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