[chrony-dev] chrony-1.31.1 released (security)

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

chrony-1.31.1 is now available. It fixes three security vulnerabilities.

The sources can be downloaded here:
http://download.tuxfamily.org/chrony/chrony-1.31.1.tar.gz

MD5 and SHA1 sums:
01e54c63d09a310f30c4e399f18499df  chrony-1.31.1.tar.gz
8e92871e164dad89b315a5dda99d94ff7b31770a  chrony-1.31.1.tar.gz

Security fixes
--------------
* Protect authenticated symmetric NTP associations against DoS attacks
  (CVE-2015-1799)
* Fix access configuration with subnet size indivisible by 4 (CVE-2015-1821)
* Fix initialization of reply slots for authenticated commands (CVE-2015-1822)


CVE-2015-1799: DoS attack on authenticated symmetric NTP associations

An attacker knowing that NTP hosts A and B are peering with each other
(symmetric association) can send a packet with random timestamps to
host A with source address of B which will set the NTP state variables
on A to the values sent by the attacker. Host A will then send on its
next poll to B a packet with originate timestamp that doesn't match
the transmit timestamp of B and the packet will be dropped. If the
attacker does this periodically for both hosts, they won't be able to
synchronize to each other.

Authentication using a symmetric key can fully protect against this
attack, but in implementations following the NTPv3 (RFC 1305) or NTPv4
(RFC 5905) specification the state variables were updated even when
the authentication check failed and the association was not protected.


CVE-2015-1821: Heap-based buffer overflow in access configuration

When NTP or cmdmon access was configured (from chrony.conf or via
authenticated cmdmon) with a subnet size that is indivisible by 4 and
an address that has nonzero bits in the 4-bit subnet remainder (e.g.
192.168.15.0/22 or f000::/3), the new setting was written to an
incorrect location, possibly outside the allocated array.

An attacker that has the command key and is allowed to access cmdmon
(only localhost is allowed by default) could exploit this to crash
chronyd or possibly execute arbitrary code with the privileges of the
chronyd process.


CVE-2015-1822: Use of uninitialized pointer in command processing

When allocating memory to save unacknowledged replies to authenticated
command requests, the last "next" pointer was not initialized to NULL.
When all allocated reply slots were used, the next reply could be
written to an invalid memory instead of allocating a new slot for it.

An attacker that has the command key and is allowed to access cmdmon
(only localhost is allowed by default) could exploit this to crash
chronyd or possibly execute arbitrary code with the privileges of the
chronyd process.

-- 
Miroslav Lichvar

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