1 /* $OpenBSD: dh_key.c,v 1.42 2024/05/09 20:43:36 tb Exp $ */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59 #include <stdio.h>
60
61 #include <openssl/bn.h>
62 #include <openssl/dh.h>
63 #include <openssl/err.h>
64
65 #include "bn_local.h"
66 #include "dh_local.h"
67
68 static int
generate_key(DH * dh)69 generate_key(DH *dh)
70 {
71 int ok = 0;
72 unsigned l;
73 BN_CTX *ctx;
74 BN_MONT_CTX *mont = NULL;
75 BIGNUM *pub_key = NULL, *priv_key = NULL;
76
77 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
78 DHerror(DH_R_MODULUS_TOO_LARGE);
79 return 0;
80 }
81
82 ctx = BN_CTX_new();
83 if (ctx == NULL)
84 goto err;
85
86 if ((priv_key = dh->priv_key) == NULL) {
87 if ((priv_key = BN_new()) == NULL)
88 goto err;
89 }
90
91 if ((pub_key = dh->pub_key) == NULL) {
92 if ((pub_key = BN_new()) == NULL)
93 goto err;
94 }
95
96 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
97 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
98 CRYPTO_LOCK_DH, dh->p, ctx);
99 if (!mont)
100 goto err;
101 }
102
103 if (dh->priv_key == NULL) {
104 if (dh->q) {
105 if (!bn_rand_interval(priv_key, 2, dh->q))
106 goto err;
107 } else {
108 /* secret exponent length */
109 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
110 if (!BN_rand(priv_key, l, 0, 0))
111 goto err;
112 }
113 }
114
115 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key, dh->p, ctx,
116 mont))
117 goto err;
118
119 dh->pub_key = pub_key;
120 dh->priv_key = priv_key;
121 ok = 1;
122 err:
123 if (ok != 1)
124 DHerror(ERR_R_BN_LIB);
125
126 if (dh->pub_key == NULL)
127 BN_free(pub_key);
128 if (dh->priv_key == NULL)
129 BN_free(priv_key);
130 BN_CTX_free(ctx);
131
132 return ok;
133 }
134
135 static int
compute_key(unsigned char * key,const BIGNUM * pub_key,DH * dh)136 compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
137 {
138 BN_CTX *ctx = NULL;
139 BN_MONT_CTX *mont = NULL;
140 BIGNUM *tmp;
141 int ret = -1;
142 int check_result;
143
144 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
145 DHerror(DH_R_MODULUS_TOO_LARGE);
146 goto err;
147 }
148
149 ctx = BN_CTX_new();
150 if (ctx == NULL)
151 goto err;
152 BN_CTX_start(ctx);
153 if ((tmp = BN_CTX_get(ctx)) == NULL)
154 goto err;
155
156 if (dh->priv_key == NULL) {
157 DHerror(DH_R_NO_PRIVATE_VALUE);
158 goto err;
159 }
160
161 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
162 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
163 CRYPTO_LOCK_DH, dh->p, ctx);
164
165 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
166
167 if (!mont)
168 goto err;
169 }
170
171 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
172 DHerror(DH_R_INVALID_PUBKEY);
173 goto err;
174 }
175
176 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx,
177 mont)) {
178 DHerror(ERR_R_BN_LIB);
179 goto err;
180 }
181
182 ret = BN_bn2bin(tmp, key);
183 err:
184 if (ctx != NULL) {
185 BN_CTX_end(ctx);
186 BN_CTX_free(ctx);
187 }
188 return ret;
189 }
190
191 static int
dh_bn_mod_exp(const DH * dh,BIGNUM * r,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx,BN_MONT_CTX * m_ctx)192 dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
193 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
194 {
195 return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx);
196 }
197
198 static int
dh_init(DH * dh)199 dh_init(DH *dh)
200 {
201 dh->flags |= DH_FLAG_CACHE_MONT_P;
202 return 1;
203 }
204
205 static int
dh_finish(DH * dh)206 dh_finish(DH *dh)
207 {
208 BN_MONT_CTX_free(dh->method_mont_p);
209 return 1;
210 }
211
212 int
DH_generate_key(DH * dh)213 DH_generate_key(DH *dh)
214 {
215 return dh->meth->generate_key(dh);
216 }
217 LCRYPTO_ALIAS(DH_generate_key);
218
219 int
DH_compute_key(unsigned char * key,const BIGNUM * pub_key,DH * dh)220 DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
221 {
222 return dh->meth->compute_key(key, pub_key, dh);
223 }
224 LCRYPTO_ALIAS(DH_compute_key);
225
226 static const DH_METHOD dh_ossl = {
227 .name = "OpenSSL DH Method",
228 .generate_key = generate_key,
229 .compute_key = compute_key,
230 .bn_mod_exp = dh_bn_mod_exp,
231 .init = dh_init,
232 .finish = dh_finish,
233 };
234
235 const DH_METHOD *
DH_OpenSSL(void)236 DH_OpenSSL(void)
237 {
238 return &dh_ossl;
239 }
240 LCRYPTO_ALIAS(DH_OpenSSL);
241