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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>
#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_CAST(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;

inst->alg.cra_blkcipher.geniv = "chainiv";

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_blkcipher.geniv = "seqiv";

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");
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