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/algapi.h>
9 #include <crypto/internal/cipher.h>
10 #include <crypto/internal/skcipher.h>
11 #include <linux/err.h>
12 #include <linux/init.h>
13 #include <linux/kernel.h>
14 #include <linux/log2.h>
15 #include <linux/module.h>
16
crypto_cbc_encrypt_segment(struct skcipher_walk * walk,struct crypto_skcipher * skcipher)17 static int crypto_cbc_encrypt_segment(struct skcipher_walk *walk,
18 struct crypto_skcipher *skcipher)
19 {
20 unsigned int bsize = crypto_skcipher_blocksize(skcipher);
21 void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
22 unsigned int nbytes = walk->nbytes;
23 u8 *src = walk->src.virt.addr;
24 u8 *dst = walk->dst.virt.addr;
25 struct crypto_cipher *cipher;
26 struct crypto_tfm *tfm;
27 u8 *iv = walk->iv;
28
29 cipher = skcipher_cipher_simple(skcipher);
30 tfm = crypto_cipher_tfm(cipher);
31 fn = crypto_cipher_alg(cipher)->cia_encrypt;
32
33 do {
34 crypto_xor(iv, src, bsize);
35 fn(tfm, dst, iv);
36 memcpy(iv, dst, bsize);
37
38 src += bsize;
39 dst += bsize;
40 } while ((nbytes -= bsize) >= bsize);
41
42 return nbytes;
43 }
44
crypto_cbc_encrypt_inplace(struct skcipher_walk * walk,struct crypto_skcipher * skcipher)45 static int crypto_cbc_encrypt_inplace(struct skcipher_walk *walk,
46 struct crypto_skcipher *skcipher)
47 {
48 unsigned int bsize = crypto_skcipher_blocksize(skcipher);
49 void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
50 unsigned int nbytes = walk->nbytes;
51 u8 *src = walk->src.virt.addr;
52 struct crypto_cipher *cipher;
53 struct crypto_tfm *tfm;
54 u8 *iv = walk->iv;
55
56 cipher = skcipher_cipher_simple(skcipher);
57 tfm = crypto_cipher_tfm(cipher);
58 fn = crypto_cipher_alg(cipher)->cia_encrypt;
59
60 do {
61 crypto_xor(src, iv, bsize);
62 fn(tfm, src, src);
63 iv = src;
64
65 src += bsize;
66 } while ((nbytes -= bsize) >= bsize);
67
68 memcpy(walk->iv, iv, bsize);
69
70 return nbytes;
71 }
72
crypto_cbc_encrypt(struct skcipher_request * req)73 static int crypto_cbc_encrypt(struct skcipher_request *req)
74 {
75 struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
76 struct skcipher_walk walk;
77 int err;
78
79 err = skcipher_walk_virt(&walk, req, false);
80
81 while (walk.nbytes) {
82 if (walk.src.virt.addr == walk.dst.virt.addr)
83 err = crypto_cbc_encrypt_inplace(&walk, skcipher);
84 else
85 err = crypto_cbc_encrypt_segment(&walk, skcipher);
86 err = skcipher_walk_done(&walk, err);
87 }
88
89 return err;
90 }
91
crypto_cbc_decrypt_segment(struct skcipher_walk * walk,struct crypto_skcipher * skcipher)92 static int crypto_cbc_decrypt_segment(struct skcipher_walk *walk,
93 struct crypto_skcipher *skcipher)
94 {
95 unsigned int bsize = crypto_skcipher_blocksize(skcipher);
96 void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
97 unsigned int nbytes = walk->nbytes;
98 u8 *src = walk->src.virt.addr;
99 u8 *dst = walk->dst.virt.addr;
100 struct crypto_cipher *cipher;
101 struct crypto_tfm *tfm;
102 u8 *iv = walk->iv;
103
104 cipher = skcipher_cipher_simple(skcipher);
105 tfm = crypto_cipher_tfm(cipher);
106 fn = crypto_cipher_alg(cipher)->cia_decrypt;
107
108 do {
109 fn(tfm, dst, src);
110 crypto_xor(dst, iv, bsize);
111 iv = src;
112
113 src += bsize;
114 dst += bsize;
115 } while ((nbytes -= bsize) >= bsize);
116
117 memcpy(walk->iv, iv, bsize);
118
119 return nbytes;
120 }
121
crypto_cbc_decrypt_inplace(struct skcipher_walk * walk,struct crypto_skcipher * skcipher)122 static int crypto_cbc_decrypt_inplace(struct skcipher_walk *walk,
123 struct crypto_skcipher *skcipher)
124 {
125 unsigned int bsize = crypto_skcipher_blocksize(skcipher);
126 void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
127 unsigned int nbytes = walk->nbytes;
128 u8 *src = walk->src.virt.addr;
129 u8 last_iv[MAX_CIPHER_BLOCKSIZE];
130 struct crypto_cipher *cipher;
131 struct crypto_tfm *tfm;
132
133 cipher = skcipher_cipher_simple(skcipher);
134 tfm = crypto_cipher_tfm(cipher);
135 fn = crypto_cipher_alg(cipher)->cia_decrypt;
136
137 /* Start of the last block. */
138 src += nbytes - (nbytes & (bsize - 1)) - bsize;
139 memcpy(last_iv, src, bsize);
140
141 for (;;) {
142 fn(tfm, src, src);
143 if ((nbytes -= bsize) < bsize)
144 break;
145 crypto_xor(src, src - bsize, bsize);
146 src -= bsize;
147 }
148
149 crypto_xor(src, walk->iv, bsize);
150 memcpy(walk->iv, last_iv, bsize);
151
152 return nbytes;
153 }
154
crypto_cbc_decrypt(struct skcipher_request * req)155 static int crypto_cbc_decrypt(struct skcipher_request *req)
156 {
157 struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
158 struct skcipher_walk walk;
159 int err;
160
161 err = skcipher_walk_virt(&walk, req, false);
162
163 while (walk.nbytes) {
164 if (walk.src.virt.addr == walk.dst.virt.addr)
165 err = crypto_cbc_decrypt_inplace(&walk, skcipher);
166 else
167 err = crypto_cbc_decrypt_segment(&walk, skcipher);
168 err = skcipher_walk_done(&walk, err);
169 }
170
171 return err;
172 }
173
crypto_cbc_create(struct crypto_template * tmpl,struct rtattr ** tb)174 static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
175 {
176 struct skcipher_instance *inst;
177 struct crypto_alg *alg;
178 int err;
179
180 inst = skcipher_alloc_instance_simple(tmpl, tb);
181 if (IS_ERR(inst))
182 return PTR_ERR(inst);
183
184 alg = skcipher_ialg_simple(inst);
185
186 err = -EINVAL;
187 if (!is_power_of_2(alg->cra_blocksize))
188 goto out_free_inst;
189
190 inst->alg.encrypt = crypto_cbc_encrypt;
191 inst->alg.decrypt = crypto_cbc_decrypt;
192
193 err = skcipher_register_instance(tmpl, inst);
194 if (err) {
195 out_free_inst:
196 inst->free(inst);
197 }
198
199 return err;
200 }
201
202 static struct crypto_template crypto_cbc_tmpl = {
203 .name = "cbc",
204 .create = crypto_cbc_create,
205 .module = THIS_MODULE,
206 };
207
crypto_cbc_module_init(void)208 static int __init crypto_cbc_module_init(void)
209 {
210 return crypto_register_template(&crypto_cbc_tmpl);
211 }
212
crypto_cbc_module_exit(void)213 static void __exit crypto_cbc_module_exit(void)
214 {
215 crypto_unregister_template(&crypto_cbc_tmpl);
216 }
217
218 subsys_initcall(crypto_cbc_module_init);
219 module_exit(crypto_cbc_module_exit);
220
221 MODULE_LICENSE("GPL");
222 MODULE_DESCRIPTION("CBC block cipher mode of operation");
223 MODULE_ALIAS_CRYPTO("cbc");
224