blob: 99e20fc63cc9ee36df9a7d5474f77b40b37fba11 [file] [log] [blame]
Salvatore Benedetto802c7f12016-06-22 17:49:14 +01001/* 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
Eric Biggersaa15fe42017-11-05 18:30:44 -080024static void dh_clear_ctx(struct dh_ctx *ctx)
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010025{
26 mpi_free(ctx->p);
27 mpi_free(ctx->g);
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010028 mpi_free(ctx->xa);
Eric Biggersaa15fe42017-11-05 18:30:44 -080029 memset(ctx, 0, sizeof(*ctx));
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010030}
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 (unlikely(!params->p || !params->g))
57 return -EINVAL;
58
59 if (dh_check_params_length(params->p_size << 3))
60 return -EINVAL;
61
62 ctx->p = mpi_read_raw_data(params->p, params->p_size);
63 if (!ctx->p)
64 return -EINVAL;
65
66 ctx->g = mpi_read_raw_data(params->g, params->g_size);
Eric Biggersaa15fe42017-11-05 18:30:44 -080067 if (!ctx->g)
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010068 return -EINVAL;
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010069
70 return 0;
71}
72
73static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
74{
75 struct dh_ctx *ctx = dh_get_ctx(tfm);
76 struct dh params;
77
Tudor-Dan Ambarus4a7e0232017-05-25 10:18:07 +030078 /* Free the old MPI key if any */
Eric Biggersaa15fe42017-11-05 18:30:44 -080079 dh_clear_ctx(ctx);
Tudor-Dan Ambarus4a7e0232017-05-25 10:18:07 +030080
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010081 if (crypto_dh_decode_key(buf, len, &params) < 0)
Eric Biggersaa15fe42017-11-05 18:30:44 -080082 goto err_clear_ctx;
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010083
84 if (dh_set_params(ctx, &params) < 0)
Eric Biggersaa15fe42017-11-05 18:30:44 -080085 goto err_clear_ctx;
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010086
87 ctx->xa = mpi_read_raw_data(params.key, params.key_size);
Eric Biggersaa15fe42017-11-05 18:30:44 -080088 if (!ctx->xa)
89 goto err_clear_ctx;
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010090
91 return 0;
Eric Biggersaa15fe42017-11-05 18:30:44 -080092
93err_clear_ctx:
94 dh_clear_ctx(ctx);
95 return -EINVAL;
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010096}
97
98static int dh_compute_value(struct kpp_request *req)
99{
100 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
101 struct dh_ctx *ctx = dh_get_ctx(tfm);
102 MPI base, val = mpi_alloc(0);
103 int ret = 0;
104 int sign;
105
106 if (!val)
107 return -ENOMEM;
108
109 if (unlikely(!ctx->xa)) {
110 ret = -EINVAL;
111 goto err_free_val;
112 }
113
114 if (req->src) {
115 base = mpi_read_raw_from_sgl(req->src, req->src_len);
116 if (!base) {
117 ret = EINVAL;
118 goto err_free_val;
119 }
120 } else {
121 base = ctx->g;
122 }
123
124 ret = _compute_val(ctx, base, val);
125 if (ret)
126 goto err_free_base;
127
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800128 ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
Salvatore Benedetto802c7f12016-06-22 17:49:14 +0100129 if (ret)
130 goto err_free_base;
131
132 if (sign < 0)
133 ret = -EBADMSG;
134err_free_base:
135 if (req->src)
136 mpi_free(base);
137err_free_val:
138 mpi_free(val);
139 return ret;
140}
141
142static int dh_max_size(struct crypto_kpp *tfm)
143{
144 struct dh_ctx *ctx = dh_get_ctx(tfm);
145
146 return mpi_get_size(ctx->p);
147}
148
149static void dh_exit_tfm(struct crypto_kpp *tfm)
150{
151 struct dh_ctx *ctx = dh_get_ctx(tfm);
152
Eric Biggersaa15fe42017-11-05 18:30:44 -0800153 dh_clear_ctx(ctx);
Salvatore Benedetto802c7f12016-06-22 17:49:14 +0100154}
155
156static struct kpp_alg dh = {
157 .set_secret = dh_set_secret,
158 .generate_public_key = dh_compute_value,
159 .compute_shared_secret = dh_compute_value,
160 .max_size = dh_max_size,
161 .exit = dh_exit_tfm,
162 .base = {
163 .cra_name = "dh",
164 .cra_driver_name = "dh-generic",
165 .cra_priority = 100,
166 .cra_module = THIS_MODULE,
167 .cra_ctxsize = sizeof(struct dh_ctx),
168 },
169};
170
171static int dh_init(void)
172{
173 return crypto_register_kpp(&dh);
174}
175
176static void dh_exit(void)
177{
178 crypto_unregister_kpp(&dh);
179}
180
181module_init(dh_init);
182module_exit(dh_exit);
183MODULE_ALIAS_CRYPTO("dh");
184MODULE_LICENSE("GPL");
185MODULE_DESCRIPTION("DH generic algorithm");