ctr.c 12.6 KB
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/*
 * 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>
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#include <crypto/ctr.h>
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#include <crypto/internal/skcipher.h>
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#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;
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};

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

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

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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;
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	int err;
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	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;
}

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

	crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
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	crypto_xor_cpy(dst, keystream, src, nbytes);
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	crypto_inc(ctrblk, bsize);
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}

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

	do {
		/* create keystream */
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		fn(crypto_cipher_tfm(tfm), dst, ctrblk);
		crypto_xor(dst, src, bsize);
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		/* increment counter in counterblock */
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		crypto_inc(ctrblk, bsize);
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		src += bsize;
		dst += bsize;
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	} while ((nbytes -= bsize) >= bsize);
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	return nbytes;
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}

static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
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				    struct crypto_cipher *tfm)
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{
	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
		   crypto_cipher_alg(tfm)->cia_encrypt;
	unsigned int bsize = crypto_cipher_blocksize(tfm);
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	unsigned long alignmask = crypto_cipher_alignmask(tfm);
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	unsigned int nbytes = walk->nbytes;
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	u8 *ctrblk = walk->iv;
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	u8 *src = walk->src.virt.addr;
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	u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
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	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
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	do {
		/* create keystream */
		fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
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		crypto_xor(src, keystream, bsize);
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		/* increment counter in counterblock */
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		crypto_inc(ctrblk, bsize);
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		src += bsize;
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	} while ((nbytes -= bsize) >= bsize);
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	return nbytes;
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}

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);

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	while (walk.nbytes >= bsize) {
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		if (walk.src.virt.addr == walk.dst.virt.addr)
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			nbytes = crypto_ctr_crypt_inplace(&walk, child);
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		else
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			nbytes = crypto_ctr_crypt_segment(&walk, child);
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		err = blkcipher_walk_done(desc, &walk, nbytes);
	}
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	if (walk.nbytes) {
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		crypto_ctr_crypt_final(&walk, child);
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		err = blkcipher_walk_done(desc, &walk, 0);
	}

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	return err;
}

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

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	cipher = crypto_spawn_cipher(spawn);
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	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;
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	struct crypto_attr_type *algt;
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	struct crypto_alg *alg;
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	u32 mask;
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	int err;

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

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

	mask = CRYPTO_ALG_TYPE_MASK |
		crypto_requires_off(algt->type, algt->mask,
				    CRYPTO_ALG_NEED_FALLBACK);

	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER, mask);
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	if (IS_ERR(alg))
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		return ERR_CAST(alg);
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	/* Block size must be >= 4 bytes. */
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	err = -EINVAL;
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	if (alg->cra_blocksize < 4)
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		goto out_put_alg;

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

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	inst = crypto_alloc_instance("ctr", alg);
	if (IS_ERR(inst))
		goto out;
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	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
	inst->alg.cra_priority = alg->cra_priority;
	inst->alg.cra_blocksize = 1;
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	inst->alg.cra_alignmask = alg->cra_alignmask;
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	inst->alg.cra_type = &crypto_blkcipher_type;

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	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;
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	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;

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

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

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

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

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	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);
	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
					  CRYPTO_TFM_RES_MASK);
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	return err;
}

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static int crypto_rfc3686_crypt(struct skcipher_request *req)
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{
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	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);
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	struct crypto_rfc3686_req_ctx *rctx =
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		(void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
	struct skcipher_request *subreq = &rctx->subreq;
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	u8 *iv = rctx->iv;
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	/* set up counter block */
	memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
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	memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
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	/* initialize counter portion of counter block */
	*(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
		cpu_to_be32(1);

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	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);
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	return crypto_skcipher_encrypt(subreq);
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}

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static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
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{
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	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;
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	unsigned long align;
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	unsigned int reqsize;
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	cipher = crypto_spawn_skcipher(spawn);
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	if (IS_ERR(cipher))
		return PTR_ERR(cipher);

	ctx->child = cipher;

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	align = crypto_skcipher_alignmask(tfm);
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	align &= ~(crypto_tfm_ctx_alignment() - 1);
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	reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
		  crypto_skcipher_reqsize(cipher);
	crypto_skcipher_set_reqsize(tfm, reqsize);
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	return 0;
}

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

	crypto_free_skcipher(ctx->child);
}
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static void crypto_rfc3686_free(struct skcipher_instance *inst)
{
	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);

	crypto_drop_skcipher(spawn);
	kfree(inst);
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}

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static int crypto_rfc3686_create(struct crypto_template *tmpl,
				 struct rtattr **tb)
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{
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	struct crypto_attr_type *algt;
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	struct skcipher_instance *inst;
	struct skcipher_alg *alg;
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	struct crypto_skcipher_spawn *spawn;
	const char *cipher_name;
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	u32 mask;

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	int err;

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	algt = crypto_get_attr_type(tb);
	if (IS_ERR(algt))
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		return PTR_ERR(algt);
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	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
		return -EINVAL;
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	cipher_name = crypto_attr_alg_name(tb[1]);
	if (IS_ERR(cipher_name))
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		return PTR_ERR(cipher_name);
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	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
	if (!inst)
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		return -ENOMEM;
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	mask = crypto_requires_sync(algt->type, algt->mask) |
		crypto_requires_off(algt->type, algt->mask,
				    CRYPTO_ALG_NEED_FALLBACK);

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	spawn = skcipher_instance_ctx(inst);
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	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
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	err = crypto_grab_skcipher(spawn, cipher_name, 0, mask);
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	if (err)
		goto err_free_inst;

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	alg = crypto_spawn_skcipher_alg(spawn);
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	/* We only support 16-byte blocks. */
	err = -EINVAL;
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	if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)
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		goto err_drop_spawn;
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	/* Not a stream cipher? */
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	if (alg->base.cra_blocksize != 1)
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		goto err_drop_spawn;
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	err = -ENAMETOOLONG;
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	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
		     "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
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		goto err_drop_spawn;
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	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
		     "rfc3686(%s)", alg->base.cra_driver_name) >=
	    CRYPTO_MAX_ALG_NAME)
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		goto err_drop_spawn;
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	inst->alg.base.cra_priority = alg->base.cra_priority;
	inst->alg.base.cra_blocksize = 1;
	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
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	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
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	inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
				CTR_RFC3686_NONCE_SIZE;
	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
				CTR_RFC3686_NONCE_SIZE;
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	inst->alg.setkey = crypto_rfc3686_setkey;
	inst->alg.encrypt = crypto_rfc3686_crypt;
	inst->alg.decrypt = crypto_rfc3686_crypt;
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	inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
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	inst->alg.init = crypto_rfc3686_init_tfm;
	inst->alg.exit = crypto_rfc3686_exit_tfm;
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	inst->free = crypto_rfc3686_free;
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	err = skcipher_register_instance(tmpl, inst);
	if (err)
		goto err_drop_spawn;

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

static struct crypto_template crypto_rfc3686_tmpl = {
	.name = "rfc3686",
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	.create = crypto_rfc3686_create,
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	.module = THIS_MODULE,
};

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static int __init crypto_ctr_module_init(void)
{
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	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;
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}

static void __exit crypto_ctr_module_exit(void)
{
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	crypto_unregister_template(&crypto_rfc3686_tmpl);
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	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");
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MODULE_ALIAS_CRYPTO("rfc3686");
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MODULE_ALIAS_CRYPTO("ctr");