1/* SPDX-License-Identifier: GPL-2.0-or-later */
  2/*
  3 * CBC: Cipher Block Chaining mode
  4 *
  5 * Copyright (c) 2016 Herbert Xu <herbert@gondor.apana.org.au>
  6 */
  7
  8#ifndef _CRYPTO_CBC_H
  9#define _CRYPTO_CBC_H
 10
 11#include <crypto/internal/skcipher.h>
 12#include <linux/string.h>
 13#include <linux/types.h>
 14
 15static inline int crypto_cbc_encrypt_segment(
 16	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 17	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 18{
 19	unsigned int bsize = crypto_skcipher_blocksize(tfm);
 20	unsigned int nbytes = walk->nbytes;
 21	u8 *src = walk->src.virt.addr;
 22	u8 *dst = walk->dst.virt.addr;
 23	u8 *iv = walk->iv;
 24
 25	do {
 26		crypto_xor(iv, src, bsize);
 27		fn(tfm, iv, dst);
 28		memcpy(iv, dst, bsize);
 29
 30		src += bsize;
 31		dst += bsize;
 32	} while ((nbytes -= bsize) >= bsize);
 33
 34	return nbytes;
 35}
 36
 37static inline int crypto_cbc_encrypt_inplace(
 38	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 39	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 40{
 41	unsigned int bsize = crypto_skcipher_blocksize(tfm);
 42	unsigned int nbytes = walk->nbytes;
 43	u8 *src = walk->src.virt.addr;
 44	u8 *iv = walk->iv;
 45
 46	do {
 47		crypto_xor(src, iv, bsize);
 48		fn(tfm, src, src);
 49		iv = src;
 50
 51		src += bsize;
 52	} while ((nbytes -= bsize) >= bsize);
 53
 54	memcpy(walk->iv, iv, bsize);
 55
 56	return nbytes;
 57}
 58
 59static inline int crypto_cbc_encrypt_walk(struct skcipher_request *req,
 60					  void (*fn)(struct crypto_skcipher *,
 61						     const u8 *, u8 *))
 62{
 63	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 64	struct skcipher_walk walk;
 65	int err;
 66
 67	err = skcipher_walk_virt(&walk, req, false);
 68
 69	while (walk.nbytes) {
 70		if (walk.src.virt.addr == walk.dst.virt.addr)
 71			err = crypto_cbc_encrypt_inplace(&walk, tfm, fn);
 72		else
 73			err = crypto_cbc_encrypt_segment(&walk, tfm, fn);
 74		err = skcipher_walk_done(&walk, err);
 75	}
 76
 77	return err;
 78}
 79
 80static inline int crypto_cbc_decrypt_segment(
 81	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 82	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 83{
 84	unsigned int bsize = crypto_skcipher_blocksize(tfm);
 85	unsigned int nbytes = walk->nbytes;
 86	u8 *src = walk->src.virt.addr;
 87	u8 *dst = walk->dst.virt.addr;
 88	u8 *iv = walk->iv;
 89
 90	do {
 91		fn(tfm, src, dst);
 92		crypto_xor(dst, iv, bsize);
 93		iv = src;
 94
 95		src += bsize;
 96		dst += bsize;
 97	} while ((nbytes -= bsize) >= bsize);
 98
 99	memcpy(walk->iv, iv, bsize);
100
101	return nbytes;
102}
103
104static inline int crypto_cbc_decrypt_inplace(
105	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
106	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
107{
108	unsigned int bsize = crypto_skcipher_blocksize(tfm);
109	unsigned int nbytes = walk->nbytes;
110	u8 *src = walk->src.virt.addr;
111	u8 last_iv[MAX_CIPHER_BLOCKSIZE];
112
113	/* Start of the last block. */
114	src += nbytes - (nbytes & (bsize - 1)) - bsize;
115	memcpy(last_iv, src, bsize);
116
117	for (;;) {
118		fn(tfm, src, src);
119		if ((nbytes -= bsize) < bsize)
120			break;
121		crypto_xor(src, src - bsize, bsize);
122		src -= bsize;
123	}
124
125	crypto_xor(src, walk->iv, bsize);
126	memcpy(walk->iv, last_iv, bsize);
127
128	return nbytes;
129}
130
131static inline int crypto_cbc_decrypt_blocks(
132	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
133	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
134{
135	if (walk->src.virt.addr == walk->dst.virt.addr)
136		return crypto_cbc_decrypt_inplace(walk, tfm, fn);
137	else
138		return crypto_cbc_decrypt_segment(walk, tfm, fn);
139}
140
141#endif	/* _CRYPTO_CBC_H */