What is it?

The Shoreline Firewall, more commonly known as "Shorewall", is a Netfilter (iptables) based firewall that can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone GNU/Linux system.

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 details.

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, 2002, 2003 Thomas M. Eastep

Getting Started with Shorewall

Looking for Information?

Running Shorewall on Mandrake with a two-interface setup?

News

7/7/2003 - Shorewall-1.4.6 Beta 2

Problems Corrected:

1. A problem seen on RH7.3 systems where Shorewall encountered start errors when started using the "service" mechanism has been worked around.
   
   
2. Where a list of IP addresses appears in the DEST column of a DNAT[-] rule, Shorewall incorrectly created multiple DNAT rules in the nat table (one for each element in the list). Shorewall now correctly creates a single DNAT rule with multiple "--to-destination" clauses.
   
   
3. Corrected a problem in Beta 1 where DNS names containing a "-" were mis-handled when they appeared in the DEST column of a rule.
   

Migration Issues:

1. In earlier versions, an undocumented feature allowed entries in the host file as follows:
   
       z    eth1:192.168.1.0/24,eth2:192.168.2.0/24
   
   This capability was never documented and has been removed in 1.4.6 to allow entries of the following format:
   
       z   eth1:192.168.1.0/24,192.168.2.0/24
   
   
2. The NAT_ENABLED, MANGLE_ENABLED and MULTIPORT options have been removed from /etc/shorewall/shorewall.conf. These capabilities are now automatically detected by Shorewall (see below).
   

New Features:

1. A 'newnotsyn' interface option has been added. This option may be specified in /etc/shorewall/interfaces and overrides the setting NEWNOTSYN=No for packets arriving on the associated interface.
   
   
2. The means for specifying a range of IP addresses in /etc/shorewall/masq to use for SNAT is now documented. ADD_SNAT_ALIASES=Yes is enabled for address ranges.
   
   
3. Shorewall can now add IP addresses to subnets other than the first one on an interface.
   
   
4. DNAT[-] rules may now be used to load balance (round-robin) over a set of servers. Servers may be specified in a range of addresses given as <first address>-<last address>.
   
   Example:
   
       DNAT net loc:192.168.10.2-192.168.10.5 tcp 80
   
   
5. The NAT_ENABLED, MANGLE_ENABLED and MULTIPORT configuration options have been removed and have been replaced by code that detects whether these capabilities are present in the current kernel. The output of the start, restart and check commands have been enhanced to report the outcome:
   
   Shorewall has detected the following iptables/netfilter capabilities:
      NAT: Available
      Packet Mangling: Available
      Multi-port Match: Available
   Verifying Configuration...
   
   
6. Support for the Connection Tracking Match Extension has been added. This extension is available in recent kernel/iptables releases and allows for rules which match against elements in netfilter's connection tracking table. Shorewall automatically detects the availability of this extension and reports its availability in the output of the start, restart and check commands.
   
   Shorewall has detected the following iptables/netfilter capabilities:
      NAT: Available
      Packet Mangling: Available
      Multi-port Match: Available
      Connection Tracking Match: Available
   Verifying Configuration...
   
   If this extension is available, the ruleset generated by Shorewall is changed in the following ways:
• To handle 'norfc1918' filtering, Shorewall will not create chains in the mangle table but will rather do all 'norfc1918' filtering in the filter table (rfc1918 chain).
• Recall that Shorewall DNAT rules generate two netfilter rules; one in the nat table and one in the filter table. If the Connection Tracking Match Extension is available, the rule in the filter table is extended to check that the original destination address was the same as specified (or defaulted to) in the DNAT rule.
  
  
7. The shell used to interpret the firewall script (/usr/share/shorewall/firewall) may now be specified using the SHOREWALL_SHELL parameter in shorewall.conf.
   
   
8. An 'ipcalc' command has been added to /sbin/shorewall.
   
         ipcalc [ <address> <netmask> | <address>/<vlsm> ]
   
   Examples:
   
         [root@wookie root]# shorewall ipcalc 192.168.1.0/24
            CIDR=192.168.1.0/24
            NETMASK=255.255.255.0
            NETWORK=192.168.1.0
            BROADCAST=192.168.1.255
         [root@wookie root]#
   
         [root@wookie root]# shorewall ipcalc 192.168.1.0 255.255.255.0
            CIDR=192.168.1.0/24
            NETMASK=255.255.255.0
            NETWORK=192.168.1.0
            BROADCAST=192.168.1.255
         [root@wookie root]#
   
   Warning:
   
   If your shell only supports 32-bit signed arithmatic (ash or dash), then the ipcalc command produces incorrect information for IP addresses 128.0.0.0-1 and for /1 networks. Bash should produce correct information for all valid IP addresses.
   
   
9. An 'iprange' command has been added to /sbin/shorewall.
   
         iprange <address>-<address>
   
   This command decomposes a range of IP addressses into a list of network and host addresses. The command can be useful if you need to construct an efficient set of rules that accept connections from a range of network addresses.
   
   Note: If your shell only supports 32-bit signed arithmetic (ash or dash) then the range may not span 128.0.0.0.
   
   Example:
   
         [root@gateway root]# shorewall iprange 192.168.1.4-192.168.12.9
         192.168.1.4/30
         192.168.1.8/29
         192.168.1.16/28
         192.168.1.32/27
         192.168.1.64/26
         192.168.1.128/25
         192.168.2.0/23
         192.168.4.0/22
         192.168.8.0/22
         192.168.12.0/29
         192.168.12.8/31
         [root@gateway root]#
   
   
10. A list of host/net addresses is now allowed in an entry in /etc/shorewall/hosts.
    
    Example:
    
        foo    eth1:192.168.1.0/24,192.168.2.0/24

6/17/2003 - Shorewall-1.4.5

Problems Corrected:

1. The command "shorewall debug try <directory>" now correctly traces the attempt.
2. The INCLUDE directive now works properly in the zones file; previously, INCLUDE in that file was ignored.
3. /etc/shorewall/routestopped records with an empty second column are no longer ignored.
   

New Features:

1. The ORIGINAL DEST column in a DNAT[-] or REDIRECT[-] rule may now contain a list of addresses. If the list begins with "!' then the rule will take effect only if the original destination address in the connection request does not match any of the addresses listed.

6/15/2003 - Shorewall, Kernel 2.4.21 and iptables 1.2.8

6/8/2003 - Updated Samples

Thanks to Francesca Smith, the samples have been updated to Shorewall version 1.4.4.

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

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