bugtraq - Re: GnuPG 1.4.12 and lower - memory access errors and keyring database corruption

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Date: Tue, 01 Jan 2013 16:24:28 -0700
From: Kurt Seifried <kseifried@...hat.com>
To: KB Sriram <kbsriram@...il.com>
CC: bugtraq@...urityfocus.com,
  "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>,
  wk@...pg.org
Subject: Re: GnuPG 1.4.12 and lower - memory access errors and keyring database
 corruption

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Hash: SHA1

On 01/01/2013 12:22 AM, Kurt Seifried wrote:
> On 12/28/2012 06:06 PM, KB Sriram wrote:
>> Versions of GnuPG <= 1.4.12 are vulnerable to memory access
>> violations and public keyring database corruption when importing
>> public keys that have been manipulated.
> 
>> An OpenPGP key can be fuzzed in such a way that gpg segfaults (or
>> has other memory access violations) when importing the key.
> 
>> The key may also be fuzzed such that gpg reports no errors when 
>> examining the key (eg: "gpg the_bad_key.pkr") but importing it
>> causes gpg to corrupt its public keyring database.
> 
>> The database corruption issue was first reported on Dec 6th,
>> through the gpg bug tracking system:
> 
>> https://bugs.g10code.com/gnupg/issue1455
> 
>> The subsequent memory access violation was discovered and reported
>> in a private email with the maintainer on Dec 20th.
> 
>> A zip file with keys that causes segfaults and other errors is 
>> available at
>> http://dl.dropbox.com/u/18852638/gnupg-issues/1455.zip and includes
>> a log file that demonstrates the issues [on MacOS X and gpg
>> 1.4.11]
> 
>> A new version of gpg -- 1.4.13 -- that addressed both these issues,
>> was independently released by the maintainer on Dec 20th.
> 
>> The simplest solution is to upgrade all gpg installs to 1.4.13.
> 
>> [Workarounds: A corrupted database may be recovered by manually 
>> copying back the pubring.gpg~ backup file. Certain errors may also
>> be prevented by never directly importing a key, but first just
>> "looking" at the key (eg: "gpg bad_key.pkr"). However, this is not
>> guaranteed to work in all cases; though upgrading to 1.4.13 does
>> work for the issues reported.]
> 
>> Discovery:
> 
>> The problem was discovered during a byte-fuzzing test of OpenPGP 
>> certificates for an unrelated application. Each byte in turn was 
>> replaced by a random byte, and the modified certificate fed to the 
>> application to check that it handled errors correctly. Gpg was used
>> as a control, but it itself turned out to have errors related to
>> packet parsing. The errors are generally triggered when fuzzing the
>> length field of OpenPGP packets, which cascades into subsequent
>> errors in certain situations.
> 
>> -kb
> 
> Has this been assigned a CVE identifier yet?

Spoke with upstream, confirmed things. Please use CVE-2012-6085 for this
issue.



- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993

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