1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * PCBC: Propagating Cipher Block Chaining mode
4 *
5 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 *
8 * Derived from cbc.c
9 * - Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
10 */
11
12#include <crypto/algapi.h>
13#include <crypto/internal/cipher.h>
14#include <crypto/internal/skcipher.h>
15#include <linux/err.h>
16#include <linux/init.h>
17#include <linux/kernel.h>
18#include <linux/module.h>
19
20static int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
21				       struct skcipher_walk *walk,
22				       struct crypto_cipher *tfm)
23{
24	int bsize = crypto_cipher_blocksize(tfm);
25	unsigned int nbytes = walk->nbytes;
26	u8 *src = walk->src.virt.addr;
27	u8 *dst = walk->dst.virt.addr;
28	u8 * const iv = walk->iv;
29
30	do {
31		crypto_xor(iv, src, bsize);
32		crypto_cipher_encrypt_one(tfm, dst, iv);
33		crypto_xor_cpy(iv, dst, src, bsize);
34
35		src += bsize;
36		dst += bsize;
37	} while ((nbytes -= bsize) >= bsize);
38
39	return nbytes;
40}
41
42static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
43				       struct skcipher_walk *walk,
44				       struct crypto_cipher *tfm)
45{
46	int bsize = crypto_cipher_blocksize(tfm);
47	unsigned int nbytes = walk->nbytes;
48	u8 *src = walk->src.virt.addr;
49	u8 * const iv = walk->iv;
50	u8 tmpbuf[MAX_CIPHER_BLOCKSIZE];
51
52	do {
53		memcpy(tmpbuf, src, bsize);
54		crypto_xor(iv, src, bsize);
55		crypto_cipher_encrypt_one(tfm, src, iv);
56		crypto_xor_cpy(iv, tmpbuf, src, bsize);
57
58		src += bsize;
59	} while ((nbytes -= bsize) >= bsize);
60
61	return nbytes;
62}
63
64static int crypto_pcbc_encrypt(struct skcipher_request *req)
65{
66	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
67	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
68	struct skcipher_walk walk;
69	unsigned int nbytes;
70	int err;
71
72	err = skcipher_walk_virt(&walk, req, false);
73
74	while (walk.nbytes) {
75		if (walk.src.virt.addr == walk.dst.virt.addr)
76			nbytes = crypto_pcbc_encrypt_inplace(req, &walk,
77							     cipher);
78		else
79			nbytes = crypto_pcbc_encrypt_segment(req, &walk,
80							     cipher);
81		err = skcipher_walk_done(&walk, nbytes);
82	}
83
84	return err;
85}
86
87static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
88				       struct skcipher_walk *walk,
89				       struct crypto_cipher *tfm)
90{
91	int bsize = crypto_cipher_blocksize(tfm);
92	unsigned int nbytes = walk->nbytes;
93	u8 *src = walk->src.virt.addr;
94	u8 *dst = walk->dst.virt.addr;
95	u8 * const iv = walk->iv;
96
97	do {
98		crypto_cipher_decrypt_one(tfm, dst, src);
99		crypto_xor(dst, iv, bsize);
100		crypto_xor_cpy(iv, dst, src, bsize);
101
102		src += bsize;
103		dst += bsize;
104	} while ((nbytes -= bsize) >= bsize);
105
106	return nbytes;
107}
108
109static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
110				       struct skcipher_walk *walk,
111				       struct crypto_cipher *tfm)
112{
113	int bsize = crypto_cipher_blocksize(tfm);
114	unsigned int nbytes = walk->nbytes;
115	u8 *src = walk->src.virt.addr;
116	u8 * const iv = walk->iv;
117	u8 tmpbuf[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));
118
119	do {
120		memcpy(tmpbuf, src, bsize);
121		crypto_cipher_decrypt_one(tfm, src, src);
122		crypto_xor(src, iv, bsize);
123		crypto_xor_cpy(iv, src, tmpbuf, bsize);
124
125		src += bsize;
126	} while ((nbytes -= bsize) >= bsize);
127
128	return nbytes;
129}
130
131static int crypto_pcbc_decrypt(struct skcipher_request *req)
132{
133	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
134	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
135	struct skcipher_walk walk;
136	unsigned int nbytes;
137	int err;
138
139	err = skcipher_walk_virt(&walk, req, false);
140
141	while (walk.nbytes) {
142		if (walk.src.virt.addr == walk.dst.virt.addr)
143			nbytes = crypto_pcbc_decrypt_inplace(req, &walk,
144							     cipher);
145		else
146			nbytes = crypto_pcbc_decrypt_segment(req, &walk,
147							     cipher);
148		err = skcipher_walk_done(&walk, nbytes);
149	}
150
151	return err;
152}
153
154static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
155{
156	struct skcipher_instance *inst;
157	int err;
158
159	inst = skcipher_alloc_instance_simple(tmpl, tb);
160	if (IS_ERR(inst))
161		return PTR_ERR(inst);
162
163	inst->alg.encrypt = crypto_pcbc_encrypt;
164	inst->alg.decrypt = crypto_pcbc_decrypt;
165
166	err = skcipher_register_instance(tmpl, inst);
167	if (err)
168		inst->free(inst);
169
170	return err;
171}
172
173static struct crypto_template crypto_pcbc_tmpl = {
174	.name = "pcbc",
175	.create = crypto_pcbc_create,
176	.module = THIS_MODULE,
177};
178
179static int __init crypto_pcbc_module_init(void)
180{
181	return crypto_register_template(&crypto_pcbc_tmpl);
182}
183
184static void __exit crypto_pcbc_module_exit(void)
185{
186	crypto_unregister_template(&crypto_pcbc_tmpl);
187}
188
189subsys_initcall(crypto_pcbc_module_init);
190module_exit(crypto_pcbc_module_exit);
191
192MODULE_LICENSE("GPL");
193MODULE_DESCRIPTION("PCBC block cipher mode of operation");
194MODULE_ALIAS_CRYPTO("pcbc");
195MODULE_IMPORT_NS(CRYPTO_INTERNAL);
196