1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * PCBC: Propagating Cipher Block Chaining mode
4  *
5  * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
6  * Written by David Howells (dhowells@redhat.com)
7  *
8  * Derived from cbc.c
9  * - Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
10  */
11 
12 #include <crypto/algapi.h>
13 #include <crypto/internal/cipher.h>
14 #include <crypto/internal/skcipher.h>
15 #include <linux/err.h>
16 #include <linux/init.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 
crypto_pcbc_encrypt_segment(struct skcipher_request * req,struct skcipher_walk * walk,struct crypto_cipher * tfm)20 static int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
21 				       struct skcipher_walk *walk,
22 				       struct crypto_cipher *tfm)
23 {
24 	int bsize = crypto_cipher_blocksize(tfm);
25 	unsigned int nbytes = walk->nbytes;
26 	u8 *src = walk->src.virt.addr;
27 	u8 *dst = walk->dst.virt.addr;
28 	u8 * const iv = walk->iv;
29 
30 	do {
31 		crypto_xor(iv, src, bsize);
32 		crypto_cipher_encrypt_one(tfm, dst, iv);
33 		crypto_xor_cpy(iv, dst, src, bsize);
34 
35 		src += bsize;
36 		dst += bsize;
37 	} while ((nbytes -= bsize) >= bsize);
38 
39 	return nbytes;
40 }
41 
crypto_pcbc_encrypt_inplace(struct skcipher_request * req,struct skcipher_walk * walk,struct crypto_cipher * tfm)42 static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
43 				       struct skcipher_walk *walk,
44 				       struct crypto_cipher *tfm)
45 {
46 	int bsize = crypto_cipher_blocksize(tfm);
47 	unsigned int nbytes = walk->nbytes;
48 	u8 *src = walk->src.virt.addr;
49 	u8 * const iv = walk->iv;
50 	u8 tmpbuf[MAX_CIPHER_BLOCKSIZE];
51 
52 	do {
53 		memcpy(tmpbuf, src, bsize);
54 		crypto_xor(iv, src, bsize);
55 		crypto_cipher_encrypt_one(tfm, src, iv);
56 		crypto_xor_cpy(iv, tmpbuf, src, bsize);
57 
58 		src += bsize;
59 	} while ((nbytes -= bsize) >= bsize);
60 
61 	return nbytes;
62 }
63 
crypto_pcbc_encrypt(struct skcipher_request * req)64 static int crypto_pcbc_encrypt(struct skcipher_request *req)
65 {
66 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
67 	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
68 	struct skcipher_walk walk;
69 	unsigned int nbytes;
70 	int err;
71 
72 	err = skcipher_walk_virt(&walk, req, false);
73 
74 	while ((nbytes = walk.nbytes)) {
75 		if (walk.src.virt.addr == walk.dst.virt.addr)
76 			nbytes = crypto_pcbc_encrypt_inplace(req, &walk,
77 							     cipher);
78 		else
79 			nbytes = crypto_pcbc_encrypt_segment(req, &walk,
80 							     cipher);
81 		err = skcipher_walk_done(&walk, nbytes);
82 	}
83 
84 	return err;
85 }
86 
crypto_pcbc_decrypt_segment(struct skcipher_request * req,struct skcipher_walk * walk,struct crypto_cipher * tfm)87 static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
88 				       struct skcipher_walk *walk,
89 				       struct crypto_cipher *tfm)
90 {
91 	int bsize = crypto_cipher_blocksize(tfm);
92 	unsigned int nbytes = walk->nbytes;
93 	u8 *src = walk->src.virt.addr;
94 	u8 *dst = walk->dst.virt.addr;
95 	u8 * const iv = walk->iv;
96 
97 	do {
98 		crypto_cipher_decrypt_one(tfm, dst, src);
99 		crypto_xor(dst, iv, bsize);
100 		crypto_xor_cpy(iv, dst, src, bsize);
101 
102 		src += bsize;
103 		dst += bsize;
104 	} while ((nbytes -= bsize) >= bsize);
105 
106 	return nbytes;
107 }
108 
crypto_pcbc_decrypt_inplace(struct skcipher_request * req,struct skcipher_walk * walk,struct crypto_cipher * tfm)109 static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
110 				       struct skcipher_walk *walk,
111 				       struct crypto_cipher *tfm)
112 {
113 	int bsize = crypto_cipher_blocksize(tfm);
114 	unsigned int nbytes = walk->nbytes;
115 	u8 *src = walk->src.virt.addr;
116 	u8 * const iv = walk->iv;
117 	u8 tmpbuf[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));
118 
119 	do {
120 		memcpy(tmpbuf, src, bsize);
121 		crypto_cipher_decrypt_one(tfm, src, src);
122 		crypto_xor(src, iv, bsize);
123 		crypto_xor_cpy(iv, src, tmpbuf, bsize);
124 
125 		src += bsize;
126 	} while ((nbytes -= bsize) >= bsize);
127 
128 	return nbytes;
129 }
130 
crypto_pcbc_decrypt(struct skcipher_request * req)131 static int crypto_pcbc_decrypt(struct skcipher_request *req)
132 {
133 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
134 	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
135 	struct skcipher_walk walk;
136 	unsigned int nbytes;
137 	int err;
138 
139 	err = skcipher_walk_virt(&walk, req, false);
140 
141 	while ((nbytes = walk.nbytes)) {
142 		if (walk.src.virt.addr == walk.dst.virt.addr)
143 			nbytes = crypto_pcbc_decrypt_inplace(req, &walk,
144 							     cipher);
145 		else
146 			nbytes = crypto_pcbc_decrypt_segment(req, &walk,
147 							     cipher);
148 		err = skcipher_walk_done(&walk, nbytes);
149 	}
150 
151 	return err;
152 }
153 
crypto_pcbc_create(struct crypto_template * tmpl,struct rtattr ** tb)154 static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
155 {
156 	struct skcipher_instance *inst;
157 	int err;
158 
159 	inst = skcipher_alloc_instance_simple(tmpl, tb);
160 	if (IS_ERR(inst))
161 		return PTR_ERR(inst);
162 
163 	inst->alg.encrypt = crypto_pcbc_encrypt;
164 	inst->alg.decrypt = crypto_pcbc_decrypt;
165 
166 	err = skcipher_register_instance(tmpl, inst);
167 	if (err)
168 		inst->free(inst);
169 
170 	return err;
171 }
172 
173 static struct crypto_template crypto_pcbc_tmpl = {
174 	.name = "pcbc",
175 	.create = crypto_pcbc_create,
176 	.module = THIS_MODULE,
177 };
178 
crypto_pcbc_module_init(void)179 static int __init crypto_pcbc_module_init(void)
180 {
181 	return crypto_register_template(&crypto_pcbc_tmpl);
182 }
183 
crypto_pcbc_module_exit(void)184 static void __exit crypto_pcbc_module_exit(void)
185 {
186 	crypto_unregister_template(&crypto_pcbc_tmpl);
187 }
188 
189 subsys_initcall(crypto_pcbc_module_init);
190 module_exit(crypto_pcbc_module_exit);
191 
192 MODULE_LICENSE("GPL");
193 MODULE_DESCRIPTION("PCBC block cipher mode of operation");
194 MODULE_ALIAS_CRYPTO("pcbc");
195 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
196