Add server extension parsing

Only accept EC J-PAKE ciphersuite if extension was present and OK (single flag
for both), and ignore extension if we have no password.

include/mbedtls/ssl_internal.h

@@ -150,6 +150,7 @@
  * of state of the renegotiation flag, so no indicator is required)
  */
 #define MBEDTLS_TLS_EXT_SUPPORTED_POINT_FORMATS_PRESENT (1 << 0)
+#define MBEDTLS_TLS_EXT_ECJPAKE_KKPP_OK                 (1 << 1)
 
 #ifdef __cplusplus
 extern "C" {

library/ssl_srv.c

@@ -318,6 +318,33 @@ static int ssl_parse_supported_point_formats( mbedtls_ssl_context *ssl,
 }
 #endif /* MBEDTLS_ECDH_C || MBEDTLS_ECDSA_C */
 
+#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
+static int ssl_parse_ecjpake_kkpp( mbedtls_ssl_context *ssl,
+                                   const unsigned char *buf,
+                                   size_t len )
+{
+    int ret;
+
+    if( mbedtls_ecjpake_check( &ssl->handshake->ecjpake_ctx ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "skip ecjpake kkpp extension" ) );
+        return( 0 );
+    }
+
+    if( ( ret = mbedtls_ecjpake_read_round_one( &ssl->handshake->ecjpake_ctx,
+                                                buf, len ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecjpake_read_round_one", ret );
+        return( ret );
+    }
+
+    /* Only mark the extension as OK when we're sure it is */
+    ssl->handshake->cli_exts |= MBEDTLS_TLS_EXT_ECJPAKE_KKPP_OK;
+
+    return( 0 );
+}
+#endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
+
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
 static int ssl_parse_max_fragment_length_ext( mbedtls_ssl_context *ssl,
                                               const unsigned char *buf,
@@ -709,10 +736,10 @@ static int ssl_ciphersuite_match( mbedtls_ssl_context *ssl, int suite_id,
 
 #if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
     if( suite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE &&
-        mbedtls_ecjpake_check( &ssl->handshake->ecjpake_ctx ) != 0 )
+        ( ssl->handshake->cli_exts & MBEDTLS_TLS_EXT_ECJPAKE_KKPP_OK ) == 0 )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 3, ( "ciphersuite mismatch: "
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "ciphersuite mismatch: ecjpake "
-                                    "ecjpake not configured" ) );
+                                    "not configured or ext missing" ) );
         return( 0 );
     }
 #endif
@@ -1571,6 +1598,16 @@ read_record_header:
             break;
 #endif /* MBEDTLS_ECDH_C || MBEDTLS_ECDSA_C */
 
+#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
+        case MBEDTLS_TLS_EXT_ECJPAKE_KKPP:
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "found ecjpake kkpp extension" ) );
+
+            ret = ssl_parse_ecjpake_kkpp( ssl, ext + 4, ext_size );
+            if( ret != 0 )
+                return( ret );
+            break;
+#endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
+
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
         case MBEDTLS_TLS_EXT_MAX_FRAGMENT_LENGTH:
             MBEDTLS_SSL_DEBUG_MSG( 3, ( "found max fragment length extension" ) );

tests/ssl-opt.sh

@@ -2507,6 +2507,8 @@ run_test    "ECJPAKE: client not configured" \
             0 \
             -C "add ciphersuite: c0ff" \
             -C "adding ecjpake_kkpp extension" \
+            -S "found ecjpake kkpp extension" \
+            -S "skip ecjpake kkpp extension" \
             -S "ciphersuite mismatch: ecjpake not configured" \
             -S "None of the common ciphersuites is usable"
 
@@ -2517,9 +2519,23 @@ run_test    "ECJPAKE: server not configured" \
             1 \
             -c "add ciphersuite: c0ff" \
             -c "adding ecjpake_kkpp extension" \
+            -s "found ecjpake kkpp extension" \
+            -s "skip ecjpake kkpp extension" \
             -s "ciphersuite mismatch: ecjpake not configured" \
             -s "None of the common ciphersuites is usable"
 
+run_test    "ECJPAKE: working, TLS" \
+            "$P_SRV debug_level=3 ecjpake_pw=bla" \
+            "$P_CLI debug_level=3 ecjpake_pw=bla \
+             force_ciphersuite=TLS-ECJPAKE-WITH-AES-128-CCM-8" \
+            1 \
+            -c "add ciphersuite: c0ff" \
+            -c "adding ecjpake_kkpp extension" \
+            -s "found ecjpake kkpp extension" \
+            -S "skip ecjpake kkpp extension" \
+            -S "ciphersuite mismatch: ecjpake not configured" \
+            -S "None of the common ciphersuites is usable"
+
 # Tests for ciphersuites per version
 
 run_test    "Per-version suites: SSL3" \