Re: [Srtp-development] srtp_protect error code 13

[David M. <mc...@ci...>]

Hi Francesco,

On Nov 16, 2006, at 3:43 AM, Francesco Andrisani wrote:

>
> Hi all,
> i want to insert a srtp protection into my code. I read with a  
> socket an RTP flow from an IP camera (i use socket functions to do  
> it) and send rtp flow to another workstation.
> My code is:
>
>   .......
>   .......
>   sec_serv_t sec_servs = sec_serv_none;
>
>   sec_servs |= sec_serv_conf;
>   sec_servs |= sec_serv_auth;
>
>   status = srtp_init();
>   if (status)
>   {
>     printf("error: srtp initialization failed with error code %d 
> \n", status);
>     return -1;
>   }
>
>   crypto_policy_set_rtp_default(&policy.rtp);
>   crypto_policy_set_rtcp_default(&policy.rtcp);
>
>
>   policy.ssrc.type  = ssrc_specific;
>   policy.ssrc.value = ssrc;
>   policy.key  =  (uint8_t *)key;
>   policy.next = NULL;
>   policy.rtp.sec_serv = sec_servs;
>   policy.rtcp.sec_serv = sec_serv_none;
>
>   status = srtp_create(&session, &policy);
>   if (status)
>   {
>     printf("error: srtp create failed with error code %d\n", status);
>     return -1;
>   }
>
>   char rtp_buffer[2048];
>   unsigned lenPacket;
>
> while(1)
> {
>
>
>   lenPacket = recvfrom(sockfd1, rtp_buffer, 2048, 0, (struct  
> sockaddr*)&serv_addr1,  &len);
>
>   printf("\nRead from socket %d bytes\n",lenPacket);
>
>   m = 0;
>   status = srtp_protect(session, rtp_buffer, &lenPacket);
>   if (status)
>   {
>         printf("\nSRTP protection error with code: %d\n",status);
>         return -1;
>   }
>   else
>   {
>         printf("\nRTP protection passed ----> SRTP packet create!\n");
>         srtp_packet_to_string((srtp_hdr_t *)rtp_buffer, lenPacket);
>         printf("%s",packet_string);
>   }
>
>   if (lenPacket >0)
>   {
>         m = sendto(sockfd1, rtp_buffer,lenPacket, 0, (struct  
> sockaddr*)&to_addr, len1);
>         printf("\nSend to socket %d bytes\n",m);
>   }
>
>   n = 0;
>   bzero(rtp_buffer,2048);
> }
>
> My code stop when it process srtp_protection...and exit with code  
> 13 (err_status_no_ctx).
> Where is my error?
>
with the lines

   policy.ssrc.value = ssrc;
   policy.ssrc.type  = ssrc_specific;

you're setting the policy to be specific to a particular RTP source  
(e.g. a particular SSRC).  Probably no context is being found because  
there is no context corresponding to the SSRC that srtp_protect() is  
seeing.  You either need to make sure that the SSRC that you're  
setting here is the one actually being used, or you need to use a  
'wildcard SSRC'.

best regards,

David

> Regards
>
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