• The SPA client system that runs the fwknop client to send SPA packets and from which SSH and RDP connections originate.
• The Amazon border firewall.
• An Ubuntu host on the VPC network where the fwknop daemon runs.
• A Windows system on the VPC network where RDP lives.

$ cat ssh_access.sh
#!/bin/sh -x

fwknop -A tcp/80 --server-port 40001 -R -D 107.23.221.41
sleep 2
ssh -p 80 -i ~/.ssh/cdyne-vpc-testing.pem ubuntu@107.23.221.41
exit

$ cat rdp_access.sh
#!/bin/sh -x

fwknop -A tcp/80 --server-port 40001 -N 10.0.0.223,3389 -R -D 107.23.221.41
sleep 2
rdesktop -u Administrator 107.23.221.41:80
exit

• Added IP protocol scan detection (nmap -sO). A new psad.conf variable PROTOCOL_SCAN_THRESHOLD defines the minimum number of different IP protocols (default = 5) that must be scanned before an alert is triggered.
• Added detection for Topera IPv6 scans when --log-ip-options is used in the ip6tables logging rule. When this option is not used, the previous psad-2.2 release detected Topera scans. An example TCP SYN packet generated by Topera when --log-ip-options is used looks like this (note the series of empty IP options strings "OPT ( )":

  Dec 20 20:10:40 rohan kernel: [  488.495776] DROP IN=eth0 OUT=
  MAC=00:1b:b9:76:9c:e4:00:13:46:3a:41:36:86:dd
  SRC=2012:1234:1234:0000:0000:0000:0000:0001
  DST=2012:1234:1234:0000:0000:0000:0000:0002 LEN=132 TC=0 HOPLIMIT=64
  FLOWLBL=0 OPT ( ) OPT ( ) OPT ( ) OPT ( ) OPT ( ) OPT ( ) OPT ( )
  OPT ( ) OPT ( ) PROTO=TCP SPT=61287 DPT=1 WINDOW=8192 RES=0x00 SYN
  URGP=0
  

• Bug fix in --Analyze mode when IP fields are to be searched with the --analysis-fields argument (such as --analysis-fields "SRC:1.2.3.4"). The bug was reported by Gregorio Narvaez, and looked like this:

  Use of uninitialized value $_[0] in length at
  ../../blib/lib/NetAddr/IP/UtilPP.pm (autosplit into
  ../../blib/lib/auto/NetAddr/IP/UtilPP/hasbits.al) line 126.
  Use of uninitialized value $_[0] in length at
  ../../blib/lib/NetAddr/IP/UtilPP.pm (autosplit into
  ../../blib/lib/auto/NetAddr/IP/UtilPP/hasbits.al) line 126.
  Bad argument length for NetAddr::IP::UtilPP::hasbits, is 0, should be
  128 at ../../blib/lib/NetAddr/IP/UtilPP.pm (autosplit into
  ../../blib/lib/auto/NetAddr/IP/UtilPP/_deadlen.al) line 122.
  

• Added --stdin argument to allow psad to collect iptables log data from STDIN in --Analyze mode. This makes it easier to run an iptables logs through psad from arbitrary files like so:

  # grep "IN=.*OUT=" /var/log/kern.log | psad -A --stdin
  

• Added the ability to acquire Snort rule 'msg' fields from fwsnort if it's also installed. A new variable FWSNORT_RULES_DIR tells psad where to look for the fwsnort rule set. This fixes a problem reported by Pui Edylie to the psad mailing list where fwsnort logged an attack that psad could not map back to a descriptive 'msg' field.
• Added the ability to set per-danger level timeouts when psad is configured to run in auto-blocking mode. These timeouts are implemented with new AUTO_BLOCK_DL*_TIMEOUT variables - one for each of the five possible danger levels that may be assigned to a scanning IP address.
• Added the ability to throttle emails generated by psad via a new EMAIL_THROTTLE variable which is implemented as a per-IP threshold. That is, if EMAIL_THROTTLE is set to "10", then psad will only send 1/10th as many emails for each scanning IP as it would have normally.

• Bug fix to ensure that !, <, >, and = chars in content strings are converted to the appropriate hex equivalents. All content strings with characters outside of [A-Za-z0-9] are now converted to hex-string format in their entirety. This should also fix an issue that results in the following error when running /var/lib/fwsnort/fwsnort.sh:

      Using intrapositioned negation (`--option ! this`) is deprecated in
      favor of extrapositioned (`! --option this`).  Bad argument `bm'
      Error occurred at line: 64
      Try `iptables-restore -h' or 'iptables-restore --help' for more information.
      Done.
  

• Bug fix to set default max string length in --no-ipt-test mode where iptables capabilities are not tested.
• (Andrew Merenbach) Bug fix to properly honor --exclude-regex filtering option.
• Added fwsnort test suite to the test/ directory. This mimics the test suites from the psad and fwknop projects, and it designed to examine many of the run time results of fwsnort.
• Added the ability to easily revert the fwsnort policy back to the original iptables policy with "/var/lib/fwsnort/fwsnort.sh -r". Note that this reverts back to the policy as it was when fwsnort itself was executed.
• Implemented a single unified function for iptables match parameter length testing, and optimized to drastically reduce run time for iptables capabilities checks (going from over 20 seconds to less than one second in some cases).
• (Dwight Davis) Contributed patches for several bugs including not handling --exclude-regex properly, not ignoring the deleted.rules file, not handling --strict mode operations correctly, and more. These issues and the corresponding patch were originally reported here: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=693000
• Bug fix for Snort rules with HOME_NET(any) -> EXTERNAL_NET(any) to ensure they go into the OUTPUT chain instead of the INPUT chain. This bug was reported by Dwight Davis.
• Updated to bundle the latest Emerging Threats rule set.

• [client] Misc fixes and the addition of save_args and last command (.fwknop.last) support on the Windows platform.
• [client] Fixed bug in username determination code where a valid value could be overrwritten in certain circumstances.
• [server] Added upstart config at extras/upstart/fwknop.conf. This allows the fwknopd to easily be managed with upstart via commands like "service fwknop start" and "service fwknop stop".
• [server] (Vlad Glagolev) Submitted a patch to fix ndbm/gdbm usage when --disable-file-cache is used for the autoconf configure script. This functionality was broken in be4193d734850fe60f14a26b547525ea0b9ce1e9 through improper handling of #define macros from --disable-file-cache.
• [server] (Vlad Glagolev) Submitted a patch to fix command exec mode under SPA message type validity test. Support for command exec mode was also added to the test suite.
• (Vlad Glagolev) Submitted an OpenBSD port for fwknop-2.0.3, and this has been checked in under the extras/openbsd/ directory.
• [server] Bug fix to allow GPG_ALLOW_NO_PW to result in not also having to specify a Rijndael key.
• [Android] Added new .properties files to allow the fwknop client to build and function properly on the latest Android release (4.1.2).
• [client] Added '-P udpraw' to allow the client to send SPA packets over UDP with a spoofed source IP address. This is in addition to the original 'tcpraw' and 'icmp' protocols that also support a spoofed source IP.
• [libfko] Bug fix to check b64_decode() return value to ensure that non-base64 encoded data is never used. Even though other validation routines checked decoded results, it is important to discard invalid data as early as possible. Note too that such invalid data would only be provided to b64_decode() after proper decryption, so the client must provide authentic SPA data.
• [libfko] Added validation of NAT access strings in the various NAT modes.
• [libfko] Restricted usernames embedded in SPA packets to be alpha-numeric along with "-" chars.
• [client] (Franck Joncourt) Contributed a patch to allow the fwknop client to be stopped during the password entry prompt with Ctrl-C before any SPA packet is sent on the wire.
• [client+server] Applied patch from Franck Joncourt to remove unnecessary chmod() call when creating client rc file and server replay cache file. The permissions are now set appropriately via open(), and at the same time this patch fixes a potential race condition since the previous code used fopen() followed by chmod().
• [server] Bug fix to accept SPA packets over ICMP if the fwknop client is executed with '-P icmp' and the user has the required privileges.
• [test suite] Applied patch from Franck Joncourt to have the perl FKO module link against libfko in the local directory (if it exists) so that it doesn't have to have libfko completely installed in the /usr/lib/ directory. This allows the test suite to run FKO tests without installing libfko.
• [test suite] Significant update to include a set of fuzzing SPA packets that are built using a patched version of libfko. These packets are located in the test/fuzzing/bogus_spa_packets file, and are designed to ensure proper validation of SPA packet data. This validation is performed in --enable-perl-module-checks mode via the perl FKO module.
• [client] Added --icmp-type and --icmp-code arguments so the user can control the icmp type/code combination for spoofed SPA packets ('-P icmp') mode.
• [client] Updated default TTL value to 64 for spoofed SPA packets. This is closer to more OS default TTL values than the previous 255.
• Updated build CFLAGS and LDFLAGS to conform to the Debian hardening-includes file for PIE support (e.g. '-fPIE' for CFLAGS and '-fPIE -pie' for LDFLAGS).
• [test suite] For GnuPG tests that require a passphrase associated with a gpg key, added a pinentry check to see if the local gpg engine requires it. If so, the gpg test that require a key are excluded since.
• [server] Added a new '--pcap-file <file>' option to allow pcap files to be processed directly by fwknopd instead of sniffing an interface. This feature is mostly intended for debugging purposes.
• [server] Added chain_exists() check to SPA rule creation so that if any of the fwknop chains are deleted out from under fwknopd they will be recreated on the fly. This mitigates scenarios where fwknopd might be started before a system level firewall policy is applied due to init script ordering, or if an iptables policy is re-applied without restarting fwknopd.

• 1. Quick Start
• Configuring fwknopd to protect sshd
• Default-drop firewall policy
• Gaining access to sshd with the fwknop client
• 2. Introduction
• What is Port Knocking?
• What is Single Packet Authorization?
• What is fwknop?
• fwknop license (GPL v2)
• 3. Installing fwknop
• Downloading the latest fwknop release
• Supported Platforms
• Notes on Specific Platforms
• Linux Notes
• FreeBSD Notes
• Mac OS X Notes
• OpenBSD Notes
• iPhone Notes
• Android Notes
• Windows Notes
• Installing from Sources
• The fwknop Test Suite
• Running the Test Suite
• --diff Mode
• valgrind Support
• Anonymizing Test Suite Output
• 4. fwknop Operations
• Starting and Stopping the fwknopd daemon
• SPA with Symmetric Keys (via Rijndael)
• SPA with Asymmetric Keys (via GnuPG)
• Hardening Multiple Services
• Handling Multiple Users
• Client Automation with the --get-key Option
• SPA Across NAT Gateways
• SPA Ghost Services
• User Interfaces
• iPhone Client
• Android Client
• Windows Morpheus UI
• Web Proxy
• SPA Packet Spoofing
• Stopping Replay Attacks
• SPA Over Tor
• 5. fwknop Design Goals
• No Heavyweight Interpreted Languages
• Support Embedded Devices
• Don't Require Admin Access to Run the SPA Client
• Don't Require the Manipulation of Raw Packet Headers
• Don't trust the IP header
• Support Server-Side NAT
• Support Cloud Computing Environments
• Support Multiple Firewalls
• Minimize Library Dependencies
• Support Both Symmetric and Asymmetric Ciphers
• Leverage Compiler and OS Security Features
• 6. fwknop Communications
• SPA Packet Format
• Raw SPA Packets
• 7. fwknop Development
• Programming Languages and Style
• Source Control (git)
• Older Perl Releases
• Submitting Patches
• Primary Developers
• Mailing List
• 8. References and Further Reading
• Reference List
• fwknop and fwknopd --help Output

• No heavyweight interpreted languages:
  Many people don't want to install perl, python, or ruby on a firewall or network gateway device. Such languages are large and complex, and are implemented by similarly complex binaries that are usually themselves written in a language like C. Firewalls are frequently stripped down systems that are designed to just filter network traffic, provide administrative interfaces and sometimes VPN services, and not do much else. Both the fwknop client and server are entirely written in C - there is no requirement for perl, python, or any other interpreted language.
  
  
• Support embedded devices:
  A consequence of fwknop being developed in C is that it only uses minimal system resources and can therefore support embedded devices that don't have a lot of computing power or main memory. For example, where the older perl version of fwknop could not run on Linksys routers supported by OpenWRT, these same routers can run the newer C version of fwknop.
  
  
• Don't require admin access to run the SPA client:
  There are many computing environments where users don't have privileged accounts. This should not present a barrier to using the SPA client. In fwknop, SPA packets are (by default) sent over a regular UDP socket and therefore require no special privileges.
  
  
• Don't require the manipulation of raw packet headers:
  There are some SPA implementations that communicate information within specially modified fields within IP or TCP headers. Such manipulation requires that the user have the ability to acquire a raw socket from the OS, and this requires admin level privileges. In addition, depending on how the SPA client manipulates packet headers when building an SPA packet, other monitoring systems such as an IDS or a passive OS fingerprinter may produce event data that unnecessarily calls attention to the SPA communications. This is not to say that that is impossible to detect SPA packets generated by fwknop - it is just that a monitoring system is more likely to flag communications that involve manipulated packet headers than to generate an event for packets produced by fwknop. For example, intrusion detection systems track TCP connections, and spoofed TCP ACK's that are not part of a proper connection (assuming non-asymmetric routing) may potentially be flagged. Also, manipulated TCP options fields that don't conform to OS defaults will cause an OS to appear to change under the observation of things like p0f. While sometimes this is an expected behavior such as if a VM is being run or a system is actually a NAT device with other systems behind it, there are plenty of deployment scenarios where this is not expected. Addressing this issue at length could be a separate blog post in itself.
  
  
• Don't trust the IP header:
  Any SPA implementation that trusts the source IP address in the IP header of the SPA packet is vulnerable to a MITM attack. An inline device that can intercept an SPA packet can hold the original packet and retransmit it but with the source IP changed to whatever the attacker wants. If the SPA server relies on the source IP in the IP header, then it has no way to know that it isn't legitimate. If an SPA implementation is going to go to the trouble of leveraging cryptography - certainly important since replay attacks among other problems can't be prevented without it - then the IP should be made part of an encrypted payload. This is exactly what fwknop does with the -a or -R arguments on the fwknop command line. An attacker can intercept an SPA packet produced by fwknop, change the source IP and retransmit, but SPA server will only allow access to the IP that was originally encrypted within the SPA payload.
  
  
• Support server-side NAT:
  There are plenty of networks with a border firewall where a remote user actually wants access to a service that is running on an internal system and not on the firewall itself. Typical ways of accessing such a service involve running VPN software, but with an SPA implementation that can manipulate NAT rules on the border firewall it is possible to transparently grant SPA users access to internal services through the firewall. With fwknop, the capability to leverage server-side NAT has been built in for a long time.
  
  
• Support multiple firewalls:
  Because fwknop does not rely on specialized logging infrastructure or link against libraries that are tied to one firewall architecture or another, it can easily support multiple firewalls just by executing the local firewall admin command line interface. It currently supports iptables on Linux, ipfw on FreeBSD and Mac OS X, and pf on OpenBSD.
  
  
• Minimize library dependencies:
  Given the design decisions made by fwknop above, it is important to minimize library dependencies and to audit the source code. Here are all library dependencies in the fwknopd daemon including GnuPG support (this is optional):

  $ ldd ./server/.libs/fwknopd
      linux-vdso.so.1 =>  (0x00007ffeebf820e0)
      libfko.so.0 => /usr/lib/libfko.so.0 (0x00007f1a6ae930e0)
      libpcap.so.0.8 => /usr/lib/x86_64-linux-gnu/libpcap.so.0.8 (0x00007e1a6a85c0e0)
      libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007e1a6a49e0a0)
      libgpgme.so.11 => /usr/lib/libgpgme.so.11 (0x00007f1aeaee800e)
      /lib64/ld-linux-x86-64.so.2 (0x00007e1a6aede0e0)
      libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0 (0x0000ef1a6a06e0e0)
  

  The libfko library is developed by the fwknop project for SPA encryption, decryption, and validation. libpcap is a standard C library that is leveraged by a lot of security projects including intrusion detection systems and more. The gpgme libraries are only used if you want GnuPG support, and the remaining libraries are standard system libraries that typical Linux binaries need. That's it. One may certainly question the use of libpcap, and in defense of this choice note that: 1) fwknopd by default does not put the sniffing interface into promiscuous mode, 2) fwknopd by default only pays attention to UDP packets to port 62201, 3) if you examine Metasploit you'll see that there only a few exploits for pcap-based software and they target what rides on top of libpcap vs. libpcap itself, and 4) even if there is a vulnerability in libpcap, the exploit model is different than it is for normal server software that you can easily scan for, and being different in this game is good.
  
  
• Support both symmetric and asymmetric ciphers:
  Some users prefer the security properties that asymmetric crypto systems have over those provided by symmetric algorithms like Rijndael, or vice versa. fwknop supports both Rijndael and GnuPG for SPA encryption/decryption. On another note, HMAC-SHA256 support is coming soon to fwknop.
  
  

• [server] Fernando Arnaboldi from IOActive found several DoS/code execution vulnerabilities for malicious fwknop clients that manage to get past the authentication stage (so a such a client must be in possession of a valid access.conf encryption key). These vulnerabilities manifested themselves in the handling of malformed access requests, and both the fwknopd server code along with libfko now perform stronger input validation of access request data. These vulnerabilities affect pre-2.0.3 fwknop releases.
• [server] Fernando Arnaboldi from IOActive found a condition in which the server did not properly validate allow IP addresses from malicious authenticated clients. This has been fixed with stronger allow IP validation.
• [client+server] Fernando Arnaboldi from IOActive found that strict filesystem permissions for various fwknop files are not verified. Added warnings whenever permissions are not strict enough, and ensured that files created by the fwknop client and server are only set to user read/write.
• [client] Fernando Arnaboldi from IOActive found a local buffer overflow in --last processing with a maliciously constructed ~/.fwknop.run file. This has been fixed with proper validation of .fwknop.run arguments.
• [server] Fernando Arnaboldi from IOActive found several conditions in which the server did not properly throw out maliciously constructed variables in the access.conf file. This has been fixed along with new fuzzing tests in the test suite.
• [test suite] Added a new fuzzing capability to ensure proper server-side input validation. Fuzzing data is constructed with modified fwknop client code that is designed to emulate malicious behavior.
• Fixed RPM builds by including the $(DESTDIR) prefix for uninstall-local and install-exec-hook stages in Makefile.am.

$ ./spa-entropy.pl -f 1000_pkts.data -r -c 1000 --base64-decode --gpg
[+] Running fwknop client via the following command:

LD_LIBRARY_PATH=../../lib/.libs ../../client/.libs/fwknop -A tcp/22 -a 127.0.0.2 -D 127.0.0.1 --get-key ../../test/local_spa.key -B 1000_pkts.data -b -v --test --gpg-recipient-key 361BBAD4 --gpg-signer-key 6A3FAD56 --gpg-home-dir ../../test/conf/client-gpg 2> /dev/null

[+] Read in 1000 SPA packets...
[+] Min entropy: 0.00 at byte: 1
[+] Max entropy: 7.85 at byte: 654
[+] Creating entropy.gif gnuplot graph...

• [server] For GPG mode, added a new access.conf variable "GPG_ALLOW_NO_PW" to make it possible to leverage a server-side GPG key pair that has no associated password. This comes in handy when a system requires the user to leverage gpg-agent / pinentry which can present a problem in automated environments as required by the fwknopd server. Now, it might seem like a problem to remove the passphrase from a GPG key pair, but it's important to note that simply doing this is little worse than storing the passphrase in the clear on disk anyway in the access.conf file. Further, this link helps provide additional detail:
  
  http://www.gnupg.org/faq/GnuPG-FAQ.html#how-can-i-use-gnupg-in-an-automated-environment
  
  
• [client] In IP resolution mode (-R) changed HTTP connection type to 'close' since there is no need for connection persistence, and indeed the client expects to just get the IP and the connection to be closed. Jonathan Schulz submitted a patch for this.
• [client] Bug fix to ensure that all data is read via recv() from a remote webserver IP resolution mode (-R). Previously IP resolution could fail if HTTP headers were transferred separately from the data (for whatever reason). Jonathan Schulz submitted a patch for this.
• [client] Added backup check against a cipherdyne.com 'myip' cgi instance in -R mode if the normal check against cipherdyne.org fails.
• [server] Bug fix to implement FLUSH_IPT_AT_INIT and FLUSH_IPT_AT_EXIT functionality. These are enabled by default, and now iptables rules added by fwknopd can be made persistant by setting these variables to "N" in the fwknopd.conf file (this is not a recommended setting however).
• [server] Added FLUSH_IPFW_AT_INIT and FLUSH_IPFW_AT_EXIT for ipfw firewalls to emulate the corresponding functionality that is implemented for iptables firewalls. This was suggested by Jonathan Schulz.
• [server] Replay attack bug fix to ensure that an attacker cannot force a replay attack by intercepting an SPA packet and the replaying it with the base64 version of "Salted__" (for Rindael) or the "hQ" prefix (for GnuPG). This is an important fix. The following comment was added into the fwknopd code:
  
  

  /* Ignore any SPA packets that contain the Rijndael or GnuPG prefixes
   * since an attacker might have tacked them on to a previously seen
   * SPA packet in an attempt to get past the replay check.  And, we're
   * no worse off since a legitimate SPA packet that happens to include
   * a prefix after the outer one is stripped off won't decrypt properly
   * anyway because libfko would not add a new one.
  */
  

• [server] Fixed a memory leak bug in the replay attack detection code. The leak was found with the test suite in --enable-valgrind mode, and here is the valgrind trace that exposed it:
  
  

  44 bytes in 1 blocks are definitely lost in loss record 2 of 2
     at 0x482BE68: malloc (in
     /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
     by 0x490EA50: strdup (strdup.c:43)
     by 0x10CD69: incoming_spa (incoming_spa.c:162)
     by 0x10E000: process_packet (process_packet.c:200)
     by 0x4862E63: ??? (in /usr/lib/i386-linux-gnu/libpcap.so.1.1.1)
     by 0x4865667: pcap_dispatch (in /usr/lib/i386-linux-gnu/libpcap.so.1.1.1)
     by 0x10DABF: pcap_capture (pcap_capture.c:226)
     by 0x10A798: main (fwknopd.c:299)
  

• [test suite] Added GPG tests for keyrings that have no associated passphrases.
• [server] Implemented a new check to ensure that the iptables 'comment' match exists to ensure the proper environment for fwknopd operations. This check is controlled by the new ENABLE_IPT_COMMENT_CHECK variable, and was suggested by Hank Leininger.
• [server] 'make install' fix to ensure restrictive permissions on the /etc/fwknop/ directory and /etc/fwknop/* files. Also updated the 'make install' step to not overwrite any existing config files in /etc/fwknop/ and instead install new copies from the source tree at /etc/fwknop/fwknopd.conf.inst and /etc/fwknop/access.conf.inst

• [server] Bug fix where the same encryption key used for two stanzas in the access.conf file would result in access requests that matched the second stanza to always be treated as a replay attack. This has been fixed for the fwknop-2.0.1 release, and was reported by Andy Rowland. Now the fwknopd server computes the SHA256 digest of raw incoming payload data before decryption, and compares this against all previous hashes. Previous to this commit, fwknopd would add a new hash to the replay digest list right after the first access.conf stanza match, so when SPA packet data matched the second access.conf stanza a matching replay digest would already be there.
• [server] Updated PCAP_LOOP_SLEEP default to 1/10th of a second (in microseconds). This was supposed to be the default anyway, but C Anthony Risinger reported a bug where fwknopd was consuming more resources than necessary, and the cause was PCAP_LOOP_SLEEP set by default to 1/100th of a second - this has been fixed.
• [libfko] Added SPA message validation calls to fko decoding routines to help ensure that SPA messages conform to expected values.
• Bug fix for PF firewalls: updated the PF anchor check to not rely on listing the PF policy - fwknopd now uses 'pfctl -s Anchor' instead.
• [test suite] Added parsing of valgrind output to produce a listing of functions that have been flagged - this assists in the development process to ensure that fwknop is not leaking memory.
• [test suite] Bug fix on Mac OS X systems to account for libfko.dylib path instead of libfko.so. This fixes the existence check for libfko.
• [test suite] Added tests for --nat-local mode.
• [client] Fixed several minor memory leaks caught by valgrind.
• [libfko] Minor gcc warning fix: fko_decode.c:43:17: warning: variable ‘edata_size’ set but not used [-Wunused-but-set-variable].
• Updated fwknopd init script for Debian systems (contributed by Franck Joncourt).

• Switched --no-ipt-sync to default to not syncing with the iptables policy. By default fwsnort attempts to match translated Snort rules to the running iptables policy, but this is tough to do well because iptables policies can be complex. And, before fwsnort switched to the iptables-save format for instantiating the policy, a large set of translated rules could take a really long time to make active within the kernel. Finally, many Snort rules restrict themselves to established TCP connections anyway, and if a restrictive policy doesn't allow connections to get into the established state for some port let's say, then there is little harm in having translated Snort rules for this port. Some kernel memory would be wasted (small), but no performance would be lost since packets won't be processed against these rules anyway. The end result is that the default behavior is now to not sync with the local iptables policy in favor of translating and instantiating as many rules as possible.
• Replaced Net::IPv4Addr with the excellent NetAddr::IP module which has comprehensive support for IPv6 address network parsing and comparisons.
• Moved the fwsnort.sh script and associated files into the /var/lib/fwsnort/ directory. This was suggested by Peter Vrabec.
• Bug fix for recent versions of iptables (such as 1.4.12) where the icmp match requires --icmp-type to be set - some Snort rules look for a string to match in icmp traffic, but don't also specify an icmp type.
• Bug fix for 'qw(...) usage as parenthesis' warnings for perl > 5.14
• Removed the ExtUtils::MakeMaker RPM build requirement from the fwsnort.spec file. This is a compromise which will allow the fwsnort RPM to be built even if RPM doesn't or can't see that ExtUtils::MakeMaker is installed - most likely it will build anyway. If it doesn't, there are bigger problems since fwsnort is written in perl. If you want to build the fwsnort RPM with a .spec file that requires ExtUtils::MakeMaker, then use the "fwsnort-require-makemaker.spec" file that is bundled in the fwsnort sources.

• Added support for detection of malicious traffic that is delivered via IPv6. This is accomplished by parsing ip6tables log messages - these are in a slightly different format than the iptables log messages. Here is an example:
  
  Mar 17 13:39:13 linux kernel: [956932.483644] DROP IN=eth0 OUT= MAC=00:13:46:3a:41:36:00:1b:b9:76:9c:e4:86:dd SRC=2001:0db8:0000:f101:0000:0000:0000:0002 DST=2001:0db8:0000:f101:0000:0000:0000:0001 LEN=80 TC=0 HOPLIMIT=64 FLOWLBL=0 PROTO=TCP SPT=50326 DPT=993 WINDOW=5760 RES=0x00 SYN URGP=0
  
  Detection of malicious IPv6 traffic can be disabled via a new ENABLE_IPV6_DETECTION config variable.
• For ICMP6 traffic, added protocol validation for ICMP6 type/code combinations.
• Added a new test suite in the test/ directory to validate psad run time operations (scan detection, signature matching, and more). To support this, a new '--install-test-dir' option was added to the install.pl script. Once this is executed, the test suite can be run via the test-psad.pl script in the test/ directory.
• Added a new MAX_SCAN_IP_PAIRS config variable to allow psad memory usage to be constrained by restricting the number of unique IP pairs that psad This is useful for when psad is deployed on systems with little memory, and is best utilized in conjunction with disabling ENABLE_PERSISTENCE so that old scans will also be deleted (and thereby making room for tracking new scans under the MAX_SCAN_IP_PAIRS threshold).
• Bug fix for 'qw(...) usage as parenthesis' warnings for perl > 5.14
• Bug fix that caused psad to emit the following:
  
  Undefined subroutine &main::LOG_DAEMON called at ./psad line 10071.
  
  This problem was noticed by Robert and reported on the psad mailing list.
• Bug fix for ICMP packet handling where psad would incorrectly interpret ICMP port unreachable messages as UDP packets because the UDP specifics are included in the iptables log message. This bug was first reported by Lukas Baxa to the Debian maintainers and was followed up by Franck Joncourt: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=596240 An example ICMP log message that exposed the bug is included below:
  
  Sep 8 18:04:26 baxic kernel: [28241.572876] IN_DROP IN=wlan0 OUT= MAC=00:1a:9f:91:df:ae:00:21:27:e8:0a:a0:08:00 SRC=10.0.0.138 DST=192.168.1.103 LEN=96 TOS=0x00 PREC=0xC0 TTL=254 ID=63642 PROTO=ICMP TYPE=3 CODE=3 [SRC=192.168.1.103 DST=10.0.0.138 LEN=68 TOS=0x00 PREC=0x00 TTL=0 ID=22458 PROTO=UDP SPT=35080 DPT=33434 LEN=48 ]

error: packfile ./objects/pack/pack-9c886ed427d9a7538093f09edf516a0a718201ac.pack does not match index
error: packfile ./objects/pack/pack-9c886ed427d9a7538093f09edf516a0a718201ac.pack cannot be accessed
fatal: git upload-pack: cannot find object 7e8e48412ff985461095a09874059e955145d513:
fatal: The remote end hung up unexpectedly

• On my system where the private repositories live, create two directories GH/ and CD/, and clone all of the github repositories into the GH directory and all cipherdyne.org repository mirrors into the CD directory. We'll assume that the private repositories live in a directory called private/
• For each repository pair in the GH and CD directories, diff the output of git rev-list --all. There should be zero differences here.
• If the step above checks out, then diff the git rev-list --all output across the GH/<repo> and private/<repo> pairs. For this step we expect that the private repositories will have local commits that are not necessarily pushed upstream - what we're concerned about is any commit in a GH/<repo> that is not in a private/<repo>.

$ for r in fwknop psad gpgdir fwsnort IPTables-Parse IPTables-ChainMgr
> do
> echo "[+] Checking $r...";
> diff -u <(cd ~/CD/$r.git && git rev-list --all ) <( cd ~/GH/$r.git && git rev-list --all)
> done
[+] Checking fwknop...
[+] Checking psad...
[+] Checking gpgdir...
[+] Checking fwsnort...
[+] Checking IPTables-Parse...
[+] Checking IPTables-ChainMgr...

$ for r in fwknop psad gpgdir fwsnort IPTables-Parse IPTables-ChainMgr
> do
> echo "[+] Checking $r...";
> diff -u <(cd ~/private/$r.git && git rev-list --all ) <( cd ~/GH/$r.git && git rev-list --all) | egrep "^\+" | grep -v @
> done
[+] Checking fwknop...
+++ /dev/fd/62  2012-03-07 22:50:48.004281002 -0500
[+] Checking psad...
+++ /dev/fd/62  2012-03-07 22:50:48.054281002 -0500
[+] Checking gpgdir...
+++ /dev/fd/62  2012-03-07 22:50:48.164281002 -0500
[+] Checking fwsnort...
+++ /dev/fd/62  2012-03-07 22:50:48.194281002 -0500
[+] Checking IPTables-Parse...
[+] Checking IPTables-ChainMgr...

+fff688f5b4275152636d8959f67bbcd46839fbbb