[FD] AST-2016-009:

Asterisk Project Security Advisory - ASTERISK-2016-009 Product Asterisk Summary Nature of Advisory Authentication Bypass Susceptibility Remote unauthenticated sessions Severity Minor Exploits Known No Reported On October 3, 2016 Reported By Walter Doekes Posted On Last Updated On December 8, 2016 Advisory Contact Mmichelson AT digium DOT com CVE Name 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. Resolution chan_sip has been patched to only treat spaces and horizontal tabs as whitespace following a header name. This allows for Asterisk and authenticating proxies to view requests the same way Affected Versions Product Release Series Asterisk Open Source 11.x All Releases Asterisk Open Source 13.x All Releases Asterisk Open Source 14.x All Releases Certified Asterisk 13.8 All Releases Corrected In Product Release Asterisk Open Source 11.25.1, 13.13.1, 14.2.1 Certified Asterisk 11.6-cert16, 13.8-cert4 Patches SVN URL Revision Links Asterisk Project Security Advisories are posted at http://ift.tt/12wGWyz This document may be superseded by later versions; if so, the latest version will be posted at http://ift.tt/2ggepnS and http://ift.tt/2ghjocO Revision History Date Editor Revisions Made November 28, 2016 Mark Michelson Initial writeup Asterisk Project Security Advisory - ASTERISK-2016-009 Copyright (c) 2016 Digium, Inc. All Rights Reserved. Permission is hereby granted to distribute and publish this advisory in its original, unaltered form.

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