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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * CBC: Cipher Block Chaining mode
4 *
5 * Copyright (c) 2006-2016 Herbert Xu <herbert@gondor.apana.org.au>
6 */
7
8#include <crypto/internal/skcipher.h>
9#include <linux/err.h>
10#include <linux/init.h>
11#include <linux/kernel.h>
12#include <linux/log2.h>
13#include <linux/module.h>
14
15static int crypto_cbc_encrypt_segment(struct crypto_lskcipher *tfm,
16 const u8 *src, u8 *dst, unsigned nbytes,
17 u8 *iv)
18{
19 unsigned int bsize = crypto_lskcipher_blocksize(tfm);
20
21 for (; nbytes >= bsize; src += bsize, dst += bsize, nbytes -= bsize) {
22 crypto_xor(iv, src, bsize);
23 crypto_lskcipher_encrypt(tfm, iv, dst, bsize, NULL);
24 memcpy(iv, dst, bsize);
25 }
26
27 return nbytes;
28}
29
30static int crypto_cbc_encrypt_inplace(struct crypto_lskcipher *tfm,
31 u8 *src, unsigned nbytes, u8 *oiv)
32{
33 unsigned int bsize = crypto_lskcipher_blocksize(tfm);
34 u8 *iv = oiv;
35
36 if (nbytes < bsize)
37 goto out;
38
39 do {
40 crypto_xor(src, iv, bsize);
41 crypto_lskcipher_encrypt(tfm, src, src, bsize, NULL);
42 iv = src;
43
44 src += bsize;
45 } while ((nbytes -= bsize) >= bsize);
46
47 memcpy(oiv, iv, bsize);
48
49out:
50 return nbytes;
51}
52
53static int crypto_cbc_encrypt(struct crypto_lskcipher *tfm, const u8 *src,
54 u8 *dst, unsigned len, u8 *iv, bool final)
55{
56 struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
57 struct crypto_lskcipher *cipher = *ctx;
58 int rem;
59
60 if (src == dst)
61 rem = crypto_cbc_encrypt_inplace(cipher, dst, len, iv);
62 else
63 rem = crypto_cbc_encrypt_segment(cipher, src, dst, len, iv);
64
65 return rem && final ? -EINVAL : rem;
66}
67
68static int crypto_cbc_decrypt_segment(struct crypto_lskcipher *tfm,
69 const u8 *src, u8 *dst, unsigned nbytes,
70 u8 *oiv)
71{
72 unsigned int bsize = crypto_lskcipher_blocksize(tfm);
73 const u8 *iv = oiv;
74
75 if (nbytes < bsize)
76 goto out;
77
78 do {
79 crypto_lskcipher_decrypt(tfm, src, dst, bsize, NULL);
80 crypto_xor(dst, iv, bsize);
81 iv = src;
82
83 src += bsize;
84 dst += bsize;
85 } while ((nbytes -= bsize) >= bsize);
86
87 memcpy(oiv, iv, bsize);
88
89out:
90 return nbytes;
91}
92
93static int crypto_cbc_decrypt_inplace(struct crypto_lskcipher *tfm,
94 u8 *src, unsigned nbytes, u8 *iv)
95{
96 unsigned int bsize = crypto_lskcipher_blocksize(tfm);
97 u8 last_iv[MAX_CIPHER_BLOCKSIZE];
98
99 if (nbytes < bsize)
100 goto out;
101
102 /* Start of the last block. */
103 src += nbytes - (nbytes & (bsize - 1)) - bsize;
104 memcpy(last_iv, src, bsize);
105
106 for (;;) {
107 crypto_lskcipher_decrypt(tfm, src, src, bsize, NULL);
108 if ((nbytes -= bsize) < bsize)
109 break;
110 crypto_xor(src, src - bsize, bsize);
111 src -= bsize;
112 }
113
114 crypto_xor(src, iv, bsize);
115 memcpy(iv, last_iv, bsize);
116
117out:
118 return nbytes;
119}
120
121static int crypto_cbc_decrypt(struct crypto_lskcipher *tfm, const u8 *src,
122 u8 *dst, unsigned len, u8 *iv, bool final)
123{
124 struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
125 struct crypto_lskcipher *cipher = *ctx;
126 int rem;
127
128 if (src == dst)
129 rem = crypto_cbc_decrypt_inplace(cipher, dst, len, iv);
130 else
131 rem = crypto_cbc_decrypt_segment(cipher, src, dst, len, iv);
132
133 return rem && final ? -EINVAL : rem;
134}
135
136static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
137{
138 struct lskcipher_instance *inst;
139 int err;
140
141 inst = lskcipher_alloc_instance_simple(tmpl, tb);
142 if (IS_ERR(inst))
143 return PTR_ERR(inst);
144
145 err = -EINVAL;
146 if (!is_power_of_2(inst->alg.co.base.cra_blocksize))
147 goto out_free_inst;
148
149 inst->alg.encrypt = crypto_cbc_encrypt;
150 inst->alg.decrypt = crypto_cbc_decrypt;
151
152 err = lskcipher_register_instance(tmpl, inst);
153 if (err) {
154out_free_inst:
155 inst->free(inst);
156 }
157
158 return err;
159}
160
161static struct crypto_template crypto_cbc_tmpl = {
162 .name = "cbc",
163 .create = crypto_cbc_create,
164 .module = THIS_MODULE,
165};
166
167static int __init crypto_cbc_module_init(void)
168{
169 return crypto_register_template(&crypto_cbc_tmpl);
170}
171
172static void __exit crypto_cbc_module_exit(void)
173{
174 crypto_unregister_template(&crypto_cbc_tmpl);
175}
176
177subsys_initcall(crypto_cbc_module_init);
178module_exit(crypto_cbc_module_exit);
179
180MODULE_LICENSE("GPL");
181MODULE_DESCRIPTION("CBC block cipher mode of operation");
182MODULE_ALIAS_CRYPTO("cbc");