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a10f554f HX |
1 | /* |
2 | * echainiv: Encrypted Chain IV Generator | |
3 | * | |
2426cdb3 HX |
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 | |
a10f554f HX |
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 | ||
d97de47c | 21 | #include <crypto/internal/geniv.h> |
a10f554f HX |
22 | #include <crypto/scatterwalk.h> |
23 | #include <linux/err.h> | |
24 | #include <linux/init.h> | |
25 | #include <linux/kernel.h> | |
a10f554f | 26 | #include <linux/module.h> |
2426cdb3 | 27 | #include <linux/slab.h> |
a10f554f HX |
28 | #include <linux/string.h> |
29 | ||
a10f554f HX |
30 | static int echainiv_encrypt(struct aead_request *req) |
31 | { | |
32 | struct crypto_aead *geniv = crypto_aead_reqtfm(req); | |
376e0d69 | 33 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); |
a10f554f | 34 | struct aead_request *subreq = aead_request_ctx(req); |
2426cdb3 HX |
35 | __be64 nseqno; |
36 | u64 seqno; | |
a10f554f | 37 | u8 *info; |
823655c9 | 38 | unsigned int ivsize = crypto_aead_ivsize(geniv); |
a10f554f HX |
39 | int err; |
40 | ||
823655c9 HX |
41 | if (req->cryptlen < ivsize) |
42 | return -EINVAL; | |
43 | ||
376e0d69 | 44 | aead_request_set_tfm(subreq, ctx->child); |
a10f554f | 45 | |
a10f554f HX |
46 | info = req->iv; |
47 | ||
a10f554f | 48 | if (req->src != req->dst) { |
a10f554f HX |
49 | struct blkcipher_desc desc = { |
50 | .tfm = ctx->null, | |
51 | }; | |
52 | ||
53 | err = crypto_blkcipher_encrypt( | |
838c9d56 HX |
54 | &desc, req->dst, req->src, |
55 | req->assoclen + req->cryptlen); | |
a10f554f HX |
56 | if (err) |
57 | return err; | |
58 | } | |
59 | ||
2426cdb3 HX |
60 | aead_request_set_callback(subreq, req->base.flags, |
61 | req->base.complete, req->base.data); | |
a10f554f | 62 | aead_request_set_crypt(subreq, req->dst, req->dst, |
5499b1a7 HX |
63 | req->cryptlen, info); |
64 | aead_request_set_ad(subreq, req->assoclen); | |
a10f554f | 65 | |
2426cdb3 HX |
66 | memcpy(&nseqno, info + ivsize - 8, 8); |
67 | seqno = be64_to_cpu(nseqno); | |
68 | memset(info, 0, ivsize); | |
69 | ||
a10f554f | 70 | scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); |
a10f554f | 71 | |
2426cdb3 HX |
72 | do { |
73 | u64 a; | |
74 | ||
75 | memcpy(&a, ctx->salt + ivsize - 8, 8); | |
76 | ||
77 | a |= 1; | |
78 | a *= seqno; | |
79 | ||
80 | memcpy(info + ivsize - 8, &a, 8); | |
81 | } while ((ivsize -= 8)); | |
82 | ||
83 | return crypto_aead_encrypt(subreq); | |
a10f554f HX |
84 | } |
85 | ||
a10f554f HX |
86 | static int echainiv_decrypt(struct aead_request *req) |
87 | { | |
88 | struct crypto_aead *geniv = crypto_aead_reqtfm(req); | |
376e0d69 | 89 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); |
a10f554f HX |
90 | struct aead_request *subreq = aead_request_ctx(req); |
91 | crypto_completion_t compl; | |
92 | void *data; | |
823655c9 HX |
93 | unsigned int ivsize = crypto_aead_ivsize(geniv); |
94 | ||
5499b1a7 | 95 | if (req->cryptlen < ivsize) |
823655c9 | 96 | return -EINVAL; |
a10f554f | 97 | |
376e0d69 | 98 | aead_request_set_tfm(subreq, ctx->child); |
a10f554f HX |
99 | |
100 | compl = req->base.complete; | |
101 | data = req->base.data; | |
102 | ||
a10f554f HX |
103 | aead_request_set_callback(subreq, req->base.flags, compl, data); |
104 | aead_request_set_crypt(subreq, req->src, req->dst, | |
105 | req->cryptlen - ivsize, req->iv); | |
374d4ad1 | 106 | aead_request_set_ad(subreq, req->assoclen + ivsize); |
a10f554f HX |
107 | |
108 | scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); | |
a10f554f HX |
109 | |
110 | return crypto_aead_decrypt(subreq); | |
111 | } | |
112 | ||
1e419c79 HX |
113 | static int echainiv_aead_create(struct crypto_template *tmpl, |
114 | struct rtattr **tb) | |
a10f554f HX |
115 | { |
116 | struct aead_instance *inst; | |
117 | struct crypto_aead_spawn *spawn; | |
118 | struct aead_alg *alg; | |
1e419c79 | 119 | int err; |
a10f554f | 120 | |
1e419c79 | 121 | inst = aead_geniv_alloc(tmpl, tb, 0, 0); |
a10f554f HX |
122 | |
123 | if (IS_ERR(inst)) | |
1e419c79 | 124 | return PTR_ERR(inst); |
a10f554f | 125 | |
d97de47c HX |
126 | spawn = aead_instance_ctx(inst); |
127 | alg = crypto_spawn_aead_alg(spawn); | |
128 | ||
1e419c79 | 129 | err = -EINVAL; |
2426cdb3 | 130 | if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) |
1e419c79 | 131 | goto free_inst; |
a10f554f | 132 | |
f261c5fb | 133 | inst->alg.encrypt = echainiv_encrypt; |
a10f554f HX |
134 | inst->alg.decrypt = echainiv_decrypt; |
135 | ||
376e0d69 HX |
136 | inst->alg.init = aead_init_geniv; |
137 | inst->alg.exit = aead_exit_geniv; | |
a10f554f | 138 | |
376e0d69 | 139 | inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); |
9d03aee1 | 140 | inst->alg.base.cra_ctxsize += inst->alg.ivsize; |
a10f554f | 141 | |
5499b1a7 HX |
142 | inst->free = aead_geniv_free; |
143 | ||
1e419c79 HX |
144 | err = aead_register_instance(tmpl, inst); |
145 | if (err) | |
146 | goto free_inst; | |
147 | ||
a10f554f | 148 | out: |
1e419c79 HX |
149 | return err; |
150 | ||
151 | free_inst: | |
152 | aead_geniv_free(inst); | |
153 | goto out; | |
a10f554f HX |
154 | } |
155 | ||
a10f554f HX |
156 | static void echainiv_free(struct crypto_instance *inst) |
157 | { | |
158 | aead_geniv_free(aead_instance(inst)); | |
a10f554f HX |
159 | } |
160 | ||
161 | static struct crypto_template echainiv_tmpl = { | |
162 | .name = "echainiv", | |
9fcc704d | 163 | .create = echainiv_aead_create, |
a10f554f HX |
164 | .free = echainiv_free, |
165 | .module = THIS_MODULE, | |
166 | }; | |
167 | ||
168 | static int __init echainiv_module_init(void) | |
169 | { | |
170 | return crypto_register_template(&echainiv_tmpl); | |
171 | } | |
172 | ||
173 | static void __exit echainiv_module_exit(void) | |
174 | { | |
175 | crypto_unregister_template(&echainiv_tmpl); | |
176 | } | |
177 | ||
178 | module_init(echainiv_module_init); | |
179 | module_exit(echainiv_module_exit); | |
180 | ||
181 | MODULE_LICENSE("GPL"); | |
182 | MODULE_DESCRIPTION("Encrypted Chain IV Generator"); | |
183 | MODULE_ALIAS_CRYPTO("echainiv"); |