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TOMOYO Linux Cross Reference
Linux/crypto/ofb.c

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  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 
 22 struct crypto_ofb_ctx {
 23         struct crypto_cipher *child;
 24         int cnt;
 25 };
 26 
 27 
 28 static 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 
 44 static 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 
 70 static 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 */
 93 static int crypto_ofb_decrypt(struct skcipher_request *req)
 94 {
 95         return crypto_ofb_encrypt(req);
 96 }
 97 
 98 static 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 
113 static 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 
120 static void crypto_ofb_free(struct skcipher_instance *inst)
121 {
122         crypto_drop_skcipher(skcipher_instance_ctx(inst));
123         kfree(inst);
124 }
125 
126 static 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 
194 out:
195         return err;
196 
197 err_drop_spawn:
198         crypto_drop_spawn(spawn);
199 err_free_inst:
200         kfree(inst);
201         goto out;
202 }
203 
204 static struct crypto_template crypto_ofb_tmpl = {
205         .name = "ofb",
206         .create = crypto_ofb_create,
207         .module = THIS_MODULE,
208 };
209 
210 static int __init crypto_ofb_module_init(void)
211 {
212         return crypto_register_template(&crypto_ofb_tmpl);
213 }
214 
215 static void __exit crypto_ofb_module_exit(void)
216 {
217         crypto_unregister_template(&crypto_ofb_tmpl);
218 }
219 
220 module_init(crypto_ofb_module_init);
221 module_exit(crypto_ofb_module_exit);
222 
223 MODULE_LICENSE("GPL");
224 MODULE_DESCRIPTION("OFB block cipher algorithm");
225 MODULE_ALIAS_CRYPTO("ofb");
226 

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