tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * OFB: Output FeedBack mode
5 *
6 * Copyright (C) 2018 ARM Limited or its affiliates.
7 * All rights reserved.
8 *
9 * Based loosely on public domain code gleaned from libtomcrypt
10 * (https://github.com/libtom/libtomcrypt).
11 */
12
13#include <crypto/algapi.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#include <linux/scatterlist.h>
20#include <linux/slab.h>
21
22struct crypto_ofb_ctx {
23 struct crypto_cipher *child;
24 int cnt;
25};
26
27
28static int crypto_ofb_setkey(struct crypto_skcipher *parent, const u8 *key,
29 unsigned int keylen)
30{
31 struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(parent);
32 struct crypto_cipher *child = ctx->child;
33 int err;
34
35 crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
36 crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &
37 CRYPTO_TFM_REQ_MASK);
38 err = crypto_cipher_setkey(child, key, keylen);
39 crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
40 CRYPTO_TFM_RES_MASK);
41 return err;
42}
43
44static int crypto_ofb_encrypt_segment(struct crypto_ofb_ctx *ctx,
45 struct skcipher_walk *walk,
46 struct crypto_cipher *tfm)
47{
48 int bsize = crypto_cipher_blocksize(tfm);
49 int nbytes = walk->nbytes;
50
51 u8 *src = walk->src.virt.addr;
52 u8 *dst = walk->dst.virt.addr;
53 u8 *iv = walk->iv;
54
55 do {
56 if (ctx->cnt == bsize) {
57 if (nbytes < bsize)
58 break;
59 crypto_cipher_encrypt_one(tfm, iv, iv);
60 ctx->cnt = 0;
61 }
62 *dst = *src ^ iv[ctx->cnt];
63 src++;
64 dst++;
65 ctx->cnt++;
66 } while (--nbytes);
67 return nbytes;
68}
69
70static int crypto_ofb_encrypt(struct skcipher_request *req)
71{
72 struct skcipher_walk walk;
73 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
74 unsigned int bsize;
75 struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
76 struct crypto_cipher *child = ctx->child;
77 int ret = 0;
78
79 bsize = crypto_cipher_blocksize(child);
80 ctx->cnt = bsize;
81
82 ret = skcipher_walk_virt(&walk, req, false);
83
84 while (walk.nbytes) {
85 ret = crypto_ofb_encrypt_segment(ctx, &walk, child);
86 ret = skcipher_walk_done(&walk, ret);
87 }
88
89 return ret;
90}
91
92/* OFB encrypt and decrypt are identical */
93static int crypto_ofb_decrypt(struct skcipher_request *req)
94{
95 return crypto_ofb_encrypt(req);
96}
97
98static int crypto_ofb_init_tfm(struct crypto_skcipher *tfm)
99{
100 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
101 struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
102 struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
103 struct crypto_cipher *cipher;
104
105 cipher = crypto_spawn_cipher(spawn);
106 if (IS_ERR(cipher))
107 return PTR_ERR(cipher);
108
109 ctx->child = cipher;
110 return 0;
111}
112
113static void crypto_ofb_exit_tfm(struct crypto_skcipher *tfm)
114{
115 struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
116
117 crypto_free_cipher(ctx->child);
118}
119
120static void crypto_ofb_free(struct skcipher_instance *inst)
121{
122 crypto_drop_skcipher(skcipher_instance_ctx(inst));
123 kfree(inst);
124}
125
126static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb)
127{
128 struct skcipher_instance *inst;
129 struct crypto_attr_type *algt;
130 struct crypto_spawn *spawn;
131 struct crypto_alg *alg;
132 u32 mask;
133 int err;
134
135 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);
136 if (err)
137 return err;
138
139 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
140 if (!inst)
141 return -ENOMEM;
142
143 algt = crypto_get_attr_type(tb);
144 err = PTR_ERR(algt);
145 if (IS_ERR(algt))
146 goto err_free_inst;
147
148 mask = CRYPTO_ALG_TYPE_MASK |
149 crypto_requires_off(algt->type, algt->mask,
150 CRYPTO_ALG_NEED_FALLBACK);
151
152 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
153 err = PTR_ERR(alg);
154 if (IS_ERR(alg))
155 goto err_free_inst;
156
157 spawn = skcipher_instance_ctx(inst);
158 err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
159 CRYPTO_ALG_TYPE_MASK);
160 crypto_mod_put(alg);
161 if (err)
162 goto err_free_inst;
163
164 err = crypto_inst_setname(skcipher_crypto_instance(inst), "ofb", alg);
165 if (err)
166 goto err_drop_spawn;
167
168 inst->alg.base.cra_priority = alg->cra_priority;
169 inst->alg.base.cra_blocksize = alg->cra_blocksize;
170 inst->alg.base.cra_alignmask = alg->cra_alignmask;
171
172 /* We access the data as u32s when xoring. */
173 inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
174
175 inst->alg.ivsize = alg->cra_blocksize;
176 inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
177 inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;
178
179 inst->alg.base.cra_ctxsize = sizeof(struct crypto_ofb_ctx);
180
181 inst->alg.init = crypto_ofb_init_tfm;
182 inst->alg.exit = crypto_ofb_exit_tfm;
183
184 inst->alg.setkey = crypto_ofb_setkey;
185 inst->alg.encrypt = crypto_ofb_encrypt;
186 inst->alg.decrypt = crypto_ofb_decrypt;
187
188 inst->free = crypto_ofb_free;
189
190 err = skcipher_register_instance(tmpl, inst);
191 if (err)
192 goto err_drop_spawn;
193
194out:
195 return err;
196
197err_drop_spawn:
198 crypto_drop_spawn(spawn);
199err_free_inst:
200 kfree(inst);
201 goto out;
202}
203
204static struct crypto_template crypto_ofb_tmpl = {
205 .name = "ofb",
206 .create = crypto_ofb_create,
207 .module = THIS_MODULE,
208};
209
210static int __init crypto_ofb_module_init(void)
211{
212 return crypto_register_template(&crypto_ofb_tmpl);
213}
214
215static void __exit crypto_ofb_module_exit(void)
216{
217 crypto_unregister_template(&crypto_ofb_tmpl);
218}
219
220module_init(crypto_ofb_module_init);
221module_exit(crypto_ofb_module_exit);
222
223MODULE_LICENSE("GPL");
224MODULE_DESCRIPTION("OFB block cipher algorithm");
225MODULE_ALIAS_CRYPTO("ofb");