Shorewall 2.0

• The 1.4 site is here.
  
• The 1.3 site is here.
• The 1.2 site is here.

Table of Contents

Introduction to Shorewall

Glossary

• Netfilter - the packet filter facility built into the 2.4 and later Linux kernels.
• ipchains - the packet filter facility built into the 2.2 Linux kernels. Also the name of the utility program used to configure and control that facility. Netfilter can be used in ipchains compatibility mode.
• iptables - the utility program used to configure and control Netfilter. The term 'iptables' is often used to refer to the combination of iptables+Netfilter (with Netfilter not in ipchains compatibility mode).

What is Shorewall?

Getting Started with Shorewall

Looking for Information?

Running Shorewall on Mandrake® with a two-interface setup?

License

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more detail.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA

News

6/2/2004 - Shorewall 2.0.2e

One problem corrected:

1. LOG rules within an action generate two Netfilter logging rules.
   

6/1/2004 - shorewall.net Downtime

The following systems will be down on Saturday 5 June for server rebuild.

• shorewall.net
• lists.shorewall.net
• www1.shorewall.net
• ftp1.shorewall.net
• cvs.shorewall.net
• rsync.shorewall.net

• Shorewall site and list archives search
• Mailing Lists
• Mailing List Archives
• CVS
• Primary shorewall.net DNS

5/28/2004 - Shorewall 2.0.2d

One problem corrected:

1. Shorewall was checking capabilities before loading kernel modules. Consequently, if kernel module autoloading was disabled, the capabilities were mis-detected.
   

5/21/2004 - Shorewall 2.0.2c

1.  DNAT rules with a dynamic source zone don't work properly. When used, these rules cause the rule to be checked against ALL input,  not just input from the designated zone.
   

5/18/2004 - Shorewall 2.0.2b 

Corrects two problems:

1. Specifying a null common action in /etc/shorewall/actions (e.g., :REJECT) results in a startup error.
   
   
2. If /var/lib/shorewall does not exist, shorewall start fails.
   

5/15/2004 - Shorewall 2.0.2a

Corrects two problems:

1. Temporary restore files were not being removed from /var/lib/shorewall. These files have names of the form 'restore-nnnnn'.  You can remove files that have accumulated with the command:
   
       rm -f /var/lib/shorewall/restore-[0-9]*
   
   
2. The restore script did not load kernel modules. The result was that after a cold load, applications like FTP and IRC DCC didn't work.
   
   To correct:
   
       1) Install 2.0.2a
       2) "shorewall restart"
       3) "shorewall save"

5/13/2004 - Shorewall 2.0.2 

Problems Corrected since 2.0.1

1. The /etc/init.d/shorewall script installed on Debian by install.sh failed silently due to a missing file (/usr/share/shorewall/wait4ifup). That file is not part of the normal Shorewall distribution and is provided by the Debian maintainer.
2. A meaningless warning message out of the proxyarp file processing has been eliminated.
3. The "shorewall delete" command now correctly removes all dynamic rules pertaining to the host(s) being deleted. Thanks to Stefan Engel for this correction.

1. Extension Scripts -- In order for extension scripts to work properly with the new iptables-save/restore integration (see New Feature 1 below), some change may be required to your extension scripts. If your extension scripts are executing commands other than iptables then those commands must also be written to the restore file (a temporary file in /var/lib/shorewall that is renamed /var/lib/shorewall/restore-base at the end of the operation).
   
   The following functions should be of help:
   
   A. save_command() -- saves the passed command to the restore file.
   
       Example:
   
           save_command echo Operation Complete
   
      That command would simply write "echo Operation Complete" to the restore file.
   
   B. run_and_save_command() -- saves the passed command to the restore file then executes it. The return value is the exit status of the command.
   
       Example:
   
          run_and_save_command "echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all"
   
       Note that as in this example, when the command involves file redirection then the entire command must be enclosed in quotes. This applies to all of the functions described here.
   
   C. ensure_and_save_command() -- runs the passed command. If the command fails, the firewall is restored to it's prior saved state and the operation is terminated. If the command succeeds, the command is written to the restore file.
   
   
2. Dynamic Zone support -- If you don't need to use the "shorewall add" and "shorewall delete commands, you should set DYNAMIC_ZONES=No in /etc/shorewall/shorewall.conf.

1. Shorewall has now been integrated with iptables-save/iptables-restore to provide very fast start and restart. The elements of this integration are as follows:
   
   a) The 'shorewall save' command now saves the current configuration in addition to the current dynamic blacklist. If you have dynamic zones, you will want to issue 'shorewall save' when the zones are empty or the current contents of the zones will be restored by the 'shorewall restore' and 'shorewall -f start' commands.
   
   b) The 'shorewall restore' command has been added. This command restores the configuration at the time of the last 'save'.
   
   c) The -f (fast) option has been added to 'shorewall start'. When specified (e.g. 'shorewall -f start'), shorewall will perform a 'shorewall restore' if there is a saved configuration. If there is no saved configuration, a normal 'shorewall start' is performed.
   
   d) The /etc/init.d/shorewall script now translates the 'start' command into 'shorewall -f start' so that fast restart is possible.
   
   e) When a state-changing command encounters an error and there is current saved configuration, that configuration will be restored (currently, the firewall is placed in the 'stopped' state).
   
   f) If you have previously saved the running configuration and want Shorewall to discard it, use the 'shorewall forget' command. WARNING: iptables 1.2.9 is broken with respect to iptables-save; if your kernel has connection tracking match support, you must patch iptables 1.2.9 with the iptables patch availale from the Shorewall errata page.
   
   
2. The previous implementation of dynamic zones was difficult to maintain. I have changed the code to make dynamic zones optional under the control of the DYNAMIC_ZONES option in /etc/shorewall/shorewall.conf.
   
   
3. In earlier Shorewall 2.0 releases, Shorewall searches in order the following directories for configuration files.
   
   a) The directory specified in a 'try' command or specified using the -c option.
   b) /etc/shorewall
   c) /usr/share/shorewall
   
   In this release, the CONFIG_PATH option is added to shorewall.conf. CONFIG_PATH contains a list of directory names separated by colons (":"). If not set or set to a null value (e.g., CONFIG_PATH="") then "CONFIG_PATH=/etc/shorewall:/usr/share/shorewall" is assumed. Now Shorewall searches for shorewall.conf according to the old rules and for other configuration files as follows:
   
   a) The directory specified in a 'try' command or specified using the -c option.
   b) Each directory in $CONFIG_PATH is searched in sequence.
   
   In case it is not obvious, your CONFIG_PATH should include /usr/share/shorewall and your shorewall.conf file must be in the directory specified via -c or in a try command, in /etc/shorewall or in /usr/share/shorewall.
   
   For distribution packagers, the default CONFIG_PATH is set in /usr/share/shorewall/configpath. You can customize this file to have a default that differs from mine.
   
   
4. Previously, in /etc/shorewall/nat a Yes (or yes) in the LOCAL column would only take effect if the ALL INTERFACES column also contained Yes or yes. Now, the LOCAL columns contents are treated independently of the contents of the ALL INTERFACES column.
   
   
5. The folks at Mandrake have created yet another kernel module naming convention (module names end in "ko.gz"). As a consequence, beginning with this release, if MODULE_SUFFIX isn't specified in shorewall.conf, then the default value is "o gz ko o.gz ko.gz".
   
   
6. An updated bogons file is included in this release.
   
   
7. In /etc/shorewall/rules and in action files generated from /usr/share/shorewall/action.template, rules that perform logging can specify an optional "log tag". A log tag is a string of alphanumeric characters and is specified by following the log level with ":" and the log tag.
   
   Example:
   
           ACCEPT:info:ftp net     dmz     tcp     21
   
   The log tag is appended to the log prefix generated by the LOGPREFIX variable in /etc/shorewall/conf. If "ACCEPT:info" generates the log prefix "Shorewall:net2dmz:ACCEPT:" then "ACCEPT:info:ftp" will generate "Shorewall:net2dmz:ACCEPT:ftp " (note the trailing blank). The maximum length of a log prefix supported by iptables is 29 characters; if a larger prefix is generated, Shorewall will issue a warning message and will truncate the prefix to 29 characters.
   
   
8. A new "-q" option has been added to /sbin/shorewall commands. It causes the start, restart, check and refresh commands to produce much less output so that warning messages are more visible (when testing this change, I discovered a bug where a bogus warning message was being generated).
   
   
9. Shorewall now uses 'modprobe' to load kernel modules if that utility is available in the PATH; otherwise, 'insmod' is used.
   
   
10. It is now possible to restrict entries in the /etc/shorewall/masq file to particular protocols and destination port(s). Two new columns (PROTO and PORT(S)) have been added to the file.
    
    Example:
    
    You want all outgoing SMTP traffic entering the firewall on eth1 to be sent from eth0 with source IP address 206.124.146.177. You want all other outgoing traffic from eth1 to be sent from eth0 with source IP address 206.124.146.176.
    
            eth0    eth1    206.124.146.177 tcp     25
            eth0    eth1    206.124.146.176
    
    THE ORDER OF THE ABOVE TWO RULES IS SIGNIFICANT!!!!!
    
    Assuming that 10.0.0.0/8 is the only host/network connected to eth1, the progress message at "shorewall start" would be:
    
        Masqueraded Networks and Hosts:
           To 0.0.0.0/0 (tcp 25) from 10.0.0.0/8 through eth0 using 206.124.146.177
           To 0.0.0.0/0 (all) from 10.0.0.0/8 through eth0 using 206.124.146.176
    
    
11. Two new actions are available in the /etc/shorewall/rules file.
    
        ACCEPT+    -- Behaves like ACCEPT with the exception that it exempts matching connections from subsequent DNAT[-] and REDIRECT[-] rules.
        NONAT      -- Exempts matching connections from subsequent DNAT[-] and REDIRECT[-] rules.
    
    
12. A new extension script 'initdone' has been added. This script is invoked at the same point as the 'common' script was previously and is useful for users who mis-used that script under Shorewall 1.x (the script was intended for adding rules to the 'common' chain but many users treated it as a script for adding rules before Shorewall's).
    
    
13. Installing/Upgrading Shorewall on Slackware has been improved. Slackware users must use the tarball and must modify settings in the install.sh script before running it as follows:
    
        DEST="/etc/rc.d"
        INIT="rc.firewall"
    
    Thanks to Alex Wilms for helping with this change.
    

4/17/2004 - Presentation at LinuxFest NW

Today I gave a presentation at LinuxFest NW in Bellingham. The presentation was entitled "Shorewall and the Enterprise" and described the history of Shorewall and gave an overview of its features.

More News

Leaf

LEAF is an open source project which provides a Firewall/router on a floppy, CD or CF. Several LEAF distributions including Bering and Bering-uClibc use Shorewall as their Netfilter configuration tool.

Donations

Shorewall is free but if you try it and find it useful, please consider making a donation to the Alzheimer's Association or to the Starlight Children's Foundation.

Thanks