crypto: add support for generating initialization vectors

There are a number of different algorithms that can be used
to generate initialization vectors for disk encryption. This
introduces a simple internal QCryptoBlockIV object to provide
a consistent internal API to the different algorithms. The
initially implemented algorithms are 'plain', 'plain64' and
'essiv', each matching the same named algorithm provided
by the Linux kernel dm-crypt driver.

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

1 files changed, 118 insertions, 0 deletions

diff --git a/crypto/ivgen-essiv.c b/crypto/ivgen-essiv.c
new file mode 100644
index 0000000..5649c01
--- /dev/null
+++ b/crypto/ivgen-essiv.c
@@ -0,0 +1,118 @@
+/*
+ * QEMU Crypto block IV generator - essiv
+ *
+ * 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/ivgen-essiv.h"
+
+typedef struct QCryptoIVGenESSIV QCryptoIVGenESSIV;
+struct QCryptoIVGenESSIV {
+    QCryptoCipher *cipher;
+};
+
+static int qcrypto_ivgen_essiv_init(QCryptoIVGen *ivgen,
+                                    const uint8_t *key, size_t nkey,
+                                    Error **errp)
+{
+    uint8_t *salt;
+    size_t nhash;
+    size_t nsalt;
+    QCryptoIVGenESSIV *essiv = g_new0(QCryptoIVGenESSIV, 1);
+
+    /* Not necessarily the same as nkey */
+    nsalt = qcrypto_cipher_get_key_len(ivgen->cipher);
+
+    nhash = qcrypto_hash_digest_len(ivgen->hash);
+    /* Salt must be larger of hash size or key size */
+    salt = g_new0(uint8_t, MAX(nhash, nsalt));
+
+    if (qcrypto_hash_bytes(ivgen->hash, (const gchar *)key, nkey,
+                           &salt, &nhash,
+                           errp) < 0) {
+        g_free(essiv);
+        return -1;
+    }
+
+    /* Now potentially truncate salt to match cipher key len */
+    essiv->cipher = qcrypto_cipher_new(ivgen->cipher,
+                                       QCRYPTO_CIPHER_MODE_ECB,
+                                       salt, MIN(nhash, nsalt),
+                                       errp);
+    if (!essiv->cipher) {
+        g_free(essiv);
+        g_free(salt);
+        return -1;
+    }
+
+    g_free(salt);
+    ivgen->private = essiv;
+
+    return 0;
+}
+
+static int qcrypto_ivgen_essiv_calculate(QCryptoIVGen *ivgen,
+                                         uint64_t sector,
+                                         uint8_t *iv, size_t niv,
+                                         Error **errp)
+{
+    QCryptoIVGenESSIV *essiv = ivgen->private;
+    size_t ndata = qcrypto_cipher_get_block_len(ivgen->cipher);
+    uint8_t *data = g_new(uint8_t, ndata);
+
+    sector = cpu_to_le64(sector);
+    memcpy(data, (uint8_t *)&sector, ndata);
+    if (sizeof(sector) < ndata) {
+        memset(data + sizeof(sector), 0, ndata - sizeof(sector));
+    }
+
+    if (qcrypto_cipher_encrypt(essiv->cipher,
+                               data,
+                               data,
+                               ndata,
+                               errp) < 0) {
+        g_free(data);
+        return -1;
+    }
+
+    if (ndata > niv) {
+        ndata = niv;
+    }
+    memcpy(iv, data, ndata);
+    if (ndata < niv) {
+        memset(iv + ndata, 0, niv - ndata);
+    }
+    g_free(data);
+    return 0;
+}
+
+static void qcrypto_ivgen_essiv_cleanup(QCryptoIVGen *ivgen)
+{
+    QCryptoIVGenESSIV *essiv = ivgen->private;
+
+    qcrypto_cipher_free(essiv->cipher);
+    g_free(essiv);
+}
+
+
+struct QCryptoIVGenDriver qcrypto_ivgen_essiv = {
+    .init = qcrypto_ivgen_essiv_init,
+    .calculate = qcrypto_ivgen_essiv_calculate,
+    .cleanup = qcrypto_ivgen_essiv_cleanup,
+};
+