SRT Security Advisory (SRT2002-06-04-1011): slurp

[zillion <zillion () snosoft com>]

======================================================================

Strategic Reconnaissance Team Security Advisory (SRT2002-06-04-1011)

Topic  : Slurp news retriever remote format string vulnerability
Date   : June 04, 2002
Credit : zillion[at]safemode.org
Site   : http://www.snosoft.com

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.: Description:
---------------

 Slurp is an advanced passive NNTP client for UNIX. It will connect to
 a remote NNTP server and retrieve articles in a specified set of Usenet
 newsgroups that have arrived after a particular date (typically the
 last time it was invoked) for processing by your local news system or
 forwarding on via UUCP to another news system. It replaces nntpxfer
 from the NNTP 1.5.12 reference implementation and nntpget from the INN
 distribution.

 This application insecurely syslogs error messages retrieved from the
 NNTP server to which it is connected. The responsible code that causes
 this security issue:

 log_doit (int sysflag, const char *fmt, va_list ap)
        {

        ...snip snip...

 #ifdef SYSLOG
                if (!debug_flag)
                        syslog (LOG_ERR, buf);
        ...snip snip...

        }

 The FreeBSD port of this application was compiled with syslog and is
 therefor affected. This format string can easily be triggered. To find
 out you have a vulnerable slurp, connect to this:

 perl -e 'print "200 Hello brother \n666 %x%x%x\n'" | nc -l -p 119

 Then check /var/log/messages for something like:

 Jun  5 05:10:22 yada slurp[39926]: do_newnews: NNTP protocol error:
 got '666 bfbff4f8804bc1bbfbff51c'

.: Impact:
----------
 Malicious server owners can use this vulnerability to execute code
 on affected systems.

.: Systems Affected:
--------------------

 Systems running slurp version 1.1.0 are known to be affected by this
 vulnerability.

Cheers,

zillion