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1 | /* | |
2 | * echainiv: Encrypted Chain IV Generator | |
3 | * | |
4 | * This generator generates an IV based on a sequence number by multiplying | |
5 | * it with a salt and then encrypting it with the same key as used to encrypt | |
6 | * the plain text. This algorithm requires that the block size be equal | |
7 | * to the IV size. It is mainly useful for CBC. | |
8 | * | |
9 | * This generator can only be used by algorithms where authentication | |
10 | * is performed after encryption (i.e., authenc). | |
11 | * | |
12 | * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> | |
13 | * | |
14 | * This program is free software; you can redistribute it and/or modify it | |
15 | * under the terms of the GNU General Public License as published by the Free | |
16 | * Software Foundation; either version 2 of the License, or (at your option) | |
17 | * any later version. | |
18 | * | |
19 | */ | |
20 | ||
21 | #include <crypto/internal/geniv.h> | |
22 | #include <crypto/scatterwalk.h> | |
23 | #include <crypto/skcipher.h> | |
24 | #include <linux/err.h> | |
25 | #include <linux/init.h> | |
26 | #include <linux/kernel.h> | |
27 | #include <linux/module.h> | |
28 | #include <linux/slab.h> | |
29 | #include <linux/string.h> | |
30 | ||
31 | static int echainiv_encrypt(struct aead_request *req) | |
32 | { | |
33 | struct crypto_aead *geniv = crypto_aead_reqtfm(req); | |
34 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); | |
35 | struct aead_request *subreq = aead_request_ctx(req); | |
36 | __be64 nseqno; | |
37 | u64 seqno; | |
38 | u8 *info; | |
39 | unsigned int ivsize = crypto_aead_ivsize(geniv); | |
40 | int err; | |
41 | ||
42 | if (req->cryptlen < ivsize) | |
43 | return -EINVAL; | |
44 | ||
45 | aead_request_set_tfm(subreq, ctx->child); | |
46 | ||
47 | info = req->iv; | |
48 | ||
49 | if (req->src != req->dst) { | |
50 | SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull); | |
51 | ||
52 | skcipher_request_set_tfm(nreq, ctx->sknull); | |
53 | skcipher_request_set_callback(nreq, req->base.flags, | |
54 | NULL, NULL); | |
55 | skcipher_request_set_crypt(nreq, req->src, req->dst, | |
56 | req->assoclen + req->cryptlen, | |
57 | NULL); | |
58 | ||
59 | err = crypto_skcipher_encrypt(nreq); | |
60 | if (err) | |
61 | return err; | |
62 | } | |
63 | ||
64 | aead_request_set_callback(subreq, req->base.flags, | |
65 | req->base.complete, req->base.data); | |
66 | aead_request_set_crypt(subreq, req->dst, req->dst, | |
67 | req->cryptlen, info); | |
68 | aead_request_set_ad(subreq, req->assoclen); | |
69 | ||
70 | memcpy(&nseqno, info + ivsize - 8, 8); | |
71 | seqno = be64_to_cpu(nseqno); | |
72 | memset(info, 0, ivsize); | |
73 | ||
74 | scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); | |
75 | ||
76 | do { | |
77 | u64 a; | |
78 | ||
79 | memcpy(&a, ctx->salt + ivsize - 8, 8); | |
80 | ||
81 | a |= 1; | |
82 | a *= seqno; | |
83 | ||
84 | memcpy(info + ivsize - 8, &a, 8); | |
85 | } while ((ivsize -= 8)); | |
86 | ||
87 | return crypto_aead_encrypt(subreq); | |
88 | } | |
89 | ||
90 | static int echainiv_decrypt(struct aead_request *req) | |
91 | { | |
92 | struct crypto_aead *geniv = crypto_aead_reqtfm(req); | |
93 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); | |
94 | struct aead_request *subreq = aead_request_ctx(req); | |
95 | crypto_completion_t compl; | |
96 | void *data; | |
97 | unsigned int ivsize = crypto_aead_ivsize(geniv); | |
98 | ||
99 | if (req->cryptlen < ivsize) | |
100 | return -EINVAL; | |
101 | ||
102 | aead_request_set_tfm(subreq, ctx->child); | |
103 | ||
104 | compl = req->base.complete; | |
105 | data = req->base.data; | |
106 | ||
107 | aead_request_set_callback(subreq, req->base.flags, compl, data); | |
108 | aead_request_set_crypt(subreq, req->src, req->dst, | |
109 | req->cryptlen - ivsize, req->iv); | |
110 | aead_request_set_ad(subreq, req->assoclen + ivsize); | |
111 | ||
112 | scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); | |
113 | ||
114 | return crypto_aead_decrypt(subreq); | |
115 | } | |
116 | ||
117 | static int echainiv_aead_create(struct crypto_template *tmpl, | |
118 | struct rtattr **tb) | |
119 | { | |
120 | struct aead_instance *inst; | |
121 | struct crypto_aead_spawn *spawn; | |
122 | struct aead_alg *alg; | |
123 | int err; | |
124 | ||
125 | inst = aead_geniv_alloc(tmpl, tb, 0, 0); | |
126 | ||
127 | if (IS_ERR(inst)) | |
128 | return PTR_ERR(inst); | |
129 | ||
130 | spawn = aead_instance_ctx(inst); | |
131 | alg = crypto_spawn_aead_alg(spawn); | |
132 | ||
133 | err = -EINVAL; | |
134 | if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) | |
135 | goto free_inst; | |
136 | ||
137 | inst->alg.encrypt = echainiv_encrypt; | |
138 | inst->alg.decrypt = echainiv_decrypt; | |
139 | ||
140 | inst->alg.init = aead_init_geniv; | |
141 | inst->alg.exit = aead_exit_geniv; | |
142 | ||
143 | inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); | |
144 | inst->alg.base.cra_ctxsize += inst->alg.ivsize; | |
145 | ||
146 | inst->free = aead_geniv_free; | |
147 | ||
148 | err = aead_register_instance(tmpl, inst); | |
149 | if (err) | |
150 | goto free_inst; | |
151 | ||
152 | out: | |
153 | return err; | |
154 | ||
155 | free_inst: | |
156 | aead_geniv_free(inst); | |
157 | goto out; | |
158 | } | |
159 | ||
160 | static void echainiv_free(struct crypto_instance *inst) | |
161 | { | |
162 | aead_geniv_free(aead_instance(inst)); | |
163 | } | |
164 | ||
165 | static struct crypto_template echainiv_tmpl = { | |
166 | .name = "echainiv", | |
167 | .create = echainiv_aead_create, | |
168 | .free = echainiv_free, | |
169 | .module = THIS_MODULE, | |
170 | }; | |
171 | ||
172 | static int __init echainiv_module_init(void) | |
173 | { | |
174 | return crypto_register_template(&echainiv_tmpl); | |
175 | } | |
176 | ||
177 | static void __exit echainiv_module_exit(void) | |
178 | { | |
179 | crypto_unregister_template(&echainiv_tmpl); | |
180 | } | |
181 | ||
182 | module_init(echainiv_module_init); | |
183 | module_exit(echainiv_module_exit); | |
184 | ||
185 | MODULE_LICENSE("GPL"); | |
186 | MODULE_DESCRIPTION("Encrypted Chain IV Generator"); | |
187 | MODULE_ALIAS_CRYPTO("echainiv"); |