[asterisk-security] AST-2016-005: TCP denial of service in PJProject

[Asterisk Security Team]

               Asterisk Project Security Advisory - AST-2016-005

         Product        Asterisk                                              
         Summary        TCP denial of service in PJProject                    
    Nature of Advisory  Crash/Denial of Service                               
      Susceptibility    Remote Unauthenticated Sessions                       
         Severity       Critical                                              
      Exploits Known    No                                                    
       Reported On      February 15, 2016                                     
       Reported By      George Joseph                                         
        Posted On       
     Last Updated On    March 3, 2016                                         
     Advisory Contact   Mark Michelson <mark DOT michelson AT digium DOT      
                        com>                                                  
         CVE Name       

    Description  PJProject has a limit on the number of TCP connections that  
                 it can accept. Furthermore, PJProject does not close TCP     
                 connections it accepts. By default, this value is            
                 approximately 60.                                            
                                                                              
                 An attacker can deplete the number of allowed TCP            
                 connections by opening TCP connections and sending no data   
                 to Asterisk.                                                 
                                                                              
                 If PJProject has been compiled in debug mode, then once the  
                 number of allowed TCP connections has been depleted, the     
                 next attempted TCP connection to Asterisk will crash due to  
                 an assertion in PJProject.                                   
                                                                              
                 If PJProject has not been compiled in debug mode, then any   
                 further TCP connection attempts will be rejected. This       
                 makes Asterisk unable to process TCP SIP traffic.            
                                                                              
                 Note that this only affects TCP/TLS, since UDP is            
                 connectionless. Also note that this does not affect          
                 chan_sip.                                                    

    Resolution  PJProject has a compile-time constant that controls the       
                maximum number of TCP connections that can be handled. Those  
                who compile PJProject on their own are encouraged to set      
                this to a value that is more amenable to the number of TCP    
                connections that Asterisk should be able to handle. In        
                PJProject's pjlib/include/pj/config_site.h, add the           
                following prior to compiling PJProject:                       
                                                                              
                # define PJ_IOQUEUE_MAX_HANDLES (FD_SETSIZE)                  
                                                                              
                This is part of a larger set of recommended definitions to    
                place in config_site.h of PJProject. See the Asterisk         
                "Building and Installing PJProject" wiki page for other       
                recommended settings.                                         
                                                                              
                Packagers of PJProject have updated their packages to have    
                these constants defined, so if your package is kept up to     
                date, you should already be fine.                             
                                                                              
                In addition, the Asterisk project has recently been modified  
                to be able to perform a static build of PJProject. By         
                running the Asterisk configure script with the                
                --with-pjproject-bundled option, the latest PJProject will    
                be downloaded and installed, and the compile-time constants   
                will be set to appropriate values.                            
                                                                              
                Asterisk has also been updated to monitor incoming TCP        
                connections. If a TCP connection is opened and no SIP         
                request is received on that connection within a certain       
                amount of time, then Asterisk will shut down the connection.  

                               Affected Versions       
                         Product                       Release  
                                                       Series   
                  Asterisk Open Source                  13.x    All Versions  

                                  Corrected In                    
                              Product                              Release    
                        Asterisk Open Source                        13.8.1    
                         Certified Asterisk                       13.1-cert5  

                                    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/AST-2016-005.pdf and             
    http://downloads.digium.com/pub/security/AST-2016-005.html                

                                Revision History
        Date            Editor                    Revisions Made              

               Asterisk Project Security Advisory - AST-2016-005
              Copyright (c) 2016 Digium, Inc. All Rights Reserved.
  Permission is hereby granted to distribute and publish this advisory in its
                           original, unaltered form.