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<base href="https://bugzilla.netfilter.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - --gid-owner ignores non-primary group memberships"
href="https://bugzilla.netfilter.org/show_bug.cgi?id=1208">1208</a>
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<th>Summary</th>
<td>--gid-owner ignores non-primary group memberships
</td>
</tr>
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<th>Product</th>
<td>netfilter/iptables
</td>
</tr>
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<th>Version</th>
<td>linux-2.6.x
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P5
</td>
</tr>
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<th>Component</th>
<td>ip_tables (kernel)
</td>
</tr>
<tr>
<th>Assignee</th>
<td>netfilter-buglog@lists.netfilter.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dguyton@gmail.com
</td>
</tr></table>
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<pre>Created <span class=""><a href="attachment.cgi?id=515" name="attach_515" title="Screenshot of iptables/netfilter man page section on -m owner">attachment 515</a> <a href="attachment.cgi?id=515&action=edit" title="Screenshot of iptables/netfilter man page section on -m owner">[details]</a></span>
Screenshot of iptables/netfilter man page section on -m owner
========
Synopsis
========
Request change to current packet owner filtering process by iptables.
=======
Problem
=======
iptables extension "-m owner --gid-owner" only examines the packet owner's
primary gid.
=================
Proposed Solution
=================
One of two steps should be taken by Dev:
1. Update man pages to declare current behavior; OR
2. Change current behavior to include examining owner's primary and secondary
group memberships, and branch --gid-owner filter if there is a match of ANY
group membership of the owner.
Solution #2 is suggested as it is in the spirit of the feature. Solution #1
would simply bring the documentation in-line with current behavior, but does
not solve the problem.
=============
Justification
=============
Common scenario consists of system environments where usernames are assigned to
multiple user groups, for purpose of filtering users based on file permissions,
access permissions, content filtering, etc. This is a very common practice.
Current behavior only allows network packet filtering based on primary user
group. This creates a challenge for programmers when packets owned by a class
of users needs to be manipulated in iptables, yet other requirements dictate
the associated username accounts cannot share a common, primary user group.
While this issue can be mitigated through the use of multiple --uid-owner
commands in iptables, doing so is inefficient and time consuming. That process
also makes server maintenance more difficult as the sysadmin must know to add a
new rule everytime a new user is created who should be branched by the same
filter. This also defeats the purpose of creating the --gid-owner parameter in
the first place.
===================
Illustrated Example
===================
Scenario: Sysadmin is creating a split VPN. A specific user group 'vpn' is
created for the purpose of forcing its network traffic through a VPN interface
and blocking it from the default internet gateway.
Problem: This won't work as desired if any target users belong to group 'vpn'
as a secondary group. It will only branch users who belong to group 'vpn' as
their primary/default user group.
`--gid-owner` only examines the primary/default group of the owner of the
packet
The user will be forced to create individual rules for each username, using
'--uid-owner' instead; a very inefficient process.</pre>
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