 11443 11445 11701

DRM 10180 10444 10443 10445 10701

TKS 13180 13444 13443 13445 13701

TPS 7888 7889 7889

Table 5.2. Default Port Assignments for Certificate System 8.0

5.6. Tokens for Storing Certificate System Subsystem Keys
and Certificates

A token is a hardware or software device that performs cryptographic functions and stores public-key
certificates, cryptographic keys, and other data.
The Certificate System defines two types of tokens, internal and external, for storing key pairs and
certificates that belong to the Certificate System subsystems.

An internal (software) token is a pair of files, usually called the certificate database (cert8.db) and
key database (key3.db), that the Certificate System uses to generate and store its key pairs and

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77

certificates. The Certificate System automatically generates these files in the filesystem of its host
machine when first using the internal token. These files are created during the Certificate System
subsystem configuration if the internal token was selected for key-pair generation.

These security databases are located in the /var/lib/subsystem_name/alias directory.

An external token refers to an external hardware device, such as a smart card or hardware security
module (HSM), that the Certificate System uses to generate and store its key pairs and certificates.
The Certificate System supports any hardware tokens that are compliant with PKCS #11.

PKCS #11 is a standard set of APIs and shared libraries which isolate an application from the details
of the cryptographic device. This enables the application to provide a unified interface for PKCS #11­compliant cryptographic devices.

The PKCS #11 module implemented in the Certificate System supports cryptographic devices supplied
by many different manufacturers. This module allows the Certificate System to plug in shared libraries
supplied by manufacturers of external encryption devices and use them for generating and storing
keys and certificates for the Certificate System managers.

Consider using external tokens for generating and storing the key pairs and certificates used by
Certificate System. These devices are another security measure to safeguard private keys because
hardware tokens are sometimes considered more secure than software tokens.

Before using external tokens, plan how the external token is going to be used with the subsystem:

• All system keys for a subsystem must be generated on the same token.

• The subsystem must be installed in an empty HSM slot. If the HSM slot has previously been used
to store other keys, then use the HSM vendor's utilities to delete the contents of the slot. The
Certificate System has to be able to create certificates and keys on the slot with default nicknames.
If not properly cleaned up, the names of these objects may collide with previous instances.

The Certificate System can also use hardware cryptographic accelerators with external tokens. Many
of the accelerators provide the following security features:

• Fast SSL connections. Speed is important to accommodate a high number of simultaneous
enrollment or service requests.

• Hardware protection of private keys. These devices behave like smart cards by not allowing private
keys to be copied or removed from the hardware token. This is important as a precaution against
key theft from an active attack of an online Certificate Manager.

The Certificate System supports the nCipher netHSM hardware security module (HSM), by default.
Certificate System-supported HSMs are automatically added to the secmod.db database with
modutil during the pre-configuration stage of the installation, if the PKCS #11 library modules are in
the default installation paths.

During configuration, the Security Modules panel displays the supported modules, along with the
NSS internal software PKCS #11 module. All supported modules that are detected show a status of
Found and is individually marked as either Logged in or Not logged in. If a token is found but not
logged in, it is possible to log in using the Login under Operations. If the administrator can log into
a token successfully, the password is stored in a configuration file. At the next start or restart of the
Certificate System instance, the passwords in the password store are used to attempt a login for each
corresponding token.

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Administrators are allowed to select any of the tokens that are logged in as the default token, which is
used to generate system keys.

5.7. Questions for Planning the Certificate System

• Will the PKI allow replacement keys? Will it require key archival and recovery?

• Will local offices need to process their own certificate requests? Will there be a large number of
certificate requests?

• Will many external clients need to validate certificate status? Can the internal OCSP in the
Certificate Manager handle the load?

• Will the organization use smart cards? If so, will temporary smart cards be allowed if smart cards
are mislaid, requiring key archival and recovery?

• What are the requirements for the CA signing certificate? Does the Certificate System need control
over attributes like the validity period? How will the CA certificates be distributed?

• Will any subsystems need to be cloned and, if so, what are the methods for securely storing their
key materials?

• How many security domains will be created, and what subsystem instances will be placed in each
domain?

• Are trusted relationships required for subsystems in different security domains?

• What kinds of certificates will be issued? What characteristics do they need to have, and what
profile settings are available for those characteristics? What restrictions need to be placed on the
certificates?

• What are the requirements for approving a certificate request? How does the requester authenticate
himself, and what kind of process is required to approve the request?

• Where will certificates and CRLs be published? What configuration needs to be done on the
receiving end for publishing to work? What kinds of certificates or CRLs need to be published and
how frequently?

• What subsystems should be placed behind firewalls? What clients or other subsystems need to
access those firewall-protected subsystems and how will access be granted? Is firewall access
allowed for the LDAP database?

• What subsystems need to be physically secured? How will access be granted, and who will be
granted access?

• What is the physical location of all agents and administrators? What is the physical location of the
subsystems? How will administrators or agents access the subsystem services in a timely-manner?
Is it necessary to have subsystems in each geographical location or time zone?

• What ports should be assigned for each subsystem? Is it necessary to have a single SSL port, or is
it better to have port separation for extra security?

Chapter 6.

79

Setting up a Common Criteria
Environment

Setting up a secure environment according to Red Hat Certificate System's Common Criteria
evaluation guidelines requires special planning for its subsystems and users. The actual installation
and configuration process is covered in the Certificate System Administrator's Guide, but the concepts,
security objectives, and considerations are covered in this chapter, as part of planning your Certificate
System deployment.

IMPORTANT

Red Hat Certificate System 8.0 is currently in the evaluation process for Common Criteria.
The complete list of products in evaluation, including Red Hat Certificate System 8.0 is
available at the National Information Assurance Partnership Common Criteria Evaluation
and Validation Scheme website, http://www.niap-ccevs.org/cc-scheme/in_evaluation/.

6.1. About Common Criteria

The Common Criteria for Information Technology Security Evaluation (ISO 15408) is an international
standard defining secure ways to install, configure, and run software and hardware. Common Criteria
allows vendors to define the most secure operating environments for their products. Administrators
can use the guidelines to plan a secure PKI deployment.

At a high level, these Common Criteria guidelines identify:

• Specific configuration and features to use in the Certificate System subsystems

• Certificate System user types, their roles in the PKI, and limits on their roles

• Requirements for the host servers

• Installation procedures for the subsystems

• Features and configurations not covered by the Common Criteria evaluation

Red Hat Certificate System 8.0 is currently in the evaluation process for Common Criteria. The
complete list of products in evaluation, including Red Hat Certificate System 8.0 is available at the
National Information Assurance Partnership Common Criteria Evaluation and Validation Scheme
website, http://www.niap-ccevs.org/cc-scheme/in_evaluation/.

6.2. Required Configuration for the Server or Network

There are two assumptions of the underlying operating system configuration which have to be met for
Certificate System to run in a proper Common Criteria environment:

• Reliable timestamp. Certificate System relies on the operating system to provide reliable
timestamps. To ensure that the certificates signed by the CA contain accurate timestamps and the
audit log events record accurate time of event occurrence, administrators need to make sure the
operating system has a time-syncing mechanism with a reliable source.

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80

• Secure password and certificate storage. Plan for the storage of any passwords and certificates.
Also define the user password policy. Make sure everyone knows and adheres to these policies.

In addition to the host configuration for passwords and timestamps, the Certificate System host server
and its network environment must both offer protection from potential security issues:

• Recover to a viable state after malicious code is introduced and damage occurs.

• Provide time stamps to ensure the sequencing of events can be verified.

• Implement automated notification or other responses to the TSF-discovered attacks in order to
identify attacks and create an attack deterrent.

• Require inspection for downloads.

• Respond to possible loss of stored audit records.

6.3. Required Features and Configurations for the

Certificate System Subsystems

For the security environment, all of these Certificate System features must be implemented.

Storing Data in a Hardware Token

Subsystem certificate private keys and secret keys are to be generated and stored in a FIPS 140-1
level 3 certified hardware cryptographic token.

Install the software and hardware for the hardware token before installing and configuring the
subsystems. Use the hardware token to create subsystem certificates as each subsystem is
configured.

Each subsystem needs at least one certified hardware cryptographic module; the DRM requires two,
one for user private key transport key and one for user private key storage key.

This environment requires a FIPS 140-1 level 3 certified hardware cryptographic module.

Revocation Checking

Revocation checking is required to verify the status of Certificate System user certificates.

SSL Client Authentication with the Internal Database

The internal LDAP database used by the subsystem must be set up for SSL client authentication.

Administrative Console

Because SSL is required for running the subsystem and using the password file to remote startup is
prohibited, the admin console cannot be used to start or restart an instance, and the passwords must
be supplied manually when the instance is started in the command line.

Audit Logs

Signed audit logs must be enabled. Certificate System 8.0 maintains all security relevant audit records
in an audit log. Each audit record includes the date, time, event, thread ID, user ID, error or return

Users, Roles, and Access Control for Common Criteria

81

messages, and other important or relevant information about the transaction, like the certificate serial
number, DN, or authentication source. The only configurable option for the audit log content is the
events which are logged.

Certificate Profiles

Any or all of the pre-defined certificate profiles can be used for certificate enrollment. It is also possible
to create modified or custom certificate profiles using the defaults, constraints, inputs, and outputs that
are already defined in Certificate System.

Custom plug-ins for any of the components of the certificate profile feature are not supported as part of
the Common Criteria Environment.

IMPORTANT

Only the Certificate System CA administrators are allowed to configure the certificate
enrollment profiles by setting ranges for fields, enabling extensions, or changing other
settings. It is the CA agents' responsibility to approve the fields and extensions in the
certificate profiles enabled by the administrators.

Key Archival and Recovery

The DRM subsystem archives user private keys for encryption-only certificates and can recover the
user private keys that it has archived. Key recovery requires Data Recovery Manager Agents to work
in cooperation.

OCSP Responder Revocation Information Store

The OCSP Responder revocation store contains information about where the CRLs can be retrieved
for serving OCSP requests. If the Online Certificate Status Manager is configured to use an LDAP
store, then the LDAP store must be configured for SSL authentication.

Other Allowed Features

All of these features can be configured in Certificate System subsystems to manage certificates, as
long as the default inputs or modules are used:

• Authentication

• CRLs

• Jobs

• Notifications

• Publishing

• Self Tests

6.4. Users, Roles, and Access Control for Common Criteria

Common Criteria requires a defined list of user types, with limited and controlled access to the
product. This section looks at Certificate System's roles and access controls.

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6.4.1. Certificate System User Types

Each Certificate System subsystem has up to four roles. While the names of the user roles
(administrator, agent, auditors, and trusted managers), the functions of each role is slightly different for
each subsystem, according to the functions of the subsystem:

• Administrators

• Can start and stop the server from the command-line.

• Can perform all configuration management for CA, including configuring certificate profiles in

the console by specifying the set of acceptable values for fields and extensions for certificate
enrollment requests.

• Agents

NOTE

All agent operations are performed over SSL or using an SSL-capable browser.

• For the Certificate Manager. Can approve the fields and extensions to be included in a certificate

in the certificate profiles that have been enabled and configured by the administrator.

• For the Certificate Manager. Can run tools to pre-approve certificate enrollment and revocation

requests.

• For the Data Recovery Manager. Can approve recovery of subject private keys.

• For the Data Recovery Manager. Can export recovered subject private keys.

• For the Online Certificate Status Manager. Can add CRLs.

• For the Online Certificate Status Manager. Can define supported CAs.

• For the Token Processing System. Can approve token enrollment requests.

• Auditors

• Can view signed audit logs from the IT environment. This is the only role allowed to view audit

logs.

• Can verify audit log signatures by running the AuditVerify tool.

• Trusted manager

The trusted manager role is a special role for other subsystem instances, not for users, for
inter-CIMC_boundary communication. The trust is established using SSL authentication and
authorization. Users cannot be assigned to this role; it is only for establishing trust between two
subsystems.

The agents roles in Certificate System for the CA, DRM, TKS, and TPS map directly to the
"Officer" role defined in the Common Criteria profile, while the OCSP agents are sub-group of the
"Administrator" role.

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83

6.4.2. Access Controls for Common Criteria

All of the subsystems and supporting network environment must support and enforce an access
control policy with the following restrictions:

• Users are only granted access to the subsystem and its data if they meet the following
requirements:

• The identity of the user is verified

• Access is allowed to the role (or roles) to which the user belongs

• The type of access is allowed

• The content of the access request is allowed

• The users possession of a secret or private key, as required

• Access must be explicitly allowed or denied, and the only permissible access types are read, write,
and execute.

• An explicit owner and role is identified for every subsystem object. Assigning and managing
authorization is the responsibility of the owner or role.

6.5. Security Objectives for the Common Criteria

Environment for Certificate System

The process for developing and defining the Certificate System Common Criteria environment had to
include defining the assumptions for how the product is used, what its potential threats are, and what
the goals of the security environment are.

6.5.1. Usage Assumptions

Usage assumptions define real-world deployment considerations, looking at people who interact with
the system, its physical location and security, and its network environment.

Objective Area Description

Auditors review audit logs Audit logs are required for security-relevant events and must be reviewed by the Auditors.

Authentication data
management

An authentication data management policy is enforced to ensure that users change their authentication data at appropriate intervals
and to appropriate values (e.g., proper lengths, histories, variations, etc.) (Note: this assumption is not applicable to biometric
authentication data.)

Competent administrators,
operators, officers and
auditors

Competent Administrators, Operators, Officers and Auditors will be assigned to manage Certificate System and the security of the
information it contains.

CPS All Administrators, Operators, Officers, and Auditors are familiar with the certificate policy (CP) and certification practices statement

(CPS) under which Certificate System is operated.

Disposal of authentication
data

Proper disposal of authentication data and associated privileges is performed after access has been removed (e.g., job termination,
change in responsibility).

Malicious code not signed Malicious code destined for Certificate System is not signed by a trusted entity.

Notify authorities of security
issues

Administrators, Operators, Officers, Auditors, and other users notify proper authorities of any security issues that impact their
systems to minimize the potential for the loss or compromise of data.

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Objective Area Description

Social engineering training General users, administrators, operators, officers and auditors are trained in techniques to thwart social engineering attacks.

Cooperative users Users need to accomplish some task or group of tasks that require a secure IT environment. The users require access to at least

some of the information managed by Certificate System and are expected to act in a cooperative manner.

Communications protection The system is adequately physically protected against loss of communications i.e., availability of communications.

Physical protection The TOE hardware, software, and firmware critical to security policy enforcement will be protected from unauthorized physical

modification.

Operating system The operating system has been selected to provide the functions required by this CIMC to counter the perceived threats for the

appropriate Security Level identified in this family of PPs.

Table 6.1. Usage Assumptions

6.5.2. Organizational Policies

The organizational policies are practices which should be employed across a company or deployment.

Objective Area Description

Authorized use of information Information shall be used only for its authorized purposes.

Cryptography FIPS-approved or NIST-recommended cryptographic functions shall be used to perform all cryptographic operations.

Table 6.2. Organizational Policies

6.5.3. Potential Threats

The first step to defining the security objectives is to first identify the potential threats to the PKI
environment.

Objective Area Description

Administrative errors of
omission

Administrators, Operators, Officers or Auditors fail to perform some function essential to security.

User abuses authorization to
collect and/or send data

User abuses granted authorizations to improperly collect and/or send sensitive or security-critical data.

User error makes data
inaccessible

User accidentally deletes user data rendering user data inaccessible.

Administrators, operators,
officers and auditors commit
errors or hostile actions

An Administrator, Operator, Officer or Auditor commits errors that change the intended security policy of the system or application or
maliciously modify the system.s configuration to allow security violations to occur.

Critical system component
fails

Failure of one or more system components results in the loss of system critical functionality.

Malicious code exploitation An authorized user, IT system, or hacker downloads and executes malicious code, which causes abnormal processes that violate the

integrity, availability, or confidentiality of the system assets.

Message content modification A hacker modifies information that is intercepted from a communications link between two unsuspecting entities before passing it on

to the intended recipient.

Flawed code A system or applications developer delivers code that does not perform according to specifications or contains security flaws.

Disclosure of private and
secret keys

A private or secret key is improperly disclosed.

Security Objectives

85

Objective Area Description

Modification of private/secret
keys

A secret/private key is modified.

Sender denies sending
information

The sender of a message denies sending the message to avoid accountability for sending the message and for subsequent action or
inaction.

Hacker gains access A hacker masquerades as an authorized user to perform operations that will be attributed to the authorized user or a system process

or gains undetected access to a system due to missing, weak and/or incorrectly implemented access control causing potential
violations of integrity, confidentiality, or availability.

Hacker physical access A hacker physically interacts with the system to exploit vulnerabilities in the physical environment, resulting in arbitrary security

compromises.

Social engineering A hacker uses social engineering techniques to gain information about system entry, system use, system design, or system

operation.

Table 6.3. Potential Threats

6.5.4. Security Objectives

In developing the Common Criteria environment, certain assumptions were made about the nature of
threats against the PKI environment, risk points, users, network environment, and, ultimately, the goals
of the secure environment.

Objective Area Description

Certificates Certificate System must be able to ensure that certificates, certificate revocation lists, and certificate status information are valid.

Preserve and trust the
recovery of a secure state

Certificate System must preserve the secure state of the system in the event of a secure component failure and then be able to
recover to a secure state.

Non-repudiation Prevent user from avoiding accountability for sending a message by providing evidence that the user sent the message.

Control unknown source
communication traffic

Control (e.g., reroute or discard) communication traffic from an unknown source to prevent potential damage.

Administrators, operators,
officers and auditors guidance
documentation

Deter Administrator, Operator, Officer or Auditor errors by providing adequate documentation on securely configuring and operating
the CIMC.

Auditors review audit logs Identify and monitor security-relevant events by requiring auditors to review audit logs on a frequency sufficient to address level of

risk.

Authentication data
management

Ensure that users change their authentication data at appropriate intervals and to appropriate values (e.g., proper lengths, histories,
variations, etc.) through enforced authentication data management (Note: this objective is not applicable to biometric authentication
data.)

Communications protection Protect the system against a physical attack on the communications capability by providing adequate physical security.

Competent administrators,
operators, officers and
auditors

Provide capable management of Certificate System by assigning competent Administrators, Operators, Officers and Auditors to
manage Certificate System and the security of the information it contains.

CPS All Administrators, Operators, Officers and Auditors shall be familiar with the certificate policy (CP) and the certification practices

statement (CPS) under which Certificate System is operated.

Disposal of authentication
data

Provide proper disposal of authentication data and associated privileges after access has been removed (e.g., job termination,
change in responsibility).

Installation Those responsible for Certificate System must ensure that Certificate System is delivered, installed, managed, and operated in a

manner which maintains IT security.

Chapter 6. Setting up a Common Criteria Environment

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Objective Area Description

Malicious code not signed Protect Certificate System from malicious code by ensuring all code is signed by a trusted entity prior to loading it into the system.

Notify authorities of security
issues

Notify proper authorities of any security issues that impact their systems to minimize the potential for the loss or compromise of data.

Physical protection Those responsible for Certificate System must ensure that the security-relevant components of Certificate System are protected from

physical attack that might compromise IT security.

Social engineering training Provide training for general users, Administrators, Operators, Officers and Auditors in techniques to thwart social engineering attacks.

Cooperative users Ensure that users are cooperative so that they can accomplish some task or group of tasks that require a secure IT environment and

information managed by Certificate System.

Lifecycle security Provide tools and techniques used during the development phase to ensure security is designed into the CIMC. Detect and resolve

flaws during the operational phase.

Repair identified security flaws The vendor repairs security flaws that have been identified by a user.

Cryptographic functions The TOE must implement approved cryptographic algorithms for encryption/decryption, authentication, and signature generation/

verification; approved key generation techniques and use validated cryptographic modules. (Validated is defined as FIPS 140-1
validated.)

Operating System The operating system used is validated to provide adequate security, including domain separation and non-bypassability, in

accordance with security requirements recommended by the National Institute of Standards and Technology.

Periodically check integrity Provide periodic integrity checks on both system and software.

Security roles Maintain security-relevant roles and the association of users with those roles.

Validation of security function Ensure that security-relevant software, hardware, and firmware are correctly functioning through features and procedures.

Trusted Path Provide a trusted path between the user and the system. Provide a trusted path to security-relevant (TSF) data in which both end

points have assured identities.

Configuration Management Implement a configuration management plan. Implement configuration management to assure identification of system connectivity

(software, hardware, and firmware), and components (software, hardware, and firmware), auditing of configuration data, and
controlling changes to configuration items.

Data import/export Protect data assets when they are being transmitted to and from Certificate System, either through intervening untrusted components

or directly to/from human users.

Detect modifications of
firmware, software, and
backup data

Provide integrity protection to detect modifications to firmware, software, and backup data.

Individual accountability and
audit records

Provide individual accountability for audited events. Record in audit records: date and time of action and the entity responsible for the
action.

Integrity protection of user
data and software

Provide appropriate integrity protection for user data and software.

Limitation of administrative
access

Design administrative functions so that Administrators, Operators, Officers and Auditors do not automatically have access to user
objects, except for necessary exceptions. Control access to the system by Operators and Administrators who troubleshoot the
system and perform system updates.

Maintain user attributes Maintain a set of security attributes (which may include role membership. access privileges, etc.) associated with individual users.

This is in addition to user identity.

Manage behavior of security
functions

Provide management functions to configure, operate, and maintain the security mechanisms.

Object and data recovery free
from malicious code

Recover to a viable state after malicious code is introduced and damage occurs. That state must be free from the original malicious
code.

Features Not Covered by Common Criteria Evaluation`

87

Objective Area Description

Procedures for preventing
malicious code

Incorporate malicious code prevention procedures and mechanisms.

Protect stored audit records Protect audit records against unauthorized access, modification, or deletion to ensure accountability of user actions.

Protect user and TSF data
during internal transfer

Ensure the integrity of user and TSF data transferred internally within the system.

Require inspection for
downloads

Require inspection of downloads/transfers.

Respond to possible loss of
stored audit records

Respond to possible loss of audit records when audit trail storage is full or nearly full by restricting auditable events.

Restrict actions before
authentication

Restrict the actions a user may perform before Certificate System authenticates the identity of the user.

Security-relevant configuration
management

Manage and update system security policy data and enforcement functions, and other security-relevant configuration data, to ensure
they are consistent with organizational security policies.

Time stamps Provide time stamps to ensure that the sequencing of events can be verified.

User authorization
management

Manage and update user authorization and privilege data to ensure they are consistent with organizational security and personnel
policies.

React to detected attacks Implement automated notification (or other responses) to the TSF-discovered attacks in an effort to identify attacks and to create an

attack deterrent.

Table 6.4. Security Objectives

6.6. Features Not Covered by Common Criteria Evaluation`

IMPORTANT

The Registration Manager (RA) is not evaluated or covered by Certificate System's
Common Criteria guidelines.

The CA, DRM, OCSP, TKS, and TPS subsystems can be deployed in any scenario or combination,
as long as they are installed and configured following the Common Criteria Environment rules and
guidelines. This includes making the CA a root or subordinate CA, installing all subsystems, installing
a subset of subsystems, and using multiple instances of a subsystem.

NOTE

For setting up bridges using cross-pair certificates, cooperate with the administrator of the
remote CA to set up the trust between the two certificates.

The Common Criteria environment does not cover any of these other features in Certificate System:

• Using the Registration Manager.

• Generating keys or storing certificates in software tokens.

• Using the password.conf file for remote startup.

• Cloning a Certificate Manager.

Chapter 6. Setting up a Common Criteria Environment

88

• Running the internal LDAP database or any publishing LDAP database without SSL.

• Adding a custom plug-in. All role users for a subsystem must carefully evaluate any custom plug-ins
before making them part of the system.

• Changing the default ACLs set for the subsystems. Be very cautious before changing any access
controls set in the subsystem.

• Using the Certificate Manager's internal OCSP services.

• SCEP enrollments.

• Challenge revocation.

89

Glossary

A

access control The process of controlling what particular users are allowed to do. For

example, access control to servers is typically based on an identity,
established by a password or a certificate, and on rules regarding
what that entity can do. See also access control list (ACL).

access control instructions
(ACI)

An access rule that specifies how subjects requesting access are
to be identified or what rights are allowed or denied for a particular
subject. See access control list (ACL).

access control list (ACL) A collection of access control entries that define a hierarchy of access

rules to be evaluated when a server receives a request for access to
a particular resource. See access control instructions (ACI).

administrator The person who installs and configures one or more Certificate

System managers and sets up privileged users, or agents, for them.
See also agent.

agent A user who belongs to a group authorized to manage agent services

for a Certificate System manager. See also Certificate Manager

agent, Data Recovery Manager agent.

agent-approved enrollment An enrollment that requires an agent to approve the request before

the certificate is issued.

agent services 1. Services that can be administered by a Certificate System agent

through HTML pages served by the Certificate System subsystem for
which the agent has been assigned the necessary privileges.

2. The HTML pages for administering such services.

attribute value assertion
(AVA)

An assertion of the form attribute = value, where attribute is a tag,
such as o (organization) or uid (user ID), and value is a value
such as "Red Hat, Inc." or a login name. AVAs are used to form the

distinguished name (DN) that identifies the subject of a certificate,

called the subject name of the certificate.

audit log A log that records various system events. This log can be signed,

providing proof that it was not tampered with, and can only be read by
an auditor user.

auditor A privileged user who can view the signed audit logs.

authentication Confident identification; assurance that a party to some computerized

transaction is not an impostor. Authentication typically involves
the use of a password, certificate, PIN, or other information to
validate identity over a computer network. See also password-based

authentication, certificate-based authentication, client authentication,
server authentication.

Glossary

90

authentication module A set of rules (implemented as a Java™ class) for authenticating

an end entity, agent, administrator, or any other entity that needs to
interact with a Certificate System subsystem. In the case of typical
end-user enrollment, after the user has supplied the information
requested by the enrollment form, the enrollment servlet uses an
authentication module associated with that form to validate the
information and authenticate the user's identity. See servlet.

authorization Permission to access a resource controlled by a server. Authorization

typically takes place after the ACLs associated with a resource have
been evaluated by a server. See access control list (ACL).

automated enrollment A way of configuring a Certificate System subsystem that allows

automatic authentication for end-entity enrollment, without human
intervention. With this form of authentication, a certificate request
that completes authentication module processing successfully is
automatically approved for profile processing and certificate issuance.

B

bind DN A user ID, in the form of a distinguished name (DN), used with a

password to authenticate to Red Hat Directory Server.

C

CA certificate A certificate that identifies a certificate authority. See also certificate

authority (CA), subordinate CA, root CA.

CA hierarchy A hierarchy of CAs in which a root CA delegates the authority to issue

certificates to subordinate CAs. Subordinate CAs can also expand
the hierarchy by delegating issuing status to other CAs. See also

certificate authority (CA), subordinate CA, root CA.

CA server key The SSL server key of the server providing a CA service.

CA signing key The private key that corresponds to the public key in the CA

certificate. A CA uses its signing key to sign certificates and CRLs.

certificate Digital data, formatted according to the X.509 standard, that specifies

the name of an individual, company, or other entity (the subject

name of the certificate) and certifies that a public key, which is also

included in the certificate, belongs to that entity. A certificate is issued
and digitally signed by a certificate authority (CA). A certificate's
validity can be verified by checking the CA's digital signature through

public-key cryptography techniques. To be trusted within a public-key
infrastructure (PKI), a certificate must be issued and signed by a CA

that is trusted by other entities enrolled in the PKI.

certificate authority (CA) A trusted entity that issues a certificate after verifying the identity

of the person or entity the certificate is intended to identify. A CA
also renews and revokes certificates and generates CRLs. The