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125 lines
4.9 KiB
Plaintext
125 lines
4.9 KiB
Plaintext
Shoreline Firewall configuration generator
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(c) Copyright 2004-2006 Paul D. Gear <paul@gear.dyndns.org>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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SHOREWALL
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The quick plug:
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- Shorewall is the only firewall i trust.
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The IT Manager plug:
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- Shorewall is a policy-driven firewall which lets you think about your
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firewall at a higher level than iptables commands.
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The hard sell to you crazy people still maintaining manual firewall scripts:
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- Shorewall is a wrapper around the kernel iptables, so your existing
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Linux firewall skills transfer. I converted from a 900-plus-line
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ipchains shell script to around 50 lines of shorewall configuration in
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less than 4 hours, with no prior experience.
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ISSUES
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- I'm paranoid - i want more than one firewall between me and the world.
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- Configuring multiple firewalls separately is a recipe for getting your
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rules out of sync, and allowing security problems to creep in.
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- IT Manager types (like me) like to know their policy is consistently
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implemented.
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SOLUTION
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Shoregen is a script that generates shorewall configurations for multiple
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firewalls from a common set of rules and policies. Only the minimal
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information necessary for operation is stored on each firewall, so, for
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example, your DMZ server doesn't need to know about the rules on your
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internal network, but at the same time, it gets consistent rules to your
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outer guard.
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PHILOSOPHY
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Shoregen assumes the X-Files approach to firewall design: trust no one.
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That is, paranoia is a virtue. All access should be as limited as possible
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for things to work. If you don't already agree with this philosophy, you
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may find some of the things shoregen does frustrating, but then again,
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you're probably not reading this document. :-)
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DESIGN
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Shoregen distinguishes between two different types of shorewall
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configuration files. Most shorewall configuration files are simply
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concatenated together from parts constructed from common and host-specific
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parts. These are called simple configs; shoregen doesn't substantially
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alter them, and uses little information from them.
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Configs with which shoregen is more concerned are treated separately, and
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additional features beyond the scope of shorewall itself are implemented.
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Most importantly, two new policy/rule keywords are introduced: WARN and
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BAN. These keywords are not included in shoregen's output, but when a
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subsequent rule or policy is encountered which matches a rule or policy
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marked WARN or BAN, an error message is issued. In the case of BAN, the
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offending line is also dropped from the output, and a non-zero return code
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issued.
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PREREQUISITES
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The tools you will need to use shoregen are:
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perl The main shoregen script is written in Perl
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rsync Used to keep /etc/shorewall directories on your firewalls
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in sync with the central repository
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ssh Encrypted transport for rsync
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make Optional, but saves a few keystrokes.
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USAGE
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Put shoregen and install_shoregen in a directory on your PATH.
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Make a central directory for your configs. I recommend somewhere in a
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trusted user's home directory or central system admin repository. This
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directory should be on a trusted machine in the most secure part of your
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network. Put all of your policies, rules, and zones together in the
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correct order in files in the top level of this directory.
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For each of the simple configs you want to generate centrally, create a
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directory, with a file called COMMON (if necessary) containing the content
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you want to see in that file on all hosts, and a file named for each host
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for host-specific content. I recommend that the default shorewall
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configuration file be placed in the COMMON file of the corresponding
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directory, with directives that are not appropriate commented out.
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When shoregen is run, it places the generated files in the directory
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SPOOL/<host>, where <host> is the hostname of the target firewall. The
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files in this directory are synchronised and the firewall checked and/or
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restarted by a simple wrapper script called install_shoregen.
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See the samples directory for a starting point configuration. It provides
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some suggested policies & rules for the network shown in example1.png. The
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sample configuration has not been tested in any way.
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I hope you find shoregen useful. I welcome your comments, contributions,
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criticisms, and questions.
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