RHSA-2015:2241 - Security Advisory

Topic

Updated chrony packages that fix three security issues, several bugs, and
add various enhancements are now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Moderate security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

The chrony suite, chronyd and chronyc, is an advanced implementation of the
Network Time Protocol (NTP), specially designed to support systems with
intermittent connections. It can synchronize the system clock with NTP
servers, hardware reference clocks, and manual input. It can also operate
as an NTPv4 (RFC 5905) server or peer to provide a time service to other
computers in the network.

An out-of-bounds write flaw was found in the way chrony stored certain
addresses when configuring NTP or cmdmon access. An attacker that has the
command key and is allowed to access cmdmon (only localhost is allowed by
default) could use this flaw to crash chronyd or, possibly, execute
arbitrary code with the privileges of the chronyd process. (CVE-2015-1821)

An uninitialized pointer use flaw was found when allocating memory to save
unacknowledged replies to authenticated command requests. An attacker that
has the command key and is allowed to access cmdmon (only localhost is
allowed by default) could use this flaw to crash chronyd or, possibly,
execute arbitrary code with the privileges of the chronyd process.
(CVE-2015-1822)

A denial of service flaw was found in the way chrony hosts that were
peering with each other authenticated themselves before updating their
internal state variables. An attacker could send packets to one peer host,
which could cascade to other peers, and stop the synchronization process
among the reached peers. (CVE-2015-1853)

These issues were discovered by Miroslav Lichvár of Red Hat.

The chrony packages have been upgraded to upstream version 2.1.1, which
provides a number of bug fixes and enhancements over the previous version.
Notable enhancements include:

• Updated to NTP version 4 (RFC 5905)
• Added pool directive to specify pool of NTP servers
• Added leapsecmode directive to select how to correct clock for leap

second

• Added smoothtime directive to smooth served time and enable leap smear
• Added asynchronous name resolving with POSIX threads
• Ready for year 2036 (next NTP era)
• Improved clock control
• Networking code reworked to open separate client sockets for each NTP

server

(BZ#1117882)

This update also fixes the following bug:

• The chronyd service previously assumed that network interfaces specified

with the "bindaddress" directive were ready when the service was started.
This could cause chronyd to fail to bind an NTP server socket to the
interface if the interface was not ready. With this update, chronyd uses
the IP_FREEBIND socket option, enabling it to bind to an interface later,
not only when the service starts. (BZ#1169353)

In addition, this update adds the following enhancement:

• The chronyd service now supports four modes of handling leap seconds,

configured using the "leapsecmode" option. The clock can be either stepped
by the kernel (the default "system" mode), stepped by chronyd ("step"
mode), slowly adjusted by slewing ("slew" mode), or the leap second can be
ignored and corrected later in normal operation ("ignore" mode). If you
select slewing, the correction will always start at 00:00:00 UTC and will
be applied at a rate specified in the "maxslewrate" option. (BZ#1206504)

All chrony users are advised to upgrade to these updated packages, which
correct these issues and add these enhancements.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.5 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.3 x86_64
• Red Hat Enterprise Linux Server - AUS 7.7 x86_64
• Red Hat Enterprise Linux Server - AUS 7.6 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 7 x86_64
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux for IBM z Systems 7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.5 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.4 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.3 s390x
• Red Hat Enterprise Linux for Power, big endian 7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.5 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.4 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.3 ppc64
• Red Hat Enterprise Linux for Scientific Computing 7 x86_64
• Red Hat Enterprise Linux Server from RHUI 7 x86_64
• Red Hat Enterprise Linux for Power, little endian 7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.6 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.5 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.4 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.3 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.2 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.7 x86_64
• Red Hat Enterprise Linux Server - TUS 7.6 x86_64
• Red Hat Enterprise Linux Server - TUS 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 7 s390x
• Red Hat Enterprise Linux EUS Compute Node 7.7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.6 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.5 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.4 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.3 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.7 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.6 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.4 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.3 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, big endian 7 ppc64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, little endian 7 ppc64le

Fixes

• BZ - 1117882 - rebase chrony to 2.1.1
• BZ - 1169353 - Chronyd not starting with bindaddress option set to bond interface
• BZ - 1206504 - RFE: option to correct clock for leap second by slewing
• BZ - 1209568 - RFE: add option for leap smear
• BZ - 1209572 - CVE-2015-1853 chrony: authentication doesn't protect symmetric associations against DoS attacks
• BZ - 1209631 - CVE-2015-1821 chrony: Heap out of bound write in address filter
• BZ - 1209632 - CVE-2015-1822 chrony: uninitialized pointer in cmdmon reply slots
• BZ - 1211600 - RFE: add support for SRV _ntp._udp resolution
• BZ - 1219492 - Use iburst option for NTP servers from DHCP

CVEs

• CVE-2015-1821
• CVE-2015-1822
• CVE-2015-1853

References

• http://www.redhat.com/security/updates/classification/#normal