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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* CBC: Cipher Block Chaining mode
*
* Copyright (c) 2006-2016 Herbert Xu <herbert@gondor.apana.org.au>
*/
#include <crypto/algapi.h>
#include <crypto/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/log2.h>
#include <linux/module.h>
static int crypto_cbc_encrypt_segment(struct skcipher_walk *walk,
struct crypto_skcipher *skcipher)
{
unsigned int bsize = crypto_skcipher_blocksize(skcipher);
void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
struct crypto_cipher *cipher;
struct crypto_tfm *tfm;
u8 *iv = walk->iv;
cipher = skcipher_cipher_simple(skcipher);
tfm = crypto_cipher_tfm(cipher);
fn = crypto_cipher_alg(cipher)->cia_encrypt;
do {
crypto_xor(iv, src, bsize);
fn(tfm, dst, iv);
memcpy(iv, dst, bsize);
src += bsize;
dst += bsize;
} while ((nbytes -= bsize) >= bsize);
return nbytes;
}
static int crypto_cbc_encrypt_inplace(struct skcipher_walk *walk,
struct crypto_skcipher *skcipher)
{
unsigned int bsize = crypto_skcipher_blocksize(skcipher);
void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
struct crypto_cipher *cipher;
struct crypto_tfm *tfm;
u8 *iv = walk->iv;
cipher = skcipher_cipher_simple(skcipher);
tfm = crypto_cipher_tfm(cipher);
fn = crypto_cipher_alg(cipher)->cia_encrypt;
do {
crypto_xor(src, iv, bsize);
fn(tfm, src, src);
iv = src;
src += bsize;
} while ((nbytes -= bsize) >= bsize);
memcpy(walk->iv, iv, bsize);
return nbytes;
}
static int crypto_cbc_encrypt(struct skcipher_request *req)
{
struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
struct skcipher_walk walk;
int err;
err = skcipher_walk_virt(&walk, req, false);
while (walk.nbytes) {
if (walk.src.virt.addr == walk.dst.virt.addr)
err = crypto_cbc_encrypt_inplace(&walk, skcipher);
else
err = crypto_cbc_encrypt_segment(&walk, skcipher);
err = skcipher_walk_done(&walk, err);
}
return err;
}
static int crypto_cbc_decrypt_segment(struct skcipher_walk *walk,
struct crypto_skcipher *skcipher)
{
unsigned int bsize = crypto_skcipher_blocksize(skcipher);
void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
struct crypto_cipher *cipher;
struct crypto_tfm *tfm;
u8 *iv = walk->iv;
cipher = skcipher_cipher_simple(skcipher);
tfm = crypto_cipher_tfm(cipher);
fn = crypto_cipher_alg(cipher)->cia_decrypt;
do {
fn(tfm, dst, src);
crypto_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 skcipher_walk *walk,
struct crypto_skcipher *skcipher)
{
unsigned int bsize = crypto_skcipher_blocksize(skcipher);
void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 last_iv[MAX_CIPHER_BLOCKSIZE];
struct crypto_cipher *cipher;
struct crypto_tfm *tfm;
cipher = skcipher_cipher_simple(skcipher);
tfm = crypto_cipher_tfm(cipher);
fn = crypto_cipher_alg(cipher)->cia_decrypt;
/* Start of the last block. */
src += nbytes - (nbytes & (bsize - 1)) - bsize;
memcpy(last_iv, src, bsize);
for (;;) {
fn(tfm, src, src);
if ((nbytes -= bsize) < bsize)
break;
crypto_xor(src, src - bsize, bsize);
src -= bsize;
}
crypto_xor(src, walk->iv, bsize);
memcpy(walk->iv, last_iv, bsize);
return nbytes;
}
static int crypto_cbc_decrypt(struct skcipher_request *req)
{
struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
struct skcipher_walk walk;
int err;
err = skcipher_walk_virt(&walk, req, false);
while (walk.nbytes) {
if (walk.src.virt.addr == walk.dst.virt.addr)
err = crypto_cbc_decrypt_inplace(&walk, skcipher);
else
err = crypto_cbc_decrypt_segment(&walk, skcipher);
err = skcipher_walk_done(&walk, err);
}
return err;
}
static int crypto_cbc_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);
err = -EINVAL;
if (!is_power_of_2(alg->cra_blocksize))
goto out_free_inst;
inst->alg.encrypt = crypto_cbc_encrypt;
inst->alg.decrypt = crypto_cbc_decrypt;
err = skcipher_register_instance(tmpl, inst);
if (err) {
out_free_inst:
inst->free(inst);
}
return err;
}
static struct crypto_template crypto_cbc_tmpl = {
.name = "cbc",
.create = crypto_cbc_create,
.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);
}
subsys_initcall(crypto_cbc_module_init);
module_exit(crypto_cbc_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("CBC block cipher mode of operation");
MODULE_ALIAS_CRYPTO("cbc");
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