crypto/ctr.c - arm/linux - Git at Google

 /*
  * CTR: Counter mode
  *
  * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
  *
  * 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.
  *
  */

 #include <crypto/algapi.h>
 #include <crypto/ctr.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>

 struct crypto_ctr_ctx {
 	struct crypto_cipher *child;
 };

 struct crypto_rfc3686_ctx {
 	struct crypto_blkcipher *child;
 	u8 nonce[CTR_RFC3686_NONCE_SIZE];
 };

 static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
 			     unsigned int keylen)
 {
 	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
 	struct crypto_cipher *child = ctx->child;
 	int err;

 	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
 				CRYPTO_TFM_REQ_MASK);
 	err = crypto_cipher_setkey(child, key, keylen);
 	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
 			     CRYPTO_TFM_RES_MASK);

 	return err;
 }

 static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
 				   struct crypto_cipher *tfm)
 {
 	unsigned int bsize = crypto_cipher_blocksize(tfm);
 	unsigned long alignmask = crypto_cipher_alignmask(tfm);
 	u8 *ctrblk = walk->iv;
 	u8 tmp[bsize + alignmask];
 	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
 	unsigned int nbytes = walk->nbytes;

 	crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
 	crypto_xor(keystream, src, nbytes);
 	memcpy(dst, keystream, nbytes);

 	crypto_inc(ctrblk, bsize);
 }

 static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
 				    struct crypto_cipher *tfm)
 {
 	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 		   crypto_cipher_alg(tfm)->cia_encrypt;
 	unsigned int bsize = crypto_cipher_blocksize(tfm);
 	u8 *ctrblk = walk->iv;
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
 	unsigned int nbytes = walk->nbytes;

 	do {
 		/* create keystream */
 		fn(crypto_cipher_tfm(tfm), dst, ctrblk);
 		crypto_xor(dst, src, bsize);

 		/* increment counter in counterblock */
 		crypto_inc(ctrblk, bsize);

 		src += bsize;
 		dst += bsize;
 	} while ((nbytes -= bsize) >= bsize);

 	return nbytes;
 }

 static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
 				    struct crypto_cipher *tfm)
 {
 	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
 		   crypto_cipher_alg(tfm)->cia_encrypt;
 	unsigned int bsize = crypto_cipher_blocksize(tfm);
 	unsigned long alignmask = crypto_cipher_alignmask(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *ctrblk = walk->iv;
 	u8 *src = walk->src.virt.addr;
 	u8 tmp[bsize + alignmask];
 	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);

 	do {
 		/* create keystream */
 		fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
 		crypto_xor(src, keystream, bsize);

 		/* increment counter in counterblock */
 		crypto_inc(ctrblk, bsize);

 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);

 	return nbytes;
 }

 static int crypto_ctr_crypt(struct blkcipher_desc *desc,
 			      struct scatterlist *dst, struct scatterlist *src,
 			      unsigned int nbytes)
 {
 	struct blkcipher_walk walk;
 	struct crypto_blkcipher *tfm = desc->tfm;
 	struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
 	struct crypto_cipher *child = ctx->child;
 	unsigned int bsize = crypto_cipher_blocksize(child);
 	int err;

 	blkcipher_walk_init(&walk, dst, src, nbytes);
 	err = blkcipher_walk_virt_block(desc, &walk, bsize);

 	while (walk.nbytes >= bsize) {
 		if (walk.src.virt.addr == walk.dst.virt.addr)
 			nbytes = crypto_ctr_crypt_inplace(&walk, child);
 		else
 			nbytes = crypto_ctr_crypt_segment(&walk, child);

 		err = blkcipher_walk_done(desc, &walk, nbytes);
 	}

 	if (walk.nbytes) {
 		crypto_ctr_crypt_final(&walk, child);
 		err = blkcipher_walk_done(desc, &walk, 0);
 	}

 	return err;
 }

 static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_instance *inst = (void *)tfm->__crt_alg;
 	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
 	struct crypto_cipher *cipher;

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

 	ctx->child = cipher;

 	return 0;
 }

 static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);

 	crypto_free_cipher(ctx->child);
 }

 static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
 {
 	struct crypto_instance *inst;
 	struct crypto_alg *alg;
 	int err;

 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 	if (err)
 		return ERR_PTR(err);

 	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 				  CRYPTO_ALG_TYPE_MASK);
 	if (IS_ERR(alg))
 		return ERR_PTR(PTR_ERR(alg));

 	/* Block size must be >= 4 bytes. */
 	err = -EINVAL;
 	if (alg->cra_blocksize < 4)
 		goto out_put_alg;

 	/* If this is false we'd fail the alignment of crypto_inc. */
 	if (alg->cra_blocksize % 4)
 		goto out_put_alg;

 	inst = crypto_alloc_instance("ctr", alg);
 	if (IS_ERR(inst))
 		goto out;

 	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 	inst->alg.cra_priority = alg->cra_priority;
 	inst->alg.cra_blocksize = 1;
 	inst->alg.cra_alignmask = alg->cra_alignmask | (__alignof__(u32) - 1);
 	inst->alg.cra_type = &crypto_blkcipher_type;

 	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 	inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 	inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;

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

 	inst->alg.cra_init = crypto_ctr_init_tfm;
 	inst->alg.cra_exit = crypto_ctr_exit_tfm;

 	inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
 	inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
 	inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;

 out:
 	crypto_mod_put(alg);
 	return inst;

 out_put_alg:
 	inst = ERR_PTR(err);
 	goto out;
 }

 static void crypto_ctr_free(struct crypto_instance *inst)
 {
 	crypto_drop_spawn(crypto_instance_ctx(inst));
 	kfree(inst);
 }

 static struct crypto_template crypto_ctr_tmpl = {
 	.name = "ctr",
 	.alloc = crypto_ctr_alloc,
 	.free = crypto_ctr_free,
 	.module = THIS_MODULE,
 };

 static int crypto_rfc3686_setkey(struct crypto_tfm *parent, const u8 *key,
 				 unsigned int keylen)
 {
 	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(parent);
 	struct crypto_blkcipher *child = ctx->child;
 	int err;

 	/* the nonce is stored in bytes at end of key */
 	if (keylen < CTR_RFC3686_NONCE_SIZE)
 		return -EINVAL;

 	memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
 	       CTR_RFC3686_NONCE_SIZE);

 	keylen -= CTR_RFC3686_NONCE_SIZE;

 	crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 	crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
 					  CRYPTO_TFM_REQ_MASK);
 	err = crypto_blkcipher_setkey(child, key, keylen);
 	crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
 				     CRYPTO_TFM_RES_MASK);

 	return err;
 }

 static int crypto_rfc3686_crypt(struct blkcipher_desc *desc,
 				struct scatterlist *dst,
 				struct scatterlist *src, unsigned int nbytes)
 {
 	struct crypto_blkcipher *tfm = desc->tfm;
 	struct crypto_rfc3686_ctx *ctx = crypto_blkcipher_ctx(tfm);
 	struct crypto_blkcipher *child = ctx->child;
 	unsigned long alignmask = crypto_blkcipher_alignmask(tfm);
 	u8 ivblk[CTR_RFC3686_BLOCK_SIZE + alignmask];
 	u8 *iv = PTR_ALIGN(ivblk + 0, alignmask + 1);
 	u8 *info = desc->info;
 	int err;

 	/* set up counter block */
 	memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
 	memcpy(iv + CTR_RFC3686_NONCE_SIZE, info, CTR_RFC3686_IV_SIZE);

 	/* initialize counter portion of counter block */
 	*(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
 		cpu_to_be32(1);

 	desc->tfm = child;
 	desc->info = iv;
 	err = crypto_blkcipher_encrypt_iv(desc, dst, src, nbytes);
 	desc->tfm = tfm;
 	desc->info = info;

 	return err;
 }

 static int crypto_rfc3686_init_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_instance *inst = (void *)tfm->__crt_alg;
 	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
 	struct crypto_blkcipher *cipher;

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

 	ctx->child = cipher;

 	return 0;
 }

 static void crypto_rfc3686_exit_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);

 	crypto_free_blkcipher(ctx->child);
 }

 static struct crypto_instance *crypto_rfc3686_alloc(struct rtattr **tb)
 {
 	struct crypto_instance *inst;
 	struct crypto_alg *alg;
 	int err;

 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 	if (err)
 		return ERR_PTR(err);

 	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
 				  CRYPTO_ALG_TYPE_MASK);
 	err = PTR_ERR(alg);
 	if (IS_ERR(alg))
 		return ERR_PTR(err);

 	/* We only support 16-byte blocks. */
 	err = -EINVAL;
 	if (alg->cra_blkcipher.ivsize != CTR_RFC3686_BLOCK_SIZE)
 		goto out_put_alg;

 	/* Not a stream cipher? */
 	if (alg->cra_blocksize != 1)
 		goto out_put_alg;

 	inst = crypto_alloc_instance("rfc3686", alg);
 	if (IS_ERR(inst))
 		goto out;

 	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 	inst->alg.cra_priority = alg->cra_priority;
 	inst->alg.cra_blocksize = 1;
 	inst->alg.cra_alignmask = alg->cra_alignmask;
 	inst->alg.cra_type = &crypto_blkcipher_type;

 	inst->alg.cra_blkcipher.ivsize = CTR_RFC3686_IV_SIZE;
 	inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize
 					      + CTR_RFC3686_NONCE_SIZE;
 	inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize
 					      + CTR_RFC3686_NONCE_SIZE;

 	inst->alg.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);

 	inst->alg.cra_init = crypto_rfc3686_init_tfm;
 	inst->alg.cra_exit = crypto_rfc3686_exit_tfm;

 	inst->alg.cra_blkcipher.setkey = crypto_rfc3686_setkey;
 	inst->alg.cra_blkcipher.encrypt = crypto_rfc3686_crypt;
 	inst->alg.cra_blkcipher.decrypt = crypto_rfc3686_crypt;

 out:
 	crypto_mod_put(alg);
 	return inst;

 out_put_alg:
 	inst = ERR_PTR(err);
 	goto out;
 }

 static struct crypto_template crypto_rfc3686_tmpl = {
 	.name = "rfc3686",
 	.alloc = crypto_rfc3686_alloc,
 	.free = crypto_ctr_free,
 	.module = THIS_MODULE,
 };

 static int __init crypto_ctr_module_init(void)
 {
 	int err;

 	err = crypto_register_template(&crypto_ctr_tmpl);
 	if (err)
 		goto out;

 	err = crypto_register_template(&crypto_rfc3686_tmpl);
 	if (err)
 		goto out_drop_ctr;

 out:
 	return err;

 out_drop_ctr:
 	crypto_unregister_template(&crypto_ctr_tmpl);
 	goto out;
 }

 static void __exit crypto_ctr_module_exit(void)
 {
 	crypto_unregister_template(&crypto_rfc3686_tmpl);
 	crypto_unregister_template(&crypto_ctr_tmpl);
 }

 module_init(crypto_ctr_module_init);
 module_exit(crypto_ctr_module_exit);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("CTR Counter block mode");
 MODULE_ALIAS("rfc3686");
	/*
	* CTR: Counter mode
	*
	* (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
	*
	* 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.
	*
	*/

	#include <crypto/algapi.h>
	#include <crypto/ctr.h>
	#include <linux/err.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/random.h>
	#include <linux/scatterlist.h>
	#include <linux/slab.h>

	struct crypto_ctr_ctx {
	struct crypto_cipher *child;
	};

	struct crypto_rfc3686_ctx {
	struct crypto_blkcipher *child;
	u8 nonce[CTR_RFC3686_NONCE_SIZE];
	};

	static int crypto_ctr_setkey(struct crypto_tfm parent, const u8 key,
	unsigned int keylen)
	{
	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
	struct crypto_cipher *child = ctx->child;
	int err;

	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
	CRYPTO_TFM_REQ_MASK);
	err = crypto_cipher_setkey(child, key, keylen);
	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
	CRYPTO_TFM_RES_MASK);

	return err;
	}

	static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
	struct crypto_cipher *tfm)
	{
	unsigned int bsize = crypto_cipher_blocksize(tfm);
	unsigned long alignmask = crypto_cipher_alignmask(tfm);
	u8 *ctrblk = walk->iv;
	u8 tmp[bsize + alignmask];
	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	unsigned int nbytes = walk->nbytes;

	crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
	crypto_xor(keystream, src, nbytes);
	memcpy(dst, keystream, nbytes);

	crypto_inc(ctrblk, bsize);
	}

	static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
	struct crypto_cipher *tfm)
	{
	void (fn)(struct crypto_tfm , u8 , const u8 ) =
	crypto_cipher_alg(tfm)->cia_encrypt;
	unsigned int bsize = crypto_cipher_blocksize(tfm);
	u8 *ctrblk = walk->iv;
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	unsigned int nbytes = walk->nbytes;

	do {
	/* create keystream */
	fn(crypto_cipher_tfm(tfm), dst, ctrblk);
	crypto_xor(dst, src, bsize);

	/* increment counter in counterblock */
	crypto_inc(ctrblk, bsize);

	src += bsize;
	dst += bsize;
	} while ((nbytes -= bsize) >= bsize);

	return nbytes;
	}

	static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
	struct crypto_cipher *tfm)
	{
	void (fn)(struct crypto_tfm , u8 , const u8 ) =
	crypto_cipher_alg(tfm)->cia_encrypt;
	unsigned int bsize = crypto_cipher_blocksize(tfm);
	unsigned long alignmask = crypto_cipher_alignmask(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *ctrblk = walk->iv;
	u8 *src = walk->src.virt.addr;
	u8 tmp[bsize + alignmask];
	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);

	do {
	/* create keystream */
	fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
	crypto_xor(src, keystream, bsize);

	/* increment counter in counterblock */
	crypto_inc(ctrblk, bsize);

	src += bsize;
	} while ((nbytes -= bsize) >= bsize);

	return nbytes;
	}

	static int crypto_ctr_crypt(struct blkcipher_desc *desc,
	struct scatterlist dst, struct scatterlist src,
	unsigned int nbytes)
	{
	struct blkcipher_walk walk;
	struct crypto_blkcipher *tfm = desc->tfm;
	struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
	struct crypto_cipher *child = ctx->child;
	unsigned int bsize = crypto_cipher_blocksize(child);
	int err;

	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt_block(desc, &walk, bsize);

	while (walk.nbytes >= bsize) {
	if (walk.src.virt.addr == walk.dst.virt.addr)
	nbytes = crypto_ctr_crypt_inplace(&walk, child);
	else
	nbytes = crypto_ctr_crypt_segment(&walk, child);

	err = blkcipher_walk_done(desc, &walk, nbytes);
	}

	if (walk.nbytes) {
	crypto_ctr_crypt_final(&walk, child);
	err = blkcipher_walk_done(desc, &walk, 0);
	}

	return err;
	}

	static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
	{
	struct crypto_instance inst = (void )tfm->__crt_alg;
	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
	struct crypto_cipher *cipher;

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

	ctx->child = cipher;

	return 0;
	}

	static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
	{
	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);

	crypto_free_cipher(ctx->child);
	}

	static struct crypto_instance crypto_ctr_alloc(struct rtattr *tb)
	{
	struct crypto_instance *inst;
	struct crypto_alg *alg;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
	if (err)
	return ERR_PTR(err);

	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
	CRYPTO_ALG_TYPE_MASK);
	if (IS_ERR(alg))
	return ERR_PTR(PTR_ERR(alg));

	/* Block size must be >= 4 bytes. */
	err = -EINVAL;
	if (alg->cra_blocksize < 4)
	goto out_put_alg;

	/* If this is false we'd fail the alignment of crypto_inc. */
	if (alg->cra_blocksize % 4)
	goto out_put_alg;

	inst = crypto_alloc_instance("ctr", alg);
	if (IS_ERR(inst))
	goto out;

	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
	inst->alg.cra_priority = alg->cra_priority;
	inst->alg.cra_blocksize = 1;
	inst->alg.cra_alignmask = alg->cra_alignmask \| (__alignof__(u32) - 1);
	inst->alg.cra_type = &crypto_blkcipher_type;

	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
	inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
	inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;

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

	inst->alg.cra_init = crypto_ctr_init_tfm;
	inst->alg.cra_exit = crypto_ctr_exit_tfm;

	inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
	inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
	inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;

	out:
	crypto_mod_put(alg);
	return inst;

	out_put_alg:
	inst = ERR_PTR(err);
	goto out;
	}

	static void crypto_ctr_free(struct crypto_instance *inst)
	{
	crypto_drop_spawn(crypto_instance_ctx(inst));
	kfree(inst);
	}

	static struct crypto_template crypto_ctr_tmpl = {
	.name = "ctr",
	.alloc = crypto_ctr_alloc,
	.free = crypto_ctr_free,
	.module = THIS_MODULE,
	};

	static int crypto_rfc3686_setkey(struct crypto_tfm parent, const u8 key,
	unsigned int keylen)
	{
	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(parent);
	struct crypto_blkcipher *child = ctx->child;
	int err;

	/* the nonce is stored in bytes at end of key */
	if (keylen < CTR_RFC3686_NONCE_SIZE)
	return -EINVAL;

	memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
	CTR_RFC3686_NONCE_SIZE);

	keylen -= CTR_RFC3686_NONCE_SIZE;

	crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
	CRYPTO_TFM_REQ_MASK);
	err = crypto_blkcipher_setkey(child, key, keylen);
	crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
	CRYPTO_TFM_RES_MASK);

	return err;
	}

	static int crypto_rfc3686_crypt(struct blkcipher_desc *desc,
	struct scatterlist *dst,
	struct scatterlist *src, unsigned int nbytes)
	{
	struct crypto_blkcipher *tfm = desc->tfm;
	struct crypto_rfc3686_ctx *ctx = crypto_blkcipher_ctx(tfm);
	struct crypto_blkcipher *child = ctx->child;
	unsigned long alignmask = crypto_blkcipher_alignmask(tfm);
	u8 ivblk[CTR_RFC3686_BLOCK_SIZE + alignmask];
	u8 *iv = PTR_ALIGN(ivblk + 0, alignmask + 1);
	u8 *info = desc->info;
	int err;

	/* set up counter block */
	memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
	memcpy(iv + CTR_RFC3686_NONCE_SIZE, info, CTR_RFC3686_IV_SIZE);

	/* initialize counter portion of counter block */
	(__be32 )(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
	cpu_to_be32(1);

	desc->tfm = child;
	desc->info = iv;
	err = crypto_blkcipher_encrypt_iv(desc, dst, src, nbytes);
	desc->tfm = tfm;
	desc->info = info;

	return err;
	}

	static int crypto_rfc3686_init_tfm(struct crypto_tfm *tfm)
	{
	struct crypto_instance inst = (void )tfm->__crt_alg;
	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
	struct crypto_blkcipher *cipher;

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

	ctx->child = cipher;

	return 0;
	}

	static void crypto_rfc3686_exit_tfm(struct crypto_tfm *tfm)
	{
	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);

	crypto_free_blkcipher(ctx->child);
	}

	static struct crypto_instance crypto_rfc3686_alloc(struct rtattr *tb)
	{
	struct crypto_instance *inst;
	struct crypto_alg *alg;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
	if (err)
	return ERR_PTR(err);

	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
	CRYPTO_ALG_TYPE_MASK);
	err = PTR_ERR(alg);
	if (IS_ERR(alg))
	return ERR_PTR(err);

	/* We only support 16-byte blocks. */
	err = -EINVAL;
	if (alg->cra_blkcipher.ivsize != CTR_RFC3686_BLOCK_SIZE)
	goto out_put_alg;

	/* Not a stream cipher? */
	if (alg->cra_blocksize != 1)
	goto out_put_alg;

	inst = crypto_alloc_instance("rfc3686", alg);
	if (IS_ERR(inst))
	goto out;

	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
	inst->alg.cra_priority = alg->cra_priority;
	inst->alg.cra_blocksize = 1;
	inst->alg.cra_alignmask = alg->cra_alignmask;
	inst->alg.cra_type = &crypto_blkcipher_type;

	inst->alg.cra_blkcipher.ivsize = CTR_RFC3686_IV_SIZE;
	inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize
	+ CTR_RFC3686_NONCE_SIZE;
	inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize
	+ CTR_RFC3686_NONCE_SIZE;

	inst->alg.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);

	inst->alg.cra_init = crypto_rfc3686_init_tfm;
	inst->alg.cra_exit = crypto_rfc3686_exit_tfm;

	inst->alg.cra_blkcipher.setkey = crypto_rfc3686_setkey;
	inst->alg.cra_blkcipher.encrypt = crypto_rfc3686_crypt;
	inst->alg.cra_blkcipher.decrypt = crypto_rfc3686_crypt;

	out:
	crypto_mod_put(alg);
	return inst;

	out_put_alg:
	inst = ERR_PTR(err);
	goto out;
	}

	static struct crypto_template crypto_rfc3686_tmpl = {
	.name = "rfc3686",
	.alloc = crypto_rfc3686_alloc,
	.free = crypto_ctr_free,
	.module = THIS_MODULE,
	};

	static int __init crypto_ctr_module_init(void)
	{
	int err;

	err = crypto_register_template(&crypto_ctr_tmpl);
	if (err)
	goto out;

	err = crypto_register_template(&crypto_rfc3686_tmpl);
	if (err)
	goto out_drop_ctr;

	out:
	return err;

	out_drop_ctr:
	crypto_unregister_template(&crypto_ctr_tmpl);
	goto out;
	}

	static void __exit crypto_ctr_module_exit(void)
	{
	crypto_unregister_template(&crypto_rfc3686_tmpl);
	crypto_unregister_template(&crypto_ctr_tmpl);
	}

	module_init(crypto_ctr_module_init);
	module_exit(crypto_ctr_module_exit);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("CTR Counter block mode");
	MODULE_ALIAS("rfc3686");