[tls] Verify the contents of the Finished record

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/net/tls.c b/src/net/tls.c
index edf8d9fbd4ba243b3a862714a8583ae0042fde42..28a4ba4ecc6876f58a14ebd92439102a76affc8a 100644 (file)
--- a/src/net/tls.c
+++ b/src/net/tls.c
@@ -997,10 +997,31 @@ static int tls_new_server_hello_done ( struct tls_session *tls,
  */
 static int tls_new_finished ( struct tls_session *tls,
                              void *data, size_t len ) {
+       struct {
+               uint8_t verify_data[12];
+               char next[0];
+       } __attribute__ (( packed )) *finished = data;
+       void *end = finished->next;
+       uint8_t digest[MD5_DIGEST_SIZE + SHA1_DIGEST_SIZE];
+       uint8_t verify_data[ sizeof ( finished->verify_data ) ];
+
+       /* Sanity check */
+       if ( end != ( data + len ) ) {
+               DBGC ( tls, "TLS %p received overlength Finished\n", tls );
+               DBGC_HD ( tls, data, len );
+               return -EINVAL;
+       }
 
-       /* FIXME: Handle this properly */
-       ( void ) data;
-       ( void ) len;
+       /* Verify data */
+       tls_verify_handshake ( tls, digest );
+       tls_prf_label ( tls, &tls->master_secret, sizeof ( tls->master_secret ),
+                       verify_data, sizeof ( verify_data ), "server finished",
+                       digest, sizeof ( digest ) );
+       if ( memcmp ( verify_data, finished->verify_data,
+                     sizeof ( verify_data ) ) != 0 ) {
+               DBGC ( tls, "TLS %p verification failed\n", tls );
+               return -EPERM;
+       }
 
        /* Mark session as ready to transmit plaintext data */
        tls->tx_ready = 1;