blob: e3d889b122e0f5c3e7b7646b704436ee5ac5910c
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"); |
188 |