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, u32 flags)
55{
56	struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
57	bool final = flags & CRYPTO_LSKCIPHER_FLAG_FINAL;
58	struct crypto_lskcipher *cipher = *ctx;
59	int rem;
60
61	if (src == dst)
62		rem = crypto_cbc_encrypt_inplace(cipher, dst, len, iv);
63	else
64		rem = crypto_cbc_encrypt_segment(cipher, src, dst, len, iv);
65
66	return rem && final ? -EINVAL : rem;
67}
68
69static int crypto_cbc_decrypt_segment(struct crypto_lskcipher *tfm,
70				      const u8 *src, u8 *dst, unsigned nbytes,
71				      u8 *oiv)
72{
73	unsigned int bsize = crypto_lskcipher_blocksize(tfm);
74	const u8 *iv = oiv;
75
76	if (nbytes < bsize)
77		goto out;
78
79	do {
80		crypto_lskcipher_decrypt(tfm, src, dst, bsize, NULL);
81		crypto_xor(dst, iv, bsize);
82		iv = src;
83
84		src += bsize;
85		dst += bsize;
86	} while ((nbytes -= bsize) >= bsize);
87
88	memcpy(oiv, iv, bsize);
89
90out:
91	return nbytes;
92}
93
94static int crypto_cbc_decrypt_inplace(struct crypto_lskcipher *tfm,
95				      u8 *src, unsigned nbytes, u8 *iv)
96{
97	unsigned int bsize = crypto_lskcipher_blocksize(tfm);
98	u8 last_iv[MAX_CIPHER_BLOCKSIZE];
99
100	if (nbytes < bsize)
101		goto out;
102
103	/* Start of the last block. */
104	src += nbytes - (nbytes & (bsize - 1)) - bsize;
105	memcpy(last_iv, src, bsize);
106
107	for (;;) {
108		crypto_lskcipher_decrypt(tfm, src, src, bsize, NULL);
109		if ((nbytes -= bsize) < bsize)
110			break;
111		crypto_xor(src, src - bsize, bsize);
112		src -= bsize;
113	}
114
115	crypto_xor(src, iv, bsize);
116	memcpy(iv, last_iv, bsize);
117
118out:
119	return nbytes;
120}
121
122static int crypto_cbc_decrypt(struct crypto_lskcipher *tfm, const u8 *src,
123			      u8 *dst, unsigned len, u8 *iv, u32 flags)
124{
125	struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
126	bool final = flags & CRYPTO_LSKCIPHER_FLAG_FINAL;
127	struct crypto_lskcipher *cipher = *ctx;
128	int rem;
129
130	if (src == dst)
131		rem = crypto_cbc_decrypt_inplace(cipher, dst, len, iv);
132	else
133		rem = crypto_cbc_decrypt_segment(cipher, src, dst, len, iv);
134
135	return rem && final ? -EINVAL : rem;
136}
137
138static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
139{
140	struct lskcipher_instance *inst;
141	int err;
142
143	inst = lskcipher_alloc_instance_simple(tmpl, tb);
144	if (IS_ERR(inst))
145		return PTR_ERR(inst);
146
147	err = -EINVAL;
148	if (!is_power_of_2(inst->alg.co.base.cra_blocksize))
149		goto out_free_inst;
150
151	if (inst->alg.co.statesize)
152		goto out_free_inst;
153
154	inst->alg.encrypt = crypto_cbc_encrypt;
155	inst->alg.decrypt = crypto_cbc_decrypt;
156
157	err = lskcipher_register_instance(tmpl, inst);
158	if (err) {
159out_free_inst:
160		inst->free(inst);
161	}
162
163	return err;
164}
165
166static struct crypto_template crypto_cbc_tmpl = {
167	.name = "cbc",
168	.create = crypto_cbc_create,
169	.module = THIS_MODULE,
170};
171
172static int __init crypto_cbc_module_init(void)
173{
174	return crypto_register_template(&crypto_cbc_tmpl);
175}
176
177static void __exit crypto_cbc_module_exit(void)
178{
179	crypto_unregister_template(&crypto_cbc_tmpl);
180}
181
182subsys_initcall(crypto_cbc_module_init);
183module_exit(crypto_cbc_module_exit);
184
185MODULE_LICENSE("GPL");
186MODULE_DESCRIPTION("CBC block cipher mode of operation");
187MODULE_ALIAS_CRYPTO("cbc");
188