RHSA-2015:1459 - Security Advisory

Topic

Updated ntp packages that fix multiple security issues, several bugs, and
add two enhancements are now available for Red Hat Enterprise Linux 6.

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 Network Time Protocol (NTP) is used to synchronize a computer's time
with another referenced time source.

It was found that because NTP's access control was based on a source IP
address, an attacker could bypass source IP restrictions and send malicious
control and configuration packets by spoofing ::1 addresses.
(CVE-2014-9298)

A denial of service flaw was found in the way NTP 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-2015-1799)

A flaw was found in the way the ntp-keygen utility generated MD5 symmetric
keys on big-endian systems. An attacker could possibly use this flaw to
guess generated MD5 keys, which could then be used to spoof an NTP client
or server. (CVE-2015-3405)

A stack-based buffer overflow was found in the way the NTP autokey protocol
was implemented. When an NTP client decrypted a secret received from an NTP
server, it could cause that client to crash. (CVE-2014-9297)

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. (CVE-2015-1798)

The CVE-2015-1798 and CVE-2015-1799 issues were discovered by Miroslav
Lichvár of Red Hat.

Bug fixes:

• The ntpd daemon truncated symmetric keys specified in the key file to 20

bytes. As a consequence, it was impossible to configure NTP authentication
to work with peers that use longer keys. The maximum length of keys has now
been changed to 32 bytes. (BZ#1053551)

• The ntp-keygen utility used the exponent of 3 when generating RSA keys,

and generating RSA keys failed when FIPS mode was enabled. ntp-keygen has
been modified to use the exponent of 65537, and generating keys in FIPS
mode now works as expected. (BZ#1184421)

• The ntpd daemon included a root delay when calculating its root

dispersion. Consequently, the NTP server reported larger root dispersion
than it should have and clients could reject the source when its distance
reached the maximum synchronization distance (1.5 seconds by default).
Calculation of root dispersion has been fixed, the root dispersion is now
reported correctly, and clients no longer reject the server due to a large
synchronization distance. (BZ#1045376)

• The ntpd daemon dropped incoming NTP packets if their source port was

lower than 123 (the NTP port). Clients behind Network Address Translation
(NAT) were unable to synchronize with the server if their source port was
translated to ports below 123. With this update, ntpd no longer checks the
source port number. (BZ#1171630)

Enhancements:

• This update introduces configurable access of memory segments used for

Shared Memory Driver (SHM) reference clocks. Previously, only the first two
memory segments were created with owner-only access, allowing just two SHM
reference clocks to be used securely on a system. Now, the owner-only
access to SHM is configurable with the "mode" option, and it is therefore
possible to use more SHM reference clocks securely. (BZ#1122015)

• Support for nanosecond resolution has been added to the SHM reference

clock. Prior to this update, when a Precision Time Protocol (PTP) hardware
clock was used as a time source to synchronize the system clock (for
example, with the timemaster service from the linuxptp package), the
accuracy of the synchronization was limited due to the microsecond
resolution of the SHM protocol. The nanosecond extension in the SHM
protocol now enables sub-microsecond synchronization of the system clock.
(BZ#1117704)

Solution

All ntp users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues and add these
enhancements. After installing the update, the ntpd daemon will
restart automatically.

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 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

• BZ - 995134 - ntp package doesn't build with net-snmp-devel
• BZ - 1045376 - Fix root distance and root dispersion calculations.
• BZ - 1117704 - SHM refclock doesn't support nanosecond resolution
• BZ - 1122015 - SHM refclock allows only two units with owner-only access
• BZ - 1165141 - ntp: mreadvar command crash in ntpq
• BZ - 1166596 - ntpd should warn when monitoring facility can't be disabled due to restrict configuration
• BZ - 1171630 - NTP drops requests when sourceport is below 123
• BZ - 1184572 - CVE-2014-9298 ntp: drop packets with source address ::1
• BZ - 1184573 - CVE-2014-9297 ntp: vallen in extension fields are not validated
• BZ - 1190619 - ntpd -x steps clock on leap second
• BZ - 1193849 - logconfig documentation needs update
• BZ - 1193850 - ntpd does not update dstadr when the routing table changes
• BZ - 1199430 - CVE-2015-1798 ntp: ntpd accepts unauthenticated packets with symmetric key crypto
• BZ - 1199435 - CVE-2015-1799 ntp: authentication doesn't protect symmetric associations against DoS attacks
• BZ - 1210324 - CVE-2015-3405 ntp: ntp-keygen may generate non-random symmetric keys on big-endian systems

CVEs

• CVE-2014-9297
• CVE-2014-9298
• CVE-2014-9750
• CVE-2014-9751
• CVE-2015-1798
• CVE-2015-1799
• CVE-2015-3405

References

• https://access.redhat.com/security/updates/classification/#moderate