Bug 1216133 (CVE-2015-2694)

Summary:	CVE-2015-2694 krb5: issues in OTP and PKINIT kdcpreauth modules leading to requires_preauth bypass
Product:	[Other] Security Response	Reporter:	Martin Prpič <mprpic>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	carnil, dpal, jplans, kerberos-dev-list, nalin, nathaniel, pkis, slawomir
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:	A flaw was found in the OTP kdcpreauth module of MIT Kerberos. A remote attacker could use this flaw to bypass the requires_preauth flag on a client principal and obtain a ciphertext encrypted in the principal's long-term key. This ciphertext could be used to conduct an off-line dictionary attack against the user's password.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-11-20 05:43:50 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:	1216134, 1218020
Bug Blocks:	1210268, 1216136

Description Martin Prpič 2015-04-28 14:46:49 UTC

The following flaw was found in MIT Kerberos:

In the OTP kdcpreauth module, the TKT_FLG_PRE_AUTH bit was set before the request was successfully verified. In the PKINIT kdcpreauth module, code 0 was returned on empty input or an unconfigured realm. Together, these bugs could cause the KDC preauth framework to erroneously treat a request as pre-authenticated.

In MIT krb5 1.12 and later, when the KDC is configured with PKINIT support, an unauthenticated remote attacker can bypass the requires_preauth flag on a client principal and obtain a ciphertext encrypted in the principal's long-term key. This ciphertext could be used to conduct an off-line dictionary attack against the user's password.

Upstream patch:

https://github.com/krb5/krb5/commit/e3b5a5e5267818c97750b266df50b6a3d4649604

Comment 1 Martin Prpič 2015-04-28 14:47:38 UTC

Created krb5 tracking bugs for this issue:

Affects: fedora-21 [bug 1216134]

Comment 3 Huzaifa S. Sidhpurwala 2015-05-04 03:38:29 UTC

Statement:

This issue does not affect the version of krb5 package as shipped with Red Hat Enterprise Linux 5 and 6.

Comment 5 Fedora Update System 2015-05-11 19:02:49 UTC

krb5-1.13.1-3.fc22 has been pushed to the Fedora 22 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 6 Fedora Update System 2015-06-21 00:28:40 UTC

krb5-1.12.2-17.fc21 has been pushed to the Fedora 21 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 7 errata-xmlrpc 2015-11-19 05:13:33 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:2154 https://rhn.redhat.com/errata/RHSA-2015-2154.html