crypto: add support for PBKDF2 algorithm

The LUKS data format includes use of PBKDF2 (Password-Based
Key Derivation Function). The Nettle library can provide
an implementation of this, but we don't want code directly
depending on a specific crypto library backend. Introduce
a new include/crypto/pbkdf.h header which defines a QEMU
API for invoking PBKDK2. The initial implementations are
backed by nettle & gcrypt, which are commonly available
with distros shipping GNUTLS.

The test suite data is taken from the cryptsetup codebase
under the LGPLv2.1+ license. This merely aims to verify
that whatever backend we provide for this function in QEMU
will comply with the spec.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/crypto/pbkdf-gcrypt.c b/crypto/pbkdf-gcrypt.c
new file mode 100644
index 0000000000..885614dfcc
--- /dev/null
+++ b/crypto/pbkdf-gcrypt.c
@@ -0,0 +1,68 @@
+/*
+ * QEMU Crypto PBKDF support (Password-Based Key Derivation Function)
+ *
+ * Copyright (c) 2015-2016 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 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 "crypto/pbkdf.h"
+#include "gcrypt.h"
+
+bool qcrypto_pbkdf2_supports(QCryptoHashAlgorithm hash)
+{
+    switch (hash) {
+    case QCRYPTO_HASH_ALG_MD5:
+    case QCRYPTO_HASH_ALG_SHA1:
+    case QCRYPTO_HASH_ALG_SHA256:
+        return true;
+    default:
+        return false;
+    }
+}
+
+int qcrypto_pbkdf2(QCryptoHashAlgorithm hash,
+                   const uint8_t *key, size_t nkey,
+                   const uint8_t *salt, size_t nsalt,
+                   unsigned int iterations,
+                   uint8_t *out, size_t nout,
+                   Error **errp)
+{
+    static const int hash_map[QCRYPTO_HASH_ALG__MAX] = {
+        [QCRYPTO_HASH_ALG_MD5] = GCRY_MD_MD5,
+        [QCRYPTO_HASH_ALG_SHA1] = GCRY_MD_SHA1,
+        [QCRYPTO_HASH_ALG_SHA256] = GCRY_MD_SHA256,
+    };
+    int ret;
+
+    if (hash >= G_N_ELEMENTS(hash_map) ||
+        hash_map[hash] == GCRY_MD_NONE) {
+        error_setg(errp, "Unexpected hash algorithm %d", hash);
+        return -1;
+    }
+
+    ret = gcry_kdf_derive(key, nkey, GCRY_KDF_PBKDF2,
+                          hash_map[hash],
+                          salt, nsalt, iterations,
+                          nout, out);
+    if (ret != 0) {
+        error_setg(errp, "Cannot derive password: %s",
+                   gcry_strerror(ret));
+        return -1;
+    }
+
+    return 0;
+}