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_______________________________________________________________________
                     Rapid7, Inc. Security Advisory
       Visit http://www.rapid7.com/ to download NeXpose,
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Rapid7 Advisory R7-0017
TCPDUMP ISAKMP payload handling denial-of-service vulnerabilities

   Published:  March 30, 2004
   Revision:   1.0
   http://www.rapid7.com/advisories/R7-0017.html

   CVE:    CAN-2004-0183, CAN-2004-0184

1. Affected system(s):

   KNOWN VULNERABLE:
    o TCPDUMP v3.8.1 and earlier versions

2. Summary

   TCPDUMP v3.8.1 and earlier versions contain multiple flaws in the
   packet display functions for the ISAKMP protocol.  Upon receiving
   specially crafted ISAKMP packets, TCPDUMP will try to read beyond
   the end of the packet capture buffer and crash.

3. Vendor status and information

   TCPDUMP
   http://www.tcpdump.org

   The vendor was notified and they have released an updated version
   of TCPDUMP, version 3.8.2, which fixes these defects.  Subsequently,
   the version number was bumped to 3.8.3 to match libpcap.

4. Solution

   Upgrade to version 3.8.3 of TCPDUMP.  You should also consider
   upgrading to version 0.8.3 of libpcap.  Note that many vendors
   package their own customized version of TCPDUMP and libpcap with
   their operating system distribution.  You may want to consider
   contacting your operating system vendor for an upgrade.

5. Detailed analysis

   To test the security and robustness of IPSEC implementations
   from multiple vendors, the security research team at Rapid7
   has designed the Striker ISAKMP Protocol Test Suite.  Striker
   is an ISAKMP packet generation tool that automatically produces
   and sends invalid and/or atypical ISAKMP packets.

   This advisory is the second in a series of vulnerability
   disclosures discovered with the Striker test suite.  Striker
   will be made available to qualified IPSEC vendors.  Please
   email advisory@rapid7.com for more information on obtaining
   Striker.

   There are two defects in the ISAKMP packet display functions in
   TCPDUMP.  Both of them require that verbose packet display be
   enabled with the -v option.  These defects result in out-of-bounds
   reads.

   Overflow in ISAKMP Delete payload with large number of SPI's
   CVE ID: CAN-2004-0183

      When displaying Delete payloads, TCPDUMP does not verify
      that (NSPIS * SPISIZE) fits within the snap buffer.

      An ISAKMP packet with a malformed Delete payload having
      a large self-reported number of SPI's will cause TCPDUMP
      to crash as it tries to read from beyond the end of the
      snap buffer.

      See section 3.15 of RFC 2408 for information on the
      Delete payload format.

   Integer underflow in ISAKMP Identification payload 
   CVE ID: CAN-2004-0184

      An ISAKMP packet with a malformed Identification payload
      with a self-reported payload length that becomes less than
      8 when its byte order is reversed will cause TCPDUMP to
      crash as it tries to read from beyond the end of the
      snap buffer.  TCPDUMP must be using a snaplen of 325 or
      greater for this underflow to be triggered.

      This is due to an inconsistency in the byte order conversion
      in the isakmp_id_print() function:

         if (sizeof(*p) < id.h.len)
            data = (u_char *)(p + 1);
         else 
            data = NULL;
         len = ntohs(id.h.len) - sizeof(*p);

      If id.h.len is equal to, say, 256 (and this fits within the snap
      buffer), then len will be equal to:

         ntohs(256) - sizeof(*p)

      which becomes a negative value on i386.

6. Contact Information

   Rapid7 Security Advisories
   Email:  advisory@rapid7.com
   Web:    http://www.rapid7.com/
   Phone:  +1 (617) 603-0700

7. Disclaimer and Copyright

   Rapid7, LLC is not responsible for the misuse of the information
   provided in our security advisories.  These advisories are a service
   to the professional security community.  There are NO WARRANTIES
   with regard to this information.  Any application or distribution of
   this information constitutes acceptance AS IS, at the user's own
   risk.  This information is subject to change without notice.

   This advisory Copyright (C) 2004 Rapid7, LLC.  Permission is
   hereby granted to redistribute this advisory, providing that no
   changes are made and that the copyright notices and disclaimers
   remain intact.
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