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
DH_check_pub_key(const DH * dh,const BIGNUM * pub_key,int * ret)62 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) {
63 *ret = 0;
64
65 BN_CTX *ctx = BN_CTX_new();
66 if (ctx == NULL) {
67 return 0;
68 }
69 BN_CTX_start(ctx);
70
71 int ok = 0;
72
73 /* Check |pub_key| is greater than 1. */
74 BIGNUM *tmp = BN_CTX_get(ctx);
75 if (tmp == NULL ||
76 !BN_set_word(tmp, 1)) {
77 goto err;
78 }
79 if (BN_cmp(pub_key, tmp) <= 0) {
80 *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
81 }
82
83 /* Check |pub_key| is less than |dh->p| - 1. */
84 if (!BN_copy(tmp, dh->p) ||
85 !BN_sub_word(tmp, 1)) {
86 goto err;
87 }
88 if (BN_cmp(pub_key, tmp) >= 0) {
89 *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
90 }
91
92 if (dh->q != NULL) {
93 /* Check |pub_key|^|dh->q| is 1 mod |dh->p|. This is necessary for RFC 5114
94 * groups which are not safe primes but pick a generator on a prime-order
95 * subgroup of size |dh->q|. */
96 if (!BN_mod_exp_mont(tmp, pub_key, dh->q, dh->p, ctx, NULL)) {
97 goto err;
98 }
99 if (!BN_is_one(tmp)) {
100 *ret |= DH_CHECK_PUBKEY_INVALID;
101 }
102 }
103
104 ok = 1;
105
106 err:
107 BN_CTX_end(ctx);
108 BN_CTX_free(ctx);
109 return ok;
110 }
111
112
DH_check(const DH * dh,int * ret)113 int DH_check(const DH *dh, int *ret) {
114 /* Check that p is a safe prime and if g is 2, 3 or 5, check that it is a
115 * suitable generator where:
116 * for 2, p mod 24 == 11
117 * for 3, p mod 12 == 5
118 * for 5, p mod 10 == 3 or 7
119 * should hold.
120 */
121 int ok = 0, r;
122 BN_CTX *ctx = NULL;
123 BN_ULONG l;
124 BIGNUM *t1 = NULL, *t2 = NULL;
125
126 *ret = 0;
127 ctx = BN_CTX_new();
128 if (ctx == NULL) {
129 goto err;
130 }
131 BN_CTX_start(ctx);
132 t1 = BN_CTX_get(ctx);
133 if (t1 == NULL) {
134 goto err;
135 }
136 t2 = BN_CTX_get(ctx);
137 if (t2 == NULL) {
138 goto err;
139 }
140
141 if (dh->q) {
142 if (BN_cmp(dh->g, BN_value_one()) <= 0) {
143 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
144 } else if (BN_cmp(dh->g, dh->p) >= 0) {
145 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
146 } else {
147 /* Check g^q == 1 mod p */
148 if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) {
149 goto err;
150 }
151 if (!BN_is_one(t1)) {
152 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
153 }
154 }
155 r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
156 if (r < 0) {
157 goto err;
158 }
159 if (!r) {
160 *ret |= DH_CHECK_Q_NOT_PRIME;
161 }
162 /* Check p == 1 mod q i.e. q divides p - 1 */
163 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) {
164 goto err;
165 }
166 if (!BN_is_one(t2)) {
167 *ret |= DH_CHECK_INVALID_Q_VALUE;
168 }
169 if (dh->j && BN_cmp(dh->j, t1)) {
170 *ret |= DH_CHECK_INVALID_J_VALUE;
171 }
172 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
173 l = BN_mod_word(dh->p, 24);
174 if (l == (BN_ULONG)-1) {
175 goto err;
176 }
177 if (l != 11) {
178 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
179 }
180 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
181 l = BN_mod_word(dh->p, 10);
182 if (l == (BN_ULONG)-1) {
183 goto err;
184 }
185 if (l != 3 && l != 7) {
186 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
187 }
188 } else {
189 *ret |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR;
190 }
191
192 r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
193 if (r < 0) {
194 goto err;
195 }
196 if (!r) {
197 *ret |= DH_CHECK_P_NOT_PRIME;
198 } else if (!dh->q) {
199 if (!BN_rshift1(t1, dh->p)) {
200 goto err;
201 }
202 r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
203 if (r < 0) {
204 goto err;
205 }
206 if (!r) {
207 *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
208 }
209 }
210 ok = 1;
211
212 err:
213 if (ctx != NULL) {
214 BN_CTX_end(ctx);
215 BN_CTX_free(ctx);
216 }
217 return ok;
218 }
219