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d02b48c6 1/* crypto/dh/dh_check.c */
58964a49 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
d02b48c6
RE
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.
ae5c8664 8 *
d02b48c6
RE
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).
ae5c8664 15 *
d02b48c6
RE
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.
ae5c8664 22 *
d02b48c6
RE
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 :-).
ae5c8664 37 * 4. If you include any Windows specific code (or a derivative thereof) from
d02b48c6
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38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
ae5c8664 40 *
d02b48c6
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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.
ae5c8664 52 *
d02b48c6
RE
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#include "cryptlib.h"
ec577822
BM
61#include <openssl/bn.h>
62#include <openssl/dh.h>
d02b48c6 63
6977c7e2
TH
64/*-
65 * Check that p is a safe prime and
5f0477f4 66 * if g is 2, 3 or 5, check that it is a suitable generator
d02b48c6
RE
67 * where
68 * for 2, p mod 24 == 11
69 * for 3, p mod 12 == 5
70 * for 5, p mod 10 == 3 or 7
71 * should hold.
72 */
73
f971ccb2 74int DH_check(const DH *dh, int *ret)
ae5c8664
MC
75{
76 int ok = 0;
77 BN_CTX *ctx = NULL;
78 BN_ULONG l;
79 BIGNUM *t1 = NULL, *t2 = NULL;
80
81 *ret = 0;
82 ctx = BN_CTX_new();
83 if (ctx == NULL)
84 goto err;
85 BN_CTX_start(ctx);
86 t1 = BN_CTX_get(ctx);
87 if (t1 == NULL)
88 goto err;
89 t2 = BN_CTX_get(ctx);
90 if (t2 == NULL)
91 goto err;
d02b48c6 92
ae5c8664
MC
93 if (dh->q) {
94 if (BN_cmp(dh->g, BN_value_one()) <= 0)
95 *ret |= DH_NOT_SUITABLE_GENERATOR;
96 else if (BN_cmp(dh->g, dh->p) >= 0)
97 *ret |= DH_NOT_SUITABLE_GENERATOR;
98 else {
99 /* Check g^q == 1 mod p */
100 if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
101 goto err;
102 if (!BN_is_one(t1))
103 *ret |= DH_NOT_SUITABLE_GENERATOR;
104 }
105 if (!BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL))
106 *ret |= DH_CHECK_Q_NOT_PRIME;
107 /* Check p == 1 mod q i.e. q divides p - 1 */
108 if (!BN_div(t1, t2, dh->p, dh->q, ctx))
109 goto err;
110 if (!BN_is_one(t2))
111 *ret |= DH_CHECK_INVALID_Q_VALUE;
112 if (dh->j && BN_cmp(dh->j, t1))
113 *ret |= DH_CHECK_INVALID_J_VALUE;
d02b48c6 114
ae5c8664
MC
115 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
116 l = BN_mod_word(dh->p, 24);
117 if (l != 11)
118 *ret |= DH_NOT_SUITABLE_GENERATOR;
119 }
4486d0cd 120#if 0
ae5c8664
MC
121 else if (BN_is_word(dh->g, DH_GENERATOR_3)) {
122 l = BN_mod_word(dh->p, 12);
123 if (l != 5)
124 *ret |= DH_NOT_SUITABLE_GENERATOR;
125 }
4486d0cd 126#endif
ae5c8664
MC
127 else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
128 l = BN_mod_word(dh->p, 10);
129 if ((l != 3) && (l != 7))
130 *ret |= DH_NOT_SUITABLE_GENERATOR;
131 } else
132 *ret |= DH_UNABLE_TO_CHECK_GENERATOR;
d02b48c6 133
ae5c8664
MC
134 if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL))
135 *ret |= DH_CHECK_P_NOT_PRIME;
136 else if (!dh->q) {
137 if (!BN_rshift1(t1, dh->p))
138 goto err;
139 if (!BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL))
140 *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
141 }
142 ok = 1;
143 err:
144 if (ctx != NULL) {
145 BN_CTX_end(ctx);
146 BN_CTX_free(ctx);
147 }
148 return (ok);
149}
bf3d6c0c
BL
150
151int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
ae5c8664
MC
152{
153 int ok = 0;
154 BIGNUM *q = NULL;
bf3d6c0c 155
ae5c8664
MC
156 *ret = 0;
157 q = BN_new();
158 if (q == NULL)
159 goto err;
160 BN_set_word(q, 1);
161 if (BN_cmp(pub_key, q) <= 0)
162 *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
163 BN_copy(q, dh->p);
164 BN_sub_word(q, 1);
165 if (BN_cmp(pub_key, q) >= 0)
166 *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
bf3d6c0c 167
ae5c8664
MC
168 ok = 1;
169 err:
170 if (q != NULL)
171 BN_free(q);
172 return (ok);
173}