1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young (eay@cryptsoft.com)"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57 #include <openssl/dh.h>
58
59 #include <openssl/bn.h>
60
61 #include "internal.h"
62
63
DH_check_pub_key(const DH * dh,const BIGNUM * pub_key,int * ret)64 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) {
65 int ok = 0;
66 BIGNUM q;
67
68 *ret = 0;
69 BN_init(&q);
70 if (!BN_set_word(&q, 1)) {
71 goto err;
72 }
73
74 if (BN_cmp(pub_key, &q) <= 0) {
75 *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
76 }
77 if (!BN_copy(&q, dh->p) ||
78 !BN_sub_word(&q, 1)) {
79 goto err;
80 }
81 if (BN_cmp(pub_key, &q) >= 0) {
82 *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
83 }
84
85 ok = 1;
86
87 err:
88 BN_free(&q);
89 return ok;
90 }
91
92
DH_check(const DH * dh,int * ret)93 int DH_check(const DH *dh, int *ret) {
94 /* Check that p is a safe prime and if g is 2, 3 or 5, check that it is a
95 * suitable generator where:
96 * for 2, p mod 24 == 11
97 * for 3, p mod 12 == 5
98 * for 5, p mod 10 == 3 or 7
99 * should hold.
100 */
101 int ok = 0;
102 BN_CTX *ctx = NULL;
103 BN_ULONG l;
104 BIGNUM *t1 = NULL, *t2 = NULL;
105
106 *ret = 0;
107 ctx = BN_CTX_new();
108 if (ctx == NULL) {
109 goto err;
110 }
111 BN_CTX_start(ctx);
112 t1 = BN_CTX_get(ctx);
113 if (t1 == NULL) {
114 goto err;
115 }
116 t2 = BN_CTX_get(ctx);
117 if (t2 == NULL) {
118 goto err;
119 }
120
121 if (dh->q) {
122 if (BN_cmp(dh->g, BN_value_one()) <= 0) {
123 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
124 } else if (BN_cmp(dh->g, dh->p) >= 0) {
125 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
126 } else {
127 /* Check g^q == 1 mod p */
128 if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx)) {
129 goto err;
130 }
131 if (!BN_is_one(t1)) {
132 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
133 }
134 }
135 if (!BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL)) {
136 *ret |= DH_CHECK_Q_NOT_PRIME;
137 }
138 /* Check p == 1 mod q i.e. q divides p - 1 */
139 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) {
140 goto err;
141 }
142 if (!BN_is_one(t2)) {
143 *ret |= DH_CHECK_INVALID_Q_VALUE;
144 }
145 if (dh->j && BN_cmp(dh->j, t1)) {
146 *ret |= DH_CHECK_INVALID_J_VALUE;
147 }
148 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
149 l = BN_mod_word(dh->p, 24);
150 if (l != 11) {
151 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
152 }
153 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
154 l = BN_mod_word(dh->p, 10);
155 if (l != 3 && l != 7) {
156 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
157 }
158 } else {
159 *ret |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR;
160 }
161
162 if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL)) {
163 *ret |= DH_CHECK_P_NOT_PRIME;
164 } else if (!dh->q) {
165 if (!BN_rshift1(t1, dh->p)) {
166 goto err;
167 }
168 if (!BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL)) {
169 *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
170 }
171 }
172 ok = 1;
173
174 err:
175 if (ctx != NULL) {
176 BN_CTX_end(ctx);
177 BN_CTX_free(ctx);
178 }
179 return ok;
180 }
181