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-rw-r--r--src/lib/libcrypto/dh/dh_check.c237
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diff --git a/src/lib/libcrypto/dh/dh_check.c b/src/lib/libcrypto/dh/dh_check.c
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1/* $OpenBSD: dh_check.c,v 1.30 2024/11/29 15:59:57 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#define DH_NUMBER_ITERATIONS_FOR_PRIME 64
69
70/*
71 * Check that p is odd and 1 < g < p - 1.
72 */
73
74static int
75DH_check_params(const DH *dh, int *flags)
76{
77 BIGNUM *max_g = NULL;
78 int ok = 0;
79
80 *flags = 0;
81
82 if (!BN_is_odd(dh->p))
83 *flags |= DH_CHECK_P_NOT_PRIME;
84
85 /*
86 * Check that 1 < dh->g < p - 1
87 */
88
89 if (BN_cmp(dh->g, BN_value_one()) <= 0)
90 *flags |= DH_NOT_SUITABLE_GENERATOR;
91 /* max_g = p - 1 */
92 if ((max_g = BN_dup(dh->p)) == NULL)
93 goto err;
94 if (!BN_sub_word(max_g, 1))
95 goto err;
96 /* check that g < max_g */
97 if (BN_cmp(dh->g, max_g) >= 0)
98 *flags |= DH_NOT_SUITABLE_GENERATOR;
99
100 ok = 1;
101
102 err:
103 BN_free(max_g);
104
105 return ok;
106}
107
108/*
109 * Check that p is a safe prime and that g is a suitable generator.
110 */
111
112int
113DH_check(const DH *dh, int *flags)
114{
115 BN_CTX *ctx = NULL;
116 int is_prime;
117 int ok = 0;
118
119 *flags = 0;
120
121 if (!DH_check_params(dh, flags))
122 goto err;
123
124 ctx = BN_CTX_new();
125 if (ctx == NULL)
126 goto err;
127 BN_CTX_start(ctx);
128
129 if (dh->q != NULL) {
130 BIGNUM *residue;
131
132 if ((residue = BN_CTX_get(ctx)) == NULL)
133 goto err;
134 if ((*flags & DH_NOT_SUITABLE_GENERATOR) == 0) {
135 /* Check g^q == 1 mod p */
136 if (!BN_mod_exp_ct(residue, dh->g, dh->q, dh->p, ctx))
137 goto err;
138 if (!BN_is_one(residue))
139 *flags |= DH_NOT_SUITABLE_GENERATOR;
140 }
141 is_prime = BN_is_prime_ex(dh->q, DH_NUMBER_ITERATIONS_FOR_PRIME,
142 ctx, NULL);
143 if (is_prime < 0)
144 goto err;
145 if (is_prime == 0)
146 *flags |= DH_CHECK_Q_NOT_PRIME;
147 /* Check p == 1 mod q, i.e., q divides p - 1 */
148 if (!BN_div_ct(NULL, residue, dh->p, dh->q, ctx))
149 goto err;
150 if (!BN_is_one(residue))
151 *flags |= DH_CHECK_INVALID_Q_VALUE;
152 }
153
154 is_prime = BN_is_prime_ex(dh->p, DH_NUMBER_ITERATIONS_FOR_PRIME,
155 ctx, NULL);
156 if (is_prime < 0)
157 goto err;
158 if (is_prime == 0)
159 *flags |= DH_CHECK_P_NOT_PRIME;
160 else if (dh->q == NULL) {
161 BIGNUM *q;
162
163 if ((q = BN_CTX_get(ctx)) == NULL)
164 goto err;
165 if (!BN_rshift1(q, dh->p))
166 goto err;
167 is_prime = BN_is_prime_ex(q, DH_NUMBER_ITERATIONS_FOR_PRIME,
168 ctx, NULL);
169 if (is_prime < 0)
170 goto err;
171 if (is_prime == 0)
172 *flags |= DH_CHECK_P_NOT_SAFE_PRIME;
173 }
174
175 ok = 1;
176
177 err:
178 BN_CTX_end(ctx);
179 BN_CTX_free(ctx);
180 return ok;
181}
182LCRYPTO_ALIAS(DH_check);
183
184int
185DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *flags)
186{
187 BN_CTX *ctx = NULL;
188 BIGNUM *max_pub_key;
189 int ok = 0;
190
191 *flags = 0;
192
193 if ((ctx = BN_CTX_new()) == NULL)
194 goto err;
195 BN_CTX_start(ctx);
196 if ((max_pub_key = BN_CTX_get(ctx)) == NULL)
197 goto err;
198
199 /*
200 * Check that 1 < pub_key < dh->p - 1
201 */
202
203 if (BN_cmp(pub_key, BN_value_one()) <= 0)
204 *flags |= DH_CHECK_PUBKEY_TOO_SMALL;
205
206 /* max_pub_key = dh->p - 1 */
207 if (!BN_sub(max_pub_key, dh->p, BN_value_one()))
208 goto err;
209
210 if (BN_cmp(pub_key, max_pub_key) >= 0)
211 *flags |= DH_CHECK_PUBKEY_TOO_LARGE;
212
213 /*
214 * If dh->q is set, check that pub_key^q == 1 mod p
215 */
216
217 if (dh->q != NULL) {
218 BIGNUM *residue;
219
220 if ((residue = BN_CTX_get(ctx)) == NULL)
221 goto err;
222
223 if (!BN_mod_exp_ct(residue, pub_key, dh->q, dh->p, ctx))
224 goto err;
225 if (!BN_is_one(residue))
226 *flags |= DH_CHECK_PUBKEY_INVALID;
227 }
228
229 ok = 1;
230
231 err:
232 BN_CTX_end(ctx);
233 BN_CTX_free(ctx);
234
235 return ok;
236}
237LCRYPTO_ALIAS(DH_check_pub_key);
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-05-06 15:58:14 +0000