Corrected crypto tag in SDP ANSWER for SRTP. (again)

The original fix (r380043) for getting Asterisk to respond with the correct
tag overlooked some corner cases, and the fact that the same code is in 1.8.

This patch moves the building of the crypto line out of
sdp_crypto_process(). Instead, it merely copies the accepted tag. The call to
sdp_crypto_offer() will build the crypto line in all cases now, using a tag of
"1" in the case of sending offers.

(closes issue ASTERISK-20849)
Reported by: José Luis Millán
Review: https://reviewboard.asterisk.org/r/2295/
........

Merged revisions 380347 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 380350 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@380383 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 20 insertions, 14 deletions

diff --git a/channels/sip/sdp_crypto.c b/channels/sip/sdp_crypto.c
index ba21316d9..c27e882c2 100644
--- a/channels/sip/sdp_crypto.c
+++ b/channels/sip/sdp_crypto.c
@@ -49,6 +49,7 @@ extern struct ast_srtp_policy_res *res_srtp_policy;
 struct sdp_crypto {
 	char *a_crypto;
 	unsigned char local_key[SRTP_MASTER_LEN];
+	char *tag;
 	char local_key64[SRTP_MASTER_LEN64];
 	unsigned char remote_key[SRTP_MASTER_LEN];
 };
@@ -64,6 +65,8 @@ void sdp_crypto_destroy(struct sdp_crypto *crypto)
 {
 	ast_free(crypto->a_crypto);
 	crypto->a_crypto = NULL;
+	ast_free(crypto->tag);
+	crypto->tag = NULL;
 	ast_free(crypto);
 }
 
@@ -197,10 +200,10 @@ int sdp_crypto_process(struct sdp_crypto *p, const char *attr, struct ast_rtp_in
 	char *key_salt = NULL;
 	char *lifetime = NULL;
 	int found = 0;
-	int attr_len = strlen(attr);
 	int key_len = 0;
 	int suite_val = 0;
 	unsigned char remote_key[SRTP_MASTER_LEN];
+	int taglen = 0;
 
 	if (!ast_rtp_engine_srtp_is_registered()) {
 		return -1;
@@ -227,9 +230,11 @@ int sdp_crypto_process(struct sdp_crypto *p, const char *attr, struct ast_rtp_in
 	if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80")) {
 		suite_val = AST_AES_CM_128_HMAC_SHA1_80;
 		ast_set_flag(srtp, SRTP_CRYPTO_TAG_80);
+		taglen = 80;
 	} else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
 		suite_val = AST_AES_CM_128_HMAC_SHA1_32;
 		ast_set_flag(srtp, SRTP_CRYPTO_TAG_32);
+		taglen = 32;
 	} else {
 		ast_log(LOG_WARNING, "Unsupported crypto suite: %s\n", suite);
 		return -1;
@@ -276,32 +281,33 @@ int sdp_crypto_process(struct sdp_crypto *p, const char *attr, struct ast_rtp_in
 		return -1;
 	}
 
-	if (!p->a_crypto) {
-		if (!(p->a_crypto = ast_calloc(1, attr_len + 11))) {
-			ast_log(LOG_ERROR, "Could not allocate memory for a_crypto\n");
+	if (!p->tag) {
+		ast_log(LOG_DEBUG, "Accepting crypto tag %s\n", tag);
+		p->tag = ast_strdup(tag);
+		if (!p->tag) {
+			ast_log(LOG_ERROR, "Could not allocate memory for tag\n");
 			return -1;
 		}
-		snprintf(p->a_crypto, attr_len + 10, "a=crypto:%s %s inline:%s\r\n", tag, suite, p->local_key64);
 	}
-	return 0;
+
+	/* Finally, rebuild the crypto line */
+	return sdp_crypto_offer(p, taglen);
 }
 
 int sdp_crypto_offer(struct sdp_crypto *p, int taglen)
 {
-	char crypto_buf[128];
-
+	/* Rebuild the crypto line */
 	if (p->a_crypto) {
-		return 0;
+		ast_free(p->a_crypto);
 	}
 
-	if (snprintf(crypto_buf, sizeof(crypto_buf), "a=crypto:1 AES_CM_128_HMAC_SHA1_%i inline:%s\r\n",
-			taglen, p->local_key64) < 1) {
+	if (ast_asprintf(&p->a_crypto, "a=crypto:%s AES_CM_128_HMAC_SHA1_%i inline:%s\r\n",
+			 p->tag ? p->tag : "1", taglen, p->local_key64) == -1) {
+			ast_log(LOG_ERROR, "Could not allocate memory for crypto line\n");
 		return -1;
 	}
 
-	if (!(p->a_crypto = ast_strdup(crypto_buf))) {
-		return -1;
-	}
+	ast_log(LOG_DEBUG, "Crypto line: %s", p->a_crypto);
 
 	return 0;
 }