crypto: add gnutls pbkdf provider

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

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

crypto/meson.build

@@ -29,7 +29,7 @@ if nettle.found()
 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')
+  crypto_ss.add(gnutls, files('hash-gnutls.c', 'hmac-gnutls.c', 'pbkdf-gnutls.c'))
 else
   crypto_ss.add(files('hash-glib.c', 'hmac-glib.c', 'pbkdf-stub.c'))
 endif

crypto/pbkdf-gnutls.c

@@ -0,0 +1,90 @@
+/*
+ * QEMU Crypto PBKDF support (Password-Based Key Derivation Function)
+ *
+ * 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/pbkdf.h"
+
+bool qcrypto_pbkdf2_supports(QCryptoHashAlgorithm hash)
+{
+    switch (hash) {
+    case QCRYPTO_HASH_ALG_MD5:
+    case QCRYPTO_HASH_ALG_SHA1:
+    case QCRYPTO_HASH_ALG_SHA224:
+    case QCRYPTO_HASH_ALG_SHA256:
+    case QCRYPTO_HASH_ALG_SHA384:
+    case QCRYPTO_HASH_ALG_SHA512:
+    case QCRYPTO_HASH_ALG_RIPEMD160:
+        return true;
+    default:
+        return false;
+    }
+}
+
+int qcrypto_pbkdf2(QCryptoHashAlgorithm hash,
+                   const uint8_t *key, size_t nkey,
+                   const uint8_t *salt, size_t nsalt,
+                   uint64_t iterations,
+                   uint8_t *out, size_t nout,
+                   Error **errp)
+{
+    static const int hash_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,
+    };
+    int ret;
+    const gnutls_datum_t gkey = { (unsigned char *)key, nkey };
+    const gnutls_datum_t gsalt = { (unsigned char *)salt, nsalt };
+
+    if (iterations > ULONG_MAX) {
+        error_setg_errno(errp, ERANGE,
+                         "PBKDF iterations %llu must be less than %lu",
+                         (long long unsigned)iterations, ULONG_MAX);
+        return -1;
+    }
+
+    if (hash >= G_N_ELEMENTS(hash_map) ||
+        hash_map[hash] == GNUTLS_DIG_UNKNOWN) {
+        error_setg_errno(errp, ENOSYS,
+                         "PBKDF does not support hash algorithm %s",
+                         QCryptoHashAlgorithm_str(hash));
+        return -1;
+    }
+
+    ret = gnutls_pbkdf2(hash_map[hash],
+                        &gkey,
+                        &gsalt,
+                        iterations,
+                        out,
+                        nout);
+    if (ret != 0) {
+        error_setg(errp, "Cannot derive password: %s",
+                   gnutls_strerror(ret));
+        return -1;
+    }
+
+    return 0;
+}