[UNIX] Squid Web Proxy Cache NTLM Authentication Helper Buffer Overflow Vulnerability
From: SecuriTeam (support_at_securiteam.com)
Date: 06/10/04
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To: list@securiteam.com Date: 10 Jun 2004 11:14:21 +0200
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Squid Web Proxy Cache NTLM Authentication Helper Buffer Overflow
Vulnerability
------------------------------------------------------------------------
SUMMARY
<http://www.squid-cache.org> Squid is "a fully-featured Web Proxy Cache
designed to run on UNIX systems and supports proxying and caching of HTTP,
FTP, and other URLs, as well as SSL support, cache hierarchies,
transparent caching, access control lists and many other features". Remote
exploitation of a buffer overflow vulnerability in Squid Web Proxy Cache
could allow a remote attacker to execute arbitrary code.
DETAILS
Vulnerable Systems:
* Squid-Proxy 2.5.*-STABLE and 3.*-PRE when Squid-Proxy is compiled with
the NTLM helper enabled.
Squid Web Proxy Cache supports Basic, Digest and NTLM authentication. The
vulnerability specifically exists within the NTLM authentication helper
routine, ntlm_check_auth(), located in helpers/ntlm_auth/SMB/libntlmssp.c:
char *ntlm_check_auth(ntlm_authenticate * auth, int auth_length)
{
int rv;
char pass[25] /*, encrypted_pass[40] */;
char *domain = credentials;
...
memcpy(pass, tmp.str, tmp.l);
...
The function contains a buffer overflow vulnerability due to a lack of
bounds checking on the values copied to the 'pass' variable. Both the
'tmp.str' and 'tmp.l' variables used in the memcpy() call contain
user-supplied data.
Analysis:
A remote attacker can compromise a target system if Squid Proxy is
configured to use the NTLM authentication helper. The attacker can send an
overly long password to overflow the buffer and execute arbitrary code.
Workaround:
Recompile Squid-Proxy with NTLM handlers disabled.
Vendor response:
A patch for this issue is available at:
<http://www.squid-cache.org/~wessels/patch/libntlmssp.c.patch>
http://www.squid-cache.org/~wessels/patch/libntlmssp.c.patch
CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0541>
CAN-2004-0541
Disclosure timeline:
04/27/04 Exploit acquired by iDEFENSE
05/19/04 iDEFENSE Clients notified
05/20/04 Initial vendor notification
05/20/04 Initial vendor response
06/08/04 Public Disclosure
ADDITIONAL INFORMATION
The information has been provided by
<mailto:idlabs-advisories@idefense.com> iDEFENSE.
The original article can be found at:
<http://www.idefense.com/application/poi/display?id=107&type=vulnerabilities> http://www.idefense.com/application/poi/display?id=107&type=vulnerabilities
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