check for a valid blocksize prior to entering loop

diff --git a/lib/gnutls_state.c b/lib/gnutls_state.c
index a609fb97a503df6a96de80e5cfa9400fe6816c7c..231e6b0b64aa028944bcace1f1ede41c571462e0 100644 (file)
--- a/lib/gnutls_state.c
+++ b/lib/gnutls_state.c
@@ -777,13 +777,13 @@ P_hash(gnutls_mac_algorithm_t algorithm,
        int output_bytes, result;
        const mac_entry_st *me = mac_to_entry(algorithm);
 
-       if (seed_size > MAX_SEED_SIZE || total_bytes <= 0) {
+       blocksize = _gnutls_mac_get_algo_len(me);
+
+       if (seed_size > MAX_SEED_SIZE || total_bytes <= 0 || blocksize == 0) {
                gnutls_assert();
                return GNUTLS_E_INTERNAL_ERROR;
        }
 
-       blocksize = _gnutls_mac_get_algo_len(me);
-
        output_bytes = 0;
        do {
                output_bytes += blocksize;