[asterisk-dev] Problem with SRTP on aastra with version 3 of Firmxare Issue: 18919

[Bernard Merindol(F)]

Hi,

I works to patch this problem: 

https://issues.asterisk.org/view.php?id=18919

My patch works when the crypto is changed in OK answer. But the new version  of AAstra phone (version 3) also change the crypto in RE-INVITE.

Example: 
Phone A :Aastra with version 3 of firmware
Phone B : Aastra phone

A  call B , B answer

A push hold button, wait and push unhold . When push unhold the phone  A send INVITE with new crypto. In this case is not works.

The audio stream sended by  A is not decoded by asterisk.

Analyse:

First problem is in chan_sip.c 

Actual code:
	if ((*srtp)->crypto && !ast_test_flag(&p->flags[0], SIP_OUTGOING)) {
		ast_debug(3, "We've already processed a crypto attribute, skipping '%s'\n", a);
		return FALSE;
	}

I change to
	if ((*srtp)->crypto && !ast_test_flag(&p->flags[0], SIP_OUTGOING)) {
		ast_debug(3, "We've already processed a crypto attribute, skipping '%s'\n", a);
	/* BUG dans le cas d'un changement de crypto lors d'un re-invite */
		// return FALSE;
	}


But in this case the new crypto is not set in  libSRTPP

I have changer in res_srtp.c the function  (ast_srtp_add_stream) this change works for the crypto change in OK but not in INVITE.

static int ast_srtp_add_stream(struct ast_srtp *srtp, struct ast_srtp_policy *policy)                                                                                                         
{                                                                                                                                                                                             
       struct ast_srtp_policy *match;                                                                                                                                                        
       err_status_t status;                                                                                                                                                                  

       if ((match = find_policy(srtp, &policy->sp, OBJ_POINTER))) {                                                                                                                          
               ast_debug(3, "Policy already exists with ssrc %x, updating.\n", policy->sp.ssrc.value);                                                                                       
               if ( policy->sp.ssrc.value == 0 )                                                                                                                                             
               {                                                                                                                                                                             
                       struct ast_rtp_instance_stats stats;                                                                                                                                  
                       ast_rtp_instance_get_stats(srtp->rtp, &stats, AST_RTP_INSTANCE_STAT_REMOTE_SSRC);                                                                                     
                       policy->sp.ssrc.type = ssrc_specific;                                                                                                                                 
                       policy->sp.ssrc.value = stats.remote_ssrc;                                                                                                                            
               }                                                                                                                                                                             
               else                                                                                                                                                                          
               {                                                                                                                                                                             
                       return 0;
               }
       }

       status = srtp_add_stream(srtp->session, &policy->sp);
       if (status != err_status_ok) {
               ast_log(LOG_ERROR, "Failed to add SRTP policy. Err=%d.\n", status);
               return -1;
       }

       ao2_t_link(srtp->policies, policy, "Added additional stream");

       return 0;
}


I need help.

Best regards
Bernard