Introduction to Shorewall
This is the Shorewall 1.4 Web Site
The information on this site applies only to 1.4.x releases of
Shorewall. For older versions:
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?
The Shoreline Firewall, more commonly known as "Shorewall", is
high-level tool for configuring Netfilter. You describe your
firewall/gateway requirements using entries in a set of configuration
files. Shorewall reads those configuration files and with the help of
the iptables utility, Shorewall configures Netfilter to match your
requirements. Shorewall can be used on a dedicated firewall system, a
multi-function gateway/router/server or on a standalone GNU/Linux
system. Shorewall does not use Netfilter's ipchains compatibility mode
and can thus take advantage of Netfilter's connection state tracking
capabilities.
Shorewall is not a
daemon. Once Shorewall has configured Netfilter, it's job is complete
although the /sbin/shorewall
program can be used at any time to monitor the Netfilter firewall.
Getting Started with Shorewall
New to Shorewall? Start by selecting the QuickStart Guide that most
closely match your environment and follow the step by step instructions.
Looking for Information?
The Documentation
Index is a good place to start as is the Quick Search in the frame
above.
License
This program is free software; you can redistribute it and/or modify it
under the terms of Version
2 of the GNU General Public License as published by the Free
Software Foundation.
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
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover, and with no Back-Cover Texts.
A copy of the license is included in the section entitled "GNU Free
Documentation License".
Copyright © 2001-2003 Thomas M. Eastep
Running Shorewall on Mandrake with a two-interface setup?
If so, the documentation on this site will not apply directly
to your setup. If you want to use the documentation that you find here,
you will want to consider uninstalling what you have and installing a
setup that matches the documentation on this site. See the Two-interface QuickStart Guide for
details.
News
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.
12/07/2003 - Shorewall 1.4.9 Beta 1
Problems Corrected since version 1.4.8:
- 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.
- The description of NEWNOTSYN in shorewall.conf has been
reworded for clarity.
- 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.
Migration Issues:
None.
New Features:
- 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'.
- 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'.
- 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"
- 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
12/03/2003 - Support Torch Passed
Effective today, I am reducing my participation in the day-to-day
support of Shorewall. As part of this shift to community-based
Shorewall support a new Shorewall
Newbies mailing list has been established to field questions and
problems from new users. I will not monitor that list personally. I
will continue my active development of Shorewall and will be available
via the development list to handle development issues -- Tom.
11/07/2003 - Shorewall 1.4.8
Problems Corrected since version 1.4.7:
- Tuomo Soini has supplied a correction to a problem that
occurs using some versions of 'ash'. The symptom is that "shorewall
start" fails with:
local: --limit: bad variable name
iptables v1.2.8: Couldn't load match
`-j':/lib/iptables/libipt_-j.so:
cannot open shared object file: No such file or directory
Try `iptables -h' or 'iptables --help' for more
information.
- Andres Zhoglo has supplied a correction that avoids trying
to use the multiport match iptables facility on ICMP rules.
Example of rule that previously caused "shorewall start"
to fail:
ACCEPT loc $FW
icmp 0,8,11,12
- Previously, if the following error message was issued,
Shorewall was left in an inconsistent state.
Error: Unable to determine the routes through interface xxx
- Handling of the LOGUNCLEAN option in shorewall.conf has
been corrected.
- In Shorewall 1.4.2, an optimization was added. This
optimization involved creating a chain named "<zone>_frwd" for
most zones defined using the /etc/shorewall/hosts file. It has since
been discovered that in many cases these new chains contain redundant
rules and that the "optimization" turns out to be less than optimal.
The implementation has now been corrected.
- When the MARK value in a tcrules entry is followed by ":F"
or ":P", the ":F" or ":P" was previously only applied to the first
Netfilter rule generated by the entry. It is now applied to all entries.
- An incorrect comment concerning Debian's use of the
SUBSYSLOCK option has been removed from shorewall.conf.
- Previously, neither the 'routefilter' interface option nor
the ROUTE_FILTER parameter were working properly. This has been
corrected (thanks to Eric Bowles for his analysis and patch). The
definition of the ROUTE_FILTER option has changed however. Previously,
ROUTE_FILTER=Yes was documented as enabling route filtering on all
interfaces (which didn't work). Beginning with this release, setting
ROUTE_FILTER=Yes will enable route filtering of all interfaces brought
up while Shorewall is started. As a consequence, ROUTE_FILTER=Yes can
coexist with the use of the 'routefilter' option in the interfaces file.
- If MAC verification was enabled on an interface with a /32
address and a broadcast address then an error would occur during
startup.
- he NONE policy's intended use is to suppress the generating
of rules that can't possibly be traversed. This means that a policy of
NONE is inappropriate where the source or destination zone is $FW or
"all". Shorewall now generates an error message if such a policy is
given in /etc/shorewall/policy. Previously such a policy caused
"shorewall start" to fail.
- The 'routeback' option was broken for wildcard interfaces
(e.g., "tun+"). This has been corrected so that 'routeback' now works
as expected in this case.
Migration Issues:
- The definition of the ROUTE_FILTER option in shorewall.conf
has changed as described in item 8) above.
New Features:
- A new QUEUE action has been introduced for rules. QUEUE
allows you to pass connection requests to a user-space filter such as
ftwall (http://p2pwall.sourceforge.net). The ftwall program allows for
effective filtering of p2p applications such as Kazaa. For example, to
use ftwall to filter P2P clients in the 'loc' zone, you would add the
following rules:
QUEUE loc
net tcp
QUEUE loc
net udp
QUEUE loc
fw udp
You would normally want to place those three rules BEFORE any ACCEPT
rules for loc->net udp or tcp.
Note: When the protocol specified is TCP ("tcp", "TCP" or "6"),
Shorewall will only pass connection requests (SYN packets) to user
space. This is for compatibility with ftwall.
- A BLACKLISTNEWNONLY option has been added to
shorewall.conf. When this option is set to "Yes", the blacklists
(dynamic and static) are only consulted for new connection requests.
When set to "No" (the default if the variable is not set), the
blacklists are consulted on every packet.
Setting this option to "No" allows blacklisting to stop existing
connections from a newly blacklisted host but is more expensive in
terms of packet processing time. This is especially true if the
blacklists contain a large number of entries.
- Chain names used in the /etc/shorewall/accounting file may
now begin with a digit ([0-9]) and may contain embedded dashes ("-").
10/26/2003 - Shorewall 1.4.7a and 1.4.7b win brown paper
bag awards Shorewall
1.4.7c released.
- The saga with "<zone>_frwd" chains continues. The
1.4.7c script produces a ruleset that should work for everyone even if
it is not quite optimal. My apologies for this ongoing mess.
10/24/2003 - Shorewall 1.4.7b
This is a bugfx rollup of the 1.4.7a fixes plus:
- The fix for problem 5 in 1.4.7a was wrong with the result
that "<zone>_frwd" chains might contain too few rules. That wrong
code is corrected in this release.
10/21/2003 - Shorewall 1.4.7a
This is a bugfix rollup of the following problem corrections:
- Tuomo Soini has supplied a correction to a problem that
occurs using some versions of 'ash'. The symptom is that "shorewall
start" fails with:
local: --limit: bad variable name
iptables v1.2.8: Couldn't load match
`-j':/lib/iptables/libipt_-j.so:
cannot open shared object file: No such file or directory
Try `iptables -h' or 'iptables --help' for more
information.
- Andres Zhoglo has supplied a correction that avoids trying
to use the multiport match iptables facility on ICMP rules.
Example of rule that previously caused "shorewall start"
to fail:
ACCEPT loc $FW
icmp 0,8,11,12
- Previously, if the following error message was issued,
Shorewall was left in an inconsistent state.
Error: Unable to determine the routes through interface xxx
- Handling of the LOGUNCLEAN option in shorewall.conf has
been corrected.
- In Shorewall 1.4.2, an optimization was added. This
optimization involved creating a chain named "<zone>_frwd" for
most zones defined using the /etc/shorewall/hosts file. It has since
been discovered that in many cases these new chains contain redundant
rules and that the "optimization" turns out to be less than optimal.
The implementation has now been corrected.
- When the MARK value in a tcrules entry is followed by ":F"
or ":P", the ":F" or ":P" was previously only applied to the first
Netfilter rule generated by the entry. It is now applied to all entries.
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
Congratulations to Jacques and Eric on the recent release of
Bering 1.2!!!
Donations
Shorewall is free but if you try it and find it useful,
please consider making a donation to Starlight
Children's Foundation. Thanks!
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