Bug 1179856 (CVE-2014-5352)

Summary: CVE-2014-5352 krb5: gss_process_context_token() incorrectly frees context (MITKRB5-SA-2015-001)
Product: [Other] Security Response Reporter: Vasyl Kaigorodov <vkaigoro>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: bbaranow, bmaxwell, cdewolf, csutherl, dandread, darran.lofthouse, dpal, fnasser, gnaik, grocha, jason.greene, jawilson, jboss-set, jclere, jdoyle, jplans, lgao, myarboro, nalin, oguzyilmaz, pgier, pkis, psakar, pslavice, rsvoboda, sbose, security-response-team, twalsh, vtunka, weli
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
A use-after-free flaw was found in the way the MIT Kerberos libgssapi_krb5 library processed valid context deletion tokens. An attacker able to make an application using the GSS-API library (libgssapi) call the gss_process_context_token() function could use this flaw to crash that application.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2015-11-04 08:48:38 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1181208, 1182882, 1182883, 1188869    
Bug Blocks: 1121513, 1179866    
Attachments:
Description Flags
krb5.patch
none
Backport of krb5.patch to krb5-1.12.2-final
none
Backport of krb5.patch to krb5-1.11.5-final
none
Backport of krb5.patch to krb5-1.10.7-final none

Description Vasyl Kaigorodov 2015-01-07 16:34:19 UTC 
Upstream reports that in the MIT krb5 libgssapi_krb5 library, after
gss_process_context_token() is used to process a valid context
deletion token, the caller is left with a security context handle
containing a dangling pointer.  Further uses of this handle will
result in use-after-free and double-free memory access violations.
libgssrpc server applications such as kadmind are vulnerable as they
can be instructed to call gss_process_context_token().

The krb5 mechanism implementation of gss_process_context_token(), upon
successfully validating a deletion token, frees the security context
structure.  This behavior is incorrect as the API has no way to alert
the caller that the security context was deleted.  The application is
left with a valid pointer to a mechglue security context structure,
containing a dangling pointer to a freed krb5 security context
structure.  Any further use of this handle will result in a
use-after-free violation and eventually a double-free when the handle
is deleted with gss_delete_sec_context().  This vulnerability could
theoretically lead to the execution of malicious code, but that is
believed to be difficult.

Applications which call gss_process_context_token() are believed to be
rare, but the server code in the old flavor of libgssrpc GSS-API
authentication can be induced to call gss_process_context_token().

In release krb5-1.9 and earlier, the krb5 GSS mechanism contained
pointer validation code which should prevent subsequent dereferences
of the freed pointer.  In these earlier releases, the vulnerability is
believed to be limited to a memory leak because
gss_delete_sec_context() will not free the mechglue security context
structure.

Suggested path to fix this vulnerability as well as CVE-2014-9421, 
CVE-2014-9422 and CVE-2014-9423 is attached.
Comment 1 Vasyl Kaigorodov 2015-01-07 17:00:05 UTC 
Created attachment 977438 [details]
krb5.patch

This patch is against release krb5-1.13. 
It will apply to krb5-1.12 and krb5-1.11 with some fuzz if the t_prf.c hunk is removed, and to krb5-1.10 if the mglueP.h hunk is also removed.
Comment 2 Vasyl Kaigorodov 2015-01-07 17:02:52 UTC 
Acknowledgements:

Red Hat would like to thank the MIT Kerberos project for reporting this issue. The MIT Kerberos project acknowledges Nico Williams for assisting with the analysis of CVE-2014-5352.
Comment 3 Vasyl Kaigorodov 2015-01-12 15:13:44 UTC 
According to MIT, kadmind in all released versions of MIT krb5 is vulnerable. Third-party server applications using libgssrpc from all releases of MIT krb5 are vulnerable if they enable the AUTH_GSSAPI authentication flavor. Third-party client and server applications using GSS-API libraries from all releases of MIT krb5 are vulnerable if they directly call gss_process_context_token(). Such applications are believed to be rare. Releases krb5-1.9 and prior may be less vulnerable due to pointer validation code within the krb5 GSS-API mechanism; applications using those releases may instead only experience a memory leak
Comment 6 Roland Mainz 2015-01-12 16:47:48 UTC 
Created attachment 979243 [details]
Backport of krb5.patch to krb5-1.12.2-final
Comment 7 Roland Mainz 2015-01-12 17:29:39 UTC 
Created attachment 979249 [details]
Backport of krb5.patch to krb5-1.11.5-final
Comment 8 Roland Mainz 2015-01-12 17:59:12 UTC 
Created attachment 979263 [details]
Backport of krb5.patch to krb5-1.10.7-final
Comment 10 Vincent Danen 2015-02-03 21:17:46 UTC 
External References:

http://web.mit.edu/Kerberos/advisories/MITKRB5-SA-2015-001.txt
Comment 11 Vincent Danen 2015-02-03 21:38:12 UTC 
Created krb5 tracking bugs for this issue:

Affects: fedora-all [bug 1188869]
Comment 12 Tomas Hoger 2015-02-04 19:43:58 UTC 
Upstream commit:

https://github.com/krb5/krb5/commit/82dc33da50338ac84c7b4102dc6513d897d0506a
Comment 13 Vasyl Kaigorodov 2015-03-02 09:17:49 UTC 
Statement:

Red Hat Enterprise Linux 5 is now in Production 3 Phase of the support and maintenance life cycle. This has been rated as having Moderate security impact and is not currently planned to be addressed in future updates. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.
Comment 14 errata-xmlrpc 2015-03-05 10:01:36 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:0439 https://rhn.redhat.com/errata/RHSA-2015-0439.html
Comment 16 Fedora Update System 2015-03-09 08:18:18 UTC 
krb5-1.11.5-18.fc20 has been pushed to the Fedora 20 stable repository.  If problems still persist, please make note of it in this bug report.
Comment 17 Fedora Update System 2015-03-12 16:33:38 UTC 
krb5-1.12.2-14.fc21 has been pushed to the Fedora 21 stable repository.  If problems still persist, please make note of it in this bug report.
Comment 18 errata-xmlrpc 2015-04-09 05:09:24 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2015:0794 https://rhn.redhat.com/errata/RHSA-2015-0794.html