# Web links

## The Linux FreeS/WAN Project

The main project web site is www.freeswan.org.

Links to other project-related sites are provided in our introduction section.

### Add-ons and patches for FreeS/WAN

Some user-contributed patches gave been integrated into the FreeS/WAN distribution. For a variety of reasons, those listed below have not.

Patches believed current at time of writing (March 2001, just before 1.9 release):

- patches and utilities for using FreeS/WAN with PGPnet
- patches for X.509 certificate support, also available from a mirror site
- a series of patches that
  - provide GOST, a Russian gov't. standard cipher, in MMX assembler
  - add GOST to OpenSSL
  - add GOST to the International kernel patch
  - let FreeS/WAN use International kernel patch ciphers
- IPv6 support

Before using these, check the mailing list for news of newer versions and to see whether they have been incorporated into more recent versions of FreeS/WAN.

Note: At one point the way PGP generates RSA keys and the way FreeS/WAN checks them for validity before using them were slightly different, so quite a few PGP-generated keys would be rejected by FreeS/WAN, confusing users no end. This is fixed in 1.9.

A set of PKIX patches were recently announced on the mailing list:

    Subject: a different PKIX patch.
       Date: Mon, 5 Mar 2001
       From: Luc Lanthier <firesoul@netwinder.org>

    I'd like to invite volunteers to use the now-complete PKIX project I've
    been working on since about August. Because of this, the patch is for
    FreeSWAN 1.5, not 1.8... I haven't really felt the need to update it since
    I don't use IPV6 nor DNSSec.

    This is similar, but different than Andreas Steffen's pkix
    implementation. I've based this work on Neil Dunbar's openssl-pkix patch
    for FreeSWAN 1.1. I've updated it to run on FreeSWAN 1.5 correctly, and
    added support for ID_DER_ASN1_DN ID packet support. It will do LDAP
    certificate lookups no problem, as well as local flatfile, directory, or
    DB lookup for testing or speed.

    IE: It's a full CA-compatible client, capable of looking up, checking the
    CRL for expiry and such. It will not only do the classic PSK and RSASIG
    freeswan methods just fine, but also does PKIX's RSASIG, PKE and
    RPKE. I've spent a lot of time adding RoadWarrior support for these last
    IKE exchange methods.

    The patch can be found as:
      ftp://ftp.netwinder.org/users/f/firesoul/freeswan-1.5-pkix_13.patch
    There are also freeswan-1.5 - kernel 2.4 patches for those who need them.

    Let me know. Feedback is appreciated.

Older patches:

- Neil Dunbar's patches for certificate support, using code from Open SSL.
- patches to add Blowfish, IDEA and CAST-128 to FreeS/WAN
- patches for aggressive mode support

These patches are for older versions of FreeS/WAN and will likely not work with the current version. Older versions of FreeS/WAN may be available on some of the distribution sites, but we recommend using the current release.

#### VPN masquerade patches

Finally, there are some patches to other code that may be useful with FreeS/WAN:

- a patch to make IPSEC, PPTP and SSH VPNs work through a Linux firewall with IP masquerade.
- Linux VPN Masquerade HOWTO

Note that this is not required if the same machine does IPSEC and masquerading, only if you want a to locate your IPSEC gateway on a masqueraded network. See our firewalls document for discussion of why this is problematic.

At last report, this patch could not co-exist with FreeS/WAN on the same machine.

### Distributions including FreeS/WAN

The introductory section of our document set lists several Linux distributions which include FreeS/WAN.

### Things FreeS/WAN uses or could use

- /dev/random support page, discussion of and code for the Linux random number driver. Out-of-date when we last checked (January 2000), but still useful.
- other programs related to random numbers:
  - audio entropy daemon to gather noise from a sound card and feed it into /dev/random
  - an entropy-gathering daemon
  - a driver for the random number generator in recent Intel chipsets
- a Linux L2TP Daemon which might be useful for communicating with Windows 2000 which builds L2TP tunnels over its IPSEC connections
- packet spy, a packet sniffer whose author said in a Dec 1999 message "It's very unfinished, especially the filter, but it can give you an ascii and hex dump at the same time. I started it specifically for snooping a FreeS/WAN installation."
- to use opportunistic encryption, you need a recent version of BIND. Get one from the FreeS/WAN site or from the Internet Software Consortium who maintain BIND.

### Other approaches to VPNs for Linux

- other Linux IPSEC implementations
- ENskip, a free implementation of Sun's SKIP protocol
- vpnd, a non-IPSEC VPN daemon for Linux which creates tunnels using Blowfish encryption
- Zebedee, a simple GPLd tunnel-building program with Linux and Win32 versions. The name is from Zlib compression, Blowfish encryption and Diffie-Hellman key exchange.
- LinuxCare's VPS (Virtual Private Server) which builds tunnels using SSH
- Moreton Bay's PoPToP, PPTP for Linux
- CIPE (crypto IP routers) project, using their own lightweight protocol to encrypt between routers
- vtun "virtual tunnels", using Blowfish
- tinc, a VPN Daemon

There is a list of Linux VPN software in the Linux Security Knowledge Base.

## The IPSEC Protocols

### General IPSEC or VPN information

- The VPN Consortium is a group for vendors of IPSEC products. Among other things, they have a good collection of IPSEC white papers.
- A VPN mailing list with a home page, a FAQ, some product comparisons, and many links.
- A list of IPSEC links from Lewis McCarthy at U Mass.
- VPN pointer page
- a collection of VPN links, and some explanation

### IPSEC overview documents or slide sets

- the FreeS/WAN document section on these protocols
- A good introductory article with links to several articles on related topics
- SSH Communications Security
- Timestep Corporation's tutorial: go to their web site, then follow the "VPN Overview" link

### IPSEC information in languages other than English

- German
- Japanese

### RFCs and other reference documents

- Our document listing the RFCs relevant to Linux FreeS/WAN and giving various ways of obtaining both RFCs and Internet Drafts.
- IPSEC standards page maintained by VPNC. This covers both RFCs and Drafts, and classifies them in a fairly helpful way.
- RFC archive
- Internet Drafts related to IPSEC
- US government site with their FIPS standards
- Archives of the ipsec@tis.com mailing list where discussion of drafts takes place.
  - Eastern Canada
  - California.

### Analysis and critiques of IPSEC protocols

- Counterpane's evaluation of the protocols
- Simpson's IKE Considered Dangerous paper. Note that this is a link to an archive of our mailing list. There are several replies in addition to the paper itself.
- Bellovin's papers page including his:
  - Security Problems in the TCP/IP Protocol Suite (1989)
  - Problem Areas for the IP Security Protocols (1996)
  - Probable Plaintext Cryptanalysis of the IP Security Protocols (1997)
- Catherine Meadows of NRL applied the NRL Protocol Analyzer to IKE. Her paper is available in PDF or Postscript.
- An errata list for the IPSEC RFCs.

### Background information on IP

- An introduction to IP addressing from 3Com
- An IP tutorial that seems to be written mainly for Netware or Microsoft LAN admins entering a new world
- IANA, Internet Assigned Numbers Authority
- CIDR, Classless Inter-Domain Routing
- Also see our bibliography

## IPSEC Implementations

### Linux products

Vendors using FreeS/WAN in turnkey firewall or VPN products are listed in our introduction.

Other vendors have Linux IPSEC products which, as far as we know, do not use FreeS/WAN

- Redcreek provide an open source Linux driver for their PCI hardware VPN card. This card has a 100 Mbit Ethernet port, an Intel 960 CPU plus more specialised crypto chips, and claimed encryption performance of 45 Mbit/sec. The PC sees it as an Ethernet board.
- Paktronix offer a Linux-based VPN with hardware encryption
- According to a report on our mailing list, Watchguard use Linux in their Firebox product.
- Entrust offer a developers' toolkit for using their PKI for IPSEC authentication
- According to a report on our mailing list, Axent have a Linux version of their product.

### IPSEC in router products

All the major router vendors support IPSEC, at least in some models.

- Cisco IPSEC information
- Ascend, now part of Lucent, have some IPSEC-based products
- Bay Networks, now part of Nortel, use IPSEC in their Contivity switch product line
- 3Com have a number of VPN products, some using IPSEC

### IPSEC in firewall products

Many firewall vendors offer IPSEC, either as a standard part of their product, or an optional extra. A few we know about are:

- Borderware
- Ashley Laurent
- Watchguard
- Injoy for OS/2

Vendors using FreeS/WAN in turnkey firewall products are listed in our introduction.

### Operating systems with IPSEC support

All the major open source operating systems support IPSEC. See below for details on BSD-derived Unix variants.

Among commercial OS vendors, IPSEC players include:

- Microsoft have put IPSEC in their Windows 2000 products
- Apple's Mac OS X has IPSEC support built in
- IBM announce a release of OS390 with IPSEC support via a crypto co-processor
- Sun include IPSEC in Solaris 8
- Hewlett Packard offer IPSEC for their Unix machines

### Open source IPSEC implementations

#### Other Linux IPSEC implementations

We like to think of FreeS/WAN as the Linux IPSEC implementation, but it is not the only one. Others we know of are:

- pipsecd, a lightweight implementation of IPSEC for Linux. Does not require kernel recompilation.
- Petr Novak's ipnsec, based on the OpenBSD IPSEC code and using Photuris for key management
- A now defunct project at U of Arizona (export controlled)
- NIST Cerebus (export controlled)

#### IPSEC for BSD Unix

- KAME, several large Japanese companies co-operating on IPv6 and IPSEC
- US Naval Research Lab implementation of IPv6 and of IPSEC for IPv4 (export controlled)
- OpenBSD includes IPSEC as a standard part of the distribution
- IPSEC for FreeBSD
- a FAQ on NetBSD's IPSEC implementation

#### IPSEC for other systems

- Helsinki U of Technolgy have implemented IPSEC for Solaris, Java and Macintosh

### Interoperability

The IPSEC protocols are designed so that different implementations should be able to work together. As they say "the devil is in the details". IPSEC has a lot of details, but considerable success has been achieved.

#### Interoperability results

Linux FreeS/WAN has been tested for interoperability with many other IPSEC implementations. Results to date are in our interoperability section.

Various other sites have information on interoperability between various IPSEC implementations:

- interop results from a bakeoff in Atlanta, September 1999.
- a French company, HSC's, interoperability test data covers FreeS/WAN, Open BSD, KAME, Linux pipsecd, Checkpoint, Red Creek Ravlin, and Cisco IOS
- ICSA offer certification programs for various security-related products. See their list of certified IPSEC products. Linux FreeS/WAN is not currently on that list, but several products with which we interoperate are.
- VPNC have a page on why they are not yet doing interoperability testing and a page on the spec conformance testing that they are doning
- a review comparing a dozen commercial IPSEC implemetations. Unfortunately, the reviewers did not look at Open Source implementations such as FreeS/WAN or OpenBSD.
- results from interoperability tests at a conference. FreeS/WAN was not tested there.
- test results from the IPSEC 2000 conference

#### Interoperability test sites

- TAHI, a Japanese IPv6 testing project with free IPSEC validation software
- National Institute of Standards and Technology
- RSA Data Security
- SSH Communications Security
- Internet Devices

## Linux links

### Basic and tutorial Linux information

- Linux Getting Started HOWTO document
- A getting started guide from the U of Oregon
- A large link collection which includes a lot of introductory and tutorial material on Unix, Linux, the net, . . .

### General Linux sites

- Gary's Encyclopedia, several thousand Linux links, over 100 categories
- Freshmeat Linux news
- Slashdot "News for Nerds"
- Linux Online
- Linux HQ
- tux.org

### Documentation

- Linux Documentation Project
  - Meta-FAQ guide to Linux information sources
  - Index of HOWTO documents
  - Kernel HOWTO
  - Security HOWTO
  - Networking Overview HOWTO
  - Net 3 HOWTO
  - System Administrator's Guide
  - Network Adminstrator's Guide
- Open Source Writers' Group, cover the BSD derivatives as well as Linux
  - document index
  - some good essays on open source ideas
- Tucows Linux HowTo collection, mostly a mirror of LDP material

### Advanced routing

The Linux IP stack is getting some new features in 2.4 kernels. Most are already available as experimental code in 2.3 kernels. Some HowTos have been written:

- several HowTos for the netfilter firewall code in newer kernels
- 2.4 networking HowTo
- 2.4 routing HowTo

### Security for Linux

- Security HOWTO
- Linux Security Knowledge Base
- Trinity OS guide to setting up Linux
- Linux Administrator's Security Guide
- Linux security page
- Unix security page
- PPDD encrypting filesystem
- Linux Encryption HowTo This does not cover FreeS/WAN (or didn't when I last checked, April 2000), only gives a pointer to our web site, but does have some good information on other things.

### Linux firewalls

- Linux Firewall page
- IP Masquerade resource page
- IP chains, the firewall code in 2.2 kernels.
- netfilter firewall code in kernels from 2.3.15 on
- Our list of general firewall references on the web
- Mason, a tool for automatically configuring Linux firewalls
- Seattle Firewall tools for building a firewall using ipchains and FreeS?WAN
- the web cache software squid and squidguard which turns Squid into a filtering web proxy

### Miscellaneous Linux information

- List of Linux distribution vendors
- FAQ for the Linux adminstration mailing list
- A web page about PPTP for Linux with a list of other Linux VPN software

## Crypto and security links

### Crypto and security resources

#### The standard link collections

Two enormous collections of links, each the standard reference in its area:

Gene Spafford's COAST hotlist
  Computer and network security.
Peter Gutmann's Encryption and Security-related Resources
  Cryptography.

#### Frequently Asked Question (FAQ) documents

- Cryptography FAQ
- Firewall FAQ
- A FAQ listing computer security mailing lists
- Secure Unix Programming FAQ
- FAQs for specific programs are listed in the tools section below.

#### Tutorials

- Gary Kessler's Overview of Cryptography
- Terry Ritter's introduction
- Kurt Seifried's online introductory book
- Peter Gutman's cryptography tutorial (500 slides in PDF format)
- Amir Herzberg of IBM's sildes for his course Introduction to Cryptography and Electronic Commerce
- the concepts section of the GNU Privacy Guard documentation
- Bruce Schneier's self-study cryptanalysis course

See also the interesting papers section below.

#### Crypto and security standards

- Common Criteria, new international computer and network security standards to replace the "Rainbow" series
- AES Advanced Encryption Standard which will replace DES
- IEEE P-1363 public key standard
- our collection of links for the IPSEC standards
- history of formal evaluation of security policies and implementation

### Cryptography law and policy

#### Surveys of crypto law

- International survey of crypto law.
- International survey of digital signature law

#### Organisations opposing crypto restrictions

- The EFF's archives on privacy and export control.
- Global Internet Liberty Campaign
- Center for Democracy and Technology
- Privacy International, who give out Big Brother Awards to snoopy organisations

#### Other information on crypto policy

- RFC 1984, the IAB and IESG Statement on Cryptographic Technology and the Internet.
- John Young's collection of documents of interest to the cryptography, open government and privacy movements, organized chronologically
- Encryption, Privacy and Security Resource Page with a mainly US focus
- Cryptography Export Control Archive, mainly links to court and govenment documents on various challenges to US law
- A good overview of the issues from Australia.

See also our documentation section on the history and politics of cryptography.

### Cryptography technical information

#### Collections of crypto links

- Counterpane
- Peter Gutman's links
- Helger Lipmaa's links
- PKI links
- Robert Guerra's links

#### Lists of online cryptography papers

- Counterpane
- cryptography.com
- Cryptosoft

#### Particularly interesting papers

These papers emphasize important issues around the use of cryptography, and the design and management of secure systems.

- Key length requirements for security
- Why Cryptosystems Fail
- Risks of escrowed encryption
- Security pitfalls in cryptography
- Reflections on Trusting Trust, Ken Thompson on Trojan horse design
- Security against Compelled Disclosure, how to maintain privacy in the face of legal or other coersion

### Computer and network security

#### Security links

- COAST Hotlist
- DMOZ open directory project computer security links
- Telstra
- Bennet Yee
- Email Security and PKI Documents
- Open SEC, a link farm full of links to freely available security tools
- Mike Fuhr's link collection
- links with an emphasis on intrusion detection

#### Firewall links

- COAST firewalls
- Firewalls Resource page
- Firewall info list
- Ami Levartovsky

#### VPN links

- VPN Consortium
- First VPN's white paper collection
- oddsites.com VPN links

#### Security tools

- Open SEC, a link farm full of links to freely available security tools
- PGP -- mail encryption
  - PGP Inc. (part of NAI) for commercial versions
  - MIT distributes the NAI product for non-commercial use
  - international distribution site
  - GNU Privacy Guard (GPG)
  - PGP FAQ
  A message in our mailing list archive has considerable detail on available versions of PGP and on IPSEC support in them.

  Note: A fairly nasty bug exists in all commercial PGP versions from 5.5 through 6.5.3. If you have one of those, read the security advisory and upgrade now.

- SSH -- secure remote login
  - SSH Communications Security, for the original software. It is free for trial, academic and non-commercial use.
  - Open SSH, the Open BSD team's free replacement
  - freessh.org, links to free implementations for many systems
  - SSH FAQ
  - Putty, an SSH client for Windows
- ssmail -- sendmail patched to do opportunistic encryption
  - web page with links to code and to a Usenix paper describing it, in PDF
- COPS Computer Oracle and Password System; tests a system for various weaknesses
- SATAN System Administrators Tool for Analysing Networks
- NMAP Network Mapper
- Internet Traffic Archive, various tools to analyze network traffic, mostly scripts to organise and format tcpdump(8) output for specific purposes
- Wietse Venema's page with various tools
- Crack password cracker
- Tripwire saves message digests of your system files. Re-calculate the digests and compare to saved values to detect any file changes.
- Deception Toolkit, a collection of "honeypot" servers which emulate widely exploited weaknesses while logging the attacks.
- Open CA project to develop a freely distributed Certification Authority for building a open Public Key Infrastructure.
- ISIC, IP stack integrity checker, generates legitmate and bogus packets "to test the stability of an IP Stack and its component stacks (TCP, UDP, ICMP et. al.)"

### Links to home pages

David Wagner at Berkeley provides a set of links to home pages of cryptographers, cypherpunks and computer security people.