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://www.asterisk.org/security                                          
                                                                              
    This document may be superseded by later versions; if so, the latest      
    version will be posted at                                                 
    http://downloads.digium.com/pub/security/ASTERISK-2016-009.pdf and        
    http://downloads.digium.com/pub/security/ASTERISK-2016-009.html           

                                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.