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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/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 crypto_lskcipher *tfm,
const u8 *src, u8 *dst, unsigned nbytes,
u8 *iv)
{
unsigned int bsize = crypto_lskcipher_blocksize(tfm);
for (; nbytes >= bsize; src += bsize, dst += bsize, nbytes -= bsize) {
crypto_xor(iv, src, bsize);
crypto_lskcipher_encrypt(tfm, iv, dst, bsize, NULL);
memcpy(iv, dst, bsize);
}
return nbytes;
}
static int crypto_cbc_encrypt_inplace(struct crypto_lskcipher *tfm,
u8 *src, unsigned nbytes, u8 *oiv)
{
unsigned int bsize = crypto_lskcipher_blocksize(tfm);
u8 *iv = oiv;
if (nbytes < bsize)
goto out;
do {
crypto_xor(src, iv, bsize);
crypto_lskcipher_encrypt(tfm, src, src, bsize, NULL);
iv = src;
src += bsize;
} while ((nbytes -= bsize) >= bsize);
memcpy(oiv, iv, bsize);
out:
return nbytes;
}
static int crypto_cbc_encrypt(struct crypto_lskcipher *tfm, const u8 *src,
u8 *dst, unsigned len, u8 *iv, bool final)
{
struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
struct crypto_lskcipher *cipher = *ctx;
int rem;
if (src == dst)
rem = crypto_cbc_encrypt_inplace(cipher, dst, len, iv);
else
rem = crypto_cbc_encrypt_segment(cipher, src, dst, len, iv);
return rem && final ? -EINVAL : rem;
}
static int crypto_cbc_decrypt_segment(struct crypto_lskcipher *tfm,
const u8 *src, u8 *dst, unsigned nbytes,
u8 *oiv)
{
unsigned int bsize = crypto_lskcipher_blocksize(tfm);
const u8 *iv = oiv;
if (nbytes < bsize)
goto out;
do {
crypto_lskcipher_decrypt(tfm, src, dst, bsize, NULL);
crypto_xor(dst, iv, bsize);
iv = src;
src += bsize;
dst += bsize;
} while ((nbytes -= bsize) >= bsize);
memcpy(oiv, iv, bsize);
out:
return nbytes;
}
static int crypto_cbc_decrypt_inplace(struct crypto_lskcipher *tfm,
u8 *src, unsigned nbytes, u8 *iv)
{
unsigned int bsize = crypto_lskcipher_blocksize(tfm);
u8 last_iv[MAX_CIPHER_BLOCKSIZE];
if (nbytes < bsize)
goto out;
/* Start of the last block. */
src += nbytes - (nbytes & (bsize - 1)) - bsize;
memcpy(last_iv, src, bsize);
for (;;) {
crypto_lskcipher_decrypt(tfm, src, src, bsize, NULL);
if ((nbytes -= bsize) < bsize)
break;
crypto_xor(src, src - bsize, bsize);
src -= bsize;
}
crypto_xor(src, iv, bsize);
memcpy(iv, last_iv, bsize);
out:
return nbytes;
}
static int crypto_cbc_decrypt(struct crypto_lskcipher *tfm, const u8 *src,
u8 *dst, unsigned len, u8 *iv, bool final)
{
struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
struct crypto_lskcipher *cipher = *ctx;
int rem;
if (src == dst)
rem = crypto_cbc_decrypt_inplace(cipher, dst, len, iv);
else
rem = crypto_cbc_decrypt_segment(cipher, src, dst, len, iv);
return rem && final ? -EINVAL : rem;
}
static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
{
struct lskcipher_instance *inst;
int err;
inst = lskcipher_alloc_instance_simple(tmpl, tb);
if (IS_ERR(inst))
return PTR_ERR(inst);
err = -EINVAL;
if (!is_power_of_2(inst->alg.co.base.cra_blocksize))
goto out_free_inst;
inst->alg.encrypt = crypto_cbc_encrypt;
inst->alg.decrypt = crypto_cbc_decrypt;
err = lskcipher_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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