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
62int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *out_flags) {
63 *out_flags = 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 *out_flags |= 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 *out_flags |= 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 *out_flags |= DH_CHECK_PUBKEY_INVALID;
101 }
102 }
103
104 ok = 1;
105
106err:
107 BN_CTX_end(ctx);
108 BN_CTX_free(ctx);
109 return ok;
110}
111
112
113int DH_check(const DH *dh, int *out_flags) {
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 int ok = 0, r;
121 BN_CTX *ctx = NULL;
122 BN_ULONG l;
123 BIGNUM *t1 = NULL, *t2 = NULL;
124
125 *out_flags = 0;
126 ctx = BN_CTX_new();
127 if (ctx == NULL) {
128 goto err;
129 }
130 BN_CTX_start(ctx);
131 t1 = BN_CTX_get(ctx);
132 if (t1 == NULL) {
133 goto err;
134 }
135 t2 = BN_CTX_get(ctx);
136 if (t2 == NULL) {
137 goto err;
138 }
139
140 if (dh->q) {
141 if (BN_cmp(dh->g, BN_value_one()) <= 0) {
142 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
143 } else if (BN_cmp(dh->g, dh->p) >= 0) {
144 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
145 } else {
146 // Check g^q == 1 mod p
147 if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) {
148 goto err;
149 }
150 if (!BN_is_one(t1)) {
151 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
152 }
153 }
154 r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
155 if (r < 0) {
156 goto err;
157 }
158 if (!r) {
159 *out_flags |= DH_CHECK_Q_NOT_PRIME;
160 }
161 // Check p == 1 mod q i.e. q divides p - 1
162 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) {
163 goto err;
164 }
165 if (!BN_is_one(t2)) {
166 *out_flags |= DH_CHECK_INVALID_Q_VALUE;
167 }
168 if (dh->j && BN_cmp(dh->j, t1)) {
169 *out_flags |= DH_CHECK_INVALID_J_VALUE;
170 }
171 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
172 l = BN_mod_word(dh->p, 24);
173 if (l == (BN_ULONG)-1) {
174 goto err;
175 }
176 if (l != 11) {
177 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
178 }
179 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
180 l = BN_mod_word(dh->p, 10);
181 if (l == (BN_ULONG)-1) {
182 goto err;
183 }
184 if (l != 3 && l != 7) {
185 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
186 }
187 } else {
188 *out_flags |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR;
189 }
190
191 r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
192 if (r < 0) {
193 goto err;
194 }
195 if (!r) {
196 *out_flags |= DH_CHECK_P_NOT_PRIME;
197 } else if (!dh->q) {
198 if (!BN_rshift1(t1, dh->p)) {
199 goto err;
200 }
201 r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
202 if (r < 0) {
203 goto err;
204 }
205 if (!r) {
206 *out_flags |= DH_CHECK_P_NOT_SAFE_PRIME;
207 }
208 }
209 ok = 1;
210
211err:
212 if (ctx != NULL) {
213 BN_CTX_end(ctx);
214 BN_CTX_free(ctx);
215 }
216 return ok;
217}
218