Merged revisions 372710 via svnmerge from

file:///srv/subversion/repos/asterisk/branches/10

................
  r372710 | mjordan | 2012-09-08 20:24:36 -0500 (Sat, 08 Sep 2012) | 24 lines
  
  Only re-create an SRTP session when needed
  
  In r356604, SRTP handling was fixed to accomodate multiple crypto keys in an
  SDP offer and the ability to re-create an SRTP session when the crypto keys
  changed.  In certain circumstances - most notably when a phone is put on
  hold after having been bridged for a significant amount of time - the act
  of re-creating the SRTP session causes problems for certain models of phones.
  The patch committed in r356604 always re-created the SRTP session regardless
  of whether or not the cryptographic keys changed.  Since this is technically
  not necessary, this patch modifies the behavior to only re-create the SRTP
  session if Asterisk detects that the remote key has changed.  This allows
  models of phones that do not handle the SRTP session changing to continue
  to work, while also providing the behavior needed for those phones that do
  re-negotiate cryptographic keys.
  
  (issue ASTERISK-20194)
  Reported by: Nicolo Mazzon
  Tested by: Nicolo Mazzon
  
  Review: https://reviewboard.asterisk.org/r/2099
  ........
  
  Merged revisions 372709 from http://svn.asterisk.org/svn/asterisk/branches/1.8
................


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10-digiumphones@372735 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/sip/sdp_crypto.c

@@ -50,6 +50,7 @@ struct sdp_crypto {
 	char *a_crypto;
 	unsigned char local_key[SRTP_MASTER_LEN];
 	char local_key64[SRTP_MASTER_LEN64];
+	unsigned char remote_key[SRTP_MASTER_LEN];
 };
 
 static int set_crypto_policy(struct ast_srtp_policy *policy, int suite_val, const unsigned char *master_key, unsigned long ssrc, int inbound);
@@ -260,12 +261,17 @@ int sdp_crypto_process(struct sdp_crypto *p, const char *attr, struct ast_rtp_in
 		return -1;
 	}
 
-
 	if ((key_len = ast_base64decode(remote_key, key_salt, sizeof(remote_key))) != SRTP_MASTER_LEN) {
-		ast_log(LOG_WARNING, "SRTP sdescriptions key %d != %d\n", key_len, SRTP_MASTER_LEN);
+		ast_log(LOG_WARNING, "SRTP descriptions key %d != %d\n", key_len, SRTP_MASTER_LEN);
 		return -1;
 	}
 
+	if (!memcmp(p->remote_key, remote_key, sizeof(p->remote_key))) {
+		ast_debug(1, "SRTP remote key unchanged; maintaining current policy\n");
+		return 0;
+	}
+	memcpy(p->remote_key, remote_key, sizeof(p->remote_key));
+
 	if (sdp_crypto_activate(p, suite_val, remote_key, rtp) < 0) {
 		return -1;
 	}