Introduction to Shorewall

This is the Shorewall 1.4 Web Site

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

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?

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

Copyright © 2001-2003 Thomas M. Eastep

Running Shorewall on Mandrake with a two-interface setup?

News

12/29/2003 - Shorewall 1.4.9 Beta 2

Problems Corrected since version 1.4.8:

1. There has been a low continuing level of confusion over the terms "Source NAT" (SNAT) and "Static NAT". To avoid future confusion, all instances of "Static NAT" have been replaced with "One-to-one NAT" in the documentation and configuration files.
2. The description of NEWNOTSYN in shorewall.conf has been reworded for clarity.
3. Wild-card rules (those involving "all" as SOURCE or DEST) will no longer produce an error if they attempt to add a rule that would override a NONE policy. The logic for expanding these wild-card rules now simply skips those (SOURCE,DEST) pairs that have a NONE policy.
4. DNAT rules that also specified SNAT now work reliably. Previously, there were cases where the SNAT specification was effectively ignored.
   

Migration Issues:

    None.

New Features:

1. The documentation has been completely rebased to Docbook XML. The documentation is now released as separate HTML and XML packages.
   
2. To cut down on the number of "Why are these ports closed rather than stealthed?" questions, the SMB-related rules in /etc/shorewall/common.def have been changed from 'reject' to 'DROP'.
3. For easier identification, packets logged under the 'norfc1918' interface option are now logged out of chains named 'rfc1918'. Previously, such packets were logged under chains named 'logdrop'.
4. Distributors and developers seem to be regularly inventing new naming conventions for kernel modules. To avoid the need to change Shorewall code for each new convention, the MODULE_SUFFIX option has been added to shorewall.conf. MODULE_SUFFIX may be set to the suffix for module names in your particular distribution. If MODULE_SUFFIX is not set in shorewall.conf, Shorewall will use the list "o gz ko o.gz".
   
   To see what suffix is used by your distribution:
   
   ls /lib/modules/$(uname -r)/kernel/net/ipv4/netfilter
   
   All of the files listed should have the same suffix (extension). Set MODULE_SUFFIX to that suffix.
   
   Examples:
   
        If all files end in ".kzo" then set MODULE_SUFFIX="kzo"
        If all files end in ".kz.o" then set MODULE_SUFFIX="kz.o"
5. Support for user defined rule ACTIONS has been implemented through two new files:
   
   /etc/shorewall/actions - used to list the user-defined ACTIONS.
   /etc/shorewall/action.template - For each user defined <action>, copy this file to /etc/shorewall/action.<action> and add the appropriate rules for that <action>. Once an <action> has been defined, it may be used like any of the builtin ACTIONS (ACCEPT, DROP, etc.) in /etc/shorewall/rules.
   
   Example: You want an action that logs a packet at the 'info' level and accepts the connection.
   
   In /etc/shorewall/actions, you would add:
   
        LogAndAccept
   
   You would then copy /etc/shorewall/action.template to /etc/shorewall/LogAndAccept and in that file, you would add the two rules:
           LOG:info
           ACCEPT
   
6. The default value for NEWNOTSYN in shorewall.conf is now "Yes" (non-syn TCP packets that are not part of an existing connection are filtered according to the rules and policies rather than being dropped). I have made this change for two reasons:
   
   a) NEWNOTSYN=No tends to result in lots of "stuck" connections since any timeout during TCP session tear down results in the firewall dropping all of the retries.
   
   b) The old default of NEWNOTSYN=No and LOGNEWNOTSYN=info resulted in lots of confusing messages when a connection got "stuck". While I could have changed the default value of LOGNEWNOTSYN to suppress logging, I dislike defaults that silently throw away packets.
   
   

12/28/2003 - www.shorewall.net/ftp.shorewall.net Back On-line

Our high-capacity server has been restored to service -- please let us know if you find any problems.

12/03/2003 - Support Torch Passed

More News

Jacques Nilo and Eric Wolzak have a LEAF (router/firewall/gateway on a floppy, CD or compact flash) distribution called Bering that features Shorewall-1.4.2 and Kernel-2.4.20. You can find their work at: http://leaf.sourceforge.net/devel/jnilo

Donations

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