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crypto: add support for PBKDF2 algorithm

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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>
This commit is contained in:
Daniel P. Berrange 2015-10-14 13:14:04 +01:00
parent b917da4cbd
commit 37788f253a
10 changed files with 853 additions and 0 deletions
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include/crypto/pbkdf.h Normal file
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/*
* 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/>.
*
*/
#ifndef QCRYPTO_PBKDF_H__
#define QCRYPTO_PBKDF_H__
#include "crypto/hash.h"
/**
* This module provides an interface to the PBKDF2 algorithm
*
* https://en.wikipedia.org/wiki/PBKDF2
*
* <example>
* <title>Generating an AES encryption key from a user password</title>
* <programlisting>
* #include "crypto/cipher.h"
* #include "crypto/random.h"
* #include "crypto/pbkdf.h"
*
* ....
*
* char *password = "a-typical-awful-user-password";
* size_t nkey = qcrypto_cipher_get_key_len(QCRYPTO_CIPHER_ALG_AES_128);
* uint8_t *salt = g_new0(uint8_t, nkey);
* uint8_t *key = g_new0(uint8_t, nkey);
* int iterations;
* QCryptoCipher *cipher;
*
* if (qcrypto_random_bytes(salt, nkey, errp) < 0) {
* g_free(key);
* g_free(salt);
* return -1;
* }
*
* iterations = qcrypto_pbkdf2_count_iters(QCRYPTO_HASH_ALG_SHA256,
* (const uint8_t *)password,
* strlen(password),
* salt, nkey, errp);
* if (iterations < 0) {
* g_free(key);
* g_free(salt);
* return -1;
* }
*
* if (qcrypto_pbkdf2(QCRYPTO_HASH_ALG_SHA256,
* (const uint8_t *)password, strlen(password),
* salt, nkey, iterations, key, nkey, errp) < 0) {
* g_free(key);
* g_free(salt);
* return -1;
* }
*
* g_free(salt);
*
* cipher = qcrypto_cipher_new(QCRYPTO_CIPHER_ALG_AES_128,
* QCRYPTO_CIPHER_MODE_ECB,
* key, nkey, errp);
* g_free(key);
*
* ....encrypt some data...
*
* qcrypto_cipher_free(cipher);
* </programlisting>
* </example>
*
*/
/**
* qcrypto_pbkdf2_supports:
* @hash: the hash algorithm
*
* Determine if the current build supports the PBKDF2 algorithm
* in combination with the hash @hash.
*
* Returns true if supported, false otherwise
*/
bool qcrypto_pbkdf2_supports(QCryptoHashAlgorithm hash);
/**
* qcrypto_pbkdf2:
* @hash: the hash algorithm to use
* @key: the user password / key
* @nkey: the length of @key in bytes
* @salt: a random salt
* @nsalt: length of @salt in bytes
* @iterations: the number of iterations to compute
* @out: pointer to pre-allocated buffer to hold output
* @nout: length of @out in bytes
* @errp: pointer to a NULL-initialized error object
*
* Apply the PBKDF2 algorithm to derive an encryption
* key from a user password provided in @key. The
* @salt parameter is used to perturb the algorithm.
* The @iterations count determines how many times
* the hashing process is run, which influences how
* hard it is to crack the key. The number of @iterations
* should be large enough such that the algorithm takes
* 1 second or longer to derive a key. The derived key
* will be stored in the preallocated buffer @out.
*
* Returns: 0 on success, -1 on error
*/
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);
/**
* qcrypto_pbkdf2_count_iters:
* @hash: the hash algorithm to use
* @key: the user password / key
* @nkey: the length of @key in bytes
* @salt: a random salt
* @nsalt: length of @salt in bytes
* @errp: pointer to a NULL-initialized error object
*
* Time the PBKDF2 algorithm to determine how many
* iterations are required to derive an encryption
* key from a user password provided in @key in 1
* second of compute time. The result of this can
* be used as a the @iterations parameter of a later
* call to qcrypto_pbkdf2().
*
* Returns: number of iterations in 1 second, -1 on error
*/
int qcrypto_pbkdf2_count_iters(QCryptoHashAlgorithm hash,
const uint8_t *key, size_t nkey,
const uint8_t *salt, size_t nsalt,
Error **errp);
#endif /* QCRYPTO_PBKDF_H__ */