AST-2017-005, AST-2017-006, and AST-2017-008. There was no release
announcement as only security patches were issued. I just found
this update while looking to see what updates I was missing for
more recent versions of Asterisk. The Asterisk 11.x series was
declared end-of-life on Oct. 25th, 2017, so there will not be any
more updates to this package (other then PKGREVISION bumps for
dependencies) before it gets deleted. There is a reasonable chance
that there are unpatched vulnerabilities in this package. Anybody
still using it should upgrade a newer version as soon as possibble.
----- AST-2017-2005 -----
Description The "strictrtp" option in rtp.conf enables a feature of the
RTP stack that learns the source address of media for a
session and drops any packets that do not originate from
the expected address. This option is enabled by default in
Asterisk 11 and above.
The "nat" and "rtp_symmetric" options for chan_sip and
chan_pjsip respectively enable symmetric RTP support in the
RTP stack. This uses the source address of incoming media
as the target address of any sent media. This option is not
enabled by default but is commonly enabled to handle
devices behind NAT.
A change was made to the strict RTP support in the RTP
stack to better tolerate late media when a reinvite occurs.
When combined with the symmetric RTP support this
introduced an avenue where media could be hijacked. Instead
of only learning a new address when expected the new code
allowed a new source address to be learned at all times.
If a flood of RTP traffic was received the strict RTP
support would allow the new address to provide media and
with symmetric RTP enabled outgoing traffic would be sent
to this new address, allowing the media to be hijacked.
Provided the attacker continued to send traffic they would
continue to receive traffic as well.
Resolution The RTP stack will now only learn a new source address if it
has been told to expect the address to change. The RTCP
support has now also been updated to drop RTCP reports that
are not regarding the RTP session currently in progress. The
strict RTP learning progress has also been improved to guard
against a flood of RTP packets attempting to take over the
media stream.
----- AST-2017-006 -----
Description The app_minivm module has an "externnotify" program
configuration option that is executed by the MinivmNotify
dialplan application. The application uses the caller-id
name and number as part of a built string passed to the OS
shell for interpretation and execution. Since the caller-id
name and number can come from an untrusted source, a
crafted caller-id name or number allows an arbitrary shell
command injection.
Resolution Patched Asterisk's app_minivm module to use a different
system call that passes argument strings in an array instead
of having the OS shell determine the application parameter
boundaries.
----- AST-2017-008 -----
Description This is a follow up advisory to AST-2017-005.
Insufficient RTCP packet validation could allow reading
stale buffer contents and when combined with the "nat" and
"symmetric_rtp" options allow redirecting where Asterisk
sends the next RTCP report.
The RTP stream qualification to learn the source address of
media always accepted the first RTP packet as the new
source and allowed what AST-2017-005 was mitigating. The
intent was to qualify a series of packets before accepting
the new source address.
Resolution The RTP/RTCP stack will now validate RTCP packets before
processing them. Packets failing validation are discarded.
RTP stream qualification now requires the intended series of
packets from the same address without seeing packets from a
different source address to accept a new source address.
2e94040785