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Linux kernel mirror (for testing)
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linux
1/* Diffie-Hellman Key Agreement Method [RFC2631]
2 *
3 * Copyright (c) 2016, Intel Corporation
4 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <crypto/internal/kpp.h>
14#include <crypto/kpp.h>
15#include <crypto/dh.h>
16#include <linux/mpi.h>
17
18struct dh_ctx {
19 MPI p;
20 MPI g;
21 MPI xa;
22};
23
24static inline void dh_clear_params(struct dh_ctx *ctx)
25{
26 mpi_free(ctx->p);
27 mpi_free(ctx->g);
28 ctx->p = NULL;
29 ctx->g = NULL;
30}
31
32static void dh_free_ctx(struct dh_ctx *ctx)
33{
34 dh_clear_params(ctx);
35 mpi_free(ctx->xa);
36 ctx->xa = NULL;
37}
38
39/*
40 * If base is g we compute the public key
41 * ya = g^xa mod p; [RFC2631 sec 2.1.1]
42 * else if base if the counterpart public key we compute the shared secret
43 * ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
44 */
45static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
46{
47 /* val = base^xa mod p */
48 return mpi_powm(val, base, ctx->xa, ctx->p);
49}
50
51static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
52{
53 return kpp_tfm_ctx(tfm);
54}
55
56static int dh_check_params_length(unsigned int p_len)
57{
58 return (p_len < 1536) ? -EINVAL : 0;
59}
60
61static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
62{
63 if (unlikely(!params->p || !params->g))
64 return -EINVAL;
65
66 if (dh_check_params_length(params->p_size << 3))
67 return -EINVAL;
68
69 ctx->p = mpi_read_raw_data(params->p, params->p_size);
70 if (!ctx->p)
71 return -EINVAL;
72
73 ctx->g = mpi_read_raw_data(params->g, params->g_size);
74 if (!ctx->g) {
75 mpi_free(ctx->p);
76 return -EINVAL;
77 }
78
79 return 0;
80}
81
82static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
83{
84 struct dh_ctx *ctx = dh_get_ctx(tfm);
85 struct dh params;
86
87 if (crypto_dh_decode_key(buf, len, ¶ms) < 0)
88 return -EINVAL;
89
90 if (dh_set_params(ctx, ¶ms) < 0)
91 return -EINVAL;
92
93 ctx->xa = mpi_read_raw_data(params.key, params.key_size);
94 if (!ctx->xa) {
95 dh_clear_params(ctx);
96 return -EINVAL;
97 }
98
99 return 0;
100}
101
102static int dh_compute_value(struct kpp_request *req)
103{
104 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
105 struct dh_ctx *ctx = dh_get_ctx(tfm);
106 MPI base, val = mpi_alloc(0);
107 int ret = 0;
108 int sign;
109
110 if (!val)
111 return -ENOMEM;
112
113 if (unlikely(!ctx->xa)) {
114 ret = -EINVAL;
115 goto err_free_val;
116 }
117
118 if (req->src) {
119 base = mpi_read_raw_from_sgl(req->src, req->src_len);
120 if (!base) {
121 ret = EINVAL;
122 goto err_free_val;
123 }
124 } else {
125 base = ctx->g;
126 }
127
128 ret = _compute_val(ctx, base, val);
129 if (ret)
130 goto err_free_base;
131
132 ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
133 if (ret)
134 goto err_free_base;
135
136 if (sign < 0)
137 ret = -EBADMSG;
138err_free_base:
139 if (req->src)
140 mpi_free(base);
141err_free_val:
142 mpi_free(val);
143 return ret;
144}
145
146static int dh_max_size(struct crypto_kpp *tfm)
147{
148 struct dh_ctx *ctx = dh_get_ctx(tfm);
149
150 return mpi_get_size(ctx->p);
151}
152
153static void dh_exit_tfm(struct crypto_kpp *tfm)
154{
155 struct dh_ctx *ctx = dh_get_ctx(tfm);
156
157 dh_free_ctx(ctx);
158}
159
160static struct kpp_alg dh = {
161 .set_secret = dh_set_secret,
162 .generate_public_key = dh_compute_value,
163 .compute_shared_secret = dh_compute_value,
164 .max_size = dh_max_size,
165 .exit = dh_exit_tfm,
166 .base = {
167 .cra_name = "dh",
168 .cra_driver_name = "dh-generic",
169 .cra_priority = 100,
170 .cra_module = THIS_MODULE,
171 .cra_ctxsize = sizeof(struct dh_ctx),
172 },
173};
174
175static int dh_init(void)
176{
177 return crypto_register_kpp(&dh);
178}
179
180static void dh_exit(void)
181{
182 crypto_unregister_kpp(&dh);
183}
184
185module_init(dh_init);
186module_exit(dh_exit);
187MODULE_ALIAS_CRYPTO("dh");
188MODULE_LICENSE("GPL");
189MODULE_DESCRIPTION("DH generic algorithm");