Bug 795853 (CVE-2012-0871)

Summary:	CVE-2012-0871 systemd: insecure file creation may lead to elevated privileges
Product:	[Other] Security Response	Reporter:	Vincent Danen <vdanen>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	jlieskov, lpoetter, mschmidt, scorneli, security-response-team
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-03-22 12:38:29 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:	799086
Bug Blocks:	795857

Description Vincent Danen 2012-02-21 16:28:44 UTC

Sebastian Krahmer of the SUSE Security Team reported that systemd-logind, a part of the systemd service and system manager, did not create certain special files in a secure way.  systemd-logind is responsible for managing and tracking user login sessions, and if a user were to log into the X11 desktop, it creates entries in /run/user/[username]/X11, where /run/user/[username] is a user-owned directory.  Because systemd-logind does not create the entries in a secure fashion, a malicious user could replace /run/user/[username]/X11 with a symlink to another root-owned directory, such as /etc/pam.d or /etc/cron.d.  This would cause a symlink named "display" to be created in the target directory, which is a symlink to a user-owned file (/tmp/.X11-unix/X0).  Using further attack vectors and this symlink, the malicious user could obtain a root shell, if he could beat two separate race conditions.


Acknowledgements:

Red Hat would like to thank Sebastian Krahmer of the SUSE Security Team for reporting this issue.

Comment 1 Vincent Danen 2012-02-21 16:42:08 UTC

Sebastian indicated that the following git commit removes the X11/ directory, rendering this ineffective, although it's not known whether this fixes the flaw fully, or simply renders this one avenue ineffective.

http://cgit.freedesktop.org/systemd/systemd/commit/?id=fc3c1c6e091ea16ad5600b145201ec535bbb5d7c

Comment 4 Stefan Cornelius 2012-03-01 09:38:36 UTC

This is public now:
http://lists.opensuse.org/opensuse-security-announce/2012-02/msg00030.html

Comment 6 Tomas Hoger 2012-03-01 12:49:17 UTC

SUSE bug report:
  https://bugzilla.novell.com/show_bug.cgi?id=747154

Comment 9 Stefan Cornelius 2012-03-01 18:37:31 UTC

Created systemd tracking bugs for this issue

Affects: fedora-all [bug 799086]

Comment 14 Fedora Update System 2012-03-11 23:20:30 UTC

systemd-37-15.fc16 has been pushed to the Fedora 16 stable repository.  If problems still persist, please make note of it in this bug report.