Change key derivation for srtp
Use the export keys functionality, to call the public API
`mbedtls_ssl_tls_prf()`, and remove the function
`mbedtls_ssl_get_dtls_srtp_key_material()`.
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index f3c3590..93fea68 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -328,10 +328,24 @@
" This cannot be used with eap_tls=1\n"
#define USAGE_NSS_KEYLOG_FILE \
" nss_keylog_file=%%s\n"
-#else
+#if defined(MBEDTLS_SSL_DTLS_SRTP)
+#define USAGE_SRTP \
+ " use_srtp=%%d default: 0 (disabled)\n" \
+ " srtp_force_profile=%%d default: all enabled\n" \
+ " available profiles:\n" \
+ " 1 - SRTP_AES128_CM_HMAC_SHA1_80\n" \
+ " 2 - SRTP_AES128_CM_HMAC_SHA1_32\n" \
+ " 3 - SRTP_NULL_HMAC_SHA1_80\n" \
+ " 4 - SRTP_NULL_HMAC_SHA1_32\n" \
+ " support_mki=%%d default: 0 (not supported)\n"
+#else /* MBEDTLS_SSL_DTLS_SRTP */
+#define USAGE_SRTP ""
+#endif
+#else /* MBEDTLS_SSL_EXPORT_KEYS */
#define USAGE_EAP_TLS ""
#define USAGE_NSS_KEYLOG ""
#define USAGE_NSS_KEYLOG_FILE ""
+#define USAGE_SRTP ""
#endif /* MBEDTLS_SSL_EXPORT_KEYS */
#if defined(MBEDTLS_SSL_CACHE_C)
@@ -414,20 +428,6 @@
#define USAGE_DTLS ""
#endif
-#if defined(MBEDTLS_SSL_DTLS_SRTP)
-#define USAGE_SRTP \
- " use_srtp=%%d default: 0 (disabled)\n" \
- " srtp_force_profile=%%d default: all enabled\n" \
- " available profiles:\n" \
- " 1 - SRTP_AES128_CM_HMAC_SHA1_80\n" \
- " 2 - SRTP_AES128_CM_HMAC_SHA1_32\n" \
- " 3 - SRTP_NULL_HMAC_SHA1_80\n" \
- " 4 - SRTP_NULL_HMAC_SHA1_32\n" \
- " support_mki=%%d default: 0 (not supported)\n"
-#else
-#define USAGE_SRTP ""
-#endif
-
#if defined(MBEDTLS_SSL_EXTENDED_MASTER_SECRET)
#define USAGE_EMS \
" extended_ms=0/1 default: (library default: on)\n"
@@ -781,7 +781,43 @@
return( ret );
}
-#endif
+#if defined( MBEDTLS_SSL_DTLS_SRTP )
+typedef struct dtls_srtp_keys
+{
+ unsigned char master_secret[48];
+ unsigned char randbytes[64];
+ mbedtls_tls_prf_types tls_prf_type;
+} dtls_srtp_keys;
+
+static int dtls_srtp_key_derivation( void *p_expkey,
+ const unsigned char *ms,
+ const unsigned char *kb,
+ size_t maclen,
+ size_t keylen,
+ size_t ivlen,
+ const unsigned char client_random[32],
+ const unsigned char server_random[32],
+ mbedtls_tls_prf_types tls_prf_type )
+{
+ dtls_srtp_keys *keys = (dtls_srtp_keys *)p_expkey;
+
+ ( ( void ) kb );
+ memcpy( keys->master_secret, ms, sizeof( keys->master_secret ) );
+ memcpy( keys->randbytes, client_random, 32 );
+ memcpy( keys->randbytes + 32, server_random, 32 );
+ keys->tls_prf_type = tls_prf_type;
+
+ if( opt.debug_level > 2 )
+ {
+ mbedtls_printf("exported maclen is %u\n", (unsigned)maclen);
+ mbedtls_printf("exported keylen is %u\n", (unsigned)keylen);
+ mbedtls_printf("exported ivlen is %u\n", (unsigned)ivlen);
+ }
+ return( 0 );
+}
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+
+#endif /* MBEDTLS_SSL_EXPORT_KEYS */
static void my_debug( void *ctx, int level,
const char *file, int line,
@@ -1824,10 +1860,6 @@
size_t context_buf_len = 0;
#endif
-#if defined(MBEDTLS_SSL_DTLS_SRTP)
- unsigned char mki[MBEDTLS_DTLS_SRTP_MAX_MKI_LENGTH];
- size_t mki_len = 0;
-#endif
int i;
char *p, *q;
const int *list;
@@ -1839,7 +1871,13 @@
unsigned char eap_tls_iv[8];
const char* eap_tls_label = "client EAP encryption";
eap_tls_keys eap_tls_keying;
-#endif
+#if defined( MBEDTLS_SSL_DTLS_SRTP )
+ /*! master keys and master salt for SRTP generated during handshake */
+ unsigned char dtls_srtp_key_material[MBEDTLS_DTLS_SRTP_MAX_KEY_MATERIAL_LENGTH];
+ const char* dtls_srtp_label = "EXTRACTOR-dtls_srtp";
+ dtls_srtp_keys dtls_srtp_keying;
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+#endif /* MBEDTLS_SSL_EXPORT_KEYS */
#if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
mbedtls_memory_buffer_alloc_init( alloc_buf, sizeof(alloc_buf) );
@@ -3164,7 +3202,14 @@
nss_keylog_export,
NULL );
}
-#endif
+#if defined( MBEDTLS_SSL_DTLS_SRTP )
+ else if( opt.use_srtp != 0 )
+ {
+ mbedtls_ssl_conf_export_keys_ext_cb( &conf, dtls_srtp_key_derivation,
+ &dtls_srtp_keying );
+ }
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+#endif /* MBEDTLS_SSL_EXPORT_KEYS */
#if defined(MBEDTLS_SSL_ALPN)
if( opt.alpn_string != NULL )
@@ -3810,7 +3855,39 @@
}
mbedtls_printf("\n");
}
-#endif
+
+#if defined( MBEDTLS_SSL_DTLS_SRTP )
+ else if( opt.use_srtp != 0 )
+ {
+ size_t j = 0;
+
+ if( ( ret = mbedtls_ssl_tls_prf( dtls_srtp_keying.tls_prf_type,
+ dtls_srtp_keying.master_secret,
+ sizeof( dtls_srtp_keying.master_secret ),
+ dtls_srtp_label,
+ dtls_srtp_keying.randbytes,
+ sizeof( dtls_srtp_keying.randbytes ),
+ dtls_srtp_key_material,
+ sizeof( dtls_srtp_key_material ) ) )
+ != 0 )
+ {
+ mbedtls_printf( " failed\n ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
+ -ret );
+ goto exit;
+ }
+
+ mbedtls_printf( " DTLS-SRTP key material is:" );
+ for( j = 0; j < sizeof( dtls_srtp_key_material ); j++ )
+ {
+ if( j % 8 == 0 )
+ mbedtls_printf("\n ");
+ mbedtls_printf("%02x ", dtls_srtp_key_material[j] );
+ }
+
+ mbedtls_printf("\n");
+ }
+#endif /* MBEDTLS_SSL_DTLS_SRTP */
+#endif /* MBEDTLS_SSL_EXPORT_KEYS */
#if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
ret = report_cid_usage( &ssl, "initial handshake" );