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Message-ID: <4F68B633.100@redhat.com>
Date: Tue, 20 Mar 2012 10:54:11 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Stefan Cornelius <scorneli@...hat.com>
Subject: Re: CVE request: libtasn1 "asn1_get_length_der()"
DER decoding issue
On 03/20/2012 06:40 AM, Stefan Cornelius wrote:
> Hi,
>
> libtasn1 version 2.12 was released fixing the following issue:
>
> - Corrected DER decoding issue (reported by Matthew Hall).
> Added self check to detect the problem, see tests/Test_overflow.c.
> This problem can lead to at least remotely triggered crashes, see
> further analysis on the libtasn1 mailing list.
>
> Further issue details from Simon Josefsson [1]:
>
> I want to mention that there were no security problem in the
> asn1_get_length_der function. It was working properly and as documented
> before. The security problem was the callers not checking that the
> returned values were reasonable, i.e., that the output length was less
> than or equal to the total length of the buffer. However, fixing all
> callers of this function would be a huge amount of work. Instead, we
> made asn1_get_length_der return an error code when the situation
> occured, to protect callers. This fix could be the wrong thing if some
> code out there calls the function with a der_len parameter that is
> smaller than the entire DER structure length. However, we are hoping
> that is not in any significant use, and that overall security will be
> improved by having the function sanity check its output rather than
> letting the caller do that. This was a judgement call.
>
> [1] http://thread.gmane.org/gmane.comp.gnu.libtasn1.general/54
>
> It appears like GnuTLS is affected as well (but probably does not need a
> separate CVE at this point):
> http://article.gmane.org/gmane.comp.encryption.gpg.gnutls.devel/5952/
> http://article.gmane.org/gmane.comp.encryption.gpg.gnutls.devel/5957/
>
> -- References --
>
> Release announcement:
> http://article.gmane.org/gmane.comp.gnu.libtasn1.general/53
>
> Small analysis + patch:
> http://thread.gmane.org/gmane.comp.gnu.libtasn1.general/54
>
> Red Hat bug:
> https://bugzilla.redhat.com/show_bug.cgi?id=804920
>
> Thanks and kind regards,
Please use CVE-2012-1569 for this issue.
--
Kurt Seifried Red Hat Security Response Team (SRT)
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