Bug 859060 (CVE-2013-4392)

Summary:	CVE-2013-4392 systemd: TOCTOU race condition when updating file permissions and SELinux security contexts
Product:	[Other] Security Response	Reporter:	Jan Lieskovsky <jlieskov>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	carnil, fweimer, jlieskov, jrusnack, jsegitz, lnykryn, lpoetter, meissner, security-response-team, systemd-maint-list, systemd-maint, xaionaro, zbyszek
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:	2015-11-03 04:57:01 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:	858760, 858766, 1043749
Bug Blocks:	859151

Description Jan Lieskovsky 2012-09-20 13:35:54 UTC

A TOCTOU (time-of-check time-of-use) race condition was found in the way systemd, a system and service manager, used to update file permissions and SELinux security contexts. A local attacker could use this flaw to conduct symbolic link attacks possibly leading to their ability to modify permissions / security context of a path different than originally intended / requested.

Issue found by Florian Weimer, Red Hat Product Security Team

Comment 1 Jan Lieskovsky 2012-09-20 13:37:33 UTC

This issue affects the versions of the systemd package, as shipped with Fedora release of 16 and 17.

Comment 3 Vincent Danen 2013-10-01 22:52:13 UTC

Acknowledgements:

This issue was discovered by Florian Weimer of the Red Hat Product Security Team.

Comment 4 Vincent Danen 2013-10-01 22:52:54 UTC

This was assigned CVE-2013-4392:

http://www.openwall.com/lists/oss-security/2013/10/01/9

Comment 5 Marcus Meissner 2013-11-22 11:00:34 UTC

Do you know at which place this happened? I have a hard time pinpointing it down. ;)

Comment 11 Florian Weimer 2014-03-24 09:05:50 UTC

This is currently blocked by the need for new system calls (or making existing system calls work with O_PATH):

http://article.gmane.org/gmane.linux.file-systems/82821

We need to open files to check their hard link count and make sure that is not greater than 1, so that we do not improperly relabel a file that is visible elsewhere in the file system.  Without O_PATH, the open operation can have side effects, so we would introduce another type of security bug.

Addressing this would also fix the other issue (lsetfilecon is called with absolute paths, which does not prevent symbol link resolution on non-final path components), but this issue could be fixed separate if desired.

Comment 12 Huzaifa S. Sidhpurwala 2014-03-24 09:35:02 UTC

This issue affects the version of systemd as shipped with Fedora 19 and Fedora 20 and is waiting on upstream fix as indicated by comment #11.