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7f470739 HX |
1 | /* |
2 | * chainiv: Chain IV Generator | |
3 | * | |
4 | * Generate IVs simply be using the last block of the previous encryption. | |
5 | * This is mainly useful for CBC with a synchronous algorithm. | |
6 | * | |
7 | * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au> | |
8 | * | |
9 | * This program is free software; you can redistribute it and/or modify it | |
10 | * under the terms of the GNU General Public License as published by the Free | |
11 | * Software Foundation; either version 2 of the License, or (at your option) | |
12 | * any later version. | |
13 | * | |
14 | */ | |
15 | ||
16 | #include <crypto/internal/skcipher.h> | |
17 | #include <linux/err.h> | |
18 | #include <linux/init.h> | |
19 | #include <linux/module.h> | |
20 | #include <linux/random.h> | |
21 | #include <linux/spinlock.h> | |
22 | #include <linux/string.h> | |
23 | ||
24 | struct chainiv_ctx { | |
25 | spinlock_t lock; | |
26 | char iv[]; | |
27 | }; | |
28 | ||
29 | static int chainiv_givencrypt(struct skcipher_givcrypt_request *req) | |
30 | { | |
31 | struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); | |
32 | struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); | |
33 | struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req); | |
34 | unsigned int ivsize; | |
35 | int err; | |
36 | ||
37 | ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv)); | |
38 | ablkcipher_request_set_callback(subreq, req->creq.base.flags & | |
39 | ~CRYPTO_TFM_REQ_MAY_SLEEP, | |
40 | req->creq.base.complete, | |
41 | req->creq.base.data); | |
42 | ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst, | |
43 | req->creq.nbytes, req->creq.info); | |
44 | ||
45 | spin_lock_bh(&ctx->lock); | |
46 | ||
47 | ivsize = crypto_ablkcipher_ivsize(geniv); | |
48 | ||
49 | memcpy(req->giv, ctx->iv, ivsize); | |
50 | memcpy(subreq->info, ctx->iv, ivsize); | |
51 | ||
52 | err = crypto_ablkcipher_encrypt(subreq); | |
53 | if (err) | |
54 | goto unlock; | |
55 | ||
56 | memcpy(ctx->iv, subreq->info, ivsize); | |
57 | ||
58 | unlock: | |
59 | spin_unlock_bh(&ctx->lock); | |
60 | ||
61 | return err; | |
62 | } | |
63 | ||
64 | static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req) | |
65 | { | |
66 | struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); | |
67 | struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); | |
68 | ||
69 | spin_lock_bh(&ctx->lock); | |
70 | if (crypto_ablkcipher_crt(geniv)->givencrypt != | |
71 | chainiv_givencrypt_first) | |
72 | goto unlock; | |
73 | ||
74 | crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt; | |
75 | get_random_bytes(ctx->iv, crypto_ablkcipher_ivsize(geniv)); | |
76 | ||
77 | unlock: | |
78 | spin_unlock_bh(&ctx->lock); | |
79 | ||
80 | return chainiv_givencrypt(req); | |
81 | } | |
82 | ||
83 | static int chainiv_init(struct crypto_tfm *tfm) | |
84 | { | |
85 | struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm); | |
86 | struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); | |
87 | ||
88 | spin_lock_init(&ctx->lock); | |
89 | ||
90 | tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request); | |
91 | ||
92 | return skcipher_geniv_init(tfm); | |
93 | } | |
94 | ||
95 | static struct crypto_template chainiv_tmpl; | |
96 | ||
97 | static struct crypto_instance *chainiv_alloc(struct rtattr **tb) | |
98 | { | |
99 | struct crypto_instance *inst; | |
100 | ||
101 | inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0, | |
102 | CRYPTO_ALG_ASYNC); | |
103 | if (IS_ERR(inst)) | |
104 | goto out; | |
105 | ||
106 | inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first; | |
107 | ||
108 | inst->alg.cra_init = chainiv_init; | |
109 | inst->alg.cra_exit = skcipher_geniv_exit; | |
110 | ||
111 | inst->alg.cra_ctxsize = sizeof(struct chainiv_ctx) + | |
112 | inst->alg.cra_ablkcipher.ivsize; | |
113 | ||
114 | out: | |
115 | return inst; | |
116 | } | |
117 | ||
118 | static struct crypto_template chainiv_tmpl = { | |
119 | .name = "chainiv", | |
120 | .alloc = chainiv_alloc, | |
121 | .free = skcipher_geniv_free, | |
122 | .module = THIS_MODULE, | |
123 | }; | |
124 | ||
125 | static int __init chainiv_module_init(void) | |
126 | { | |
127 | return crypto_register_template(&chainiv_tmpl); | |
128 | } | |
129 | ||
130 | static void __exit chainiv_module_exit(void) | |
131 | { | |
132 | crypto_unregister_template(&chainiv_tmpl); | |
133 | } | |
134 | ||
135 | module_init(chainiv_module_init); | |
136 | module_exit(chainiv_module_exit); | |
137 | ||
138 | MODULE_LICENSE("GPL"); | |
139 | MODULE_DESCRIPTION("Chain IV Generator"); |