Bug 948072 (CVE-2013-1923)

Summary:	CVE-2013-1923 nfs-utils: rpc.gssd is vulnerable to DNS spoofing
Product:	[Other] Security Response	Reporter:	Vincent Danen <vdanen>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED WONTFIX	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	bfields, jkurik, jlieskov, rmainz, security-response-team, steved
Target Milestone:	---	Keywords:	Reopened, Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-08-22 06:24:20 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:	948078
Bug Blocks:	948077

Description Vincent Danen 2013-04-03 22:27:44 UTC

It was reported [1],[2] that rpc.gssd in nfs-utils is vulnerable to DNS spoofing due to it depending on PTR resolution for GSSAPI authentication.  Because of this, if a user where able to poison DNS to a victim's computer, they would be able to trick rpc.gssd into talking to another server (perhaps with less security) than the intended server (with stricter security).  If the victim has write access to the second (less secure) server, and the attacker has read access (when they normally might not on the secure server), the victim could write files to that server, which the attacker could obtain (when normally they would not be able to).  To the victim this is transparent because the victim's computer asks the KDC for a ticket to the second server due to reverse DNS resolution; in this case Krb5 authentication does not fail because the victim is talking to the "correct" server.

A patch that prevents this issue has been posted [3].

To workaround this issue, set the IP/host pair in /etc/hosts so that it cannot be spoofed.

A good explanation is also available here [4].

[1] http://marc.info/?l=linux-nfs&m=136491998607561&w=2
[2] http://marc.info/?l=linux-nfs&m=136500502805121&w=2
[3] http://marc.info/?l=linux-nfs&m=136493115612397&w=2
[4] http://ssimo.org/blog/id_015.html

Comment 1 Vincent Danen 2013-04-03 22:42:01 UTC

Created nfs-utils tracking bugs for this issue

Affects: fedora-all [bug 948078]

Comment 2 Vincent Danen 2013-04-04 20:52:47 UTC

This was assigned CVE-2013-1923:

http://www.openwall.com/lists/oss-security/2013/04/04/5

Comment 6 Jan Lieskovsky 2013-05-09 10:12:47 UTC

Direct link to upstream patch:
  http://git.linux-nfs.org/?p=steved/nfs-utils.git;a=commitdiff;h=f9f5450f8f946ffc664397c86d05d27ba0406e21

Comment 7 Vincent Danen 2014-01-11 19:34:33 UTC

Current Fedora 19+ ship with nfs-utils 1.2.8 which includes the fix.

Comment 9 Vincent Danen 2015-08-22 06:23:58 UTC

Statement:

Red Hat Product Security has rated this issue as having Low security impact. This issue is not currently planned to be addressed in future updates. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.