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
15 static 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
30 static 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
49 out:
50 return nbytes;
51 }
52
53 static 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
69 static 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
90 out:
91 return nbytes;
92 }
93
94 static 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
118 out:
119 return nbytes;
120 }
121
122 static 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
138 static 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) {
159 out_free_inst:
160 inst->free(inst);
161 }
162
163 return err;
164 }
165
166 static struct crypto_template crypto_cbc_tmpl = {
167 .name = "cbc",
168 .create = crypto_cbc_create,
169 .module = THIS_MODULE,
170 };
171
172 static int __init crypto_cbc_module_init(void)
173 {
174 return crypto_register_template(&crypto_cbc_tmpl);
175 }
176
177 static void __exit crypto_cbc_module_exit(void)
178 {
179 crypto_unregister_template(&crypto_cbc_tmpl);
180 }
181
182 subsys_initcall(crypto_cbc_module_init);
183 module_exit(crypto_cbc_module_exit);
184
185 MODULE_LICENSE("GPL");
186 MODULE_DESCRIPTION("CBC block cipher mode of operation");
187 MODULE_ALIAS_CRYPTO("cbc");
188
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