Bug 1297472 (CVE-2016-1567)

Summary:	CVE-2016-1567 chrony: missing key check allows impersonation between authenticated peers (VU#357792)
Product:	[Other] Security Response	Reporter:	Martin Prpič <mprpic>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED WONTFIX	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	carnil, dkholia, jrusnack, mlichvar, 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:	2016-01-20 14:32:15 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:	1300274, 1300275
Bug Blocks:	1297474

Description Martin Prpič 2016-01-11 15:35:56 UTC

The following flaw was found in chrony:

Symmetric key encryption requires a single trusted key to be specified for each server configuration. A key specified only for one server should only work to authenticate that server, other trusted keys should be refused.

However, when symmetric key authentication is verified, there is no check that the key used is the key specified for the address, any trusted key can be used as long as the keyid references another key the systems share and that key is used to compute the MAC.

An authenticated client (A) could use this flaw to modify a packet sent between a server (B) and a client (C) using a key that is different from the one known to the client (A).

Upstream patch:

https://git.tuxfamily.org/chrony/chrony.git/commit/?id=a78bf9725a7b481

Comment 2 Martin Prpič 2016-01-20 11:54:31 UTC

External References:

http://chrony.tuxfamily.org/news.html#_20_jan_2016_chrony_2_2_1_and_chrony_1_31_2_released
http://www.talosintel.com/reports/TALOS-2016-0071/

Comment 3 Martin Prpič 2016-01-20 11:55:12 UTC

Created chrony tracking bugs for this issue:

Affects: fedora-all [bug 1300274]
Affects: epel-all [bug 1300275]

Comment 4 Martin Prpič 2016-01-20 14:32:15 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/.

Comment 5 Fedora Update System 2016-01-24 03:30:34 UTC

chrony-2.1.1-2.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.

Comment 6 Fedora Update System 2016-02-02 00:53:15 UTC

chrony-2.1.1-2.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.