DSPAM Default Permissions Vulnerability

["Jonathan A. Zdziarski" <jonathan () nuclearelephant com>]

Date: September 15, 2003
Description: DSPAM Default Permissions Vulnerability
Affected Versions: 2.6.5, 2.6.5.1

About DSPAM:

DSPAM is an advanced anti-spam solution compatible with most UNIX email
server implementations.  DSPAM combines deobfuscation techniques, token
chains, and bayesian statistical analysis to create a very effective
anti-spam engine capable of teaching itself.  DSPAM masquerades as the
system's local delivery agent and performs analysis on a per-user basis.

Synopsis:

In order for the DSPAM agent to function correctly when called by the
quarantine CGI or by some MTAs which drop privileges prior to calling
dspam, the dspam agent must be setgid to have access to its own data. 
In most installations, dspam runs under the group 'mail'.

DSPAM v2.6.5 introduced a new feature providing the ability to change
the delivery agent and quarantine agents via commandline.  Due to the
default installation permissions of DSPAM, however, this functionality
was provided to any users capable of executing the dspam agent enabling
them to run commands in this new group. 

Solution:

Unset the world-execute bit of the dspam agent's file permissions, or
upgrade to v2.6.5.2.  Alternatively, more daring users may try
v2.7.0.beta.3, which incorporates trusted user security.

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