<div dir="ltr">Hey all -<div><br></div><div>The Asterisk project just released a security advisory for a security vulnerability in which Asterisk using chan_sip with a proxy can allow for unauthenticated calls. This affects all supported versions of Asterisk (11, 13, 14). Since that may be relevant to those on this mailing list who are not also on the asterisk-users mailing list, I thought it prudent to mention it here as well.</div><div><br></div><div>A description of the vulnerability follows:</div><div><br></div><div><pre style="white-space:pre-wrap;color:rgb(0,0,0)"> Description The chan_sip channel driver has a liberal definition for
whitespace when attempting to strip the content between a
SIP header name and a colon character. Rather than
following RFC 3261 and stripping only spaces and horizontal
tabs, Asterisk treats any non-printable ASCII character as
if it were whitespace. This means that headers such as
Contact\x01:
will be seen as a valid Contact header.
This mostly does not pose a problem until Asterisk is
placed in tandem with an authenticating SIP proxy. In such
a case, a crafty combination of valid and invalid To
headers can cause a proxy to allow an INVITE request into
Asterisk without authentication since it believes the
request is an in-dialog request. However, because of the
bug described above, the request will look like an
out-of-dialog request to Asterisk. Asterisk will then
process the request as a new call. The result is that
Asterisk can process calls from unvetted sources without
any authentication.
If you do not use a proxy for authentication, then this
issue does not affect you.
If your proxy is dialog-aware (meaning that the proxy keeps
track of what dialogs are currently valid), then this issue
does not affect you.
If you use chan_pjsip instead of chan_sip, then this issue
does not affect you. </pre></div><div><br></div><div>The announcement can be seen here:</div><div><br></div><div><a href="http://lists.digium.com/pipermail/asterisk-announce/2016-December/000662.html">http://lists.digium.com/pipermail/asterisk-announce/2016-December/000662.html</a></div><div><br></div><div>Thanks again to Walter Doekes for reporting the vulnerability and providing the patch to fix it.</div><div><br></div><div>Matt<br clear="all"><div><br></div>-- <br><div class="gmail_signature">Matthew Jordan<br>Digium, Inc. | CTO<br>445 Jan Davis Drive NW - Huntsville, AL 35806 - USA<br>Check us out at: <a href="http://digium.com" target="_blank">http://digium.com</a> & <a href="http://asterisk.org" target="_blank">http://asterisk.org</a></div>
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