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207 lines
7.0 KiB
XML
207 lines
7.0 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<article id="UserSets">
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<articleinfo>
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<title>Controlling Output Traffic by UID/GID</title>
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<authorgroup>
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<author>
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<firstname>Tom</firstname>
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<surname>Eastep</surname>
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</author>
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</authorgroup>
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<pubdate>2003-09-19</pubdate>
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<copyright>
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<year>2003</year>
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<holder>Thomas M. Eastep</holder>
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</copyright>
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<legalnotice>
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<para>Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version
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1.2 or any later version published by the Free Software Foundation; with
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no Invariant Sections, with no Front-Cover, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled "<ulink
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url="GnuCopyright.htm">GNU Free Documentation License</ulink>".</para>
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</legalnotice>
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</articleinfo>
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<section>
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<title>Overview</title>
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<para>This capability was added in Shorewall release 1.4.7.</para>
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<para>Netfilter provides the capability to filter packets generated on the
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firewall system by User Id and/or Group Id. Shorewall provides two
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separate but related ways to use this Netfilter capability:</para>
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<itemizedlist>
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<listitem>
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<para>Shorewall allows you to define collections of users called "<link
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linkend="UserSet">User Sets</link>" and then to restrict certain
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rules in /etc/shorewall/rules to a given User Set.</para>
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</listitem>
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<listitem>
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<para>Shorewall also allows you to restrict a given <link
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linkend="Rule">rule</link> to a particular user and/or group.</para>
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</listitem>
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</itemizedlist>
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<para>Since only packets created by programs running on the Shorewall box
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itself, only rules whose SOURCE is the firewall ($FW) may be restricted
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using either of the facilities.</para>
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</section>
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<section id="UserSet">
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<title>User Sets</title>
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<para>Given the way that this facility is implemented in Shorewall, it is
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not possible to control logging of individual rules using a User Set and
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logging is rather specified on the User Set itself.</para>
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<para>User Sets are defined in the /etc/shorewall/usersets file. Columns
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in that file include:</para>
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<variablelist>
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<varlistentry>
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<term>USERSET</term>
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<listitem>
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<para>The name of a User Set. Must be a legal shell identifier of no
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more than six (6) characters in length.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>REJECT</term>
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<listitem>
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<para>Log level for connections rejected for this User Set.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>ACCEPT</term>
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<listitem>
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<para>Log level for connections accepted for this User Set.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>DROP</term>
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<listitem>
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<para>Log level for connections dropped for this User Set.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>In the REJECT and ACCEPT columns, if you don't want to specify a
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value in the column but you want to specify a value in a following column,
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you may enter "-".</para>
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<para>Users and/or groups are added to User Sets using the
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/etc/shorewall/users file. Columns in that file are:</para>
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<variablelist>
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<varlistentry>
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<term>USERSET</term>
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<listitem>
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<para>The name of a User Set defined in /etc/shorewall/usersets.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>USER</term>
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<listitem>
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<para>The name of a user defined on the system or a user number.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>GROUP</term>
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<listitem>
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<para>The name of a group defined on the system or a number.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Only one of the USER and GROUP column needs to be non-empty. If you
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wish to specify a GROUP but not a USER, enter "-" in the user
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column.</para>
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<para>If both USER and GROUP are specified then only programs running
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under that USER:GROUP pair will match rules specifying the User Set named
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in the USERSET column.</para>
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<para>Once a user set has been defined, its name may be placed in the USER
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SET column of the /etc/shorewall/rules file.</para>
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<important>
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<para>When the name of a user set is given in the USER SET column, you
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may not include a log level in the ACTION column; logging of such rules
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is governed solely by the user set's definition in the
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/etc/shorewall/userset file. </para>
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</important>
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<example>
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<title>You want members of the 'admin' group and 'root'
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to be able to use ssh on the firewall to connect to local systems. You
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want to log all connections accepted for these users using syslog at the
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'info' level.</title>
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<para>/etc/shorewall/usersets</para>
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<programlisting>#USERSET REJECT ACCEPT DROP
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admins - info</programlisting>
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<para>/etc/shorewall/users</para>
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<programlisting>#USERSET USER GROUP
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admins - admin
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admins root</programlisting>
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<para>/etc/shorewall/rules</para>
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<programlisting>#ACTION SOURCE DESTINATION PROTO PORT SOURCE ORIGINAL RATE USER
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# PORT(S) DESTINATION SET
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ACCEPT $FW loc tcp 22 - - - admins</programlisting>
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</example>
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</section>
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<section id="Rule">
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<title>Restricting a rule to a particular user and/or group</title>
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<para>In cases where you may want to restrict a rule to a particular user
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and/or group, the USER SET column in the rules file may be specified as:</para>
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<programlisting>[ <<emphasis>user name or number</emphasis>> ] : [ <<emphasis>group name or number</emphasis>> ]</programlisting>
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<para>When a user and/or group name is given in the USER SET column, it is
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OK to specify a log level in the ACTION column. </para>
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<example>
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<title>You want user <emphasis role="bold">mail</emphasis> to be able to
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send email from the firewall to the local net zone</title>
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<para>/etc/shorewall/rules (be sure to note the ":" in the USER
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SET column entry).</para>
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<programlisting>#ACTION SOURCE DESTINATION PROTO PORT SOURCE ORIGINAL RATE USER
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# PORT(S) DESTINATION SET
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ACCEPT $FW loc tcp 25 - - - mail:</programlisting>
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</example>
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</section>
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</article> |