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1 | // SPDX-License-Identifier: GPL-2.0-or-later | |
2 | /* | |
3 | * echainiv: Encrypted Chain IV Generator | |
4 | * | |
5 | * This generator generates an IV based on a sequence number by multiplying | |
6 | * it with a salt and then encrypting it with the same key as used to encrypt | |
7 | * the plain text. This algorithm requires that the block size be equal | |
8 | * to the IV size. It is mainly useful for CBC. | |
9 | * | |
10 | * This generator can only be used by algorithms where authentication | |
11 | * is performed after encryption (i.e., authenc). | |
12 | * | |
13 | * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> | |
14 | */ | |
15 | ||
16 | #include <crypto/internal/geniv.h> | |
17 | #include <crypto/scatterwalk.h> | |
18 | #include <crypto/skcipher.h> | |
19 | #include <linux/err.h> | |
20 | #include <linux/init.h> | |
21 | #include <linux/kernel.h> | |
22 | #include <linux/module.h> | |
23 | #include <linux/slab.h> | |
24 | #include <linux/string.h> | |
25 | ||
26 | static int echainiv_encrypt(struct aead_request *req) | |
27 | { | |
28 | struct crypto_aead *geniv = crypto_aead_reqtfm(req); | |
29 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); | |
30 | struct aead_request *subreq = aead_request_ctx(req); | |
31 | __be64 nseqno; | |
32 | u64 seqno; | |
33 | u8 *info; | |
34 | unsigned int ivsize = crypto_aead_ivsize(geniv); | |
35 | int err; | |
36 | ||
37 | if (req->cryptlen < ivsize) | |
38 | return -EINVAL; | |
39 | ||
40 | aead_request_set_tfm(subreq, ctx->child); | |
41 | ||
42 | info = req->iv; | |
43 | ||
44 | if (req->src != req->dst) { | |
45 | SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull); | |
46 | ||
47 | skcipher_request_set_sync_tfm(nreq, ctx->sknull); | |
48 | skcipher_request_set_callback(nreq, req->base.flags, | |
49 | NULL, NULL); | |
50 | skcipher_request_set_crypt(nreq, req->src, req->dst, | |
51 | req->assoclen + req->cryptlen, | |
52 | NULL); | |
53 | ||
54 | err = crypto_skcipher_encrypt(nreq); | |
55 | if (err) | |
56 | return err; | |
57 | } | |
58 | ||
59 | aead_request_set_callback(subreq, req->base.flags, | |
60 | req->base.complete, req->base.data); | |
61 | aead_request_set_crypt(subreq, req->dst, req->dst, | |
62 | req->cryptlen, info); | |
63 | aead_request_set_ad(subreq, req->assoclen); | |
64 | ||
65 | memcpy(&nseqno, info + ivsize - 8, 8); | |
66 | seqno = be64_to_cpu(nseqno); | |
67 | memset(info, 0, ivsize); | |
68 | ||
69 | scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); | |
70 | ||
71 | do { | |
72 | u64 a; | |
73 | ||
74 | memcpy(&a, ctx->salt + ivsize - 8, 8); | |
75 | ||
76 | a |= 1; | |
77 | a *= seqno; | |
78 | ||
79 | memcpy(info + ivsize - 8, &a, 8); | |
80 | } while ((ivsize -= 8)); | |
81 | ||
82 | return crypto_aead_encrypt(subreq); | |
83 | } | |
84 | ||
85 | static int echainiv_decrypt(struct aead_request *req) | |
86 | { | |
87 | struct crypto_aead *geniv = crypto_aead_reqtfm(req); | |
88 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); | |
89 | struct aead_request *subreq = aead_request_ctx(req); | |
90 | crypto_completion_t compl; | |
91 | void *data; | |
92 | unsigned int ivsize = crypto_aead_ivsize(geniv); | |
93 | ||
94 | if (req->cryptlen < ivsize) | |
95 | return -EINVAL; | |
96 | ||
97 | aead_request_set_tfm(subreq, ctx->child); | |
98 | ||
99 | compl = req->base.complete; | |
100 | data = req->base.data; | |
101 | ||
102 | aead_request_set_callback(subreq, req->base.flags, compl, data); | |
103 | aead_request_set_crypt(subreq, req->src, req->dst, | |
104 | req->cryptlen - ivsize, req->iv); | |
105 | aead_request_set_ad(subreq, req->assoclen + ivsize); | |
106 | ||
107 | scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); | |
108 | ||
109 | return crypto_aead_decrypt(subreq); | |
110 | } | |
111 | ||
112 | static int echainiv_aead_create(struct crypto_template *tmpl, | |
113 | struct rtattr **tb) | |
114 | { | |
115 | struct aead_instance *inst; | |
116 | int err; | |
117 | ||
118 | inst = aead_geniv_alloc(tmpl, tb, 0, 0); | |
119 | ||
120 | if (IS_ERR(inst)) | |
121 | return PTR_ERR(inst); | |
122 | ||
123 | err = -EINVAL; | |
124 | if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) | |
125 | goto free_inst; | |
126 | ||
127 | inst->alg.encrypt = echainiv_encrypt; | |
128 | inst->alg.decrypt = echainiv_decrypt; | |
129 | ||
130 | inst->alg.init = aead_init_geniv; | |
131 | inst->alg.exit = aead_exit_geniv; | |
132 | ||
133 | inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); | |
134 | inst->alg.base.cra_ctxsize += inst->alg.ivsize; | |
135 | ||
136 | err = aead_register_instance(tmpl, inst); | |
137 | if (err) { | |
138 | free_inst: | |
139 | inst->free(inst); | |
140 | } | |
141 | return err; | |
142 | } | |
143 | ||
144 | static struct crypto_template echainiv_tmpl = { | |
145 | .name = "echainiv", | |
146 | .create = echainiv_aead_create, | |
147 | .module = THIS_MODULE, | |
148 | }; | |
149 | ||
150 | static int __init echainiv_module_init(void) | |
151 | { | |
152 | return crypto_register_template(&echainiv_tmpl); | |
153 | } | |
154 | ||
155 | static void __exit echainiv_module_exit(void) | |
156 | { | |
157 | crypto_unregister_template(&echainiv_tmpl); | |
158 | } | |
159 | ||
160 | subsys_initcall(echainiv_module_init); | |
161 | module_exit(echainiv_module_exit); | |
162 | ||
163 | MODULE_LICENSE("GPL"); | |
164 | MODULE_DESCRIPTION("Encrypted Chain IV Generator"); | |
165 | MODULE_ALIAS_CRYPTO("echainiv"); |