Hp sa3110, sa3150, sa3400, sa3450 virtual private networking concepts guide

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hewlett-packard company

virtual private networking

concepts guide

Hewlett-Packard Company

HP: 5971-3009

P/N: A5 5310-00 1

March 2001

Disclaimer

DisclaimerDisclaimer

Information in this document is provided in connection with Hewlett-Packard Company products. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this d ocument. Except as provided in Hewlett-Packard Company’s Terms and Conditi on s of Sale for such products, Hewlett-Packard Company assumes no liability whatsoever, and Hewlett-Packard Company disclaims any express or implied warranty, relating to sale and/or use of Hewlett-Packard Company products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. Hewlett-Packard Company products are not intended for use in medical, life saving, or life sustaining applications.

Hewlett-Packard Company may make changes to specifications and product descriptions at any time, without notice.

Hewlett-Packard Company Virtual Private Networking

This

Concepts Guide

furnishe d under lic e ns e and ma y only be u s ed or copied i n accordance with the terms of the license. The in formation in this manual is furnished for inf ormation al use onl y, is subject t o change without notice, and should not be construed as a commitment by Hewlett -Packard Company. Hewlett-Packard Company assumes no respon sibility or liabil ity for any errors or inaccuracies that may appear in this document or any software that may be provided in association with this document.

, as well as the software described in it is

Except as permitted by such license, no part of this document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means without the express written consent of Hewlett-Packard Company.

iii

Contents

ContentsContents

HP VPN Concepts Guide Overview

HP VPN Concepts Guide OverviewHP VPN Concepts Guide Overview

HP VPN Concepts Guide Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

HP VPN Suite Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Operational Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

TCP/IP Basics Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Cryptographic Systems and Encryption Terminology

Cryptographic Systems and Encryption TerminologyCryptographic Systems and Encryption Terminology

Cryptographic Systems and Encryption Terminology Overview . . . . . . . . . . . . . . . . . 2-1

Symmetric Cryptographic Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Data Encryption Standard (DES) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Triple Pass DES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

3DES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Outer Cipher Block Chaining (CBC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

Asymmetric Cryptographic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Symmetric Vs. Asymmetric Cryptography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Diffie-Hellman Session Key Exchange. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Key Space and Brute Force Attacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Encapsulation and Packet Handling

Encapsulation and Packet HandlingEncapsulation and Packet Handling

Encapsulation Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Secure Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

ESP Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

SST Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Packet Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Packet Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Authentication Methods

Authentication MethodsAuthentication Methods

Authentication Methods Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Certificate Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Challenge Phrase Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

SecurID Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

RADIUS Authentication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Entrust Authentication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Firewalls and Tunnels

Firewalls and TunnelsFirewalls and Tunnels

Firewall and Tunnels Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Firewall Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Hewlett-Packard Company Virtual Private Networking Concepts Guide i

Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Tunnel Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Site-to-Site Tunnels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Single-User Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

Multiuser Tunnels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16

Tunnel Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

One-Way In Firewall Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

One-Way Out Firewall Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24

Outbound Proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

Inbound Proxy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

Tunnel Termination and Firewall Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31

Load Balancing and Redundancy

Load Balancing and RedundancyLoad Balancing and Redundancy

Load Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Redundancy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Hewlett-Packard Company Virtual Private Networking Concepts Guide ii

HP VPN Concepts Guide Overview

HP VPN Concepts Guide OverviewHP VPN Concepts Guide Overview

HP VPN Concepts Guide Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

HP VPN Suite Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Operational Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5

TCP/IP Basics Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6

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Hewlett-Packar d Company Virtual Pri vate Networking Concepts Guide

HP VPN Concep ts Guide Overview

HP VPN Concepts Guide Overview

HP VPN Concepts Guide OverviewHP VPN Concepts Guide Overview

The purpose of this HP VPN Concepts Guide is to provide you with information on the Hewlett-Packard Company virtual private networking (VPN) suite, consisting of five modular components that work together to provide s ecu re communications across any network. The term VPN device is used in this document to refer to the HP VPN Server Appliance SA3110/SA3150/SA3400/SA3450 devices.

In addition, the

Networking Concepts Guide

and theory on topics ranging from firewall functions and cryptographic systems to authentication types and encapsulation.

Contents

Contents HP VPN Suite Overview (page1-2)

ContentsContents

Operational Overview (page 1-5) TCP/IP Basics Overview (page 1-6) Encapsulation Overview (page 3-1) Packet Handling (page 3-7) Authentication Methods Overview (page 4-1) Cryptographic Systems and Encryption Terminology Overview

(page 2-1) Firewall and Tunnels Overview (page 5-1) Load Balancing (page 6-1) Redundancy (page 6-2)

Hewlett-Packard Compan y Vi rtual Private

provides background information

Hewlett-Packard Company Virtual Private Networking Concepts Guide 1-1

HP VPN Concepts Guide Overview

HP VPN Suite Overview

HP VPN Suite OverviewHP VPN Suite Overview

The HP virtual private networking (VPN) suite consists of three modular components that work together to provide secure communications acro ss any network:

• VPN device

• HP SA3000 Series VPN Manager

• HP SA3000 Series VPN Client

VPN Device

VPN Device The VPN device is a hardware/software security system,

VPN DeviceVPN Device

responsible for processing data packets as they pass between the public side and the private side of a network. The VPN device is designed to perform three major functions:

• At the communications level, the VPN device can act as either a router or as a bridge.

• As a packet encryptor, the VPN device can selectively encrypt and decrypt data b ased on source and dest in ation addresses and ports. This provides t he flexibility of sending both encrypted and clear data us ing the same infrastructure, without compromising your centrally managed security policy.

• As a firewall, the VPN device can be used as a packet filter and a stateful inspe ction proxy. The VPN device goes further than tr aditional firewalls , howeve r , by adding authe ntica tion to the fir ewall function, which allows the creation of truly secure virtual private networks.

The VPN device includes an industry-standard PCI bus card, which accelerates encryption and decryption to Local Area Network speeds. The card incorporates a dedicated ASIC chip optimized for DES and Triple Pass DES encryption and provides a significant increase in throughput over software-only encryption impleme ntat io ns.

HP SA3000

HP SA3000 HP SA3000 Series VPN

Series VPN

Series VPN Series VPN Manager

Manager

ManagerManager

1-2 Hewlett-Packard Company Virtual Private Networking Concepts Guide

The VPN Manager is a software p ackage based in Windows 95 or Windows NT that ce ntrall y monitors and configures the VPN devices in your network. Using a powerful graphical user interface (GUI), you can configure and monitor VPN devices deployed in the field. The VPN Manager is also used to define and grant access to VPN Client users.

HP SA3000

HP SA3000 HP SA3000 Series VPN

Series VPN

Series VPN Series VPN Client

Client

ClientClient

HP VPN Server

HP VPN Server HP VPN Server Appliance

Appliance

Appliance Appliance SA3110/SA3150/

SA3110/SA3150/

SA3110/SA3150/SA3110/SA3150/ SA3400/SA3450

SA3400/SA3450

SA3400/SA3450 SA3400/SA3450 Product Suite

Product Suite

Product SuiteProduct Suite

HP VPN Suite Overview

The VPN Client is a software package based in Windows 95 or Windows NT th at provides deskto p-to-gatewa y secu rity withi n a LAN or across any WAN.

Because all VPN devices operate at the network layer, the VPN Client is completely transparent to users and works with any application. With the VPN Client, users ca n dial in to any Internet service provider (ISP) and create a secure channel back to your network, which eliminates the need for expensive dial-in equipment and toll-charges.

The VPN suite supports the use of secure tokens. These tokens are a tamper-resistant PCMCIA card designed to meet FIPS-1401 level 2 criteria. The token stores and performs all public key operations while keeping private keys secure from attacks.

The VPN devices are designed to grow with your network. If you only have a few sites, you can operate them wi th only a few VPN devices. As your network grows, you can add additional VPN devices, remote clients, and central management at any time. These components are illustrated next in a typical network configuration.

Hewlett-Packard Company Virtual Private Networking Concepts Guide

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HP VPN Concepts Guide Overview

Branch or Supplier's Office

Related Related Information

Information

InformationInformation

Office PCs

VPN Device

Office PCs

Existing

Server

Branch or Supplier's Office

VPN Device

Firewall

Figu r e : Typical Netw ork Configura t i on

Figu r e : Typical Netw ork Configura t i onFigu r e : Typical Netw ork Configura t i on

(Mail, Web)

Router

VPN ManagerServers

Internet

Operational Overview (page 1-5) TCP/IP Basics Overview (page 1-6)

Office PCs

Servers

(Mail, Web)

Router

Laptop Computers

With modems

Router

Internet Sites

VPN Client

HP VPN Concepts Guide Overview (page1-1)

1-4 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Related Related Information

Information

InformationInformation

Operational Overview

Operational OverviewOperational Overview

The VPN devices fit into typical network configurations in various locations. VPN devices often sit at the gateway between LANs and WANs. All data into and out of a protected LAN passes through the VPN device for proces sing. The VPN Client software package runs on PCs either directly connected to a LAN or remotely located and connect to the WAN by means of a dial-up connection.

VPN devic es are configu red by using the VPN Ma nager (which runs on a Windows 95 or Win dows NT workstat ion), a command line interface from a console, or through a Telnet sess ion from a computer on the VPN's trusted netw or k.

HP VPN Conce pts Guide Overview (page1-1) TCP/IP Basics Overview (page 1-6)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

1-5

HP VPN Concepts Guide Overview

TCP/IP Basics Over view

TCP/IP Basics Over viewTCP/IP Basics Over view

The VPN devices operate on Transmission Control Protocol/ Internet Protocol (TCP/IP) ne tw orks . TCP/IP is the foundation of the Internet. To fully appreciate how the VPN devices work, you need to understand some basic TCP/IP terms.

Packe ts an d

Packe ts an d Packe ts an d Packe t H e ade rs

Packe t H e ade rs

Packe t H e ade rsPack e t H e ade rs

Communications in a TCP/IP network are broken into small chunks called packets. The typical maximum packet size carried over TCP/IP networks is 1500 bytes. Each packet carries s o me user data called payl oad. Th e payl oad could be part of an e- mail message or a Web page. Every packet also has some control information that i ndicates w here the packet origi nated, where it is going, and what application should receive it when it arrives. This information is referred to as the packet header. A simplified packet example is shown in the following diagram.

Figure:

Figure: Simple Packet Diagram

Figure: Figure:

Simple Packet Diagram

Simple Packet DiagramSimple Packet Diagram

IP Address

IP Address All devices on a TCP/IP network must have at least one address

IP AddressIP Address

called an IP address. This address uniquely identifi es the device on a network (actually in the entire world). For example, "Test Company's" Web server has the following IP address:

205.250.128.2.

There are some reserved IP addresses that are never assigned, which are called unroutable. Anyo ne can use these add resses on a closed network. Well-known unroutable IP addresses start with 10.x.x.x and 192. 168. x.x, w here x is an y n umb er between 1 and 254.

Subnet Mask

Subnet Mask One function of a subnet mask is to tell a device what other

Subnet MaskSubnet Mask

addresses it can directly communicate with. An example of a subnet mask is 255.255.255.0, which defines a class C subnet. Each component of the subnet mask (either 255 or 0 in the example) is called an octet. A class C subnet mask means that there are 254 addresses with which the device can directly communicate.

1-6 Hewlett-Packard Company Virtual Private Networking Concepts Guide

TCP/IP Basics Overview

For example, "Test C ompany" is assigned a full class C. This means "Test Company" can use any address betwe e n

205.250.128.1 up to 205.250.128. 254. The addresses 205.250.128.0

and 205.250.128.255 are also part of the addresses in the class C subnet, but are res erved for broadcasting and cannot be assigned to any devices on the network (often called bo undar y addresses).

If you want to break your clas s C into separate networks, y o u do this by varying the last octet of the subnet mask. If you make your subnet mask 255.255.255.128, your class C is split into 2 parts. This gives you one subnet containing the addresses from

205.250.128.1 to 205.250.128.126 and another subnet containing

205.250.128.129 to 205.250.128.254.

When you work with the full class C, there are 2 boundary addresses reser ved for broadcasts. E very subnet requires 2 addresses for broadcasts. When you split your class C into 2 parts, you must still have broadcast ad dr esses in each subnet. The first subnet uses 205.250.128.0 and 205.250.128.127 for broadcasts while the second uses 205.250.128.128 and

205.250.128.255.

When you have the full class C, there are 254 addresses you can use. Once the class C is split into two subnets, there are 126 addresses in each subnet for a total of 252 addresses.

The following values, if placed in the last octet of the subnet mask, divide a class C subnet into smaller subnets.

Decimal Value

Decimal Value Decimal Value (Binary Value)

(Binary Value)

(Binary Value)(Binary Value)

Number of Subnets

Number of SubnetsNumber of Subnets

255 (1111-1111) 254 1 254 (1111-1110) 128 0 252 (1111-1100) 64 2 248 (1111-1000) 32 6 240 (1111-0000) 16 14 224 (1110-0000) 8 30

Hewlett-Packard Company Virtual Private Networking Concepts Guide

Number of

Number of Number of Addresses in Each

Addresses in Each

Addresses in Each Addresses in Each Subnet

Subnet

SubnetSubnet

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HP VPN Concepts Guide Overview

192 (1100-0000) 4 62 128 (1000-0000) 2 126 0 (0000-0000) 1 254

Note:

Note: If you d ivide your class C into more and mor e subnets, the

Note: Note: number of available addresses becomes smaller and smaller.

Routing Table

Routing Table When a device creates a packet for transmission, it looks at the

Routing TableRouting Table

destina t ion IP address. If the address is on t he same su bn et as the device (as defined by the subnet mask), the device looks for the address on its LAN. If the destination device responds, the originating device transmits the packet directly to the destination. However, if the destination device is not found locally, the originating de vice must decide what to do with the packet.

The rules upon which the device bases the decision are called routes, which are stored in a routing table. The routing table maps network addresses to gateways. B asi cally, it tells the device that if it has a packet dest ined for a certain network, the packet should be sent to a specific gateway. The gateway can be any device such as a router or a switch that can send the packet out of the local subnet.

Static routes are entries in the routing table that do not change. They are often defined on routers and switches when network topologies become complex and the network administrator wants to force packets to go in a certain k nown direc t ion (that is, through a specif ic gateway ). Dynamic rou tes are e ntries in the routing table that may change over time. This type of route is usually added automatically, based on some network routing protocol.

Default Gateway

Default Gateway The routing table usually has a route of last resort known as a

Default GatewayDefault Gateway

default gateway. The default gateway is where the originating device sends any packet for which it has no specific rule in its routing table. Most desktop computers do not have static routes added to them and therefore rely on the default gateway being set to be able to communicate outside t heir lo cal subnet. This

1-8 Hewlett-Packard Company Virtual Private Networking Concepts Guide

TCP/IP Basics Overview

implies that the default gateway's IP address must be on the same subnet as the originating device. Computers can directly communicate only wit h devices on their local subnet (as defined by their IP address and subnet mask).

Default gateways are what make the Internet work. When a packet is created by a desktop computer destined for an address on the Internet, the desktop computer often sends the packet to its default gateway. The default gateway is often an edge router connecting the LAN (on which the desktop computer is sitting) to the Internet. The edge router probably does not have specific routes telling it what to do with the packet. The edge router, therefore, most l ikely sends the pack et off to its def ault gateway. This cycle occurs until th e packet arrives at a devi ce that knows where to find the destination address.

Application Port

Application Port When a computer (or an y network device) receives a packet, the

Application PortApplication Port

computer decides what to do with it. The computer may have many different program s running simultane ously (for example, a mail server and a Web server). Each program expecting to receive or send packets from or to a network opens something called a socket. If you look at an IP address as a street address that identifies a building, then an open socket can be compared to a room number within the building. The number given to a socket is called an applica t i o n port number.

Each packet contains both a source application port and destination application po rt in it s hea der. The destination application port number is used by the receiving computer to decide which pro gram should be given the payload of the packet for final proce ssi ng.

Many application port numbers are standard. Some common numbers ar e port 80, which is associated wit h http (www ) packets; port 25, wh ich is associated with SMTP mail; port 110 (POP3 mail); port 23 (Telnet); and port 21 (FTP). Therefore, when Web servers start, they usually connect to port 80 and listen for requests to come in. Note that a Web server can be configured to listen on another port, but most follow the standard.

Packets with the source and destination applic ati o n ports set to 2233 are encrypted with a HP VPN device.

Hewlett-Packard Company Virtual Private Networking Concepts Guide

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HP VPN Concepts Guide Overview

Related Related Information

Information

InformationInformation

HP VPN Concepts Guide Overview (page1-1) Operational Overview (page 1-5)

The Template Concept

1-10 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Cryptographic Systems and Encryption Terminology

Cryptographic Systems and Encryption TerminologyCryptographic Systems and Encryption Terminology

Cryptographic Systems and Encryption Terminology Overview . . . . . . . . . . . . . . . . . 2-1

Symmetric Cryptographic Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

Data Encryption Standard (DES) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Triple Pass DES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

3DES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7

Outer Cipher Block Chaining (CBC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Asymmetric Cryptographic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

Symmetric Vs. Asymmetric Cryptography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

Diffie-Hellman Session Key Exchange. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-11

Key Space and Brute Force Attacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13

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Hewlett-Packar d Company Virtual Pri vate Networking Concepts Guide

Cryptographic Systems and Encryption Terminology

Cryptographic Systems and E ncryption

Cryptographic Systems and E ncryption Cryptographic Systems and E ncryption

Terminology Overview

Terminology OverviewTerminology Overview

When Julius Caesar sent messages to his trusted acquaintances, he did not trust the mes sengers. So he replaced every A with a D, every B with an E, and so on throughout the alphabet. This was the beginning of cryptography. Only those who knew the "shift by 3" rule could decipher his messages.

A cryptographic system is a method of disguising messages so that only certain people can see through the disguise. Cryptography is the art of creating and using cryptographic systems.

The original message is called a plaintext. The disguise d message is called ciphertext. Encryption means any procedure to conver t plaintext into ciphertext. Decryption means any procedure to convert ciphertext into plaintext.

The term cryptographic system refers to a set of encryption and decryption algorith ms. The algorithms are labeled and the labels are called keys. For example, Caesar probably used "shift by n" encryption for several different values of n. It is natural to say that n is the key here.

Two general types of cryptograp hic systems exist: symmetric cryptographic systems and asymmetric cryptographic systems.

Encryption

Encryption Encryption is a mathematical operation that transforms data

EncryptionEncryption

from cle a r te xt to cipher text. Us ually the math ema tical operation requires that a key be supplied along with the clear text.

Encryption, therefore, can be expressed as t he formula:

Cipher Text = f ( Clear Text , Ke )

In this formula, f represents some mathematical operati on or algorithm and Ke represents a key.

Decryption is the opposite of encryption, a mathematical operation that transforms cipher text to clear text. Decryption usually requires a key and can be expressed as the formula:

Clear Text = g ( Cipher Text , Kd )

Hewlett-Packard Company Virtual Private Networking Concepts Guide 2-1

Cryptographic Systems and Encryption Terminology

In this formula, g represents a mathematical operation, which "undoe s" the s t eps per formed b y the algorithm f, and Kd represents a key.

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Symmetric Cryptographic Systems (page 2-3) Asymmetric Cryptographic Systems (page 2-9) Symmetric Vs. Asymmetric Cryptography (page 2-10)

2-2 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Symmetric Cryptographic Systems

Symmetric Cryptographic Sys tems

Symmetric Cryptographic Sys temsSymmetr ic Cr yptographic Sys tems

A very simple encryption algorithm involves shifting the letters of the alphabet to the right by some offset. For example if you had the clear text "AT" and decided to encrypt this data by shifting each letter 3 letters to the right, you would end up with DW. In this example, the clear text is AT, the key is 3, the algorithm is "shift K letters to the right," and the cipher text i s DW. Your encryption formula would look like this:

DW = shift-right ( AT , 3 )

Of course, decryption in this case involves shifting the letters of the cipher text to the left by the same offset used when the data was encrypted. Therefore, your decryption formula would look like this:

AT = shift-left ( DW , 3 )

Note that the key used to encrypt the data is the same key used to decrypt the data.

Ke = Kd

This algorithm is therefore referred to as symmetric. In this case, the person encrypting the data and the person decrypting the data must both know the same key. The strength of the system relies on the key being kept secret. Symmetric cryptography is therefore often referred to as secret key cryptography.

A real world metaphor for symmetric cryptography is a lock box with a single lock. To safely transfer an object from one person to another, the first person opens the box with a key, puts the object in the box, and then locks the box. The second person needs only a copy of the key, and can then open the box and retrieve the object.

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Hewlett-Packard Company Virtual Private Networking Concepts Guide

Data Encryption Standard (DES) (page 2-4) Triple Pass DES (page 2-5) 3DES (page 2-7)

2-3

Cryptographic Systems and Encryption Terminology

Data Encryption Standard (DES)

Data Encryption Standard (DES)Data Encryption Standard (DES)

The Data Encryption Standard (DES) is a well-known and thoroughly tested cryptographic system. The DES algorithm is a very complex symmetric algorithm that specifies that data be encrypted in 64-bit b lo cks . A 64-bit block of clear text goes into the algorithm al ong with a 56-bit ke y. The resul t is a 64-b it block of cipher text. Since the key size is fixed at 56 bits, the number of keys available (the key space) is 256 different keys (about 72,000,000,000,000,000 keys). This is a huge increase over the size of the key space in simple cryptographic systems.

A recent report by a group of scientists from AT&T Research, Sun Microsystems, the MIT Laboratory for Computer Science, the San Diego Supercomputer Center, Bell Northern Research and others, entitled "Minimal Key Lengths for Symmetric Ciphers to Provi de Adequate Commercial S ecurity (Blaze, Dif fie, Rivest, Schneier, Shimomura, Thompson and Wiener)" found that a pedestrian hacker with US $400 to spend requires about 38 years of effort to decode data encrypted with DES with its large key space. Unfortunately, they also determined that a large organization with US $300 million to spend could crack a 56-bit key space in about 12 seconds, using brute force techniques. They estimate that a 90-bit key protects data for about 20 years in the face of expected advances in computing power.

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2-4 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Triple Pass DES (page 2-5) 3DES (page 2-7) Outer Cipher Block Chaining (CBC) (page 2-8)

Triple Pass DES

Triple P ass DES

Triple P ass DESTriple P ass DES

Triple Pass DES is a cryptographic system that uses multiple passes of the DES algorithm to increase the effective key space available to the system. In triple pass DES, the clear text data is first encrypted with a 56-bit key. The resul ting cipher text is th en decrypted with a different key. Decrypting cipher text w i th the wrong key will result in unreadable data. Finally the unread able data is encrypted again wi th the first key. This implementatio n of triple pass DES is known as EDE (for Encr ypt, Decrypt, Encrypt) and the technique increases the effective key len gth from 56 bits to 112 bits. Note that 90-bit keys should protect encrypted data for about 20 years.

Go back to the simple Symmetric Cryptographic Systems (page 2-3) to illustrate the EDE technique. Assuming that the

clear text is AT

1. Encrypt with the key set to 3.

DW = shift-right( AT , K1 = 3 )

2. Decrypt the result DW with a different key (for example, 5 ).

YR = shift-left( DW , K2 = 5 )

Note that the result in this case is not the original clear text. Now encrypt the result YR wi th the key used in the first step.

BU = shift-right( YR , K1 = 3 )

the following steps are involved:

The final cipher text is BU. When this cipher text is received, the decoding process must be performed in reverse (DED). The decoder must know the 2 keys (K1 = 3 and K2 = 5) and then make 3 passes:

1. Decrypt with the key set to 3.

YR = shift-left( BU , K1 = 3 )

2. Encrypt with the key set to 5.

DW = shift-right( YR , K2 = 5 )

3. Decrypt with the key set to 3.

AT = shift-left( DW , K1 = 3 )

The steps for both the triple pass DES technique and the 3DES technique are illustrated with the simple symmetric cryptographic system in the following table.

Hewlett-Packard Company Virtual Private Networking Concepts Guide

2-5

Cryptographic Systems and Encryption Terminology

Algorithm

AlgorithmAlgorithm

Clear

Clear Clear Text

Text

TextText

After

After After First

First

First First Encrypt

Encrypt

Encrypt Encrypt EEEE

After

After After First

First

First First Decrypt

Decrypt

Decrypt Decrypt DDDD

After

After After Second

Second

Second Second Encrypt

Encrypt

Encrypt Encrypt EEEE

Related Related Information

Information

InformationInformation

Triple Pass DES (Key Space = 2*26

AT K1 = 3

=52) 3DES

(Key Space = 3*26

AT K1 = 3

=78)

3DES (page 2-7) Data Encryption Standard (DES) (page 2-4) Outer Cipher Block Chaining (CBC) (page 2-8)

K2 = 5 YR

K1 = 3 BU

K3 = 4 CV

2-6 Hewlett-Packard Company Virtual Private Networking Concepts Guide

3DES

3DES3DES

3DES is a symmetric cryptographic system that uses multiple passes of the DES algorithm to increase the effective key space available to the system even further than triple pas s DES. Use the same EDE technique as in Triple Pass DES (page 2-5), except that 3 different keys are u sed. Therefore, in pass 3 of Triple Pass DES, you would sel ect a third key (K3 = 4), which increases the effective key length from 56 bits for simple DES to 168 bits for 3DES.

The steps for both the triple pass DES technique and the 3DES technique are illustrated with the simple symmetric cryptographic system in the following table.

After

Algorithm

AlgorithmAlgorithm

Clear

Clear Clear Text

Text

TextText

After

After After First

First

First First Encrypt

Encrypt

Encrypt Encrypt EEEE

After

After After First

First

First First Decrypt

Decrypt

Decrypt Decrypt DDDD

3DES

After

After After Second

Second

Second Second Encrypt

Encrypt

Encrypt Encrypt EEEE

Related Related Information

Information

InformationInformation

Triple Pass DES (Key Space = 2*26

AT K1 = 3

=52) 3DES

(Key Space = 3*26

AT K1 = 3

=78)

Data Encryption Standard (DES) (page 2-4) Outer Cipher Block Chaining (CBC) (page 2-8)

K2 = 5 YR

K1 = 3 BU

K3 = 4 CV

Hewlett-Packard Company Virtual Private Networking Concepts Guide

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Cryptographic Systems and Encryption Terminology

Outer Cipher Block Chaining (CBC)

Outer Cipher Block Chaining (CBC)Outer Cipher Block Chaining (CBC)

Outer Cipher Block Chain ing or outer-CBC is a techni que used to further strengthen the DES, triple pass DES, and 3DES algorithms. This technique involves injecting random spoiler data into the encryption algo rithm so that identical blocks of clear text d oes not resul t in the s ame cipher text even if the same key is used repeatedly. Therefore, if the clear text s tri ng " A T" is encrypted a thousand times with the same key, the resulting cipher text would be different each time. This is important since most file structures and application protocols use identical header information.

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Data Encryption Standard (DES) (page 2-4) Triple Pass DES (page 2-5) 3DES (page 2-7)

2-8 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Asymmetric Cryptographic Systems

Asymmetric Cryptographic SystemsAsymmetric Cryptographic Systems

Some algorithms do not use the same key to encrypt and d ecrypt. These algorithms are referred to as asymmetric, are usually complex, and often rely on the properties of very large prime numbers. A simple asymmetric algorithm, similar to the symmetric example, uses the same formula for encryption:

DW = shift-right ( AT , 3 )

In the symmetric examp le the encryption was "undone" usin g the mathematical operation of "shift-left." If you change the decryption operatio n to "shift- righ t," you need a di ffere n t key to arrive back at the clear text:

AT = shift-right ( DW , -3 )

Note that the key used to decrypt the cipher text in this case is different from the key used to encrypt th e clear text. T he keys, however, are related. The relationship between the keys in the simple asymmetric algorithm can be expressed:

Ke = -1 * Kd

When asymmetric cryptography is used, the person doing the encrypting does not need to know the same key as the person doing the decrypting.

Asymmetric cryptography is often referred to as a public key cryptography. The public and private keys used in asymmetric cryptography are sometimes called key pairs, and are always related through some mathematical operation.

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Hewlett-Packard Company Virtual Private Networking Concepts Guide

Symmetric Cryptographic Systems (page 2-3) Symmetric Vs. Asymmetric Cryptography (page 2-10) Key Space and Brute Force Attacks (page 2-13)

2-9

Cryptographic Systems and Encryption Terminology

Symmetric Vs. Asymmetr ic Cryptogra phy

Symmetric Vs. Asymmetr ic Cryptogra phySymmetric Vs. Asymmetr ic Cryptogra phy

Symmetric and asymmetric cryp tograph y have some significant differences. Symmetric cryptography tends to be fast compared to asymmetric cryptography. Therefore, symmetric algorithms are often used when large quantities of data need to be exchanged and the 2 parties are known to each other. Conversely, a symm et ric algorithms are used when small quantities of data need to be exchanged or the 2 parties are not known to each other.

Asymm et r ic cryptogr aphy is often used during authentication processes. Another significant di fference between the 2 types of cryptographic systems is the length of the keys required by the algorithms. The keys used in symmetric algorithms are usually much smaller than those used in asymmetric algorithms, as described in the following table.

Speed Fast Slow

Symmetric

Symmetric Asymmetric

SymmetricSymmetric

Asymmetric

AsymmetricAsymmetric

Key size Relatively small Extremely large Key usage Shared secret Public/private Usual usage Bulk data transfer Authentication Examples DES, Triple Pass

DES, 3DES, rc4

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2-10 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Asymmetric Cryptographic Systems (page 2-9) Symmetric Cryptographic Systems (page 2-3) Key Space and Brute Force Attacks (page 2-13)

RSA, PGP

Diffie-Hell man Session Key Exchange

Diffie-Hellman Session K ey Exchange

Diffie-Hellman Session K ey ExchangeDiffie-Hellman Session K ey Exchange

The Diffie-Hellman key exchange protocol is based on an asymmetric algorithm. In asymmetric cryptographic systems, the key used to encrypt data is different from the key used to decrypt it. The key used to encrypt the data is usually referred to as a public key, while the key used to decrypt the data is called the private key, and the public key is derived from the private key. The length of the public and private keys can be 512 bits, 1024 bits, or 2048 bits.

The problem of key exchange between VPN devices is solved using a protocol known as the Diffie-Hellman key exchange protocol. This protocol must be followed whenever two VPN devices first begin to communicate, or when a session key expires. The strength of this protocol is that it allows the two devices to negotiate or deci de on a common session key with out ever exchanging the key.

In general, when two devices exchange some data using an asymmetric cryptographic system, each device first requests the public key of the other device. They then use the public key of the other device to encrypt the data. When the other device receives the data, it can then use its private key to decrypt the data. As the name suggests, public keys are not secret and are made known to any device that requests them. Private keys, however, should never be revealed or distributed.

The Diffie-Hellman protocol specifies that the two devices negotiating a common session key should each select half of a session key. They must also each derive some parameters that can be used to calculate the same half-session key. It is these parameters that are exchanged using the public/private key technique. Once the parameters are exchanged, then the secon d half of the session key can be calculated.

Notice that the session keys are never actually exchanged. The parameters for calculating half a session key are sent. To derive the full session k ey, both packets must be trapped and then broken. The effort required to break keys with lengths of 512, 1024, or 2048 bits makes this attack impractical.

The vulnerability of this type of key exchange protocol is the public key exchange.

Hewlett-Packard Company Virtual Private Networking Concepts Guide

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Cryptographic Systems and Encryption Terminology

Crypto Perio d

Crypto Perio d A crypto period defines how long a session key is actually used.

Crypto Perio dCrypto Perio d

Key lifetimes (crypto-periods) affect encryption strength because the longer the same session key is used the greater the chance that it is compromised. Additionally, the more data that is secured with a given key, the greater the loss if the key is compromised.

Long crypto-periods (key lives) also provide more ammunition for an adversary to break the key since the adversary potentially has access to significantly more data to work with. Finally, the longer a key is in use, the greater the temptation to break the keys since breaking the key provides the adversary with access to significantly more valuable data.

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Triple Pass DES (page 2-5) 3DES (page 2-7) Packet Keys (page 3-8)

2-12 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Key Space and Brute Force Attacks

Key Space and Brute Force AttacksKey Space and Brute Force Attacks

Before reading this section, review Symmet ric C r yptographic Systems (page 2-3) and Asymmetric Cryptographic Systems (page 2-9).

Key Space

Key Space In the simple cryptographic systems, up to 26 different possible

Key SpaceKey Space

keys can be selected. The keys availa ble range from 1 to 26 since there are 26 letters in the alphabet. If 27 is used as your key, it would produce the same cipher text as if 1 was selected for your key. Therefore, your key space contains exactly 26 keys.

The longer the key length, the more possible combinations a potential code-breaker would have to test. The following table shows the number of possibilities for common key length (Source: FreeMarket.Net: Policy Spotlight, October -Nov ember

1997).

Key Length

Key Length Possible Keys

Key LengthKey Length

40 bits 1,099,511,627,776

Possible Keys

Possible KeysPossible Keys

56 bits 72,057,594,037,927,900 90 bits 1,237,940,039,285,380,000,000,000,000 128 bits 340,282,366,920,938,000,000,000,000,000,000,000,000

Brut e F or ce

Brut e F or ce Brut e F or ce Attacks

Attacks

AttacksAttacks

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Hewlett-Packard Company Virtual Private Networking Concepts Guide

A brute force attack captures some cipher text and then tries all 26 different possible keys. Given enough cipher text, a brute force attack could be quite effective. Obviously, if you can increase the number of different keys available, brute force attacks become correspondingly more difficult or time consuming. The trick is to find an algorithm that allows for an extremely large number of keys. The higher the key space, the more difficult the encryption is to break.

Symmetric Cryptographic Systems (page 2-3) Asymmetric Cryptographic Systems (page 2-9)

2-13

Cryptographic Systems and Encryption Terminology

Symmetric Vs. Asymmetric Cryptography (page 2-10)

2-14 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Encapsulation and Packet Handling

Encapsulation and Packet HandlingEncapsulation and Packet Handling

Encapsulation Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Secure Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

ESP Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

SST Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6

Packet Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-7

Packet Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-8

E nn

Pa aa

Ha aa

Hewlett-Packard Company Virtual Private Networking Concepts Guide

an HH

ac PP

nc E

Hewlett-Packar d Company Virtual Pri vate Networking Concepts Guide

Related Related Information

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Encapsulation an d Packet Handling

Encapsulation Overview

Encapsulation OverviewEncapsulation Overview

There are two types of encapsulation available with HP VPN products. The first is Shiva Smart Tunneling (SST) encapsulation. The secon d, called Encapsulating Security Payload (ESP) enc apsulation, is an emerging standard as d efined by IPSec. ESP (both 32- or 64-bit vers ions) shoul d be used wh en you communicate with another non–HP VPN device (such as a firewall or router) that has implemented the ESP portion of the IPSec standard.

Encapsulation works in the following manner: when a packet is encrypted, a brand new packet is created. This new packet contains the entire ori ginal packet (inclu ding the header), which has been encrypted, a new header, and some information required by the device that finally decrypts the packet. The original packet is said to be encapsulated.

Secure Profiles (page 3-2) ESP Encapsulation (page 3-4) SST Encapsulation (page 3-6)

Hewlett-Packard Company Virtual Private Networking Concepts Guide 3-1

Encapsulation and Packet Handling

Secure Profiles

Secure ProfilesSecure Profiles

Secure profiles are used to define how packets are encrypted when passing t hrough a tunnel an d how the estab lishment of the communication session is authenticated. Secure profiles must contain the following information to be complete.

Name

Name The name is a descripti ve alphanum eric string used to referen ce

NameName

the secure profile when it is applied to a tunnel. Although no naming convention is imposed, it is wise to define one prior to creating your profiles. Suggested naming conventions indicate either the intended use of th e profile (for example , Interoffice or Dial-up user), the relative strength of the profile (for example, Strict or Ver y Strict), or the c ontents of t he p rofile (fo r exampl e, ESP-3DES-K1024-C12HRS for ESP encapsulation, 3DES, authentication key wit h 1024-bit public keys, and a crypto period of 12 hours).

Algorithm

Algorithm The algorithm can be set to Data Encryption Standard (DES),

AlgorithmAlgorithm

Triple Pass DES, 3D ES, or 40-bi t DES for ESPv2 ( IPSec) tunnels.

Keepalive

Keepalive The keepalive interval can be set between 1 and 299 seconds or

KeepaliveKeepalive

disabled (0). T he keepalive feature is u sually specified in p rofiles that are ap pl ied to rem o t e links a nd has two main uses . The first is to ensure that the link status displayed on the remote VPN device accurately r eflects the status o f the tunn el. The second is to ensure that other VPN device s can sense that a remote device has dropped its connection and therefore the tunnel must be renegotiated. Note that setting the keepalive to a small value causes many keepalive packets to be sent. This may impact the responsiveness of the remo te connec tion.

Timeout

Timeout The keepalive timeout can be set between 2 and 300 seconds.

TimeoutTimeout

This specifies how long a VPN device should wait for a packet from an opposing VPN device before declaring the session terminated and attempting to renegotiate the tunnel. If you specify a timeout on one end of a tunnel, you must specify a keepalive on the other end of the tunnel.

3-2 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Secure Profiles

Encapsulation

Encapsulation The encapsulation can be set to either Shiva Smart Tunneling

EncapsulationEncapsulation

(SST) Encapsulation or to Encapsulating Security Payload (ESP) Encapsulation. ESP is the security po rtion of th e IPSec stan dard. SST encapsulation is recommended for data exchange between VPN devices, as it is stronger than ESP encapsulation.

ESP (either version) should be used when you communicate with another non–HP VPN device (such as a firewall or router) that ha s impleme nt e d the ESP po rtion of the IPSe c st andard.

The E SP implementation in all HP VPN devices is tunnel mod e. However, you can use transport mode by selecting ESP (either version), setting the ESP authenticatio n to none, and selecti ng a value for the Authentication Header (AH). Transport mode encrypts only the payload.

Related Related Information

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SST Encapsulation (page 3-6) ESP Encapsulation (page 3-4) Encapsulation Overview (page 3-1)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

3-3

Encapsulation and Packet Handling

ESP Encapsula tion

ESP Encapsula tionESP Encapsula tion

When the encapsulat ion is set to Encapsulating Secu rity Payload (ESP), tun nel mode, t he follo wing in formation m ust be specified to fully define the security profile.

IV Length

IV Length IV Length (Encapsulation)

(Encapsulation)

(Encapsulation)(Encapsulation)

Authentication

Authentication Authentication Header

Header

HeaderHeader

The iv (initialization vector) length must be set to either 32 bits or 64 bits. This value is used during the outer cipher block chainin g oper ation to e n sur e t hat the same packet encrypte d multiple times wil l not generate the same cipher text. Bot h 32-bit and 64-bit iv's offer the same level of randomness, but 32- bit iv's use more system CPU and less bandwidth while 64-bit iv's use less CPU and more bandwidth. The actual difference in CPU usage and bandwidth usage is very small, and the industry tendency is to use a 64-bit iv length.

This value can be set to keyed MD5, H MA C MD5 , keyed SHA 1, HMAC SHA1, or none. An authentication header (AH) is added to an ESP encapsulated packet (either version) to ensure that the packet is not altered during transmissi on, and is constructed by hashing the entire encrypted packet.

Setting the AH type specifies which algorithm to use for hashing. The SHA1 hashing a lgorithm is slightly more secure t han MD5, but also slightly slower. MD5 adds 16 bytes of overhead to each packet, while SHA1 adds 20 bytes overhead. HMAC MD5 and SHA1 are slightly more secure than keyed MD5 and SHA1 respe c t ivel y. Onc e again, the differences are marginal.

Ensure that the device on the other end (the firewall or router) conforms to the IPSec standards to ensure its interoperability with a VPN device.

AH Key Length

AH Key Length If you select either keyed MD5 or keyed SHA1 for your

AH Key LengthAH Key Length

authentication header t ype, the value must be s et bet ween 0 and 55 bytes. If you select either HMAC MD5 or HMAC SHA1 for your authentication header (AH) type , the value must be set between 0 and 64 bytes. This value specifies the length of the key to be used when hashing the packet to produce the authentication header. The longer the key, the more secure the authentication, but the more time-consuming to manually enter.

3-4 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Related Related Information

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ESP Encapsulation

SST Encapsulation (page 3-6) Packet Handling (page 3-7) Packet Keys (page 3-8)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

3-5

Encapsulation and Packet Handling

SST Encapsulation

SST EncapsulationSST Encapsulation

When the encapsulation is set to Shiva Smart Tunneling (SST), the following information must be specified to fully define the security profile.

Authentication

Authentication Authentication Method

Method

MethodMethod

Public Key

Public Key Public Key Length

Length

LengthLength

Crypto Period

Crypto Period Crypto Period Length

Length

LengthLength

The authentication method must be set to either certificates, challenge phrases, SecurID, or RADIUS. Challenge phrases are often referred to as authentication keys. Sometimes challenge phrases are called passwords, but th is is not a good synonym.

The public key length must be set to 512 bits, 1024 bits, or 2048 bits. Note that public keys are used during the authentication and session key exchange processes. The longer the public key length, the more secure the session negotiation will be.

The crypto period length defines how long a session key will be used. The default value for the crypto period is 1 month, although it can be set to as low as 3 hours. Given that a packet encrypted with a 90-bit key will require about 20 years of effort by a well-funded dedicated adversary to crack, it is often sufficient to use the default value for crypto period length.

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3-6 Hewlett-Packard Company Virtual Private Networking Concepts Guide

ESP Encapsulation (page 3-4) Packet Handling (page 3-7) Packet Keys (page 3-8)

Packet Handling

Packet HandlingPacket Handling

When a computer or network device communicates over a network (either a LAN or a WAN such as the Internet), the devices all perform similar functions. The application program (for example, a mail program) formulates a message, which is then passed to a set of functions collectively known as the TCP/ IP stack. The TCP/IP stack looks at the message to determine if it needs to be sent out of the computer and then breaks the message into small packets and adds some header infor mat ion to each packet.

The header information includes the following information:

• The destination addre ss o f the packet (the IP address of the mail server)

• The application port on the destination computer (for example, port 25 indicates that a SMTP mail server should be the application listening at the destination address)

• The source address of the sender (the IP address of the computer where the e-mail client is running)

• The application port that the sending machine used (usually randomly assigned)

• The protocol used (for SMTP mail, the protocol is TCP)

The maximum size of these packets including the header is usually 1500 bytes. Therefore, if your e-mail message is longer than 1500 bytes (1500 characters), it will be broken into several packets before being sent to the network layer and f in ally bein g transmitted onto the network. A si mplified packet as released by the TCP/IP stack is shown next.

DestIPSrc

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Hewlett-Packard Company Virtual Private Networking Concepts Guide

Packet Keys (page 3-8) Encapsulation Overview (page 3-1)

Dest

Port

Figure: Simplified Packet

Figure: Simplified PacketFigure: Simplified Packet

Src

Port

Prot Payload Data

3-7

Encapsulation and Packet Handling

Packet Keys

Packet KeysPacket Keys

The key (or keys in the case of trip le pass DE S or 3DES) use d to encrypt a packet in SST encapsulation is called a packet key. A new packet key is randomly generated for every packet. This step, along with the ou ter-CBC technique, ensures that no matter how many ident ical original pa ckets are sent, t he new encrypted packets are significan tly different each t ime. A simplified packet as released by a VPN device is shown next.

Dest Enc IP

Source and Destination ports set to 2233

Dest

Src

Port=

Enc IP

2233

Source and destination IPs set to encryptor IPs

Src Port= 2233

Protocol set to UDP

DestIPSrcIPDest

Prot= UDP

Figure:

Figure: Encrypted Packet

Figure: Figure:

Encrypted Packet

Encrypted PacketEncrypted Packet

Original packet encrypted with packet key

Src

Port

Prot Payload Data

Packet keys encrypted with session keys

Pck Keys

This new packet has many interesting features. Note that the destination and source IP addresses of the original packet are different from the destination and source IP addresses of the new packet. The new IP addresses are the IP addresses of the VPN device that encrypted the packet. In many cases, these addresses are the IP addresses of the WA N interfaces of t he VPN device that secure the communication.

In a typical network configuration, a packet traveling from the Web server at the main office to a PC on the Branch office network has the IP addresses set t o the WAN side IP addresses of the VPN devices at the gateways to these networks. The IP address of the Web server and the PC are hidden from anyone intercepting the packet and the interceptor gains no knowledge about the LANs.

Note also that the destination and source ports are both set to

2233. This application port number i nd icates only that the

packet is encrypted. The source port in the original packet would be set to port 80 to indi cate th at this i s World W i d e Web traffic. Therefore, the nature of the packet is hidden from anyone intercepting the packet.

The protocol has been modified and set to UDP. The original packet, if it was an http (www) packet, has its protocol set to

3-8 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Packet Keys

TCP and indicates to an intruder that an ackn owledgment packet is expected. Trapping acknowl edgment packets is a good way to gain some knowledge of the contents of an encrypted packet, which can be used to help break the encryption. Setting all the encrypted packet p rot o co ls to UDP rem ove s this b it of knowledge and further secures the communication.

The entire original packet is encrypted. Some other solutions only encrypt the payload data and expose a wealth of information about the nature of the packet and the source and destinati o n networks .

Finally, the packet keys are encrypted with session keys and appended to the new packet. Remember that DES, triple pass DES, and 3DES are symmetric algorithms. Therefore, both the device encrypting the packet and the device decrypting the packet must know the s ame keys. The packet ke ys, however, are randomly generated for each packet. Assuming that both the encryptor and the decryptor know the same session keys, this technique makes the encryption more secure in 2 ways. Attempts to break the packet keys are not practical since it changes with every packet. The most that can be gained is about 1400 bytes of data from an operation that will take years. The session keys are used to encrypt a very small amount of data (only the packet keys), which is random. If the session keys are changed periodically, then even this small target is moving and attacks are made more difficult. The frequency with which session keys are changed is called the crypto period.

Related Related Information

Information

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Hewlett-Packard Company Virtual Private Networking Concepts Guide

Packet Handling (page 3-7)

The Template Concept

3-9

Encapsulation and Packet Handling

3-10 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Authentication Methods

Authentication MethodsAuthentication Methods

Authentication Methods Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Certificate Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Challenge Phrase Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

SecurID Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

RADIUS Authentication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Entrust Authentication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

A uu

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Hewlett-Packar d Company Virtual Pri vate Networking Concepts Guide

Related Related Information

Information

InformationInformation

Authentication Methods

Authentication Methods Overview

Authentication Methods OverviewAuthentication Methods Overview

An authentication method defines how an HP VPN device validates the identity of another device. The identity of a device includes its n a me , its IP address, and its p u bli c k ey. Wh en the packet encapsul ation type is se t to Shiva Smart Tunneling (SST), there are five possible authentication methods:

• Certificates by means of the certificate authority

• Challenge Phrase

• SecurID

• RADIUS

• Entrust by means of the Entrust Certificate Authority

Challenge Phrase Authentication (page 4-2) SecurID Authentication (page 4-3) RADIUS Authentication (page 4-4) Entrust Authentication (page 4-5)

Hewlett-Packard Company Virtual Private Networking Concepts Guide 4-1

Authenticat ion Methods

Certificate Authentication

Certificate AuthenticationCertificate Authentication

The first thing that two VPN devices d o when they enter into a communication is to exchange their certificates. Next, they verify the authenticity of the certificates by ensuring that:

• The identifying information and the digital signature are separated.

• A new MD5 digest of the identifying information is generated.

• The digital signature is decrypted.

The result is the MD5 digest (or summary) of the identifying information that was generated by the certificate aut hority when the certificate was created.

The new MD5 digest and the digest extracted from the digital signature are then compared. If they are exactly the same, the device is sure that the certificate is valid.

Note that the certificate authority is not involved in the authentication process. Once the authentication p ro cess is complete on both sides, the two devices can then begin the session key exchange process or negotiation.

Related Related Information

Information

InformationInformation

4-2 Hewlett-Packard Company Virtual Private Networking Concepts Guide

SecurID Authentication (page 4-4) RADIUS Authentication (page 4-5) Challenge Phrase Authentication (page 4-3) Entrust Authenticat ion (page 4-6)

Related Related Information

Information

InformationInformation

Challenge Phrase Authentication

Challenge Phrase AuthenticationChallenge Phrase Authentication

Authentication using challenge phrases is very similar to authentication using certificates. The difference is that a certificate authority is not present to create and certify a certificate. Therefore, the VPN d evices must creat e a certificate for themselves. This ty pe of cert ificate is esse ntially the sa me as a certificate generated by a certificate authority except that the digital signature is encrypted with a challenge phrase rather than with the private key of the certificate authority. The implication is that when two devices attempt to authenticate each other for the first time, they must both know the challenge phrase of the other device. Therefore, the challenge phrase for a particular device must be input on the device and m ust also be input on any other device with which it needs to communicate.

SecurID Authentication (page 4-4) RADIUS Authentication (page 4-5) Entrust Authenticat ion (page 4-6)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

4-3

Authenticat ion Methods

Related Related Information

Information

InformationInformation

SecurID Authentication

SecurID AuthenticationSecurID Authentication

SecurID is an authentication method licensed from Security Dynam ics that the HP VPN Suit e supp orts . Sec urID is used on ly between a VPN Client and a VPN device. As with certificates, SecurID enlists a trusted third party to positively identify a device. Here, the third party is an ACE/Server.

Unlike a certificate authority server, however, the ACE/Server must be availabl e whenever a secu re tunnel is being est ablished. Whenever a remote user attempts to establish a secure tunnel with a VPN device , the user mu st provide a us er name and a t imedepend ent pass code that the VPN device then verifies with the ACE/Server before allowing the tunnel to be established. Typically, the pass c ode is composed o f two parts: a PIN nu mber and a SecurID access code.

For further information on using SecurID, consult Security Dynamics' SecurID docu m entat ion.

RADIUS Authentication (page 4-5) Challenge Phrase Authentication (page 4-3) Entrust Authenticat ion (page 4-6)

4-4 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Related Related Information

Information

InformationInformation

RADIUS Authentication

RADIUS AuthenticationRADIUS Authentication

The RADIUS authentication method is very similar to the SecurID authentication method in that it uses a trusted third party to authenticate tunnels between VPN Clients and VPN devices. The trusted third party is a RADIUS Authentication Server. When a VPN Client attempts to establish a tunnel wit h a VPN device, the VPN device asks the VPN Client to provide its RADIUS user name and password . The VPN device then uses its own secret key to co ntact th e RADIUS Aut hentic at ion Server to verify the VPN Client's identity.

There is a second type of RADIUS server supported by the HP VPN suite: a RADIUS Accounting Server. Th is server kee ps track of those remote u sers who have e stablished co nnections to VPN devices, and the amount of time each connection is maintained. It is not necessary to have a RADIUS Accounting Server to use the RADIUS method of a uthentication.

Challenge Phrase Authentication (page 4-3) SecurID Authentication (page 4-4) Entrust Authenticat ion (page 4-6)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

4-5

Authenticat ion Methods

Related Related Information

Information

InformationInformation

Entrust Authentication

Entrust AuthenticationEntrust Authentication

Entrust authentication is an authentication method licensed from Entrust Technologies that the HP VPN suite supports. Entrust authentication is supported for tunnels made between two VPN devices (including IP Sec tunnels) and between a VPN Client and a VPN device using the Shiva Smart Tunneling (SST) protocol. Entrust enlists a trusted third party to positively identify a device using X.509 certificates and performs key and certificate functions.

The Entrust Server main tains a list of all of the public keys that have been created and also issues, revokes, recovers certificates, and maintain s a revocation list. The VPN device acts as an Entrus t client us ing Entrus t services, has i ts own certificate issued by the Certificate Authority, and updates its own revocation by means of the Certificate Authority.

SecurID Authentication (page 4-4) RADIUS Authentication (page 4-5)

The Template Concept

4-6 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Firewalls and Tunnels

Firewalls and TunnelsFirewalls and Tunnels

Firewall and Tunnels Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Firewall Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2

Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

Tunnel Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8

Site-to-Site Tunnels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-9

Single-User Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12

Multiuser Tunnels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-16

Tunnel Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-20

One-Way In Firewall Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-22

One-Way Out Firewall Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-24

Outbound Proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-26

Inbound Proxy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-28

Tunnel Termination and Firewall Rules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-31

F ii

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Hewlett-Packar d Company Virtual Pri vate Networking Concepts Guide

Firewalls and Tunnels

Firewall and Tunnels Overview

Firewalls

Firewalls Firewalls control access between a red (trusted) network and a

FirewallsFirewalls

Tunnels

Tunnels The ter m tunnel, when used in the contex t of a network and

TunnelsTunnels

Firewall and Tunnels Overview

Firewall and Tunnels OverviewFirewall and Tunnels Overview

Firewalls and tunn els are the core parts of a net work that control the flow of data packe ts in and out of a trusted and un tr us te d network.

black (untrusted) network. The black (untrusted) network is often the Internet. A VPN device can act like a firewall that can be configured to contain rules. Firewall rules determine which packets can pass through the gateway between the trusted and untrus t e d ne t w or k.

Using a firewall around a network helps to protect that network from unwanted d ata packets entering or leavi ng the network, but it has some fundamental flaws. First, the data packets can be captured as they move through the firewall connecting the networks. Data cou l d b e e xt r act ed from the packets or a new packet could take the place of the original packet. All a hacker needs to do is replace the original packet with a new packet to gain access to the destination network.

firewall solution, can be explained by the following: A tunnel acts as a means of transport for data packets. In most

cases, a tunnel en crypts the dat a packets, making them unusable should they be intercepted by an unintended user and hackers. A tunnel also transports th e packets to their destination and decrypts them, prov idi ng an overall secure means of transportation.

Related Related Information

Information

InformationInformation

Hewlett-Packard Company Virtual Private Networking Concepts Guide 5-1

Firewall Functions (page 5-2) Tunnel Types (page 5-8) Tunnel Modes (page 5-20) Tunnel Termination and Firewall Rules (page 5-31)

Firewalls and Tunnels

;

Firewall Functions

Firewall FunctionsFirewall Functions

Each VPN device has a t least two physical interf aces (that is, two Ethernet cards) . Each interfac e is assigned a color, either red or black. If both interface s have the same color, the VPN device will not perform any firewall functions between the interfaces. In this case, the VPN device becomes a router (or bridge) and an encryptor.

When two interfaces on a VPN device have different colors, packets arriving at one interface must pass through the firewall to move to the other interface.

Red Network (Private/Trusted)

VPN Device

;;;

Red Interface Black Interface

Firewall

Figure:

Figure: VPN Device as a Firewall

Figure: Figure:

Stateless

Stateless The VPN device is instructed to allow or disallow all packets

StatelessStateless

VPN Device as a Firewall

VPN Device as a FirewallVP N Device as a Firewall

Black Network (Public/Untrusted)

traveling between the red (trusted) and black (untrusted) network. The VPN device checks each packet as it arrives to ensure it is valid. I f the packet m atche s the filt er rule (shown in the following table), it passes from one interface to the other. The VPN device then immediately looks for the next incoming packet. This is called stateles s filt erin g, s in ce th e VPN device does not reme m ber that a packet pass ed throu gh a filter rule. I f a packet is considered invalid, it is simply not a llowed entry to the red (trusted) network.

5-2 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Firewall F u n c tions

Parameter

Parameter Parameter Descriptio n

Descriptio n

Descriptio nDes cr i pt ion

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

From IP address 10.1.1.193 User chris is

assigned Client IP

10.1.1.193.

From subnet ma sk 255.255.255.224 A maximum of 30

users with addresses starti ng from 10.1.1.193 are allowe d th ro ugh the firewall.

From application port

ALL The application port

used t o m a ke the HTTP (www) request i s usually unknown.

To IP address 10.1.1.2 The Web Server’s IP

address.

To subnet mask 255.255.255.255 Access Web Server

only.

To application port 80 Web servers usually

listen on this port. Action Stateful Direction Inbound The group comes

from the black

(untrusted) and

crosses to the red

(trusted). NAT No Protocol TCP HTTP is transported

by means of TCP,

not UDP.

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-3

Firewalls and Tunnels

Stateful

Stateful All other firewall rules are stateful, which means that a

StatefulStateful

communication session is established between a device inside the firewall (on the red network) and a device outside the firewall (on the black network). In this way when a device on a red (trusted) n etwork (in the case of a one-way outboun d link or outbound proxy) makes a request to a device on a black (untrusted) network that requires a response, the response is allowed back into the network.

The VPN device is also con figured to allow data pa ckets from the black (untrusted) network to establish a link with a specific IP address inside the red (trusted) network. In this case, the VPN device stores the IP address of the computer sending the data packets from the black (untrusted) net wo rk, so if the link is dropped and tries to reestabl ish, the VPN device remem bers the IP address of the computer that created the initial link. This typ e of stateful connection is known as an inbound proxy or one-way in firewall rule. The only difference between an inbound proxy and a one-way in firewall rule is the point at which a data packet is removed from encapsulation and the firewall rules are applied.

The inbound data packets from the originating device look directly for the IP addre ss of the VPN device, not the real address of the destination comput er. When the data packet arrives at the gateway, the gateway checks the validity of the packet, maintains the state of the transmission, and the packets are permitted or denied based on the stateful rules configured in the VPN device. Only if the packe t is permitted by t he firewall rule is it then routed to the destination computer according to the IP addressing information it carries.

5-4 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Firewall

Firewall F u n c tions

Red-trusted LAN

Related Related Information

Information

InformationInformation

Gate through

firewall

protected by

guard

Figure:

Figure: A Firewalled LAN

Figure: Figure:

A Firewalled LAN

A Firewalled LANA Firewalled LAN

Comm link to

untrusted network

(internet)

One-Way Out Firewall Rules (page 5-24) One-Way In Firewall Rules (page 5-22) Tunnel Types (page 5-8)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-5

Firewalls and Tunnels

Filters

FiltersFilters

Filters are used to allow or block (permit or deny) the flow of packets through the VPN de vice. The sour ce device in itiating the session can be either on the red (trusted) or the black (untrusted) su bnet. Think of a filt er as a hole through the firewall through which specified devices can communicate. Packets passing through a fil ter are no t modified in any way and no state information is maintained.

Other Network Devices on

198.53.144.xxx

IP=198.53.144.1

IP=198.53.144.2

DNS and Mail Server

Primary IP=

205.250.128.240

Figure:

Figure: Example o f a Filter

Figure: Figure:

Secondary IP=

205.250.128.21

Internet

Example of a Filter

Example of a Filter Example of a Filter

If you want a public domain name server (DNS) to execute on a machine on a red network, define a filter as described in the following table.

Parameter

Parameter Parameter Description

Description

DescriptionDescription

5-6 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

Filters

To IP address 0.0.0.0 Do not limit which

addresses can

access or be

accessed by the

DNS. To subnet 0.0.0.0 To port 53 DNS updates are

requeste d on this

port. From IP address 198.53.144.2 You allow only the

DNS machine to be

addressed on the

red (trusted)

network. From subnet 255.255.255.255 From port 53 Make DNS requests

on this port. Protocol TCP Make DNS requests

Action permit You allow access.

Related Related Information

Information

InformationInformation

Hewlett-Packard Company Virtual Private Networking Concepts Guide

Firewall and Tunnels Overview (page 5-1) Tunnel Types (page 5-8) Tunnel Termination and Firewall Rules (page 5-31)

and refreshes over

TCP, not UDP.

5-7

Firewalls and Tunnels

Tunnel Types

Tunnel TypesTunnel Types

There are three types of tunnels:

• Site-to-Site

• Single-User

• Multiuser

If two networks want to communicate and not be subject to the packets being hijacked while en route, tunnels can be established between the networks. This a ssumes, of course, th at two networks want to communicate safely and are both protected by firewalls. The tunnels can be started either inside or outside o f a firewal l. When a tunnel is started in side a firewall , then the packets entering or leaving the tunnel do not need to pass through the gateway and are not subject to the firewall rules that the gateway is configured to follow. If a tunnel is started outsid e the firewall , then p ackets ent ering or leaving the tunnel must pass through the gateway. They are then subjected to the firewall r ule s befor e passi ng t hr ou gh the gat eway .

The VPN devices impleme nt t unnels using authenticati on methods and encryption techniques. Since the traffic passing between two VPN devices is encrypted , it is as i f the data is traveling in a tunnel.

Related Related Information

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InformationInformation

5-8 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Site-to-Site Tunnels (page 5-9) Single-User Tunnels (page 5-12) Multiuser Tunnels (page 5-16)

Site-to-Site Tunnels

Site-to-Site TunnelsSite-to-Site Tunnels

A site-t o-site tunn el is define d between tw o devices wit h fixed IP addresses. A fixed IP address implies that the device is always present and the VPN device on the other end of the tunnel can initiate comm u nic ation w it h the fixed devic e . Thi s beha vior can be overridden on one end of the tunnel, if desired. A site-to-site tunnel is usually defined when the tunnel is between two networks and both ends of the tu nnel are avail able through VPN devices.

A site-to-site tunnel is fully defined with the following devices:

• IP address of the opposing VPN device

• Secure profile to be applied to the communication

• Colo r ( m ode) of the tunnel

• IP route pushing packets into the tunnel

The IP address of the opposing VPN device highlights the fact that a tunnel cannot exist without a VPN device on the other end. A secure profile defines how the establishment of the tunnel should be authenticated and how the co m m unication should be secured. The mode of the tunnel specifies where the tunnel terminates. Finally, the IP route specifies which packets should enter the tunnel.

The following exam ple illustrates a secure tunnel, wh ich secures all communication between two networks.

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-9

Firewalls and Tunnels

Other Network Devices on

10.1.1.xxx

Red IP=10.1.1.1

Black IP=

205.250.128.240

Other Network Devices on

IP=10.1.1.2

Web Server

Figure: A Secure Tunnel

Figure: A Secure TunnelFigure: A Secure Tunnel

192.168.10.xxx

Internet

IP=192.168.10.15

Web Server

Red IP=192.168.10.1

Black IP=

205.250.128.240

Tunnel Definit ion

Tunnel Definit ion Tunnel Definition Parameters

Parameters

ParametersParameters

VPN Device A

VPN Device A VPN Device B

VPN Device AVPN Device A

VPN Device B

VPN Device BVPN Device B

Opposing device 198.53.144.120 205.250.128.240 Secure profile (must

Very strict Very strict be previously defined)

Tunnel mode Red Red IP route IP route

192.168.10.0

255.255.255.0

198.53.144.120

IP rou te

10.1.1.0

255.255.255.0

205.250.128.240

Note that the tunnel has to be defined on both VPN devices. Therefore, when you specify the opposin g VPN device on device

5-10 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Related Related Information

Information

InformationInformation

Site-to-Site Tunnels

A, point at device B. Also , define the same secure profile on both VPN devices. The tunnel mode, however, can be differe nt o n each VPN device. Finally, the rou te statement s tell the VPN devices which packe ts shou ld ente r th e tu nn el.

Single-User Tunnels (page 5-12) Multiuser Tunnels (page 5-16) Tunnel Types (page 5-8)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-11

Firewalls and Tunnels

Single-User Tunnels

Single-User TunnelsSingle-User Tunnels

A single-user tunnel is defined between a fixed device and one with no fixed IP address, which implies that the device on the other end of the tunnel is not always present or may change its address. A single-user tunn el is usually defined on a VPN device when the other end of the tunnel is an HP VPN Client.

You can assign a known IP address to the remote device using network address translat io n (NAT). This address is know n as the Client I P. When a tunnel has been established with the remote device, all packets coming from the remote device will have their actual source address replaced with the Client IP address.

DestIPSrc

DestIPClientIPDest

Figure:

Figure: Network Address Trans lation

Figure: Figure:

Dest

Port

Network Address Translation

Network Address TranslationNetwork Address Translation

Src

Port

Src

Port

Prot Payload Data

Network Address Translation

Prot Payload Data

A single-user tunnel is fully defined with the following devices:

• User name of the opposing HP VPN Client

• Secure profile to be applied to the communication

• Colo r ( mode) of the tu nnel

• Client IP if NAT is being used

Identify the opposing HP VPN device by a user name instead of an IP address. The secure profile d efines how the establishmen t of the tunnel is authenticated and how the communication is secured. The mode of the tunnel specifies where the tunnel terminates. The IP route is no longer required.

Full Access

Full Access The following t able descri bes a tu nnel that allows a rem ote user

Full AccessFull Access

(called chris) full access to the red (trusted) network available through VPN devic e A , while not allowing access to the network available through VPN device B.

5-12 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Single-User Tunnels

;

Tunnel Defini t i on

Tunnel Defini t i on Tunnel Definition Parameters

Parameters

ParametersParameters

VPN Device A

VPN Device A HP VPN Client

VPN Device AVPN Device A

HP VPN Cl ient

HP VPN Cl ientHP V PN Client

Remote user name chris (the VPN’s name) Secure profile (must

be previously defined)

dial-up Accept peer

proposa l or sa me parameters as dial-

up profile Tunnel mode Red Not applicable IP route Not required Not applicable Client IP 0.0.0.0 (not

Not applicable

required)

In the previous table, user chris is given complete access to the trusted network.

Limited Access

Limited Access The following f igure shows how to use a combinatio n of a tunn el

Limited AccessLimited Access

and a firewall rule to give a remote user limited access to the trusted network.

Tunnel terminates on the Black

;;

Firewall rule allows traffic through to the Red

Figure: Source Address Change

Figure: Source Address ChangeFigure: Source Address Change

For example, to allow a remote user (called leslie) access to the Web server available through VPN device A while not allowing access to the rest of that network or to the network available

Hewlett-Packard Company Virtual Private Networking Concepts Guide

NAT

Source address changed to Client IP

5-13

Firewalls and Tunnels

through VPN device B, a tunnel is defined for the user to the black (untrusted) side of the VPN device and a firewall rule i s created to allow the traffic from the black (untrusted) network to the red (trusted) network. In this case a Client IP is used to assign the remote user a known IP address on the red (trusted) network. This address is needed in order to identif y th e remote user in the firewall rule .

Tunnel Definit ion

Tunnel Definit ion Tunnel Definition Parameters

Parameters

ParametersParameters

VPN Device A

VPN Device A VPN Device B

VPN Device AVPN Device A

VPN Device B

VPN Device BVPN D evice B

Remote user name leslie No access Secure profile (must

dialup Not applica ble be previously defined)

Tunnel mode Black Not applicable IP route Not required Not applicable Client IP 10.1.1.193 Not applicable

Firewall Rule

Firewall Rule The following table describes the firewall rule.

Firewall RuleFirewall Rule

Parameter

Parameter Parameter Description

Description

DescriptionDescription

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

From IP address 10.1.1.193 User leslie is being

assigned Client IP

10.1.1.193. From subnet mask 255.255.255.255 From application

port

ALL The appli cation po rt

used to make the HTTP (www) request is usuall y unknown.

5-14 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Single-User Tunnels

Parameter

Parameter Parameter Descriptio n

Descriptio n

Descriptio nDes cr i pt ion

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

To IP address 10.1.1.2 The Web Server’s IP

address.

To subnet mask 255.255.255.255 Access Web Server

only.

To application port 80 Web servers usually

listen on this port. Action Stateful Direction Inbound The group comes

from the black

(untrusted) n etwork

and crosses to the

red (trusted)

network. NAT No Protocol TCP HTTP is transported

Related Related Information

Information

InformationInformation

Site-to-Site Tunnels (page 5-9) Multiuser Tunnels (page 5-16) Tunnel Types (page 5-8)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

by means of TCP,

not UDP.

5-15

Firewalls and Tunnels

Multiuser Tunnels

Multiuser TunnelsMultiuser Tunnels

A multiuser tunnel is d efined between a fixed devi ce and a gr oup of rem ote us ers , whi ch impli es tha t t he dev ic es on the oth er en d of the tunn el are no t always present or may change their addresses. A mu ltiuser tunnel is usually d efined on a VPN d evice for the ease of administration, simplification of the overall configuration, a n d to limit the number of VPN Client users that can access the network through the VPN device at any given time.

Any member of the remote user group that attempts to connect through the tunnel when the preset number of other users are already connected is refused. This feature is useful for large organization s in that it allows them to prioritiz e access throug h the VPN device by groups, thereby avoiding situations where important tu nnel reque sts are refused bec ause a ll 1024 available sessions are in use.

Any remote device that connects successfully is given one of a preset group of IP addresses with whic h it appears on the network, acces sible through the Gateway. Hence, all connections usin g mu lt iuser tunnels use network addres s translation (NAT). A multiuse r tu nnel is fully defi ned with the following devices:

• Group name

• Number of users that can establish tunnels at any given time and associated NAT IP addresses (known as Client IP)

• Secure profile to be applied to the communication

• Color (mode) of the tunnel

The group of opposing VPN devices is now identified by a group name. The secure profile defines how the establishment of the tunnel should be authenticated and how the communication should be secured. The mode of t h e tu nnel spe cifies where the tunnel terminates. The IP route is no longer required.

Note:

No t e : I f the ahuthenticat ion met hod sp eci fied i n the secure

Note: Note: profile associated with a multiuser tunnel is a challenge phrase, the sa me chal le ng e phr as e mu st be g iven out to each m em ber of the group. This is not recommended.

5-16 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Multiuser Tunnels

Full Access

Full Access The following table shows a tunnel that would allow a group

Full AccessFull Access

(called audit) full access to the red (trusted) network available through VPN device A, w hile not al lowing access to the netw ork available through VPN device B. Note that a maximum of 30 members o f the group wi ll be allowed to use the tunnel at once.

Tunnel Defini t i on

Tunnel Defini t i on Tunnel Definition Parameters

Parameters

ParametersParameters

VPN Device A

VPN Device A VPN Device B

VPN Device AVPN Device A

VPN Device B

VPN Device BVPN Device B

Group name audi t N o access Client IP 10.1.1.193 Not applicable Number of clients 30 Secure profile (must

dial-up Not applicable be previously defined)

Tunnel mode Red Not applicable IP route Not required Not applicable

In the previous table, gro up audit is given comple te access to the trusted network.

Limited Access

Limited Access The next table shows how to use a combination of a tunnel and

Limited AccessLimited Access

a firewall rule to give a group limited access to the red (trusted) network. For example, to allow a group called sales access to the Web server available through VPN device A while not allowing access to the rest of that network or to the network available through VPN device B, a tunnel is defined for the group to the black side of the VPN device and a firewall rule is created to allow the traffic from the black (untrusted) network to the red (trusted) network.

Tunnel Defini t i on

Tunnel Defini t i on Tunnel Definition Parameters

Parameters

ParametersParameters

VPN Device A

VPN Device A VPN Device B

VPN Device AVPN Device A

VPN Device B

VPN Device BVPN Device B

Group name sales No access

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-17

Firewalls and Tunnels

Client IP 10.1.1.193 Not applicable Number of clients 30 Not applicable Secure profile (must

dial-up Not ap plicable be previously defined)

Tunnel mode Black Not applicable IP route Not required Not applicable

Firewall Rule

Firewall Rule The firewall rule is explained in the following table.

Firewall RuleFirewall Rule

Parameter

Parameter Parameter Description

Description

DescriptionDescription

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

From IP address 10.1.1.192 From subnet mask 255.255.255.224 A maximum of 30

users with addresses starting from 10.1.1.193 are allowed thro ugh the firewall.

From application port

ALL The appli cation po rt

used to make the HTTP (www) request is usuall y unknown.

To IP address 10.1.1.2 The Web Server’s IP

address.

To subnet mask 255. 255.255.255 Access Web Server

only.

Parameter

Parameter Parameter Description

Description

DescriptionDescription

5-18 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

Related Related Information

Information

InformationInformation

Multiuser Tunnels

To application port 80 Web servers usually

listen on this port. Action Stateful Direction Inbound The group comes

from the black

(untrusted) n etwork

and crosses to the

red (trusted)

network. NAT No Protocol TCP HTTP is transported

by means of TCP,

not UDP.

Site-to-Site Tunnels (page 5-9) Single-User Tunnels (page 5-12) Tunnel Types (page 5-8)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-19

Firewalls and Tunnels

Tunnel Modes

Tunnel ModesTunnel Modes

VPN tunnels are assigned a mode of either red or black. The color of the tunnel indi cates whether the device on the other en d of the tunnel is trust ed; red is trusted and black is untrusted.

When a tunnel starts inside a trusted network, it indicates that the packets entering or leaving the tunnel are trusted. This is known as a red tunnel. C onversely , when a tunnel s tarts outs ide the trusted network, it indicates that the data packets are not trusted. This is known as a black tunnel. In bot h cases, the data packets can travel between the two networks safely.

There are three possible w ays exist to bu il d a tunnel, depending on where the two ends terminate:

• If both ends of the tunnel terminate inside the trusted network, then the tunnel is called a red-red network. In this case, the two networks trust each other.

• If both ends of the tunnel terminate outside the network, the tunnel is called a black-black network, and neither network trusts the other completely.

• Finally, if one end of a tunnel terminates insid e a network, while the other end terminates outside the network, then the tunnel is called a red-black network or a black-red network. In this case, one network trusts the other while the trust is not reciprocated.

5-20 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Black Red Tunnel

Red - Red Tunnel

Black Black Tunnel

Figure: Firewalled LANs With Encrypted Tunnels

Figure: Firewalled LANs With Encrypted TunnelsFigure: Firewalled LANs With Encrypted Tunnels

Tunnel Modes

Related Related Information

Information

InformationInformation

Hewlett-Packard Company Virtual Private Networking Concepts Guide

Tunnel Types (page 5-8) Tunnel Termination and Firewall Rules (page 5-31)

5-21

Firewalls and Tunnels

One-Way In Firewall Rules

One-Way In Firewall RulesOne-Way In Firewall Rules

One-way in firewall rules allow devices on a black (untrusted) network to establish communication sessions with devices on the red (trusted) network. No network address translation (NAT) is per formed wh en a sessio n is established through a stateful one-way in firewall rule. One-way in firewall rules can grant access to ser vices executing on devices on a red (trust ed) subnet having routed IP addresses.

If you want to allo w SMTP mail from people on the Interne t to be sent into the mai l server, define a one-w ay in rule as described in the following table.

Parameter

Parameter Parameter Description

Description

DescriptionDescription

From IP address 0.0.0.0 The mail can come

From subnet mask 0.0.0.0

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

from any IP ad dress.

From application port

To IP address 198.53.144.2 Assumes that the

To subnet mask 255. 255.255.255 The mail must

To application port 25 The SMTP mail

5-22 Hewlett-Packard Company Virtual Private Networking Concepts Guide

ALL The appli cation po rt

used to send the mail is usually unknown.

mail record associated with your domain name points to this address.

arrive at this IP address only.

server listens on this port.

Related Related Information

Information

InformationInformation

One-Way In Firewall Rules

Protocol TCP SMTP is transported

by means of TCP, not UDP.

Inbound Proxy (page 5- 2 8) Outbound Proxy (page 5-26) One-Way Out Firewall Rules (page 5-24)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-23

Firewalls and Tunnels

One-Way Out Firewall Rules

One-Way Out Firewall RulesOne-Way Out Firewall Rules

One-way out firewall rules allow devices on a red (trusted) network to establish communication sessions with devices on a black (untrusted) networ k. On e-way out firewall rules allow users on routed red (trusted) subn ets to have access to services on a black (untrusted) subnet.

No network address translation (NAT) is performed when a session is established through a one-way out firewall rule. Therefore, the source address of the packets leaving the red (trusted) network must be routable on the black (untrusted) network. Routable means that the devices on the black (untrusted) network know how to send packets to the source address.

If you want to allow people on the red (trusted) network to brows e the W orld Wide Web on the Int ernet, de fine a oneway out firewall rule as descri bed in t he foll o wing table.

Parameter

Parameter Parameter Description

Description

DescriptionDescription

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

From IP address 198.53.144.0 This address allows

anyone on the red (trusted) network whose IP address starts with

198.53.144. From subnet mask 255.255.255.0 From application

port

To IP address 0.0.0.0 This address allows

5-24 Hewlett-Packard Company Virtual Private Networking Concepts Guide

ALL The appli cation po rt

used to make the HTTP (www) request is usuall y unknown.

you to go to any Web site on the Internet.

Related Related Information

Information

InformationInformation

One-Way Out Firewall Rules

To subnet mask 0.0.0.0

Parameter

Parameter Parameter Descriptio n

Descriptio n

Descriptio nDes cr i pt ion

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

To application port 80 Web servers usually

listen on this port.

Protocol TCP HTTP is transported

by means of TCP, not UDP.

Inbound Proxy (page 5- 2 8) Outbound Proxy (page 5-26) One-Way In Firewall Rules (page 5-22)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-25

Firewalls and Tunnels

Outbound Proxy

Outbound ProxyOutbound Proxy

Outbound proxies allow devices on a red subnet to establish communication with devices on black subnets. The outbound proxy function performs a network address translation (NAT) on any packets passing through the proxy. Outbound proxies are, therefore, often used to allo w users on unrouted red subnets to have access to services on a black subnet.

If you want to allow people on the red network to browse the World Wide Web on the Internet, define an outbound proxy as described in the following table.

Parameter

Parameter Parameter Description

Description

DescriptionDescription

Outbound proxy IP 205.250.128.240 The address the

From IP address 10.1.1.0 This address allows

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

packets take on as they exit the red (trusted) network.

anyone on the red (trusted) network whose IP address starts with 10.1.1 to go out to t he black (untrusted)

network. From subnet mask 255.255.255.0 From application

port

To IP address 0.0.0.0 This address allows

5-26 Hewlett-Packard Company Virtual Private Networking Concepts Guide

ALL The appli cation po rt

used to make the

HTTP (www)

request is usuall y

unknown.

you to go to any

Web site on the

Internet.

Related Related Information

Information

InformationInformation

Outbound Proxy

To subnet mask 0.0.0.0

Parameter

Parameter Parameter Descriptio n

Descriptio n

Descriptio nDes cr i pt ion

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

To application port 80 Web servers usually

listen on this port. Protocol TCP HTTP is transported

by means of TCP,

not UDP.

Inbound Proxy (page 5- 2 8) One-Way Out Firewall Rules (page 5-24) One-Way In Firewall Rules (page 5-22)

Hewlett-Packard Company Virtual Private Networking Concepts Guide

5-27

Firewalls and Tunnels

Inbound Proxy

Inbound ProxyInbound Proxy

Inbound proxies allow devices on a black (untrusted) subnet to establish communication sessions with a device on a red (trusted) subnet. Inbound proxies can grant access to services executing on devices on a red (trus ted) subn et hav ing un rout ed or private IP addresses. When you define an inbound proxy, the devices on the black (untrusted) network must address their packets to the black (untrusted) interface of th e VPN device. The VPN device then looks at where the packet originated, what the destination address is, what the destination port is, and decides to which address on the red (trusted) network to send the packet.

Other Network Devices on

10.1.1.xxx IP=10.1.1.2

Mail Server

Red IP=10.1.1.1

Primary Black IP=

205.250.128.240

Figure:

Figure: Inbound and Outbound Proxies

Figure: Figure:

Inbound and Outbound Proxies

Inbound and Outbound ProxiesInbound and Outbound Proxies

Secondary Black IP=

205.250.128.21

Internet

If you want to allo w SMTP mail from people on the Interne t to be sent into a mai l server, defin e an inbound proxy a s described in the following table.

5-28 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Inbound Proxy

Parameter

Parameter Parameter Descriptio n

Descriptio n

Descriptio nDes cr i pt ion

Parameter Value

Parameter Value Comments

Parameter ValueParameter Value

Comments

CommentsComments

Inbound proxy IP 10.1.1.2 This is where the

packets should end up.

From IP address 0.0.0.0 The mail could

come from any IP

address. From subnet ma sk 0.0.0.0 From application

port

ALL The application port

used t o se nd the

mail is usually

unknown. To IP address 205.250.128.21 Assumes that the

mail record

associated with

your domain name

points to this

address. To subnet mask 255.255.255.255 The mail must

arrive at this IP

address only. To application port 25 The SMTP mail

server listens on

this port. Protocol TCP SMTP is transported

by means of TCP,

not UDP.

Related Related Information

Information

InformationInformation

Hewlett-Packard Company Virtual Private Networking Concepts Guide

Outbound Proxy (page 5-26)

5-29

Firewalls and Tunnels

One-Way Out Firewall Rules (page 5-24) One-Way In Firewall Rules (page 5-22)

5-30 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Tunnel Termination and Firewall Rules

Tunnel Termination and Firewall RulesTunnel Termination and Firewall Rules

When a tunnel terminates outside a firewall, a packet must be compared to the firewall rules, which determine whether or not to let the packet through the gateway. In this way, tunnels and firewall rules can be used together to specify what traf fic passes through the VPN device. Four basic permutations of tunnel termination and traffic destinations exist:

• The tunnel termin ates on the re d (trusted) n etwork or interface a nd the traffic is destined for the red (trusted) network or interface.

• The tunnel terminates on the black (untrusted) network or interface, but the tra ffic is destined for the red (trusted) network or interface.

• The tunnel terminates on the red (trusted) network or interface, but the traffic is destined for the black (untrusted) network or interface.

• The tunnel terminates on the black (untrusted) network or interface and th e traffic is destined for the black (untrusted) network or i n terface.

Note:

Note: The terms network and interface are used

Note: Note: interchangeably.

Tunnel

Tunnel Tunnel Terminates in

Terminates in

Terminates in Terminates in the Red

the Red

the Red the Red (Trusted)

(Trusted)

(Trusted) (Trusted) Netwo rk

Netwo rk

Netwo rkNetw or k

Hewlett-Packard Company Virtual Private Networking Concepts Guide

The case where a tunnel t erminates in the red (trusted) n etwork and the traffic is destined for the red (trusted) network is the typical case of giving a remote device complete access to the trusted side of the VPN device. Beca use t he tunnel bypasses the firewall, the destination addresses of the traffic are examined only for the purpose of routing the packets to their destination.

5-31

Firewalls and Tunnels

;

Tunnel terminates on the Red

;;

Tunnel

Tunnel Tunnel Terminates in

Terminates in

Terminates in Terminates in the Black

the Black

the Black the Black (Untrusted)

(Untrusted)

(Untrusted) (Untrusted) Netwo rk

Netwo rk

Netwo rkNetw or k

Traffic is routed out the Red interface without crossing the Firewall

Figure: Tunnel Terminates in the Red (Trusted) Network

Figure: Tunnel Terminates in the Red (Trusted) NetworkFigure: Tunnel Terminates in the Red (Trusted) Network

;;

A tunnel that terminates in the black (untrusted) network but where the traffic is destined for the red (trusted) network gets the traffic to the VPN Gateway safely and then blocks it at the firewall. A firewall rule must be in place to allow the traffic through.

Firewall rule allows traffic through to the Red

Figure: Tunnel Terminates in the Black (Untrusted) Network

Figure: Tunnel Terminates in the Black (Untrusted) NetworkFigure: Tunnel Terminates in the Black (Untrusted) Network

;;

Tunnel terminates on the Black

5-32 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Tunnel

;

Tunnel

Tunnel Tunnel Terminates in

Terminates in

Terminates in Terminates in the Red

the Red

the Red the Red (Trusted)

(Trusted)

(Trusted) (Trusted) Network,

Network,

Network, Network, Destined for the

Destined for the

Destined for the Destined for the Black

Black

Black Black (Untrusted)

(Untrusted)

(Untrusted) (Untrusted) Netwo rk

Netwo rk

Netwo rkNetw or k

Tunnel Termination and Firewall Rules

The third possibility is that the tunnel terminates in the red (trusted) network, but the traffic is destined for the bla ck (untrusted) network. In other words, although the traffic is destined for an untrusted locatio n, the opposin g device has sent the traffic through a safe tunnel to the trusted side of the network. The packets must then pass through the firewall back to the black (untrusted) interface.

Tunnel terminates on the Red

;;

Firewall rule allows traffic through to the Black

Figure: Tunnel Terminates on the Red (Trusted) Network,

Figure: Tunnel Terminates on the Red (Trusted) Network, Figure: Tunnel Terminates on the Red (Trusted) Network,

Destined for the Black (Untrusted) Network

Destined for the Black (Untrusted) NetworkDestined for the Black (Untrusted) Network

Tunnel

Tunnel Tunnel Terminates on

Terminates on

Terminates on Terminates on the Black

the Black

the Black the Black (Untrusted)

(Untrusted)

(Untrusted) (Untrusted) Network,

Network,

Network, Network, Destined for the

Destined for the

Destined for the Destined for the Black

Black

Black Black (Untrusted)

(Untrusted)

(Untrusted) (Untrusted) Netwo rk

Netwo rk

Netwo rkNetw or k

Hewlett-Packard Company Virtual Private Networking Concepts Guide

Finally, the tunnel may terminate on the black (untrusted) network and the traffic be destined for the black (untrusted) network. In this case th e pac kets do not n eed to cross the firewall.

5-33

Firewalls and Tunnels

;

Tunnel terminates on the Black

;;

Related Related Information

Information

InformationInformation

;;

Figure: Tunnel Terminates on the Black (Untrusted)

Figure: Tunnel Terminates on the Black (Untrusted) Figure: Tunnel Terminates on the Black (Untrusted)

Network, Destined for the Black (Untrusted) Netwo rk

Network, Destined for the Black (Untrusted) Netwo rkNetwork, Destined for the Black (Untrusted) Netwo rk

Traffic is routed out the Black interface without crossing the Firewall

Tunnel Modes (page 5-20) One-Way Out Firewall Rules (page 5-24) One-Way In Firewall Rules (page 5-22)

The Template Concept

5-34 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Load Balancing and Redundancy

Load Balancing and RedundancyLoad Balancing and Redundancy

Load Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Redundancy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2

Ba aa

Re ee

Hewlett-Packard Company Virtual Private Networking Concepts Guide

ed RR

al BB

Hewlett-Packar d Company Virtual Pri vate Networking Concepts Guide

Load Balancing and Redundancy

Load Balancing

Tunnel De finition

Tunnel De finition Tunnel Definiti on Parameters

Parameters

ParametersParameters

Group name sales sales Client IP 10.1.1.193 10.1.1.225

Load Balancing

Load BalancingLoad Balancing

Given the presence of more than one VPN device in parallel, it makes sense that each VPN device handles an equal portion of the traffic. This equal portioning is called load balancing, which is accomplished in two ways. Given that a tunnel is established with the VPN device that answers first and that the VPN device that answers first do es so because i t is not busy, th e load should be fairly evenly distributed.

In addition, the number of clients set for Client IP can be used to divide up the total load among the VPN device d evices. As shown in the followi ng example, if the total number of clients desire d is 60 and there are two VPN devices, the number of clients on each VPN device should be set to 30. In this way a maximum of 30 clients could establ ish tunn els with each VPN device.

VPN Device A

VPN Device A VPN Device B

VPN Device AVPN Device A

VPN Device B

VPN Device BVPN Device B

Number of clients 30 30 Secure profile (must

be previously defined)

Tunnel mode Red Red IP route Not required Not required

Related Related Information

Information

InformationInformation

Hewlett-Packard Company Virtual Private Networking Concepts Guide 6-1

Redundancy (page 6-2) Tunnel Modes (page 5-20) Tunnel Types (page 5-8)

dialup dialup

Load Balancing and Redundancy

Redundancy

RedundancyRedundancy

Because the VPN device is such a critical device of a virtual private network (VPN), you should have more than one VPN device supporting the network. By placing more than one VPN device in parallel, the network can continue functioning even if one of the VPN device devices has to be shut down for any reason. This is known as redundancy. Another r eason for having more than one VPN device in parall el is to handle more than 102 4 active sessions, which is the maximum for a single VPN device.

Redundancy can be implemented for single-user tunnels and for multiuser tunnels only. You cannot apply redundancy to site-tosite tunnels. The reason for this is that redundancy relies on the Client IP address, which only exists for remote user tunnels. You need the Client IP for the device on the red network to know which VPN device to send its replies to. In other words, a different set of Client IPs is u sed on each gateway.

An example of redundancy is shown in the following figure.

Figure:

Figure: Enterprise Redundancy

Figure: Figure:

6-2 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Enterprise Redundancy

Enterprise RedundancyEnterprise Redundancy

Redundancy

If a client user named John Doe wants to chec k his mail on the mail s er ve r on the red network, h e can do so thr oug h either VPN device A or VPN device B. If the link definition on the client includes both VPN device devices, the tunnel to the red side is established with t he VPN device that respon ds first. The question for the mail server b ecomes which VPN devic e to send its rep lies through.

Since the tunnel is established only on one VPN device, all replies must go thro ugh that VPN devi ce. This is accomplished using Client IPs. Since the set of Client IPs is different on each VPN device, when the mail server uses the Client IP as the destination address o n its rep lies, only the VPN d evice on whi ch the tunnel has been established accepts the packets for processing. The tunnel definitions for the two VPN device devices appear as show n in the following table.

Tunnel De finition

Tunnel De finition Tunnel Definiti on Parameters

Parameters

ParametersParameters

VPN Device A

VPN Device A VPN Device B

VPN Device AVPN Device A

VPN Device B

VPN Device BVPN Device B

Group name s ales sales Client IP 10.1.1.193 10.1.1.225 Number of clients 30 30 Secure profile (must

dialup dialup be previously defined)

Tunnel mode Red Red IP route Not required Not required

Related Related Information

Information

InformationInformation

Load Balancing (page 6-1) Tunnel Modes (page 5-20) Tunnel Types (page 5-8)

The Template Concept

Hewlett-Packard Company Virtual Private Networking Concepts Guide

6-3

Load Balancing and Redundancy

6-4 Hewlett-Packard Company Virtual Private Networking Concepts Guide

Index

IndexIndex

Numerics

NumericsNumeri c s 3DES

...................................................

AAAA AH key length algorithms

See also

application ports assymetric cryptographic systems authenticatio n headers authenticatio n methods

certificate authentication challenge phrase authentication Entrust authentication RADIUS authen tication SecurID authentication

BBBB black networks black tunnels brute force attacks

CCCC CBC (outer cipher block chaining) certificate authentication challenge phrase authentication crypto period lengt h crypto periods cryptographic systems

3DES asymmetric symmetric symmetric v. asymmetric triple pass DES

DDDD Data Encryption Standard (DES) default gateways DES (Data Encryption Stan da rd) Diffie-Hellman key exch ange p ro to col

.......................................

............................................

secure profiles

...................................

..........................

.............

3-6, 4-1–4-6

.................

.....................

...................

....................

.....................................

.......................................

...............................

.........

.......................

.............

..............................

.....................................

...................

.............................................

....................................

......................................

................

...............................

............

...................................

............

2-9, 2-10

.......

5-20 2-13

2-12

2-1–2-10

2-10

2-11

...

2-7

3-4 3-2

1-9 3-4 4-2

4-3 4-6 4-5 4-4

5-2

2-8 4-2 4-3 3-6

2-7 2-9 2-3

2-5

2-4 1-8 2-4

EEEE Encapsulating Security Payload (ESP)

AH key length authentication headers iv length

See also

encapsulation

Encapsulating Security Payload (ESP) Shiva Smart Tunneling (SST)

See also

encryption Entrust authentication

FFFF filters firewall rules

firewalls full access

functions of

IIII inbound proxies IP addresses

iv (initialization vector) length KKKK

keepalive key operations

............................................

...................................................

and tunnel termination multiuser tunnels one-way in firewall rules one-way out firewall rules single-user tu nn e ls stateful stateless

...............................................

multiuser tunnels single-user tu nn e ls

HP SA3000 Series VPN Client HP SA3000 Series VPN Manager VPN device

network address translation (N AT)

..............................................

See also

.................................

....................

.........................................

encapsulation

.......................................

...........

secure profiles

...........................

...................

...........................

.................

...............

.........................

...........................................

.........................................

...........................

.........................

...........

.......

.....................................

...................................

.........................................

...............

secure profiles

................................

3-4 3-4 3-4

3-3

3-1

3-1 2-1

4-6

5-6

5-31 5-18 5-22 5-24 5-14

5-4 5-2 5-1

5-17 5-12

1-3 1-2 1-2

5-28

1-6

5-12

3-4

3-2

1-3, 2-9

Index-1

key pairs key spaces

.............................................

...........................................

2-10 2-13

redundancy routing tables

..........................................

.......................................

6-2 1-8

LLLL limited access

multiuser tunnels single-user tunnels

load balancing MMMM

modular components of VPN suite multiuser tunnels

firewall ru le full access limited access

NNNN names

..................................................

See also

network address translation (NAT) network configurations of VPN components

networks OOOO

one-way in firewall rules one-way out firewall rules outbound proxies outer cipher block chaining (CBC)

PPPP packet handling packet keys packets and packet headers private keys proxies public key length public keys

RRRR RADIUS authenticatio n

red networks

red tunnels

secure profiles

1-5

.............................................

..........................................

....................................

.......................................

...........................................

........................................

..........................................

...........................

.........................

......................................

.........................

...................................

.....................................

................................

.......................

.....................

.................................

....................................

...................

..................................

.........................

5-17 5-13

.........

5-16–5-19

5-18 5-17 5-17

5-12

.......

5-20

5-22 5-24 5-26

.........

1-3, 2-9

5-26–5-29

5-20

6-1

1-2

3-2

2-8

3-7 3-8 1-6

3-6 2-9

4-5 5-2

SSSS secure profiles

algorithms encapsulation keepalive names

timeout secure tokens SecurID authentication Shiva Smart Tunneling (SST)

authentication methods

crypto period length

public key length

See also

single-user tunnels

firewall ru le

full access

limited acces s site-to-site tunnels stateful filtering stateless filtering subnet masks symmetric cryptographic systems

TTTT TCP/IP

timeout Transmission Control Protocol/Internet trusted networks

trusted tunnels tunnel modes tunnel terminat ion and firewall rules tunnels

.................................................

IP addresses of devices

................................................

See also

Protocol (TCP/IP)

...........................................

firewall ru les

full access with multiuser

full access with single-user

................................

......................................

.................................

........................................

............................................

..........................................

.......................................

..........................

...................

........................

............................

encapsulation

.......................

...................................

.....................................

................................

.................................

....................................

..................................

.......................................

...................

secure profiles

.....................

.................................

....................................

.......................................

.........................

...............

3-2–3-3

5-12–5-15

2-3, 2-10

.....

5-1–5-8

5-14, 5-18

.............

3-2 3-3 3-2 3-2 3-2 1-3 4-4

3-6 3-6 3-6

5-14 5-12 5-13

5-9 5-4 5-2 1-6

1-6 1-6 3-2

1-6 5-20 5-20 5-20 5-31

5-17 5-12

Index-2

Index

IndexIndex

limited access with mu lti user limited access with singl e-user modes multiuser single-user site-to-site trusted untrusted

UUUU untrusted networks untrusted tunnels

VVVV virtual priva te net work ing suit e VPN Client

functions of

VPN device

firewall functions

VPN Manager

functions of

...........................................

...............................

.............................

......................................

..........................................

......................................

..............................

.................................

....................................

............................

....................................

..........

........

5-16–5-19 5-12–5-15

..............

5-17 5-13 5-20

5-9 5-20 5-20

5-20 5-20

1-1

1-3

5-2

1-2

Index-3

Hp sa3110, sa3150, sa3400, sa3450 virtual private networking concepts guide

Specifications and Main Features

Frequently Asked Questions

User Manual