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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Diffie-Hellman Key Agreement Method [RFC2631]
3 *
4 * Copyright (c) 2016, Intel Corporation
5 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
6 */
7
8#include <linux/module.h>
9#include <crypto/internal/kpp.h>
10#include <crypto/kpp.h>
11#include <crypto/dh.h>
12#include <linux/mpi.h>
13
14struct dh_ctx {
15 MPI p; /* Value is guaranteed to be set. */
16 MPI q; /* Value is optional. */
17 MPI g; /* Value is guaranteed to be set. */
18 MPI xa; /* Value is guaranteed to be set. */
19};
20
21static void dh_clear_ctx(struct dh_ctx *ctx)
22{
23 mpi_free(ctx->p);
24 mpi_free(ctx->q);
25 mpi_free(ctx->g);
26 mpi_free(ctx->xa);
27 memset(ctx, 0, sizeof(*ctx));
28}
29
30/*
31 * If base is g we compute the public key
32 * ya = g^xa mod p; [RFC2631 sec 2.1.1]
33 * else if base if the counterpart public key we compute the shared secret
34 * ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
35 */
36static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
37{
38 /* val = base^xa mod p */
39 return mpi_powm(val, base, ctx->xa, ctx->p);
40}
41
42static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
43{
44 return kpp_tfm_ctx(tfm);
45}
46
47static int dh_check_params_length(unsigned int p_len)
48{
49 return (p_len < 1536) ? -EINVAL : 0;
50}
51
52static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
53{
54 if (dh_check_params_length(params->p_size << 3))
55 return -EINVAL;
56
57 ctx->p = mpi_read_raw_data(params->p, params->p_size);
58 if (!ctx->p)
59 return -EINVAL;
60
61 if (params->q && params->q_size) {
62 ctx->q = mpi_read_raw_data(params->q, params->q_size);
63 if (!ctx->q)
64 return -EINVAL;
65 }
66
67 ctx->g = mpi_read_raw_data(params->g, params->g_size);
68 if (!ctx->g)
69 return -EINVAL;
70
71 return 0;
72}
73
74static int dh_set_secret(struct crypto_kpp *tfm, const void *buf,
75 unsigned int len)
76{
77 struct dh_ctx *ctx = dh_get_ctx(tfm);
78 struct dh params;
79
80 /* Free the old MPI key if any */
81 dh_clear_ctx(ctx);
82
83 if (crypto_dh_decode_key(buf, len, ¶ms) < 0)
84 goto err_clear_ctx;
85
86 if (dh_set_params(ctx, ¶ms) < 0)
87 goto err_clear_ctx;
88
89 ctx->xa = mpi_read_raw_data(params.key, params.key_size);
90 if (!ctx->xa)
91 goto err_clear_ctx;
92
93 return 0;
94
95err_clear_ctx:
96 dh_clear_ctx(ctx);
97 return -EINVAL;
98}
99
100/*
101 * SP800-56A public key verification:
102 *
103 * * If Q is provided as part of the domain paramenters, a full validation
104 * according to SP800-56A section 5.6.2.3.1 is performed.
105 *
106 * * If Q is not provided, a partial validation according to SP800-56A section
107 * 5.6.2.3.2 is performed.
108 */
109static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
110{
111 if (unlikely(!ctx->p))
112 return -EINVAL;
113
114 /*
115 * Step 1: Verify that 2 <= y <= p - 2.
116 *
117 * The upper limit check is actually y < p instead of y < p - 1
118 * as the mpi_sub_ui function is yet missing.
119 */
120 if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0)
121 return -EINVAL;
122
123 /* Step 2: Verify that 1 = y^q mod p */
124 if (ctx->q) {
125 MPI val = mpi_alloc(0);
126 int ret;
127
128 if (!val)
129 return -ENOMEM;
130
131 ret = mpi_powm(val, y, ctx->q, ctx->p);
132
133 if (ret) {
134 mpi_free(val);
135 return ret;
136 }
137
138 ret = mpi_cmp_ui(val, 1);
139
140 mpi_free(val);
141
142 if (ret != 0)
143 return -EINVAL;
144 }
145
146 return 0;
147}
148
149static int dh_compute_value(struct kpp_request *req)
150{
151 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
152 struct dh_ctx *ctx = dh_get_ctx(tfm);
153 MPI base, val = mpi_alloc(0);
154 int ret = 0;
155 int sign;
156
157 if (!val)
158 return -ENOMEM;
159
160 if (unlikely(!ctx->xa)) {
161 ret = -EINVAL;
162 goto err_free_val;
163 }
164
165 if (req->src) {
166 base = mpi_read_raw_from_sgl(req->src, req->src_len);
167 if (!base) {
168 ret = -EINVAL;
169 goto err_free_val;
170 }
171 ret = dh_is_pubkey_valid(ctx, base);
172 if (ret)
173 goto err_free_base;
174 } else {
175 base = ctx->g;
176 }
177
178 ret = _compute_val(ctx, base, val);
179 if (ret)
180 goto err_free_base;
181
182 ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
183 if (ret)
184 goto err_free_base;
185
186 if (sign < 0)
187 ret = -EBADMSG;
188err_free_base:
189 if (req->src)
190 mpi_free(base);
191err_free_val:
192 mpi_free(val);
193 return ret;
194}
195
196static unsigned int dh_max_size(struct crypto_kpp *tfm)
197{
198 struct dh_ctx *ctx = dh_get_ctx(tfm);
199
200 return mpi_get_size(ctx->p);
201}
202
203static void dh_exit_tfm(struct crypto_kpp *tfm)
204{
205 struct dh_ctx *ctx = dh_get_ctx(tfm);
206
207 dh_clear_ctx(ctx);
208}
209
210static struct kpp_alg dh = {
211 .set_secret = dh_set_secret,
212 .generate_public_key = dh_compute_value,
213 .compute_shared_secret = dh_compute_value,
214 .max_size = dh_max_size,
215 .exit = dh_exit_tfm,
216 .base = {
217 .cra_name = "dh",
218 .cra_driver_name = "dh-generic",
219 .cra_priority = 100,
220 .cra_module = THIS_MODULE,
221 .cra_ctxsize = sizeof(struct dh_ctx),
222 },
223};
224
225static int dh_init(void)
226{
227 return crypto_register_kpp(&dh);
228}
229
230static void dh_exit(void)
231{
232 crypto_unregister_kpp(&dh);
233}
234
235subsys_initcall(dh_init);
236module_exit(dh_exit);
237MODULE_ALIAS_CRYPTO("dh");
238MODULE_LICENSE("GPL");
239MODULE_DESCRIPTION("DH generic algorithm");
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 License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, 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 void dh_clear_ctx(struct dh_ctx *ctx)
25{
26 mpi_free(ctx->p);
27 mpi_free(ctx->g);
28 mpi_free(ctx->xa);
29 memset(ctx, 0, sizeof(*ctx));
30}
31
32/*
33 * If base is g we compute the public key
34 * ya = g^xa mod p; [RFC2631 sec 2.1.1]
35 * else if base if the counterpart public key we compute the shared secret
36 * ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
37 */
38static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
39{
40 /* val = base^xa mod p */
41 return mpi_powm(val, base, ctx->xa, ctx->p);
42}
43
44static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
45{
46 return kpp_tfm_ctx(tfm);
47}
48
49static int dh_check_params_length(unsigned int p_len)
50{
51 return (p_len < 1536) ? -EINVAL : 0;
52}
53
54static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
55{
56 if (dh_check_params_length(params->p_size << 3))
57 return -EINVAL;
58
59 ctx->p = mpi_read_raw_data(params->p, params->p_size);
60 if (!ctx->p)
61 return -EINVAL;
62
63 ctx->g = mpi_read_raw_data(params->g, params->g_size);
64 if (!ctx->g)
65 return -EINVAL;
66
67 return 0;
68}
69
70static int dh_set_secret(struct crypto_kpp *tfm, const void *buf,
71 unsigned int len)
72{
73 struct dh_ctx *ctx = dh_get_ctx(tfm);
74 struct dh params;
75
76 /* Free the old MPI key if any */
77 dh_clear_ctx(ctx);
78
79 if (crypto_dh_decode_key(buf, len, ¶ms) < 0)
80 goto err_clear_ctx;
81
82 if (dh_set_params(ctx, ¶ms) < 0)
83 goto err_clear_ctx;
84
85 ctx->xa = mpi_read_raw_data(params.key, params.key_size);
86 if (!ctx->xa)
87 goto err_clear_ctx;
88
89 return 0;
90
91err_clear_ctx:
92 dh_clear_ctx(ctx);
93 return -EINVAL;
94}
95
96static int dh_compute_value(struct kpp_request *req)
97{
98 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
99 struct dh_ctx *ctx = dh_get_ctx(tfm);
100 MPI base, val = mpi_alloc(0);
101 int ret = 0;
102 int sign;
103
104 if (!val)
105 return -ENOMEM;
106
107 if (unlikely(!ctx->xa)) {
108 ret = -EINVAL;
109 goto err_free_val;
110 }
111
112 if (req->src) {
113 base = mpi_read_raw_from_sgl(req->src, req->src_len);
114 if (!base) {
115 ret = -EINVAL;
116 goto err_free_val;
117 }
118 } else {
119 base = ctx->g;
120 }
121
122 ret = _compute_val(ctx, base, val);
123 if (ret)
124 goto err_free_base;
125
126 ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
127 if (ret)
128 goto err_free_base;
129
130 if (sign < 0)
131 ret = -EBADMSG;
132err_free_base:
133 if (req->src)
134 mpi_free(base);
135err_free_val:
136 mpi_free(val);
137 return ret;
138}
139
140static unsigned int dh_max_size(struct crypto_kpp *tfm)
141{
142 struct dh_ctx *ctx = dh_get_ctx(tfm);
143
144 return mpi_get_size(ctx->p);
145}
146
147static void dh_exit_tfm(struct crypto_kpp *tfm)
148{
149 struct dh_ctx *ctx = dh_get_ctx(tfm);
150
151 dh_clear_ctx(ctx);
152}
153
154static struct kpp_alg dh = {
155 .set_secret = dh_set_secret,
156 .generate_public_key = dh_compute_value,
157 .compute_shared_secret = dh_compute_value,
158 .max_size = dh_max_size,
159 .exit = dh_exit_tfm,
160 .base = {
161 .cra_name = "dh",
162 .cra_driver_name = "dh-generic",
163 .cra_priority = 100,
164 .cra_module = THIS_MODULE,
165 .cra_ctxsize = sizeof(struct dh_ctx),
166 },
167};
168
169static int dh_init(void)
170{
171 return crypto_register_kpp(&dh);
172}
173
174static void dh_exit(void)
175{
176 crypto_unregister_kpp(&dh);
177}
178
179module_init(dh_init);
180module_exit(dh_exit);
181MODULE_ALIAS_CRYPTO("dh");
182MODULE_LICENSE("GPL");
183MODULE_DESCRIPTION("DH generic algorithm");