crypto/lrw.c - SHIFTPHONES/mainline/linux - Gitiles

 /* LRW: as defined by Cyril Guyot in
  *	http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
  *
  * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
  *
  * Based on ecb.c
  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
  * Software Foundation; either version 2 of the License, or (at your option)
  * any later version.
  */
 /* This implementation is checked against the test vectors in the above
  * document and by a test vector provided by Ken Buchanan at
  * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
  *
  * The test vectors are included in the testing module tcrypt.[ch] */

 #include <crypto/internal/skcipher.h>
 #include <crypto/scatterwalk.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>

 #include <crypto/b128ops.h>
 #include <crypto/gf128mul.h>

 #define LRW_BLOCK_SIZE 16

 struct priv {
 	struct crypto_skcipher *child;

 	/*
 	 * optimizes multiplying a random (non incrementing, as at the
 	 * start of a new sector) value with key2, we could also have
 	 * used 4k optimization tables or no optimization at all. In the
 	 * latter case we would have to store key2 here
 	 */
 	struct gf128mul_64k *table;

 	/*
 	 * stores:
 	 *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
 	 *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
 	 *  key2*{ 0,0,...1,1,1,1,1 }, etc
 	 * needed for optimized multiplication of incrementing values
 	 * with key2
 	 */
 	be128 mulinc[128];
 };

 struct rctx {
 	be128 t;
 	struct skcipher_request subreq;
 };

 static inline void setbit128_bbe(void *b, int bit)
 {
 	__set_bit(bit ^ (0x80 -
 #ifdef __BIG_ENDIAN
 			 BITS_PER_LONG
 #else
 			 BITS_PER_BYTE
 #endif
 			), b);
 }

 static int setkey(struct crypto_skcipher *parent, const u8 *key,
 		  unsigned int keylen)
 {
 	struct priv *ctx = crypto_skcipher_ctx(parent);
 	struct crypto_skcipher *child = ctx->child;
 	int err, bsize = LRW_BLOCK_SIZE;
 	const u8 *tweak = key + keylen - bsize;
 	be128 tmp = { 0 };
 	int i;

 	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 					 CRYPTO_TFM_REQ_MASK);
 	err = crypto_skcipher_setkey(child, key, keylen - bsize);
 	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
 					  CRYPTO_TFM_RES_MASK);
 	if (err)
 		return err;

 	if (ctx->table)
 		gf128mul_free_64k(ctx->table);

 	/* initialize multiplication table for Key2 */
 	ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
 	if (!ctx->table)
 		return -ENOMEM;

 	/* initialize optimization table */
 	for (i = 0; i < 128; i++) {
 		setbit128_bbe(&tmp, i);
 		ctx->mulinc[i] = tmp;
 		gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
 	}

 	return 0;
 }

 /*
  * Returns the number of trailing '1' bits in the words of the counter, which is
  * represented by 4 32-bit words, arranged from least to most significant.
  * At the same time, increments the counter by one.
  *
  * For example:
  *
  * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
  * int i = next_index(&counter);
  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
  */
 static int next_index(u32 *counter)
 {
 	int i, res = 0;

 	for (i = 0; i < 4; i++) {
 		if (counter[i] + 1 != 0)
 			return res + ffz(counter[i]++);

 		counter[i] = 0;
 		res += 32;
 	}

 	/*
 	 * If we get here, then x == 128 and we are incrementing the counter
 	 * from all ones to all zeros. This means we must return index 127, i.e.
 	 * the one corresponding to key2*{ 1,...,1 }.
 	 */
 	return 127;
 }

 /*
  * We compute the tweak masks twice (both before and after the ECB encryption or
  * decryption) to avoid having to allocate a temporary buffer and/or make
  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
  * just doing the next_index() calls again.
  */
 static int xor_tweak(struct skcipher_request *req, bool second_pass)
 {
 	const int bs = LRW_BLOCK_SIZE;
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct priv *ctx = crypto_skcipher_ctx(tfm);
 	struct rctx *rctx = skcipher_request_ctx(req);
 	be128 t = rctx->t;
 	struct skcipher_walk w;
 	__be32 *iv;
 	u32 counter[4];
 	int err;

 	if (second_pass) {
 		req = &rctx->subreq;
 		/* set to our TFM to enforce correct alignment: */
 		skcipher_request_set_tfm(req, tfm);
 	}

 	err = skcipher_walk_virt(&w, req, false);
 	if (err)
 		return err;

 	iv = (__be32 *)w.iv;
 	counter[0] = be32_to_cpu(iv[3]);
 	counter[1] = be32_to_cpu(iv[2]);
 	counter[2] = be32_to_cpu(iv[1]);
 	counter[3] = be32_to_cpu(iv[0]);

 	while (w.nbytes) {
 		unsigned int avail = w.nbytes;
 		be128 *wsrc;
 		be128 *wdst;

 		wsrc = w.src.virt.addr;
 		wdst = w.dst.virt.addr;

 		do {
 			be128_xor(wdst++, &t, wsrc++);

 			/* T <- I*Key2, using the optimization
 			 * discussed in the specification */
 			be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
 		} while ((avail -= bs) >= bs);

 		if (second_pass && w.nbytes == w.total) {
 			iv[0] = cpu_to_be32(counter[3]);
 			iv[1] = cpu_to_be32(counter[2]);
 			iv[2] = cpu_to_be32(counter[1]);
 			iv[3] = cpu_to_be32(counter[0]);
 		}

 		err = skcipher_walk_done(&w, avail);
 	}

 	return err;
 }

 static int xor_tweak_pre(struct skcipher_request *req)
 {
 	return xor_tweak(req, false);
 }

 static int xor_tweak_post(struct skcipher_request *req)
 {
 	return xor_tweak(req, true);
 }

 static void crypt_done(struct crypto_async_request *areq, int err)
 {
 	struct skcipher_request *req = areq->data;

 	if (!err)
 		err = xor_tweak_post(req);

 	skcipher_request_complete(req, err);
 }

 static void init_crypt(struct skcipher_request *req)
 {
 	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 	struct rctx *rctx = skcipher_request_ctx(req);
 	struct skcipher_request *subreq = &rctx->subreq;

 	skcipher_request_set_tfm(subreq, ctx->child);
 	skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
 	/* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
 	skcipher_request_set_crypt(subreq, req->dst, req->dst,
 				   req->cryptlen, req->iv);

 	/* calculate first value of T */
 	memcpy(&rctx->t, req->iv, sizeof(rctx->t));

 	/* T <- I*Key2 */
 	gf128mul_64k_bbe(&rctx->t, ctx->table);
 }

 static int encrypt(struct skcipher_request *req)
 {
 	struct rctx *rctx = skcipher_request_ctx(req);
 	struct skcipher_request *subreq = &rctx->subreq;

 	init_crypt(req);
 	return xor_tweak_pre(req) ?:
 		crypto_skcipher_encrypt(subreq) ?:
 		xor_tweak_post(req);
 }

 static int decrypt(struct skcipher_request *req)
 {
 	struct rctx *rctx = skcipher_request_ctx(req);
 	struct skcipher_request *subreq = &rctx->subreq;

 	init_crypt(req);
 	return xor_tweak_pre(req) ?:
 		crypto_skcipher_decrypt(subreq) ?:
 		xor_tweak_post(req);
 }

 static int init_tfm(struct crypto_skcipher *tfm)
 {
 	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 	struct priv *ctx = crypto_skcipher_ctx(tfm);
 	struct crypto_skcipher *cipher;

 	cipher = crypto_spawn_skcipher(spawn);
 	if (IS_ERR(cipher))
 		return PTR_ERR(cipher);

 	ctx->child = cipher;

 	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
 					 sizeof(struct rctx));

 	return 0;
 }

 static void exit_tfm(struct crypto_skcipher *tfm)
 {
 	struct priv *ctx = crypto_skcipher_ctx(tfm);

 	if (ctx->table)
 		gf128mul_free_64k(ctx->table);
 	crypto_free_skcipher(ctx->child);
 }

 static void free(struct skcipher_instance *inst)
 {
 	crypto_drop_skcipher(skcipher_instance_ctx(inst));
 	kfree(inst);
 }

 static int create(struct crypto_template *tmpl, struct rtattr **tb)
 {
 	struct crypto_skcipher_spawn *spawn;
 	struct skcipher_instance *inst;
 	struct crypto_attr_type *algt;
 	struct skcipher_alg *alg;
 	const char *cipher_name;
 	char ecb_name[CRYPTO_MAX_ALG_NAME];
 	int err;

 	algt = crypto_get_attr_type(tb);
 	if (IS_ERR(algt))
 		return PTR_ERR(algt);

 	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 		return -EINVAL;

 	cipher_name = crypto_attr_alg_name(tb[1]);
 	if (IS_ERR(cipher_name))
 		return PTR_ERR(cipher_name);

 	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 	if (!inst)
 		return -ENOMEM;

 	spawn = skcipher_instance_ctx(inst);

 	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 	err = crypto_grab_skcipher(spawn, cipher_name, 0,
 				   crypto_requires_sync(algt->type,
 							algt->mask));
 	if (err == -ENOENT) {
 		err = -ENAMETOOLONG;
 		if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
 			goto err_free_inst;

 		err = crypto_grab_skcipher(spawn, ecb_name, 0,
 					   crypto_requires_sync(algt->type,
 								algt->mask));
 	}

 	if (err)
 		goto err_free_inst;

 	alg = crypto_skcipher_spawn_alg(spawn);

 	err = -EINVAL;
 	if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
 		goto err_drop_spawn;

 	if (crypto_skcipher_alg_ivsize(alg))
 		goto err_drop_spawn;

 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
 				  &alg->base);
 	if (err)
 		goto err_drop_spawn;

 	err = -EINVAL;
 	cipher_name = alg->base.cra_name;

 	/* Alas we screwed up the naming so we have to mangle the
 	 * cipher name.
 	 */
 	if (!strncmp(cipher_name, "ecb(", 4)) {
 		unsigned len;

 		len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
 		if (len < 2 || len >= sizeof(ecb_name))
 			goto err_drop_spawn;

 		if (ecb_name[len - 1] != ')')
 			goto err_drop_spawn;

 		ecb_name[len - 1] = 0;

 		if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 			     "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
 			err = -ENAMETOOLONG;
 			goto err_drop_spawn;
 		}
 	} else
 		goto err_drop_spawn;

 	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 	inst->alg.base.cra_priority = alg->base.cra_priority;
 	inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
 	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 				       (__alignof__(__be32) - 1);

 	inst->alg.ivsize = LRW_BLOCK_SIZE;
 	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 				LRW_BLOCK_SIZE;
 	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 				LRW_BLOCK_SIZE;

 	inst->alg.base.cra_ctxsize = sizeof(struct priv);

 	inst->alg.init = init_tfm;
 	inst->alg.exit = exit_tfm;

 	inst->alg.setkey = setkey;
 	inst->alg.encrypt = encrypt;
 	inst->alg.decrypt = decrypt;

 	inst->free = free;

 	err = skcipher_register_instance(tmpl, inst);
 	if (err)
 		goto err_drop_spawn;

 out:
 	return err;

 err_drop_spawn:
 	crypto_drop_skcipher(spawn);
 err_free_inst:
 	kfree(inst);
 	goto out;
 }

 static struct crypto_template crypto_tmpl = {
 	.name = "lrw",
 	.create = create,
 	.module = THIS_MODULE,
 };

 static int __init crypto_module_init(void)
 {
 	return crypto_register_template(&crypto_tmpl);
 }

 static void __exit crypto_module_exit(void)
 {
 	crypto_unregister_template(&crypto_tmpl);
 }

 module_init(crypto_module_init);
 module_exit(crypto_module_exit);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("LRW block cipher mode");
 MODULE_ALIAS_CRYPTO("lrw");
	/* LRW: as defined by Cyril Guyot in
	* http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
	*
	* Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
	*
	* Based on ecb.c
	* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License as published by the Free
	* Software Foundation; either version 2 of the License, or (at your option)
	* any later version.
	*/
	/* This implementation is checked against the test vectors in the above
	* document and by a test vector provided by Ken Buchanan at
	* http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
	*
	* The test vectors are included in the testing module tcrypt.[ch] */

	#include <crypto/internal/skcipher.h>
	#include <crypto/scatterwalk.h>
	#include <linux/err.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/scatterlist.h>
	#include <linux/slab.h>

	#include <crypto/b128ops.h>
	#include <crypto/gf128mul.h>

	#define LRW_BLOCK_SIZE 16

	struct priv {
	struct crypto_skcipher *child;

	/*
	* optimizes multiplying a random (non incrementing, as at the
	* start of a new sector) value with key2, we could also have
	* used 4k optimization tables or no optimization at all. In the
	* latter case we would have to store key2 here
	*/
	struct gf128mul_64k *table;

	/*
	* stores:
	* key2{ 0,0,...0,0,0,0,1 }, key2{ 0,0,...0,0,0,1,1 },
	* key2{ 0,0,...0,0,1,1,1 }, key2{ 0,0,...0,1,1,1,1 }
	* key2*{ 0,0,...1,1,1,1,1 }, etc
	* needed for optimized multiplication of incrementing values
	* with key2
	*/
	be128 mulinc[128];
	};

	struct rctx {
	be128 t;
	struct skcipher_request subreq;
	};

	static inline void setbit128_bbe(void *b, int bit)
	{
	__set_bit(bit ^ (0x80 -
	#ifdef __BIG_ENDIAN
	BITS_PER_LONG
	#else
	BITS_PER_BYTE
	#endif
	), b);
	}

	static int setkey(struct crypto_skcipher parent, const u8 key,
	unsigned int keylen)
	{
	struct priv *ctx = crypto_skcipher_ctx(parent);
	struct crypto_skcipher *child = ctx->child;
	int err, bsize = LRW_BLOCK_SIZE;
	const u8 *tweak = key + keylen - bsize;
	be128 tmp = { 0 };
	int i;

	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
	CRYPTO_TFM_REQ_MASK);
	err = crypto_skcipher_setkey(child, key, keylen - bsize);
	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
	CRYPTO_TFM_RES_MASK);
	if (err)
	return err;

	if (ctx->table)
	gf128mul_free_64k(ctx->table);

	/* initialize multiplication table for Key2 */
	ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
	if (!ctx->table)
	return -ENOMEM;

	/* initialize optimization table */
	for (i = 0; i < 128; i++) {
	setbit128_bbe(&tmp, i);
	ctx->mulinc[i] = tmp;
	gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
	}

	return 0;
	}

	/*
	* Returns the number of trailing '1' bits in the words of the counter, which is
	* represented by 4 32-bit words, arranged from least to most significant.
	* At the same time, increments the counter by one.
	*
	* For example:
	*
	* u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
	* int i = next_index(&counter);
	* // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
	*/
	static int next_index(u32 *counter)
	{
	int i, res = 0;

	for (i = 0; i < 4; i++) {
	if (counter[i] + 1 != 0)
	return res + ffz(counter[i]++);

	counter[i] = 0;
	res += 32;
	}

	/*
	* If we get here, then x == 128 and we are incrementing the counter
	* from all ones to all zeros. This means we must return index 127, i.e.
	* the one corresponding to key2*{ 1,...,1 }.
	*/
	return 127;
	}

	/*
	* We compute the tweak masks twice (both before and after the ECB encryption or
	* decryption) to avoid having to allocate a temporary buffer and/or make
	* mutliple calls to the 'ecb(..)' instance, which usually would be slower than
	* just doing the next_index() calls again.
	*/
	static int xor_tweak(struct skcipher_request *req, bool second_pass)
	{
	const int bs = LRW_BLOCK_SIZE;
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct priv *ctx = crypto_skcipher_ctx(tfm);
	struct rctx *rctx = skcipher_request_ctx(req);
	be128 t = rctx->t;
	struct skcipher_walk w;
	__be32 *iv;
	u32 counter[4];
	int err;

	if (second_pass) {
	req = &rctx->subreq;
	/* set to our TFM to enforce correct alignment: */
	skcipher_request_set_tfm(req, tfm);
	}

	err = skcipher_walk_virt(&w, req, false);
	if (err)
	return err;

	iv = (__be32 *)w.iv;
	counter[0] = be32_to_cpu(iv[3]);
	counter[1] = be32_to_cpu(iv[2]);
	counter[2] = be32_to_cpu(iv[1]);
	counter[3] = be32_to_cpu(iv[0]);

	while (w.nbytes) {
	unsigned int avail = w.nbytes;
	be128 *wsrc;
	be128 *wdst;

	wsrc = w.src.virt.addr;
	wdst = w.dst.virt.addr;

	do {
	be128_xor(wdst++, &t, wsrc++);

	/* T <- I*Key2, using the optimization
	* discussed in the specification */
	be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
	} while ((avail -= bs) >= bs);

	if (second_pass && w.nbytes == w.total) {
	iv[0] = cpu_to_be32(counter[3]);
	iv[1] = cpu_to_be32(counter[2]);
	iv[2] = cpu_to_be32(counter[1]);
	iv[3] = cpu_to_be32(counter[0]);
	}

	err = skcipher_walk_done(&w, avail);
	}

	return err;
	}

	static int xor_tweak_pre(struct skcipher_request *req)
	{
	return xor_tweak(req, false);
	}

	static int xor_tweak_post(struct skcipher_request *req)
	{
	return xor_tweak(req, true);
	}

	static void crypt_done(struct crypto_async_request *areq, int err)
	{
	struct skcipher_request *req = areq->data;

	if (!err)
	err = xor_tweak_post(req);

	skcipher_request_complete(req, err);
	}

	static void init_crypt(struct skcipher_request *req)
	{
	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
	struct rctx *rctx = skcipher_request_ctx(req);
	struct skcipher_request *subreq = &rctx->subreq;

	skcipher_request_set_tfm(subreq, ctx->child);
	skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
	/* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
	skcipher_request_set_crypt(subreq, req->dst, req->dst,
	req->cryptlen, req->iv);

	/* calculate first value of T */
	memcpy(&rctx->t, req->iv, sizeof(rctx->t));

	/* T <- IKey2 /
	gf128mul_64k_bbe(&rctx->t, ctx->table);
	}

	static int encrypt(struct skcipher_request *req)
	{
	struct rctx *rctx = skcipher_request_ctx(req);
	struct skcipher_request *subreq = &rctx->subreq;

	init_crypt(req);
	return xor_tweak_pre(req) ?:
	crypto_skcipher_encrypt(subreq) ?:
	xor_tweak_post(req);
	}

	static int decrypt(struct skcipher_request *req)
	{
	struct rctx *rctx = skcipher_request_ctx(req);
	struct skcipher_request *subreq = &rctx->subreq;

	init_crypt(req);
	return xor_tweak_pre(req) ?:
	crypto_skcipher_decrypt(subreq) ?:
	xor_tweak_post(req);
	}

	static int init_tfm(struct crypto_skcipher *tfm)
	{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
	struct priv *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *cipher;

	cipher = crypto_spawn_skcipher(spawn);
	if (IS_ERR(cipher))
	return PTR_ERR(cipher);

	ctx->child = cipher;

	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
	sizeof(struct rctx));

	return 0;
	}

	static void exit_tfm(struct crypto_skcipher *tfm)
	{
	struct priv *ctx = crypto_skcipher_ctx(tfm);

	if (ctx->table)
	gf128mul_free_64k(ctx->table);
	crypto_free_skcipher(ctx->child);
	}

	static void free(struct skcipher_instance *inst)
	{
	crypto_drop_skcipher(skcipher_instance_ctx(inst));
	kfree(inst);
	}

	static int create(struct crypto_template tmpl, struct rtattr *tb)
	{
	struct crypto_skcipher_spawn *spawn;
	struct skcipher_instance *inst;
	struct crypto_attr_type *algt;
	struct skcipher_alg *alg;
	const char *cipher_name;
	char ecb_name[CRYPTO_MAX_ALG_NAME];
	int err;

	algt = crypto_get_attr_type(tb);
	if (IS_ERR(algt))
	return PTR_ERR(algt);

	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
	return -EINVAL;

	cipher_name = crypto_attr_alg_name(tb[1]);
	if (IS_ERR(cipher_name))
	return PTR_ERR(cipher_name);

	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
	if (!inst)
	return -ENOMEM;

	spawn = skcipher_instance_ctx(inst);

	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
	err = crypto_grab_skcipher(spawn, cipher_name, 0,
	crypto_requires_sync(algt->type,
	algt->mask));
	if (err == -ENOENT) {
	err = -ENAMETOOLONG;
	if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
	cipher_name) >= CRYPTO_MAX_ALG_NAME)
	goto err_free_inst;

	err = crypto_grab_skcipher(spawn, ecb_name, 0,
	crypto_requires_sync(algt->type,
	algt->mask));
	}

	if (err)
	goto err_free_inst;

	alg = crypto_skcipher_spawn_alg(spawn);

	err = -EINVAL;
	if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
	goto err_drop_spawn;

	if (crypto_skcipher_alg_ivsize(alg))
	goto err_drop_spawn;

	err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
	&alg->base);
	if (err)
	goto err_drop_spawn;

	err = -EINVAL;
	cipher_name = alg->base.cra_name;

	/* Alas we screwed up the naming so we have to mangle the
	* cipher name.
	*/
	if (!strncmp(cipher_name, "ecb(", 4)) {
	unsigned len;

	len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
	if (len < 2 \|\| len >= sizeof(ecb_name))
	goto err_drop_spawn;

	if (ecb_name[len - 1] != ')')
	goto err_drop_spawn;

	ecb_name[len - 1] = 0;

	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
	"lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
	err = -ENAMETOOLONG;
	goto err_drop_spawn;
	}
	} else
	goto err_drop_spawn;

	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
	inst->alg.base.cra_priority = alg->base.cra_priority;
	inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
	inst->alg.base.cra_alignmask = alg->base.cra_alignmask \|
	(__alignof__(__be32) - 1);

	inst->alg.ivsize = LRW_BLOCK_SIZE;
	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
	LRW_BLOCK_SIZE;
	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
	LRW_BLOCK_SIZE;

	inst->alg.base.cra_ctxsize = sizeof(struct priv);

	inst->alg.init = init_tfm;
	inst->alg.exit = exit_tfm;

	inst->alg.setkey = setkey;
	inst->alg.encrypt = encrypt;
	inst->alg.decrypt = decrypt;

	inst->free = free;

	err = skcipher_register_instance(tmpl, inst);
	if (err)
	goto err_drop_spawn;

	out:
	return err;

	err_drop_spawn:
	crypto_drop_skcipher(spawn);
	err_free_inst:
	kfree(inst);
	goto out;
	}

	static struct crypto_template crypto_tmpl = {
	.name = "lrw",
	.create = create,
	.module = THIS_MODULE,
	};

	static int __init crypto_module_init(void)
	{
	return crypto_register_template(&crypto_tmpl);
	}

	static void __exit crypto_module_exit(void)
	{
	crypto_unregister_template(&crypto_tmpl);
	}

	module_init(crypto_module_init);
	module_exit(crypto_module_exit);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("LRW block cipher mode");
	MODULE_ALIAS_CRYPTO("lrw");