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142 lines
6.1 KiB
HTML
142 lines
6.1 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Language" content="en-us">
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<meta http-equiv="Content-Type"
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content="text/html; charset=windows-1252">
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<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
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<meta name="ProgId" content="FrontPage.Editor.Document">
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<title>Controlling Traffic by UID/GID</title>
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<meta name="author" content="Tom Eastep">
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</head>
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<body>
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<table border="0" cellpadding="0" cellspacing="0"
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style="border-collapse: collapse;" bordercolor="#111111" width="100%"
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id="AutoNumber1" bgcolor="#3366ff" height="90">
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<tbody>
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<tr>
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<td width="100%">
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<h1 align="center"><font color="#ffffff">Controlling Output
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Traffic by UID/GID<br>
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</font></h1>
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</td>
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</tr>
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</tbody>
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</table>
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This capability was added in Shorewall release
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1.4.7.<br>
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<br>
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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:<br>
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<ol>
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<li>Shorewall allows you to
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define collections of users called "<a href="#UserSet">User Sets</a>"
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and then to restrict
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certain rules in /etc/shorewall/rules to a given User Set.</li>
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<li>Shorewall also allows you to restrict a given <a href="#Rule">rule
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</a>to a particular user and/or group.<br>
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</li>
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</ol>
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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.<br>
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<h2><a name="UserSet"></a>User Sets<br>
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</h2>
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Given the way that this facility is implemented in Shorewall, it is not
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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.<br>
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<br>
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User Sets are defined in the /etc/shorewall/usersets file. Columns in
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that file include:<br>
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<br>
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<div style="margin-left: 40px;">USERSET
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The name of a User Set. Must be a legal
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shell
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identifier of no more than six (6) characters in length.<br>
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REJECT
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Log level for connections rejected for this User Set.<br>
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ACCEPT Log
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level for connections accepted for this User Set.<br>
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DROP
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Log level for connections dropped for this User Set.<br>
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</div>
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<br>
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In the REJECT and ACCEPT columns, if you don't want to specify a value
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in the column but you want to specify a value in a following column,
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you may enter "-".<br>
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<br>
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Users and/or groups are added to User Sets using the
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/etc/shorewall/users file. Columns in that file are:<br>
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<br>
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<div style="margin-left: 40px;">USERSET
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The name of a User Set defined in
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/etc/shorewall/usersets.<br>
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USER
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The name of a user defined on the system or a user number.<br>
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GROUP
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The name of a group defined on the system or a number.<br>
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</div>
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<p align="left">Only one of the USER and GROUP
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column needs to be non-empty. If you wish to specify a GROUP but not a
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USER, enter "-" in the user column.<br>
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</p>
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<p align="left">If both USER and GROUP are
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specified then only programs running under that USER:GROUP pair will
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match rules specifying the User Set named in the USERSET column.<br>
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</p>
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<p align="left">Once a user set has been defined, its name may be
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placed in the USER SET column of the /etc/shorewall/rules file. <span
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style="color: rgb(255, 0, 0);"><span style="font-weight: bold;">IMPORTANT:
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</span></span>When
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the name of a user set is given in the USER SET column, you may not
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include a log level in the ACTION column; logging of such rules is
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governed solely by the user set's definition in the
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/etc/shorewall/userset file.
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</p>
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<p align="left">Example: You want members of the
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'admin' group and 'root' to be able to use ssh on the firewall to
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connect to local systems. You want to log all connections accepted for
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these users using syslog at the 'info' level.<br>
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</p>
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<div style="margin-left: 40px;"></div>
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<p align="left" style="margin-left: 40px;">/etc/shorewall/usersets</p>
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<div style="margin-left: 40px;"></div>
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<pre style="margin-left: 80px;">#USERSET REJECT ACCEPT DROP<br>admins - info<br></pre>
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<div style="margin-left: 40px;"></div>
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<p align="left" style="margin-left: 40px;">/etc/shorewall/users<br>
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</p>
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<div style="margin-left: 40px;"></div>
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<pre style="margin-left: 80px;">#USERSET USER GROUP<br>admins - admin<br>admins root<br></pre>
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<div style="margin-left: 40px;">/etc/shorewall/rules<br>
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</div>
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<pre style="margin-left: 80px;">#ACTION SOURCE DESTINATION PROTO PORT SOURCE ORIGINAL RATE USER<br># PORT(S) DESTINATION SET<br><br>ACCEPT $FW loc tcp 22 - - - admins<br></pre>
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<h2><a name="Rule"></a>Restricting a rule to a particular user and/or
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group<br>
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</h2>
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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:<br>
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<br>
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<div style="margin-left: 40px;">[ <<span style="font-style: italic;">user
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name or number</span>> ] : [ <<span style="font-style: italic;">group
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name or number</span>> ]<br>
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<div style="text-align: left;"><br>
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</div>
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</div>
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When a user and/or group name is given in the USER SET column, it is OK
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to specify a log level in the ACTION column. <br>
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<br>
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Example: You want user <span style="font-style: italic;">mail </span>to
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be able to send email from the firewall to the local net zone<br>
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<br>
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<div style="margin-left: 40px;">/etc/shorewall/rules (be sure to note
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the ":" in the USER SET column entry).<br>
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<pre>#ACTION SOURCE DESTINATION PROTO PORT SOURCE ORIGINAL RATE USER<br># PORT(S) DESTINATION SET<br><br>ACCEPT $FW loc tcp 25 - - - mail:</pre>
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</div>
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<p align="left"><font size="2">Last updated 9/19/2003 - <a
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href="support.htm">Tom Eastep</a></font></p>
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<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
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<EFBFBD> <font size="2">2003 Thomas M. Eastep.</font></a></font></p>
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</body>
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</html>
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