path: root/drivers/md/dm-crypt.c

/*
 * Copyright (C) 2003 Christophe Saout <christophe@saout.de>
 * Copyright (C) 2004 Clemens Fruhwirth <clemens@endorphin.org>
 *
 * This file is released under the GPL.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/mempool.h>
#include <linux/slab.h>
#include <linux/crypto.h>
#include <linux/workqueue.h>
#include <asm/atomic.h>
#include <asm/scatterlist.h>
#include <asm/page.h>

#include "dm.h"

#define PFX	"crypt: "

/*
 * per bio private data
 */
struct crypt_io {
	struct dm_target *target;
	struct bio *bio;
	struct bio *first_clone;
	struct work_struct work;
	atomic_t pending;
	int error;
};

/*
 * context holding the current state of a multi-part conversion
 */
struct convert_context {
	struct bio *bio_in;
	struct bio *bio_out;
	unsigned int offset_in;
	unsigned int offset_out;
	unsigned int idx_in;
	unsigned int idx_out;
	sector_t sector;
	int write;
};

struct crypt_config;

struct crypt_iv_operations {
	int (*ctr)(struct crypt_config *cc, struct dm_target *ti,
	           const char *opts);
	void (*dtr)(struct crypt_config *cc);
	const char *(*status)(struct crypt_config *cc);
	int (*generator)(struct crypt_config *cc, u8 *iv, sector_t sector);
};

/*
 * Crypt: maps a linear range of a block device
 * and encrypts / decrypts at the same time.
 */
struct crypt_config {
	struct dm_dev *dev;
	sector_t start;

	/*
	 * pool for per bio private data and
	 * for encryption buffer pages
	 */
	mempool_t *io_pool;
	mempool_t *page_pool;

	/*
	 * crypto related data
	 */
	struct crypt_iv_operations *iv_gen_ops;
	char *iv_mode;
	void *iv_gen_private;
	sector_t iv_offset;
	unsigned int iv_size;

	struct crypto_tfm *tfm;
	unsigned int key_size;
	u8 key[0];
};

#define MIN_IOS        256
#define MIN_POOL_PAGES 32
#define MIN_BIO_PAGES  8

static kmem_cache_t *_crypt_io_pool;

/*
 * Mempool alloc and free functions for the page
 */
static void *mempool_alloc_page(unsigned int __nocast gfp_mask, void *data)
{
	return alloc_page(gfp_mask);
}

static void mempool_free_page(void *page, void *data)
{
	__free_page(page);
}


/*
 * Different IV generation algorithms:
 *
 * plain: the initial vector is the 32-bit low-endian version of the sector
 *        number, padded with zeros if neccessary.
 *
 * ess_iv: "encrypted sector|salt initial vector", the sector number is
 *         encrypted with the bulk cipher using a salt as key. The salt
 *         should be derived from the bulk cipher's key via hashing.
 *
 * plumb: unimplemented, see:
 * http://article.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/454
 */

static int crypt_iv_plain_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
	memset(iv, 0, cc->iv_size);
	*(u32 *)iv = cpu_to_le32(sector & 0xffffffff);

	return 0;
}

static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
	                      const char *opts)
{
	struct crypto_tfm *essiv_tfm;
	struct crypto_tfm *hash_tfm;
	struct scatterlist sg;
	unsigned int saltsize;
	u8 *salt;

	if (opts == NULL) {
		ti->error = PFX "Digest algorithm missing for ESSIV mode";
		return -EINVAL;
	}

	/* Hash the cipher key with the given hash algorithm */
	hash_tfm = crypto_alloc_tfm(opts, CRYPTO_TFM_REQ_MAY_SLEEP);
	if (hash_tfm == NULL) {
		ti->error = PFX "Error initializing ESSIV hash";
		return -EINVAL;
	}

	if (crypto_tfm_alg_type(hash_tfm) != CRYPTO_ALG_TYPE_DIGEST) {
		ti->error = PFX "Expected digest algorithm for ESSIV hash";
		crypto_free_tfm(hash_tfm);
		return -EINVAL;
	}

	saltsize = crypto_tfm_alg_digestsize(hash_tfm);
	salt = kmalloc(saltsize, GFP_KERNEL);
	if (salt == NULL) {
		ti->error = PFX "Error kmallocing salt storage in ESSIV";
		crypto_free_tfm(hash_tfm);
		return -ENOMEM;
	}

	sg.page = virt_to_page(cc->key);
	sg.offset = offset_in_page(cc->key);
	sg.length = cc->key_size;
	crypto_digest_digest(hash_tfm, &sg, 1, salt);
	crypto_free_tfm(hash_tfm);

	/* Setup the essiv_tfm with the given salt */
	essiv_tfm = crypto_alloc_tfm(crypto_tfm_alg_name(cc->tfm),
	                             CRYPTO_TFM_MODE_ECB |
	                             CRYPTO_TFM_REQ_MAY_SLEEP);
	if (essiv_tfm == NULL) {
		ti->error = PFX "Error allocating crypto tfm for ESSIV";
		kfree(salt);
		return -EINVAL;
	}
	if (crypto_tfm_alg_blocksize