blob: 87e3542cf1b89e836b1316476d09031010abdea7 [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
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
Eric Biggers5527dfb2017-02-24 15:46:58 -080082static int dh_set_secret(struct crypto_kpp *tfm, const void *buf,
83 unsigned int len)
Salvatore Benedetto802c7f12016-06-22 17:49:14 +010084{
85 struct dh_ctx *ctx = dh_get_ctx(tfm);
86 struct dh params;
87
88 if (crypto_dh_decode_key(buf, len, &params) < 0)
89 return -EINVAL;
90
91 if (dh_set_params(ctx, &params) < 0)
92 return -EINVAL;
93
94 ctx->xa = mpi_read_raw_data(params.key, params.key_size);
95 if (!ctx->xa) {
96 dh_clear_params(ctx);
97 return -EINVAL;
98 }
99
100 return 0;
101}
102
103static int dh_compute_value(struct kpp_request *req)
104{
105 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
106 struct dh_ctx *ctx = dh_get_ctx(tfm);
107 MPI base, val = mpi_alloc(0);
108 int ret = 0;
109 int sign;
110
111 if (!val)
112 return -ENOMEM;
113
114 if (unlikely(!ctx->xa)) {
115 ret = -EINVAL;
116 goto err_free_val;
117 }
118
119 if (req->src) {
120 base = mpi_read_raw_from_sgl(req->src, req->src_len);
121 if (!base) {
Mat Martineau8edda7d2016-11-08 15:48:22 -0800122 ret = -EINVAL;
Salvatore Benedetto802c7f12016-06-22 17:49:14 +0100123 goto err_free_val;
124 }
125 } else {
126 base = ctx->g;
127 }
128
129 ret = _compute_val(ctx, base, val);
130 if (ret)
131 goto err_free_base;
132
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800133 ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
Salvatore Benedetto802c7f12016-06-22 17:49:14 +0100134 if (ret)
135 goto err_free_base;
136
137 if (sign < 0)
138 ret = -EBADMSG;
139err_free_base:
140 if (req->src)
141 mpi_free(base);
142err_free_val:
143 mpi_free(val);
144 return ret;
145}
146
147static int dh_max_size(struct crypto_kpp *tfm)
148{
149 struct dh_ctx *ctx = dh_get_ctx(tfm);
150
151 return mpi_get_size(ctx->p);
152}
153
154static void dh_exit_tfm(struct crypto_kpp *tfm)
155{
156 struct dh_ctx *ctx = dh_get_ctx(tfm);
157
158 dh_free_ctx(ctx);
159}
160
161static struct kpp_alg dh = {
162 .set_secret = dh_set_secret,
163 .generate_public_key = dh_compute_value,
164 .compute_shared_secret = dh_compute_value,
165 .max_size = dh_max_size,
166 .exit = dh_exit_tfm,
167 .base = {
168 .cra_name = "dh",
169 .cra_driver_name = "dh-generic",
170 .cra_priority = 100,
171 .cra_module = THIS_MODULE,
172 .cra_ctxsize = sizeof(struct dh_ctx),
173 },
174};
175
176static int dh_init(void)
177{
178 return crypto_register_kpp(&dh);
179}
180
181static void dh_exit(void)
182{
183 crypto_unregister_kpp(&dh);
184}
185
186module_init(dh_init);
187module_exit(dh_exit);
188MODULE_ALIAS_CRYPTO("dh");
189MODULE_LICENSE("GPL");
190MODULE_DESCRIPTION("DH generic algorithm");