crypto/ctr.c - pub/scm/linux/kernel/git/peterz/queue - Git at Google


            
            // SPDX-License-Identifier: GPL-2.0-or-later

            
            /*

            
             * CTR: Counter mode

            
             *

            
             * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>

            
             */


            #include <crypto/algapi.h>

            
            #include <crypto/ctr.h>

            
            #include <crypto/internal/cipher.h>

            
            #include <crypto/internal/skcipher.h>

            
            #include <linux/err.h>

            
            #include <linux/init.h>

            
            #include <linux/kernel.h>

            
            #include <linux/module.h>

            
            #include <linux/slab.h>


            struct crypto_rfc3686_ctx {

            
            	struct crypto_skcipher *child;

            
            	u8 nonce[CTR_RFC3686_NONCE_SIZE];

            
            };


            struct crypto_rfc3686_req_ctx {

            
            	u8 iv[CTR_RFC3686_BLOCK_SIZE];

            
            	struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;

            
            };


            static void crypto_ctr_crypt_final(struct skcipher_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[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_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_cpy(dst, keystream, src, nbytes);


            	crypto_inc(ctrblk, bsize);

            
            }


            static int crypto_ctr_crypt_segment(struct skcipher_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 skcipher_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[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_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 skcipher_request *req)

            
            {

            
            	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);

            
            	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);

            
            	const unsigned int bsize = crypto_cipher_blocksize(cipher);

            
            	struct skcipher_walk walk;

            
            	unsigned int nbytes;

            
            	int err;


            	err = skcipher_walk_virt(&walk, req, false);


            	while (walk.nbytes >= bsize) {

            
            		if (walk.src.virt.addr == walk.dst.virt.addr)

            
            			nbytes = crypto_ctr_crypt_inplace(&walk, cipher);

            
            		else

            
            			nbytes = crypto_ctr_crypt_segment(&walk, cipher);


            		err = skcipher_walk_done(&walk, nbytes);

            
            	}


            	if (walk.nbytes) {

            
            		crypto_ctr_crypt_final(&walk, cipher);

            
            		err = skcipher_walk_done(&walk, 0);

            
            	}


            	return err;

            
            }


            static int crypto_ctr_create(struct crypto_template *tmpl, struct rtattr **tb)

            
            {

            
            	struct skcipher_instance *inst;

            
            	struct crypto_alg *alg;

            
            	int err;


            	inst = skcipher_alloc_instance_simple(tmpl, tb);

            
            	if (IS_ERR(inst))

            
            		return PTR_ERR(inst);


            	alg = skcipher_ialg_simple(inst);


            	/* Block size must be >= 4 bytes. */

            
            	err = -EINVAL;

            
            	if (alg->cra_blocksize < 4)

            
            		goto out_free_inst;


            	/* If this is false we'd fail the alignment of crypto_inc. */

            
            	if (alg->cra_blocksize % 4)

            
            		goto out_free_inst;


            	/* CTR mode is a stream cipher. */

            
            	inst->alg.base.cra_blocksize = 1;


            	/*

            
            	 * To simplify the implementation, configure the skcipher walk to only

            
            	 * give a partial block at the very end, never earlier.

            
            	 */

            
            	inst->alg.chunksize = alg->cra_blocksize;


            	inst->alg.encrypt = crypto_ctr_crypt;

            
            	inst->alg.decrypt = crypto_ctr_crypt;


            	err = skcipher_register_instance(tmpl, inst);

            
            	if (err) {

            
            out_free_inst:

            
            		inst->free(inst);

            
            	}


            	return err;

            
            }


            static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,

            
            				 const u8 *key, unsigned int keylen)

            
            {

            
            	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);

            
            	struct crypto_skcipher *child = ctx->child;


            	/* 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_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);

            
            	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &

            
            					 CRYPTO_TFM_REQ_MASK);

            
            	return crypto_skcipher_setkey(child, key, keylen);

            
            }


            static int crypto_rfc3686_crypt(struct skcipher_request *req)

            
            {

            
            	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);

            
            	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);

            
            	struct crypto_skcipher *child = ctx->child;

            
            	unsigned long align = crypto_skcipher_alignmask(tfm);

            
            	struct crypto_rfc3686_req_ctx *rctx =

            
            		(void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);

            
            	struct skcipher_request *subreq = &rctx->subreq;

            
            	u8 *iv = rctx->iv;


            	/* set up counter block */

            
            	memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);

            
            	memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);


            	/* initialize counter portion of counter block */

            
            	*(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =

            
            		cpu_to_be32(1);


            	skcipher_request_set_tfm(subreq, child);

            
            	skcipher_request_set_callback(subreq, req->base.flags,

            
            				      req->base.complete, req->base.data);

            
            	skcipher_request_set_crypt(subreq, req->src, req->dst,

            
            				   req->cryptlen, iv);


            	return crypto_skcipher_encrypt(subreq);

            
            }


            static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)

            
            {

            
            	struct skcipher_instance *inst = skcipher_alg_instance(tfm);

            
            	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);

            
            	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);

            
            	struct crypto_skcipher *cipher;

            
            	unsigned long align;

            
            	unsigned int reqsize;


            	cipher = crypto_spawn_skcipher(spawn);

            
            	if (IS_ERR(cipher))

            
            		return PTR_ERR(cipher);


            	ctx->child = cipher;


            	align = crypto_skcipher_alignmask(tfm);

            
            	align &= ~(crypto_tfm_ctx_alignment() - 1);

            
            	reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +

            
            		  crypto_skcipher_reqsize(cipher);

            
            	crypto_skcipher_set_reqsize(tfm, reqsize);


            	return 0;

            
            }


            static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)

            
            {

            
            	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);


            	crypto_free_skcipher(ctx->child);

            
            }


            static void crypto_rfc3686_free(struct skcipher_instance *inst)

            
            {

            
            	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);


            	crypto_drop_skcipher(spawn);

            
            	kfree(inst);

            
            }


            static int crypto_rfc3686_create(struct crypto_template *tmpl,

            
            				 struct rtattr **tb)

            
            {

            
            	struct skcipher_instance *inst;

            
            	struct crypto_skcipher_spawn *spawn;

            
            	struct skcipher_alg_common *alg;

            
            	u32 mask;

            
            	int err;


            	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);

            
            	if (err)

            
            		return err;


            	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);

            
            	if (!inst)

            
            		return -ENOMEM;


            	spawn = skcipher_instance_ctx(inst);


            	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),

            
            				   crypto_attr_alg_name(tb[1]), 0, mask);

            
            	if (err)

            
            		goto err_free_inst;


            	alg = crypto_spawn_skcipher_alg_common(spawn);


            	/* We only support 16-byte blocks. */

            
            	err = -EINVAL;

            
            	if (alg->ivsize != CTR_RFC3686_BLOCK_SIZE)

            
            		goto err_free_inst;


            	/* Not a stream cipher? */

            
            	if (alg->base.cra_blocksize != 1)

            
            		goto err_free_inst;


            	err = -ENAMETOOLONG;

            
            	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,

            
            		     "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)

            
            		goto err_free_inst;

            
            	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,

            
            		     "rfc3686(%s)", alg->base.cra_driver_name) >=

            
            	    CRYPTO_MAX_ALG_NAME)

            
            		goto err_free_inst;


            	inst->alg.base.cra_priority = alg->base.cra_priority;

            
            	inst->alg.base.cra_blocksize = 1;

            
            	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;


            	inst->alg.ivsize = CTR_RFC3686_IV_SIZE;

            
            	inst->alg.chunksize = alg->chunksize;

            
            	inst->alg.min_keysize = alg->min_keysize + CTR_RFC3686_NONCE_SIZE;

            
            	inst->alg.max_keysize = alg->max_keysize + CTR_RFC3686_NONCE_SIZE;


            	inst->alg.setkey = crypto_rfc3686_setkey;

            
            	inst->alg.encrypt = crypto_rfc3686_crypt;

            
            	inst->alg.decrypt = crypto_rfc3686_crypt;


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


            	inst->alg.init = crypto_rfc3686_init_tfm;

            
            	inst->alg.exit = crypto_rfc3686_exit_tfm;


            	inst->free = crypto_rfc3686_free;


            	err = skcipher_register_instance(tmpl, inst);

            
            	if (err) {

            
            err_free_inst:

            
            		crypto_rfc3686_free(inst);

            
            	}

            
            	return err;

            
            }


            static struct crypto_template crypto_ctr_tmpls[] = {

            
            	{

            
            		.name = "ctr",

            
            		.create = crypto_ctr_create,

            
            		.module = THIS_MODULE,

            
            	}, {

            
            		.name = "rfc3686",

            
            		.create = crypto_rfc3686_create,

            
            		.module = THIS_MODULE,

            
            	},

            
            };


            static int __init crypto_ctr_module_init(void)

            
            {

            
            	return crypto_register_templates(crypto_ctr_tmpls,

            
            					 ARRAY_SIZE(crypto_ctr_tmpls));

            
            }


            static void __exit crypto_ctr_module_exit(void)

            
            {

            
            	crypto_unregister_templates(crypto_ctr_tmpls,

            
            				    ARRAY_SIZE(crypto_ctr_tmpls));

            
            }


            subsys_initcall(crypto_ctr_module_init);

            
            module_exit(crypto_ctr_module_exit);


            MODULE_LICENSE("GPL");

            
            MODULE_DESCRIPTION("CTR block cipher mode of operation");

            
            MODULE_ALIAS_CRYPTO("rfc3686");

            
            MODULE_ALIAS_CRYPTO("ctr");

            
            MODULE_IMPORT_NS(CRYPTO_INTERNAL);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* CTR: Counter mode
	*
	* (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
	*/

	#include <crypto/algapi.h>
	#include <crypto/ctr.h>
	#include <crypto/internal/cipher.h>
	#include <crypto/internal/skcipher.h>
	#include <linux/err.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/slab.h>

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

	struct crypto_rfc3686_req_ctx {
	u8 iv[CTR_RFC3686_BLOCK_SIZE];
	struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;
	};

	static void crypto_ctr_crypt_final(struct skcipher_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[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_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_cpy(dst, keystream, src, nbytes);

	crypto_inc(ctrblk, bsize);
	}

	static int crypto_ctr_crypt_segment(struct skcipher_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 skcipher_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[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_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 skcipher_request *req)
	{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
	const unsigned int bsize = crypto_cipher_blocksize(cipher);
	struct skcipher_walk walk;
	unsigned int nbytes;
	int err;

	err = skcipher_walk_virt(&walk, req, false);

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

	err = skcipher_walk_done(&walk, nbytes);
	}

	if (walk.nbytes) {
	crypto_ctr_crypt_final(&walk, cipher);
	err = skcipher_walk_done(&walk, 0);
	}

	return err;
	}

	static int crypto_ctr_create(struct crypto_template tmpl, struct rtattr *tb)
	{
	struct skcipher_instance *inst;
	struct crypto_alg *alg;
	int err;

	inst = skcipher_alloc_instance_simple(tmpl, tb);
	if (IS_ERR(inst))
	return PTR_ERR(inst);

	alg = skcipher_ialg_simple(inst);

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

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

	/* CTR mode is a stream cipher. */
	inst->alg.base.cra_blocksize = 1;

	/*
	* To simplify the implementation, configure the skcipher walk to only
	* give a partial block at the very end, never earlier.
	*/
	inst->alg.chunksize = alg->cra_blocksize;

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

	err = skcipher_register_instance(tmpl, inst);
	if (err) {
	out_free_inst:
	inst->free(inst);
	}

	return err;
	}

	static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
	const u8 *key, unsigned int keylen)
	{
	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
	struct crypto_skcipher *child = ctx->child;

	/* 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_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
	CRYPTO_TFM_REQ_MASK);
	return crypto_skcipher_setkey(child, key, keylen);
	}

	static int crypto_rfc3686_crypt(struct skcipher_request *req)
	{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *child = ctx->child;
	unsigned long align = crypto_skcipher_alignmask(tfm);
	struct crypto_rfc3686_req_ctx *rctx =
	(void )PTR_ALIGN((u8 )skcipher_request_ctx(req), align + 1);
	struct skcipher_request *subreq = &rctx->subreq;
	u8 *iv = rctx->iv;

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

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

	skcipher_request_set_tfm(subreq, child);
	skcipher_request_set_callback(subreq, req->base.flags,
	req->base.complete, req->base.data);
	skcipher_request_set_crypt(subreq, req->src, req->dst,
	req->cryptlen, iv);

	return crypto_skcipher_encrypt(subreq);
	}

	static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
	{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *cipher;
	unsigned long align;
	unsigned int reqsize;

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

	ctx->child = cipher;

	align = crypto_skcipher_alignmask(tfm);
	align &= ~(crypto_tfm_ctx_alignment() - 1);
	reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
	crypto_skcipher_reqsize(cipher);
	crypto_skcipher_set_reqsize(tfm, reqsize);

	return 0;
	}

	static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
	{
	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);

	crypto_free_skcipher(ctx->child);
	}

	static void crypto_rfc3686_free(struct skcipher_instance *inst)
	{
	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);

	crypto_drop_skcipher(spawn);
	kfree(inst);
	}

	static int crypto_rfc3686_create(struct crypto_template *tmpl,
	struct rtattr **tb)
	{
	struct skcipher_instance *inst;
	struct crypto_skcipher_spawn *spawn;
	struct skcipher_alg_common *alg;
	u32 mask;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
	if (err)
	return err;

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

	spawn = skcipher_instance_ctx(inst);

	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
	crypto_attr_alg_name(tb[1]), 0, mask);
	if (err)
	goto err_free_inst;

	alg = crypto_spawn_skcipher_alg_common(spawn);

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

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

	err = -ENAMETOOLONG;
	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
	"rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
	goto err_free_inst;
	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
	"rfc3686(%s)", alg->base.cra_driver_name) >=
	CRYPTO_MAX_ALG_NAME)
	goto err_free_inst;

	inst->alg.base.cra_priority = alg->base.cra_priority;
	inst->alg.base.cra_blocksize = 1;
	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;

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

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

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

	inst->alg.init = crypto_rfc3686_init_tfm;
	inst->alg.exit = crypto_rfc3686_exit_tfm;

	inst->free = crypto_rfc3686_free;

	err = skcipher_register_instance(tmpl, inst);
	if (err) {
	err_free_inst:
	crypto_rfc3686_free(inst);
	}
	return err;
	}

	static struct crypto_template crypto_ctr_tmpls[] = {
	{
	.name = "ctr",
	.create = crypto_ctr_create,
	.module = THIS_MODULE,
	}, {
	.name = "rfc3686",
	.create = crypto_rfc3686_create,
	.module = THIS_MODULE,
	},
	};

	static int __init crypto_ctr_module_init(void)
	{
	return crypto_register_templates(crypto_ctr_tmpls,
	ARRAY_SIZE(crypto_ctr_tmpls));
	}

	static void __exit crypto_ctr_module_exit(void)
	{
	crypto_unregister_templates(crypto_ctr_tmpls,
	ARRAY_SIZE(crypto_ctr_tmpls));
	}

	subsys_initcall(crypto_ctr_module_init);
	module_exit(crypto_ctr_module_exit);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("CTR block cipher mode of operation");
	MODULE_ALIAS_CRYPTO("rfc3686");
	MODULE_ALIAS_CRYPTO("ctr");
	MODULE_IMPORT_NS(CRYPTO_INTERNAL);