crypto: perform runtime check for hash/hmac support in gcrypt

gcrypto has the ability to dynamically disable hash/hmac algorithms
at runtime, so QEMU must perform a runtime check.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

crypto/hash-gcrypt.c

@@ -43,7 +43,7 @@ gboolean qcrypto_hash_supports(QCryptoHashAlgo alg)
 {
     if (alg < G_N_ELEMENTS(qcrypto_hash_alg_map) &&
         qcrypto_hash_alg_map[alg] != GCRY_MD_NONE) {
-        return true;
+        return gcry_md_test_algo(qcrypto_hash_alg_map[alg]) == 0;
     }
     return false;
 }

crypto/hmac-gcrypt.c

@@ -40,7 +40,7 @@ bool qcrypto_hmac_supports(QCryptoHashAlgo alg)
 {
     if (alg < G_N_ELEMENTS(qcrypto_hmac_alg_map) &&
         qcrypto_hmac_alg_map[alg] != GCRY_MAC_NONE) {
-        return true;
+        return gcry_mac_test_algo(qcrypto_hmac_alg_map[alg]) == 0;
     }
 
     return false;