forked from torvalds/linux
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cbc.c
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cbc.c
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/*
* CBC: Cipher Block Chaining mode
*
* 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.
*
*/
#include <crypto/algapi.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>
struct crypto_cbc_ctx {
struct crypto_cipher *child;
void (*xor)(u8 *dst, const u8 *src, unsigned int bs);
};
static int crypto_cbc_setkey(struct crypto_tfm *parent, const u8 *key,
unsigned int keylen)
{
struct crypto_cbc_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 int crypto_cbc_encrypt_segment(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
struct crypto_cipher *tfm,
void (*xor)(u8 *, const u8 *,
unsigned int))
{
void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
crypto_cipher_alg(tfm)->cia_encrypt;
int bsize = crypto_cipher_blocksize(tfm);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
u8 *iv = walk->iv;
do {
xor(iv, src, bsize);
fn(crypto_cipher_tfm(tfm), dst, iv);
memcpy(iv, dst, bsize);
src += bsize;
dst += bsize;
} while ((nbytes -= bsize) >= bsize);
return nbytes;
}
static int crypto_cbc_encrypt_inplace(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
struct crypto_cipher *tfm,
void (*xor)(u8 *, const u8 *,
unsigned int))
{
void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
crypto_cipher_alg(tfm)->cia_encrypt;
int bsize = crypto_cipher_blocksize(tfm);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *iv = walk->iv;
do {
xor(src, iv, bsize);
fn(crypto_cipher_tfm(tfm), src, src);
iv = src;
src += bsize;
} while ((nbytes -= bsize) >= bsize);
memcpy(walk->iv, iv, bsize);
return nbytes;
}
static int crypto_cbc_encrypt(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_cbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;
void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor;
int err;
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt(desc, &walk);
while ((nbytes = walk.nbytes)) {
if (walk.src.virt.addr == walk.dst.virt.addr)
nbytes = crypto_cbc_encrypt_inplace(desc, &walk, child,
xor);
else
nbytes = crypto_cbc_encrypt_segment(desc, &walk, child,
xor);
err = blkcipher_walk_done(desc, &walk, nbytes);
}
return err;
}
static int crypto_cbc_decrypt_segment(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
struct crypto_cipher *tfm,
void (*xor)(u8 *, const u8 *,
unsigned int))
{
void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
crypto_cipher_alg(tfm)->cia_decrypt;
int bsize = crypto_cipher_blocksize(tfm);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
u8 *iv = walk->iv;
do {
fn(crypto_cipher_tfm(tfm), dst, src);
xor(dst, iv, bsize);
iv = src;
src += bsize;
dst += bsize;
} while ((nbytes -= bsize) >= bsize);
memcpy(walk->iv, iv, bsize);
return nbytes;
}
static int crypto_cbc_decrypt_inplace(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
struct crypto_cipher *tfm,
void (*xor)(u8 *, const u8 *,
unsigned int))
{
void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
crypto_cipher_alg(tfm)->cia_decrypt;
int bsize = crypto_cipher_blocksize(tfm);
unsigned long alignmask = crypto_cipher_alignmask(tfm);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 stack[bsize + alignmask];
u8 *first_iv = (u8 *)ALIGN((unsigned long)stack, alignmask + 1);
memcpy(first_iv, walk->iv, bsize);
/* Start of the last block. */
src += nbytes - nbytes % bsize - bsize;
memcpy(walk->iv, src, bsize);
for (;;) {
fn(crypto_cipher_tfm(tfm), src, src);
if ((nbytes -= bsize) < bsize)
break;
xor(src, src - bsize, bsize);
src -= bsize;
}
xor(src, first_iv, bsize);
return nbytes;
}
static int crypto_cbc_decrypt(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_cbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;
void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor;
int err;
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt(desc, &walk);
while ((nbytes = walk.nbytes)) {
if (walk.src.virt.addr == walk.dst.virt.addr)
nbytes = crypto_cbc_decrypt_inplace(desc, &walk, child,
xor);
else
nbytes = crypto_cbc_decrypt_segment(desc, &walk, child,
xor);
err = blkcipher_walk_done(desc, &walk, nbytes);
}
return err;
}
static void xor_byte(u8 *a, const u8 *b, unsigned int bs)
{
do {
*a++ ^= *b++;
} while (--bs);
}
static void xor_quad(u8 *dst, const u8 *src, unsigned int bs)
{
u32 *a = (u32 *)dst;
u32 *b = (u32 *)src;
do {
*a++ ^= *b++;
} while ((bs -= 4));
}
static void xor_64(u8 *a, const u8 *b, unsigned int bs)
{
((u32 *)a)[0] ^= ((u32 *)b)[0];
((u32 *)a)[1] ^= ((u32 *)b)[1];
}
static void xor_128(u8 *a, const u8 *b, unsigned int bs)
{
((u32 *)a)[0] ^= ((u32 *)b)[0];
((u32 *)a)[1] ^= ((u32 *)b)[1];
((u32 *)a)[2] ^= ((u32 *)b)[2];
((u32 *)a)[3] ^= ((u32 *)b)[3];
}
static int crypto_cbc_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_instance *inst = (void *)tfm->__crt_alg;
struct crypto_spawn *spawn = crypto_instance_ctx(inst);
struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(tfm);
struct crypto_cipher *cipher;
switch (crypto_tfm_alg_blocksize(tfm)) {
case 8:
ctx->xor = xor_64;
break;
case 16:
ctx->xor = xor_128;
break;
default:
if (crypto_tfm_alg_blocksize(tfm) % 4)
ctx->xor = xor_byte;
else
ctx->xor = xor_quad;
}
cipher = crypto_spawn_cipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
ctx->child = cipher;
return 0;
}
static void crypto_cbc_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_cbc_ctx *ctx = crypto_tfm_ctx(tfm);
crypto_free_cipher(ctx->child);
}
static struct crypto_instance *crypto_cbc_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_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
CRYPTO_ALG_TYPE_MASK);
if (IS_ERR(alg))
return ERR_PTR(PTR_ERR(alg));
inst = crypto_alloc_instance("cbc", alg);
if (IS_ERR(inst))
goto out_put_alg;
inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
inst->alg.cra_priority = alg->cra_priority;
inst->alg.cra_blocksize = alg->cra_blocksize;
inst->alg.cra_alignmask = alg->cra_alignmask;
inst->alg.cra_type = &crypto_blkcipher_type;
if (!(alg->cra_blocksize % 4))
inst->alg.cra_alignmask |= 3;
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_cbc_ctx);
inst->alg.cra_init = crypto_cbc_init_tfm;
inst->alg.cra_exit = crypto_cbc_exit_tfm;
inst->alg.cra_blkcipher.setkey = crypto_cbc_setkey;
inst->alg.cra_blkcipher.encrypt = crypto_cbc_encrypt;
inst->alg.cra_blkcipher.decrypt = crypto_cbc_decrypt;
out_put_alg:
crypto_mod_put(alg);
return inst;
}
static void crypto_cbc_free(struct crypto_instance *inst)
{
crypto_drop_spawn(crypto_instance_ctx(inst));
kfree(inst);
}
static struct crypto_template crypto_cbc_tmpl = {
.name = "cbc",
.alloc = crypto_cbc_alloc,
.free = crypto_cbc_free,
.module = THIS_MODULE,
};
static int __init crypto_cbc_module_init(void)
{
return crypto_register_template(&crypto_cbc_tmpl);
}
static void __exit crypto_cbc_module_exit(void)
{
crypto_unregister_template(&crypto_cbc_tmpl);
}
module_init(crypto_cbc_module_init);
module_exit(crypto_cbc_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("CBC block cipher algorithm");