dm-crypt.c

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	 * The block layer might modify the bvec array, so always
	 * copy the required bvecs because we need the original
	 * one in order to decrypt the whole bio data *afterwards*.
	 */
	clone = bio_alloc_bioset(GFP_NOIO, bio_segments(base_bio), cc->bs);
	if (unlikely(!clone)) {
		crypt_dec_pending(io, -ENOMEM);
		return;
	}

	clone_init(io, clone);
	clone->bi_idx = 0;
	clone->bi_vcnt = bio_segments(base_bio);
	clone->bi_size = base_bio->bi_size;
	clone->bi_sector = cc->start + sector;
	memcpy(clone->bi_io_vec, bio_iovec(base_bio),
	       sizeof(struct bio_vec) * clone->bi_vcnt);

	generic_make_request(clone);
}

static void process_write(struct dm_crypt_io *io)
{
	struct crypt_config *cc = io->target->private;
	struct bio *base_bio = io->base_bio;
	struct bio *clone;
	struct convert_context ctx;
	unsigned remaining = base_bio->bi_size;
	sector_t sector = base_bio->bi_sector - io->target->begin;

	atomic_inc(&io->pending);

	crypt_convert_init(cc, &ctx, NULL, base_bio, sector, 1);

	/*
	 * The allocated buffers can be smaller than the whole bio,
	 * so repeat the whole process until all the data can be handled.
	 */
	while (remaining) {
		clone = crypt_alloc_buffer(io, remaining);
		if (unlikely(!clone)) {
			crypt_dec_pending(io, -ENOMEM);
			return;
		}

		ctx.bio_out = clone;
		ctx.idx_out = 0;

		if (unlikely(crypt_convert(cc, &ctx) < 0)) {
			crypt_free_buffer_pages(cc, clone);
			bio_put(clone);
			crypt_dec_pending(io, -EIO);
			return;
		}

		/* crypt_convert should have filled the clone bio */
		BUG_ON(ctx.idx_out < clone->bi_vcnt);

		clone->bi_sector = cc->start + sector;
		remaining -= clone->bi_size;
		sector += bio_sectors(clone);

		/* Grab another reference to the io struct
		 * before we kick off the request */
		if (remaining)
			atomic_inc(&io->pending);

		generic_make_request(clone);

		/* Do not reference clone after this - it
		 * may be gone already. */

		/* out of memory -> run queues */
		if (remaining)
			congestion_wait(WRITE, HZ/100);
	}
}

static void process_read_endio(struct dm_crypt_io *io)
{
	struct crypt_config *cc = io->target->private;
	struct convert_context ctx;

	crypt_convert_init(cc, &ctx, io->base_bio, io->base_bio,
			   io->base_bio->bi_sector - io->target->begin, 0);

	crypt_dec_pending(io, crypt_convert(cc, &ctx));
}

static void kcryptd_do_work(struct work_struct *work)
{
	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);

	if (bio_data_dir(io->base_bio) == READ)
		process_read(io);
}

static void kcryptd_do_crypt(struct work_struct *work)
{
	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);

	if (bio_data_dir(io->base_bio) == READ)
		process_read_endio(io);
	else
		process_write(io);
}

/*
 * Decode key from its hex representation
 */
static int crypt_decode_key(u8 *key, char *hex, unsigned int size)
{
	char buffer[3];
	char *endp;
	unsigned int i;

	buffer[2] = '\0';

	for (i = 0; i < size; i++) {
		buffer[0] = *hex++;
		buffer[1] = *hex++;

		key[i] = (u8)simple_strtoul(buffer, &endp, 16);

		if (endp != &buffer[2])
			return -EINVAL;
	}

	if (*hex != '\0')
		return -EINVAL;

	return 0;
}

/*
 * Encode key into its hex representation
 */
static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
{
	unsigned int i;

	for (i = 0; i < size; i++) {
		sprintf(hex, "%02x", *key);
		hex += 2;
		key++;
	}
}

static int crypt_set_key(struct crypt_config *cc, char *key)
{
	unsigned key_size = strlen(key) >> 1;

	if (cc->key_size && cc->key_size != key_size)
		return -EINVAL;

	cc->key_size = key_size; /* initial settings */

	if ((!key_size && strcmp(key, "-")) ||
	   (key_size && crypt_decode_key(cc->key, key, key_size) < 0))
		return -EINVAL;

	set_bit(DM_CRYPT_KEY_VALID, &cc->flags);

	return 0;
}

static int crypt_wipe_key(struct crypt_config *cc)
{
	clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
	memset(&cc->key, 0, cc->key_size * sizeof(u8));
	return 0;
}

/*
 * Construct an encryption mapping:
 * <cipher> <key> <iv_offset> <dev_path> <start>
 */
static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
	struct crypt_config *cc;
	struct crypto_blkcipher *tfm;
	char *tmp;
	char *cipher;
	char *chainmode;
	char *ivmode;
	char *ivopts;
	unsigned int key_size;
	unsigned long long tmpll;

	if (argc != 5) {
		ti->error = "Not enough arguments";
		return -EINVAL;
	}

	tmp = argv[0];
	cipher = strsep(&tmp, "-");
	chainmode = strsep(&tmp, "-");
	ivopts = strsep(&tmp, "-");
	ivmode = strsep(&ivopts, ":");

	if (tmp)
		DMWARN("Unexpected additional cipher options");

	key_size = strlen(argv[1]) >> 1;

 	cc = kzalloc(sizeof(*cc) + key_size * sizeof(u8), GFP_KERNEL);
	if (cc == NULL) {
		ti->error =
			"Cannot allocate transparent encryption context";
		return -ENOMEM;
	}

 	if (crypt_set_key(cc, argv[1])) {
		ti->error = "Error decoding key";
		goto bad_cipher;
	}

	/* Compatiblity mode for old dm-crypt cipher strings */
	if (!chainmode || (strcmp(chainmode, "plain") == 0 && !ivmode)) {
		chainmode = "cbc";
		ivmode = "plain";
	}

	if (strcmp(chainmode, "ecb") && !ivmode) {
		ti->error = "This chaining mode requires an IV mechanism";
		goto bad_cipher;
	}

	if (snprintf(cc->cipher, CRYPTO_MAX_ALG_NAME, "%s(%s)",
		     chainmode, cipher) >= CRYPTO_MAX_ALG_NAME) {
		ti->error = "Chain mode + cipher name is too long";
		goto bad_cipher;
	}

	tfm = crypto_alloc_blkcipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(tfm)) {
		ti->error = "Error allocating crypto tfm";
		goto bad_cipher;
	}

	strcpy(cc->cipher, cipher);
	strcpy(cc->chainmode, chainmode);
	cc->tfm = tfm;

	/*
	 * Choose ivmode. Valid modes: "plain", "essiv:<esshash>", "benbi".
	 * See comments at iv code
	 */

	if (ivmode == NULL)
		cc->iv_gen_ops = NULL;
	else if (strcmp(ivmode, "plain") == 0)
		cc->iv_gen_ops = &crypt_iv_plain_ops;
	else if (strcmp(ivmode, "essiv") == 0)
		cc->iv_gen_ops = &crypt_iv_essiv_ops;
	else if (strcmp(ivmode, "benbi") == 0)
		cc->iv_gen_ops = &crypt_iv_benbi_ops;
	else if (strcmp(ivmode, "null") == 0)
		cc->iv_gen_ops = &crypt_iv_null_ops;
	else {
		ti->error = "Invalid IV mode";
		goto bad_ivmode;
	}

	if (cc->iv_gen_ops && cc->iv_gen_ops->ctr &&
	    cc->iv_gen_ops->ctr(cc, ti, ivopts) < 0)
		goto bad_ivmode;

	cc->iv_size = crypto_blkcipher_ivsize(tfm);
	if (cc->iv_size)
		/* at least a 64 bit sector number should fit in our buffer */
		cc->iv_size = max(cc->iv_size,
				  (unsigned int)(sizeof(u64) / sizeof(u8)));
	else {
		if (cc->iv_gen_ops) {
			DMWARN("Selected cipher does not support IVs");
			if (cc->iv_gen_ops->dtr)
				cc->iv_gen_ops->dtr(cc);
			cc->iv_gen_ops = NULL;
		}
	}

	cc->io_pool = mempool_create_slab_pool(MIN_IOS, _crypt_io_pool);
	if (!cc->io_pool) {
		ti->error = "Cannot allocate crypt io mempool";
		goto bad_slab_pool;
	}

	cc->page_pool = mempool_create_page_pool(MIN_POOL_PAGES, 0);
	if (!cc->page_pool) {
		ti->error = "Cannot allocate page mempool";
		goto bad_page_pool;
	}

	cc->bs = bioset_create(MIN_IOS, MIN_IOS);
	if (!cc->bs) {
		ti->error = "Cannot allocate crypt bioset";
		goto bad_bs;
	}

	if (crypto_blkcipher_setkey(tfm, cc->key, key_size) < 0) {
		ti->error = "Error setting key";
		goto bad_device;
	}

	if (sscanf(argv[2], "%llu", &tmpll) != 1) {
		ti->error = "Invalid iv_offset sector";
		goto bad_device;
	}
	cc->iv_offset = tmpll;

	if (sscanf(argv[4], "%llu", &tmpll) != 1) {
		ti->error = "Invalid device sector";
		goto bad_device;
	}
	cc->start = tmpll;

	if (dm_get_device(ti, argv[3], cc->start, ti->len,
			  dm_table_get_mode(ti->table), &cc->dev)) {
		ti->error = "Device lookup failed";
		goto bad_device;
	}

	if (ivmode && cc->iv_gen_ops) {
		if (ivopts)
			*(ivopts - 1) = ':';
		cc->iv_mode = kmalloc(strlen(ivmode) + 1, GFP_KERNEL);
		if (!cc->iv_mode) {
			ti->error = "Error kmallocing iv_mode string";
			goto bad_ivmode_string;
		}
		strcpy(cc->iv_mode, ivmode);
	} else
		cc->iv_mode = NULL;

	cc->io_queue = create_singlethread_workqueue("kcryptd_io");
	if (!cc->io_queue) {
		ti->error = "Couldn't create kcryptd io queue";
		goto bad_io_queue;
	}

	cc->crypt_queue = create_singlethread_workqueue("kcryptd");
	if (!cc->crypt_queue) {
		ti->error = "Couldn't create kcryptd queue";
		goto bad_crypt_queue;
	}

	ti->private = cc;
	return 0;

bad_crypt_queue:
	destroy_workqueue(cc->io_queue);
bad_io_queue:
	kfree(cc->iv_mode);
bad_ivmode_string:
	dm_put_device(ti, cc->dev);
bad_device:
	bioset_free(cc->bs);
bad_bs:
	mempool_destroy(cc->page_pool);
bad_page_pool:
	mempool_destroy(cc->io_pool);
bad_slab_pool:
	if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
		cc->iv_gen_ops->dtr(cc);
bad_ivmode:
	crypto_free_blkcipher(tfm);
bad_cipher:
	/* Must zero key material before freeing */
	memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
	kfree(cc);
	return -EINVAL;
}

static void crypt_dtr(struct dm_target *ti)
{
	struct crypt_config *cc = (struct crypt_config *) ti->private;

	destroy_workqueue(cc->io_queue);
	destroy_workqueue(cc->crypt_queue);

	bioset_free(cc->bs);
	mempool_destroy(cc->page_pool);
	mempool_destroy(cc->io_pool);

	kfree(cc->iv_mode);
	if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
		cc->iv_gen_ops->dtr(cc);
	crypto_free_blkcipher(cc->tfm);
	dm_put_device(ti, cc->dev);

	/* Must zero key material before freeing */
	memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
	kfree(cc);
}

static int crypt_map(struct dm_target *ti, struct bio *bio,
		     union map_info *map_context)
{
	struct crypt_config *cc = ti->private;
	struct dm_crypt_io *io;

	io = mempool_alloc(cc->io_pool, GFP_NOIO);
	io->target = ti;
	io->base_bio = bio;
	io->error = 0;
	atomic_set(&io->pending, 0);

	if (bio_data_dir(io->base_bio) == READ)
		kcryptd_queue_io(io);
	else
		kcryptd_queue_crypt(io);

	return DM_MAPIO_SUBMITTED;
}

static int crypt_status(struct dm_target *ti, status_type_t type,
			char *result, unsigned int maxlen)
{
	struct crypt_config *cc = (struct crypt_config *) ti->private;
	unsigned int sz = 0;

	switch (type) {
	case STATUSTYPE_INFO:
		result[0] = '\0';
		break;

	case STATUSTYPE_TABLE:
		if (cc->iv_mode)
			DMEMIT("%s-%s-%s ", cc->cipher, cc->chainmode,
			       cc->iv_mode);
		else
			DMEMIT("%s-%s ", cc->cipher, cc->chainmode);

		if (cc->key_size > 0) {
			if ((maxlen - sz) < ((cc->key_size << 1) + 1))
				return -ENOMEM;

			crypt_encode_key(result + sz, cc->key, cc->key_size);
			sz += cc->key_size << 1;
		} else {
			if (sz >= maxlen)
				return -ENOMEM;
			result[sz++] = '-';
		}

		DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
				cc->dev->name, (unsigned long long)cc->start);
		break;
	}
	return 0;
}

static void crypt_postsuspend(struct dm_target *ti)
{
	struct crypt_config *cc = ti->private;

	set_bit(DM_CRYPT_SUSPENDED, &cc->flags);
}

static int crypt_preresume(struct dm_target *ti)
{
	struct crypt_config *cc = ti->private;

	if (!test_bit(DM_CRYPT_KEY_VALID, &cc->flags)) {
		DMERR("aborting resume - crypt key is not set.");
		return -EAGAIN;
	}

	return 0;
}

static void crypt_resume(struct dm_target *ti)
{
	struct crypt_config *cc = ti->private;

	clear_bit(DM_CRYPT_SUSPENDED, &cc->flags);
}

/* Message interface
 *	key set <key>
 *	key wipe
 */
static int crypt_message(struct dm_target *ti, unsigned argc, char **argv)
{
	struct crypt_config *cc = ti->private;

	if (argc < 2)
		goto error;

	if (!strnicmp(argv[0], MESG_STR("key"))) {
		if (!test_bit(DM_CRYPT_SUSPENDED, &cc->flags)) {
			DMWARN("not suspended during key manipulation.");
			return -EINVAL;
		}
		if (argc == 3 && !strnicmp(argv[1], MESG_STR("set")))
			return crypt_set_key(cc, argv[2]);
		if (argc == 2 && !strnicmp(argv[1], MESG_STR("wipe")))
			return crypt_wipe_key(cc);
	}

error:
	DMWARN("unrecognised message received.");
	return -EINVAL;
}

static struct target_type crypt_target = {
	.name   = "crypt",
	.version= {1, 5, 0},
	.module = THIS_MODULE,
	.ctr    = crypt_ctr,
	.dtr    = crypt_dtr,
	.map    = crypt_map,
	.status = crypt_status,
	.postsuspend = crypt_postsuspend,
	.preresume = crypt_preresume,
	.resume = crypt_resume,
	.message = crypt_message,
};

static int __init dm_crypt_init(void)
{
	int r;

	_crypt_io_pool = KMEM_CACHE(dm_crypt_io, 0);
	if (!_crypt_io_pool)
		return -ENOMEM;

	r = dm_register_target(&crypt_target);
	if (r < 0) {
		DMERR("register failed %d", r);
		kmem_cache_destroy(_crypt_io_pool);
	}

	return r;
}

static void __exit dm_crypt_exit(void)
{
	int r = dm_unregister_target(&crypt_target);

	if (r < 0)
		DMERR("unregister failed %d", r);

	kmem_cache_destroy(_crypt_io_pool);
}

module_init(dm_crypt_init);
module_exit(dm_crypt_exit);

MODULE_AUTHOR("Christophe Saout <[e-mail]>");
MODULE_DESCRIPTION(DM_NAME " target for transparent encryption / decryption");
MODULE_LICENSE("GPL");