Add RFC5764 - SRTP key generation during DTLS handshake
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 34953f2..d739dfc 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -871,6 +871,30 @@
(void) ssl;
#endif
+#if defined(MBEDTLS_SSL_DTLS_SRTP)
+ /* check if we have a chosen srtp protection profile */
+ if (ssl->chosen_dtls_srtp_profile != MBEDTLS_SRTP_UNSET_PROFILE) {
+ /* derive key material for srtp session RFC5764 section 4.2 */
+ /* master key and master salt are respectively 128 bits and 112 bits for all currently available modes :
+ * SRTP_AES128_CM_HMAC_SHA1_80, SRTP_AES128_CM_HMAC_SHA1_32
+ * SRTP_NULL_HMAC_SHA1_80, SRTP_NULL_HMAC_SHA1_32
+ * So we must export 2*(128 + 112) = 480 bits
+ */
+ ssl->dtls_srtp_keys_len = 60;
+
+ ssl->dtls_srtp_keys = (unsigned char *)mbedtls_calloc(1, ssl->dtls_srtp_keys_len);
+
+ ret = handshake->tls_prf( session->master, 48, "EXTRACTOR-dtls_srtp",
+ handshake->randbytes, 64, ssl->dtls_srtp_keys, ssl->dtls_srtp_keys_len );
+
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "dtls srtp prf", ret );
+ return( ret );
+ }
+ }
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+
/*
* Some data just needs copying into the structure
*/
@@ -3859,6 +3883,14 @@
mbedtls_ssl_reset_in_out_pointers( ssl );
+#if defined(MBEDTLS_SSL_DTLS_SRTP)
+ ssl->dtls_srtp_profiles_list = NULL;
+ ssl->dtls_srtp_profiles_list_len = 0;
+ ssl->chosen_dtls_srtp_profile = MBEDTLS_SRTP_UNSET_PROFILE;
+ ssl->dtls_srtp_keys = NULL;
+ ssl->dtls_srtp_keys_len = 0;
+#endif
+
if( ( ret = ssl_handshake_init( ssl ) ) != 0 )
goto error;
@@ -4685,6 +4717,48 @@
}
#endif /* MBEDTLS_SSL_ALPN */
+#if defined(MBEDTLS_SSL_DTLS_SRTP)
+int mbedtls_ssl_set_dtls_srtp_protection_profiles( mbedtls_ssl_context *ssl, const enum mbedtls_DTLS_SRTP_protection_profiles *profiles, size_t profiles_number)
+{
+ size_t i;
+ /* check in put validity : must be a list of profiles from enumeration */
+ /* maximum length is 4 as only 4 protection profiles are defined */
+ if (profiles_number>4) {
+ return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
+ }
+
+ mbedtls_free(ssl->dtls_srtp_profiles_list);
+ ssl->dtls_srtp_profiles_list = (enum mbedtls_DTLS_SRTP_protection_profiles *)mbedtls_calloc(1, profiles_number*sizeof(enum mbedtls_DTLS_SRTP_protection_profiles));
+
+ for (i=0; i<profiles_number; i++) {
+ switch (profiles[i]) {
+ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80:
+ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32:
+ case MBEDTLS_SRTP_NULL_HMAC_SHA1_80:
+ case MBEDTLS_SRTP_NULL_HMAC_SHA1_32:
+ ssl->dtls_srtp_profiles_list[i] = profiles[i];
+ break;
+ default:
+ mbedtls_free(ssl->dtls_srtp_profiles_list);
+ ssl->dtls_srtp_profiles_list = NULL;
+ ssl->dtls_srtp_profiles_list_len = 0;
+ return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
+ }
+ }
+
+ /* assign array length */
+ ssl->dtls_srtp_profiles_list_len = profiles_number;
+
+ return( 0 );
+}
+
+enum mbedtls_DTLS_SRTP_protection_profiles mbedtls_ssl_get_dtls_srtp_protection_profile( const mbedtls_ssl_context *ssl)
+{
+ return( ssl->chosen_dtls_srtp_profile);
+}
+
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+
void mbedtls_ssl_conf_max_version( mbedtls_ssl_config *conf, int major, int minor )
{
conf->max_major_ver = major;
@@ -6782,6 +6856,11 @@
mbedtls_free( ssl->cli_id );
#endif
+#if defined (MBEDTLS_SSL_DTLS_SRTP)
+ mbedtls_free( ssl->dtls_srtp_profiles_list );
+ mbedtls_free( ssl->dtls_srtp_keys );
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= free" ) );
/* Actually clear after last debug message */