Bug 1199430 – CVE-2015-1798 ntp: ntpd accepts unauthenticated packets with symmetric key crypto

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Bug 1199430 - (CVE-2015-1798) CVE-2015-1798 ntp: ntpd accepts unauthenticated packets with symmetric key crypto

Summary:	CVE-2015-1798 ntp: ntpd accepts unauthenticated packets with symmetric key cr...

Status:	CLOSED ERRATA

Aliases:	CVE-2015-1798

Product:	Security Response
Classification:	Other
Component:	vulnerability (Show other bugs)
Sub Component:
Version:	unspecified
Hardware:	Unspecified Unspecified

Priority	low Severity low
Target Milestone:	---
Target Release:	---
Assigned To:	Red Hat Product Security
QA Contact:
Docs Contact:

URL:
Whiteboard:	impact=low,public=20150407,reported=2...
Keywords:	Security

Depends On:	1209578 1215935 1221564 1221565
Blocks:	1193283 1200382 1210268
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Reported:	2015-03-06 04:30 EST by Miroslav Lichvar
Modified:	2016-02-15 09:24 EST (History)
CC List:	14 users (show)

See Also:
Fixed In Version:
Doc Type:	Bug Fix
Doc Text:	It was found that ntpd did not check whether a Message Authentication Code (MAC) was present in a received packet when ntpd was configured to use symmetric cryptographic keys. A man-in-the-middle attacker could use this flaw to send crafted packets that would be accepted by a client or a peer without the attacker knowing the symmetric key.
Story Points:	---
Clone Of:
Environment:
Last Closed:	2015-11-20 00:34:11 EST
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

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External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2015:1459	normal	SHIPPED_LIVE	Moderate: ntp security, bug fix, and enhancement update	2015-07-21 10:15:04 EDT
Red Hat Product Errata	RHSA-2015:2231	normal	SHIPPED_LIVE	Moderate: ntp security, bug fix, and enhancement update	2015-11-19 04:03:04 EST

Groups: None (edit)

Description Miroslav Lichvar 2015-03-06 04:30:30 EST

When ntpd is configured to use a symmetric key with an NTP server/peer, it checks if the NTP message authentication code (MAC) in received packets is valid, but not if there actually is any MAC included. Packets without MAC are accepted as if they had a valid MAC. This allows a MITM attacker to send false packets that are accepted by the client/peer without having to know the symmetric key.

It seems this bug was introduced in 4.2.5p99 and is in all later stable versions up to 4.2.8p1. Authentication using autokey doesn't have this problem as there is a check that requires the key ID to be larger than NTP_MAXKEY, which fails for packets without MAC.

Comment 3 Martin Prpič 2015-03-10 08:47:31 EDT

Acknowledgements:

This issue was discovered by Miroslav Lichvár of Red Hat.

Comment 7 Kurt Seifried 2015-04-07 12:56:44 EDT

Created ntp tracking bugs for this issue:

Affects: fedora-all [bug 1209578]

Comment 8 Kurt Seifried 2015-04-08 12:00:49 EDT

This issue was fixed upstream:

http://support.ntp.org/bin/view/Main/SecurityNotice#Recent_Vulnerabilities

The updated version is available at:

http://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-4.2.8p2.tar.gz

Comment 14 Fedora Update System 2015-04-22 18:55:44 EDT

ntp-4.2.6p5-22.fc20 has been pushed to the Fedora 20 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 15 Fedora Update System 2015-04-22 18:56:00 EDT

ntp-4.2.6p5-30.fc22 has been pushed to the Fedora 22 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 18 Fedora Update System 2015-04-28 09:00:58 EDT

ntp-4.2.6p5-30.fc21 has been pushed to the Fedora 21 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 21 errata-xmlrpc 2015-07-22 03:00:45 EDT

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2015:1459 https://rhn.redhat.com/errata/RHSA-2015-1459.html

Comment 23 errata-xmlrpc 2015-11-19 03:38:42 EST

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:2231 https://rhn.redhat.com/errata/RHSA-2015-2231.html

Comment 24 Huzaifa S. Sidhpurwala 2015-11-20 00:34:11 EST

Statement:

This issue did not affect the version of ntp as shipped with Red Hat Enterprise Linux 5

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