Should reject signatures that we can't properly verify

and couldn't generate
(as pointed out by Ernst G Giessmann)

crypto/ecdsa/ecs_ossl.c

@@ -384,6 +384,21 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
 		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
 		goto err;
 	}
+	if (8 * dgst_len > BN_num_bits(order))
+	{
+		/* XXX
+		 * 
+		 * Should provide for optional hash truncation:
+		 * Keep the BN_num_bits(order) leftmost bits of dgst
+		 * (see March 2006 FIPS 186-3 draft, which has a few
+		 * confusing errors in this part though)
+		 */
+
+		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY,
+			ECDSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+		ret = 0;
+		goto err;
+	}
 
 	if (BN_is_zero(sig->r)          || BN_is_negative(sig->r) || 
 	    BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s)  ||