crypto: add gnutls hash provider

This adds support for using gnutls as a provider of the crypto
hash APIs.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

crypto/hash-gnutls.c

@@ -0,0 +1,104 @@
+/*
+ * QEMU Crypto hash algorithms
+ *
+ * Copyright (c) 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include <gnutls/crypto.h>
+#include "qapi/error.h"
+#include "crypto/hash.h"
+#include "hashpriv.h"
+
+
+static int qcrypto_hash_alg_map[QCRYPTO_HASH_ALG__MAX] = {
+    [QCRYPTO_HASH_ALG_MD5] = GNUTLS_DIG_MD5,
+    [QCRYPTO_HASH_ALG_SHA1] = GNUTLS_DIG_SHA1,
+    [QCRYPTO_HASH_ALG_SHA224] = GNUTLS_DIG_SHA224,
+    [QCRYPTO_HASH_ALG_SHA256] = GNUTLS_DIG_SHA256,
+    [QCRYPTO_HASH_ALG_SHA384] = GNUTLS_DIG_SHA384,
+    [QCRYPTO_HASH_ALG_SHA512] = GNUTLS_DIG_SHA512,
+    [QCRYPTO_HASH_ALG_RIPEMD160] = GNUTLS_DIG_RMD160,
+};
+
+gboolean qcrypto_hash_supports(QCryptoHashAlgorithm alg)
+{
+    size_t i;
+    const gnutls_digest_algorithm_t *algs;
+    if (alg >= G_N_ELEMENTS(qcrypto_hash_alg_map) ||
+        qcrypto_hash_alg_map[alg] == GNUTLS_DIG_UNKNOWN) {
+        return false;
+    }
+    algs = gnutls_digest_list();
+    for (i = 0; algs[i] != GNUTLS_DIG_UNKNOWN; i++) {
+        if (algs[i] == qcrypto_hash_alg_map[alg]) {
+            return true;
+        }
+    }
+    return false;
+}
+
+
+static int
+qcrypto_gnutls_hash_bytesv(QCryptoHashAlgorithm alg,
+                           const struct iovec *iov,
+                           size_t niov,
+                           uint8_t **result,
+                           size_t *resultlen,
+                           Error **errp)
+{
+    int i, ret;
+    gnutls_hash_hd_t hash;
+
+    if (!qcrypto_hash_supports(alg)) {
+        error_setg(errp,
+                   "Unknown hash algorithm %d",
+                   alg);
+        return -1;
+    }
+
+    ret = gnutls_hash_get_len(qcrypto_hash_alg_map[alg]);
+    if (*resultlen == 0) {
+        *resultlen = ret;
+        *result = g_new0(uint8_t, *resultlen);
+    } else if (*resultlen != ret) {
+        error_setg(errp,
+                   "Result buffer size %zu is smaller than hash %d",
+                   *resultlen, ret);
+        return -1;
+    }
+
+    ret = gnutls_hash_init(&hash, qcrypto_hash_alg_map[alg]);
+    if (ret < 0) {
+        error_setg(errp,
+                   "Unable to initialize hash algorithm: %s",
+                   gnutls_strerror(ret));
+        return -1;
+    }
+
+    for (i = 0; i < niov; i++) {
+        gnutls_hash(hash, iov[i].iov_base, iov[i].iov_len);
+    }
+
+    gnutls_hash_deinit(hash, *result);
+    return 0;
+}
+
+
+QCryptoHashDriver qcrypto_hash_lib_driver = {
+    .hash_bytesv = qcrypto_gnutls_hash_bytesv,
+};

crypto/meson.build

@@ -28,6 +28,8 @@ if nettle.found()
   endif
 elif gcrypt.found()
   crypto_ss.add(gcrypt, files('hash-gcrypt.c', 'hmac-gcrypt.c', 'pbkdf-gcrypt.c'))
+elif gnutls_crypto.found()
+  crypto_ss.add(gnutls, files('hash-gnutls.c', 'hmac-glib.c', 'pbkdf-stub.c')
 else
   crypto_ss.add(files('hash-glib.c', 'hmac-glib.c', 'pbkdf-stub.c'))
 endif