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, 206 insertions, 0 deletions

diff --git a/include/crypto/ivgen.h b/include/crypto/ivgen.h
new file mode 100644
index 0000000000..09cdb6fcd9
--- /dev/null
+++ b/include/crypto/ivgen.h
@@ -0,0 +1,206 @@
+/*
+ * QEMU Crypto block IV generator
+ *
+ * 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/>.
+ *
+ */
+
+#ifndef QCRYPTO_IVGEN_H__
+#define QCRYPTO_IVGEN_H__
+
+#include "crypto/cipher.h"
+#include "crypto/hash.h"
+
+/**
+ * This module provides a framework for generating initialization
+ * vectors for block encryption schemes using chained cipher modes
+ * CBC. The principle is that each disk sector is assigned a unique
+ * initialization vector for use for encryption of data in that
+ * sector.
+ *
+ * <example>
+ *   <title>Encrypting block data with initialiation vectors</title>
+ *   <programlisting>
+ * uint8_t *data = ....data to encrypt...
+ * size_t ndata = XXX;
+ * uint8_t *key = ....some encryption key...
+ * size_t nkey = XXX;
+ * uint8_t *iv;
+ * size_t niv;
+ * size_t sector = 0;
+ *
+ * g_assert((ndata % 512) == 0);
+ *
+ * QCryptoIVGen *ivgen = qcrypto_ivgen_new(QCRYPTO_IVGEN_ALG_ESSIV,
+ *                                         QCRYPTO_CIPHER_ALG_AES_128,
+ *                                         QCRYPTO_HASH_ALG_SHA256,
+ *                                         key, nkey, errp);
+ * if (!ivgen) {
+ *    return -1;
+ * }
+ *
+ * QCryptoCipher *cipher = qcrypto_cipher_new(QCRYPTO_CIPHER_ALG_AES_128,
+ *                                            QCRYPTO_CIPHER_MODE_CBC,
+ *                                            key, nkey, errp);
+ * if (!cipher) {
+ *     goto error;
+ * }
+ *
+ * niv =  qcrypto_cipher_get_iv_len(QCRYPTO_CIPHER_ALG_AES_128,
+ *                                  QCRYPTO_CIPHER_MODE_CBC);
+ * iv = g_new0(uint8_t, niv);
+ *
+ *
+ * while (ndata) {
+ *     if (qcrypto_ivgen_calculate(ivgen, sector, iv, niv, errp) < 0) {
+ *         goto error;
+ *     }
+ *     if (qcrypto_cipher_setiv(cipher, iv, niv, errp) < 0) {
+ *         goto error;
+ *     }
+ *     if (qcrypto_cipher_encrypt(cipher,
+ *                                data + (sector * 512),
+ *                                data + (sector * 512),
+ *                                512, errp) < 0) {
+ *         goto error;
+ *     }
+ *     sector++;
+ *     ndata -= 512;
+ * }
+ *
+ * g_free(iv);
+ * qcrypto_ivgen_free(ivgen);
+ * qcrypto_cipher_free(cipher);
+ * return 0;
+ *
+ *error:
+ * g_free(iv);
+ * qcrypto_ivgen_free(ivgen);
+ * qcrypto_cipher_free(cipher);
+ * return -1;
+ *   </programlisting>
+ * </example>
+ */
+
+typedef struct QCryptoIVGen QCryptoIVGen;
+
+/* See also QCryptoIVGenAlgorithm enum in qapi/crypto.json */
+
+
+/**
+ * qcrypto_ivgen_new:
+ * @alg: the initialization vector generation algorithm
+ * @cipheralg: the cipher algorithm or 0
+ * @hash: the hash algorithm or 0
+ * @key: the encryption key or NULL
+ * @nkey: the size of @key in bytes
+ *
+ * Create a new initialization vector generator that uses
+ * the algorithm @alg. Whether the remaining parameters
+ * are required or not depends on the choice of @alg
+ * requested.
+ *
+ * - QCRYPTO_IVGEN_ALG_PLAIN
+ *
+ * The IVs are generated by the 32-bit truncated sector
+ * number. This should never be used for block devices
+ * that are larger than 2^32 sectors in size.
+ * All the other parameters are unused.
+ *
+ * - QCRYPTO_IVGEN_ALG_PLAIN64
+ *
+ * The IVs are generated by the 64-bit sector number.
+ * All the other parameters are unused.
+ *
+ * - QCRYPTO_IVGEN_ALG_ESSIV:
+ *
+ * The IVs are generated by encrypting the 64-bit sector
+ * number with a hash of an encryption key. The @cipheralg,
+ * @hash, @key and @nkey parameters are all required.
+ *
+ * Returns: a new IV generator, or NULL on error
+ */
+QCryptoIVGen *qcrypto_ivgen_new(QCryptoIVGenAlgorithm alg,
+                                QCryptoCipherAlgorithm cipheralg,
+                                QCryptoHashAlgorithm hash,
+                                const uint8_t *key, size_t nkey,
+                                Error **errp);
+
+/**
+ * qcrypto_ivgen_calculate:
+ * @ivgen: the IV generator object
+ * @sector: the 64-bit sector number
+ * @iv: a pre-allocated buffer to hold the generated IV
+ * @niv: the number of bytes in @iv
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Calculate a new initialiation vector for the data
+ * to be stored in sector @sector. The IV will be
+ * written into the buffer @iv of size @niv.
+ *
+ * Returns: 0 on success, -1 on error
+ */
+int qcrypto_ivgen_calculate(QCryptoIVGen *ivgen,
+                            uint64_t sector,
+                            uint8_t *iv, size_t niv,
+                            Error **errp);
+
+
+/**
+ * qcrypto_ivgen_get_algorithm:
+ * @ivgen: the IV generator object
+ *
+ * Get the algorithm used by this IV generator
+ *
+ * Returns: the IV generator algorithm
+ */
+QCryptoIVGenAlgorithm qcrypto_ivgen_get_algorithm(QCryptoIVGen *ivgen);
+
+
+/**
+ * qcrypto_ivgen_get_cipher:
+ * @ivgen: the IV generator object
+ *
+ * Get the cipher algorithm used by this IV generator (if
+ * applicable)
+ *
+ * Returns: the cipher algorithm
+ */
+QCryptoCipherAlgorithm qcrypto_ivgen_get_cipher(QCryptoIVGen *ivgen);
+
+
+/**
+ * qcrypto_ivgen_get_hash:
+ * @ivgen: the IV generator object
+ *
+ * Get the hash algorithm used by this IV generator (if
+ * applicable)
+ *
+ * Returns: the hash algorithm
+ */
+QCryptoHashAlgorithm qcrypto_ivgen_get_hash(QCryptoIVGen *ivgen);
+
+
+/**
+ * qcrypto_ivgen_free:
+ * @ivgen: the IV generator object
+ *
+ * Release all resources associated with @ivgen, or a no-op
+ * if @ivgen is NULL
+ */
+void qcrypto_ivgen_free(QCryptoIVGen *ivgen);
+
+#endif /* QCRYPTO_IVGEN_H__ */