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3c4b2390 SB |
1 | /* ECDH key-agreement protocol |
2 | * | |
3 | * Copyright (c) 2016, Intel Corporation | |
4 | * Authors: Salvator Benedetto <salvatore.benedetto@intel.com> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
c0ca1215 | 7 | * modify it under the terms of the GNU General Public License |
3c4b2390 | 8 | * as published by the Free Software Foundation; either version |
c0ca1215 | 9 | * 2 of the License, or (at your option) any later version. |
3c4b2390 SB |
10 | */ |
11 | ||
12 | #include <linux/module.h> | |
13 | #include <crypto/internal/kpp.h> | |
14 | #include <crypto/kpp.h> | |
15 | #include <crypto/ecdh.h> | |
16 | #include <linux/scatterlist.h> | |
17 | #include "ecc.h" | |
18 | ||
19 | struct ecdh_ctx { | |
20 | unsigned int curve_id; | |
21 | unsigned int ndigits; | |
22 | u64 private_key[ECC_MAX_DIGITS]; | |
23 | u64 public_key[2 * ECC_MAX_DIGITS]; | |
24 | u64 shared_secret[ECC_MAX_DIGITS]; | |
25 | }; | |
26 | ||
27 | static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm) | |
28 | { | |
29 | return kpp_tfm_ctx(tfm); | |
30 | } | |
31 | ||
32 | static unsigned int ecdh_supported_curve(unsigned int curve_id) | |
33 | { | |
34 | switch (curve_id) { | |
35 | case ECC_CURVE_NIST_P192: return 3; | |
36 | case ECC_CURVE_NIST_P256: return 4; | |
37 | default: return 0; | |
38 | } | |
39 | } | |
40 | ||
5527dfb6 EB |
41 | static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, |
42 | unsigned int len) | |
3c4b2390 SB |
43 | { |
44 | struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); | |
45 | struct ecdh params; | |
46 | unsigned int ndigits; | |
47 | ||
48 | if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) | |
49 | return -EINVAL; | |
50 | ||
51 | ndigits = ecdh_supported_curve(params.curve_id); | |
52 | if (!ndigits) | |
53 | return -EINVAL; | |
54 | ||
55 | ctx->curve_id = params.curve_id; | |
56 | ctx->ndigits = ndigits; | |
57 | ||
58 | if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, | |
ad269597 | 59 | (const u64 *)params.key, params.key_size) < 0) |
3c4b2390 SB |
60 | return -EINVAL; |
61 | ||
62 | memcpy(ctx->private_key, params.key, params.key_size); | |
63 | ||
64 | return 0; | |
65 | } | |
66 | ||
67 | static int ecdh_compute_value(struct kpp_request *req) | |
68 | { | |
69 | int ret = 0; | |
70 | struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); | |
71 | struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); | |
72 | size_t copied, nbytes; | |
73 | void *buf; | |
74 | ||
75 | nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; | |
76 | ||
77 | if (req->src) { | |
78 | copied = sg_copy_to_buffer(req->src, 1, ctx->public_key, | |
79 | 2 * nbytes); | |
80 | if (copied != 2 * nbytes) | |
81 | return -EINVAL; | |
82 | ||
8f44df15 | 83 | ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, |
ad269597 TDA |
84 | ctx->private_key, |
85 | ctx->public_key, | |
86 | ctx->shared_secret); | |
3c4b2390 SB |
87 | |
88 | buf = ctx->shared_secret; | |
89 | } else { | |
90 | ret = ecdh_make_pub_key(ctx->curve_id, ctx->ndigits, | |
ad269597 | 91 | ctx->private_key, ctx->public_key); |
3c4b2390 SB |
92 | buf = ctx->public_key; |
93 | /* Public part is a point thus it has both coordinates */ | |
94 | nbytes *= 2; | |
95 | } | |
96 | ||
97 | if (ret < 0) | |
98 | return ret; | |
99 | ||
100 | copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes); | |
101 | if (copied != nbytes) | |
102 | return -EINVAL; | |
103 | ||
104 | return ret; | |
105 | } | |
106 | ||
107 | static int ecdh_max_size(struct crypto_kpp *tfm) | |
108 | { | |
109 | struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); | |
110 | int nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; | |
111 | ||
112 | /* Public key is made of two coordinates */ | |
113 | return 2 * nbytes; | |
114 | } | |
115 | ||
116 | static void no_exit_tfm(struct crypto_kpp *tfm) | |
117 | { | |
118 | return; | |
119 | } | |
120 | ||
121 | static struct kpp_alg ecdh = { | |
122 | .set_secret = ecdh_set_secret, | |
123 | .generate_public_key = ecdh_compute_value, | |
124 | .compute_shared_secret = ecdh_compute_value, | |
125 | .max_size = ecdh_max_size, | |
126 | .exit = no_exit_tfm, | |
127 | .base = { | |
128 | .cra_name = "ecdh", | |
129 | .cra_driver_name = "ecdh-generic", | |
130 | .cra_priority = 100, | |
131 | .cra_module = THIS_MODULE, | |
132 | .cra_ctxsize = sizeof(struct ecdh_ctx), | |
133 | }, | |
134 | }; | |
135 | ||
136 | static int ecdh_init(void) | |
137 | { | |
138 | return crypto_register_kpp(&ecdh); | |
139 | } | |
140 | ||
141 | static void ecdh_exit(void) | |
142 | { | |
143 | crypto_unregister_kpp(&ecdh); | |
144 | } | |
145 | ||
146 | module_init(ecdh_init); | |
147 | module_exit(ecdh_exit); | |
148 | MODULE_ALIAS_CRYPTO("ecdh"); | |
149 | MODULE_LICENSE("GPL"); | |
150 | MODULE_DESCRIPTION("ECDH generic algorithm"); |