Bug 1485510 (CVE-2017-7562)

Summary:	CVE-2017-7562 krb5: Authentication bypass by improper validation of certificate EKU and SAN
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	abokovoy, bmaxwell, cdewolf, chazlett, csutherl, darran.lofthouse, dimitris, dosoudil, dpal, fgavrilo, gzaronik, jawilson, jclere, jondruse, jplans, jshepherd, j, lgao, mbabacek, mturk, myarboro, nalin, npmccallum, pgier, pjurak, pkis, ppalaga, psakar, pslavice, rharwood, rnetuka, rstancel, rsvoboda, sardella, sbose, ssorce, twalsh, vtunka, weli
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	An authentication bypass flaw was found in the way krb5's certauth interface handled the validation of client certificates. A remote attacker able to communicate with the KDC could potentially use this flaw to impersonate arbitrary principals under rare and erroneous circumstances.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-06-08 03:22:16 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:	1498767
Bug Blocks:	1485513, 1498774

Description Pedro Sampaio 2017-08-25 22:00:29 UTC

A flaw was found in krb5 certificate EKU validation which could lead to improper authorization if a forged certificate with the right EKU and no SAN is used.

The PKINIT certauth eku module should never authoritatively authorize
a certificate, because an extended key usage does not establish a
relationship between the certificate and any specific user; it only
establishes that the certificate was created for PKINIT client
authentication.

Upstream bug:

https://github.com/krb5/krb5/pull/694

Upstream patch:

https://github.com/krb5/krb5/pull/694/commits/50fe4074f188c2d4da0c421e96553acea8378db2
https://github.com/krb5/krb5/pull/694/commits/1de6ca2f2eb1fdbab51f1549a25a6903aefcc196
https://github.com/krb5/krb5/pull/694/commits/b7af544e50a4d8291524f590e20dd44430bf627d

Comment 7 errata-xmlrpc 2018-04-10 08:02:54 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2018:0666 https://access.redhat.com/errata/RHSA-2018:0666