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031e5cce SM |
1 | /* crypto/dh/dh_check.c */ |
2 | /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) | |
3 | * All rights reserved. | |
3e575651 | 4 | * |
031e5cce SM |
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.] | |
3e575651 SL |
57 | */ |
58 | ||
59 | #include <stdio.h> | |
031e5cce | 60 | #include "cryptlib.h" |
3e575651 | 61 | #include <openssl/bn.h> |
031e5cce | 62 | #include <openssl/dh.h> |
3e575651 | 63 | |
d3819813 MTL |
64 | /*- |
65 | * Check that p is a safe prime and | |
3e575651 SL |
66 | * if g is 2, 3 or 5, check that it is a suitable generator |
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 | ||
3e575651 | 74 | int DH_check(const DH *dh, int *ret) |
d3819813 | 75 | { |
031e5cce | 76 | int ok = 0; |
d3819813 MTL |
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; | |
3e575651 | 92 | |
d3819813 MTL |
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 | } | |
031e5cce | 105 | if (!BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL)) |
d3819813 MTL |
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; | |
3e575651 | 114 | |
d3819813 MTL |
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; | |
031e5cce SM |
119 | } |
120 | #if 0 | |
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 | } | |
126 | #endif | |
127 | else if (BN_is_word(dh->g, DH_GENERATOR_5)) { | |
d3819813 MTL |
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; | |
3e575651 | 133 | |
031e5cce | 134 | if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL)) |
d3819813 MTL |
135 | *ret |= DH_CHECK_P_NOT_PRIME; |
136 | else if (!dh->q) { | |
137 | if (!BN_rshift1(t1, dh->p)) | |
138 | goto err; | |
031e5cce | 139 | if (!BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL)) |
d3819813 MTL |
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 | } | |
3e575651 SL |
150 | |
151 | int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) | |
d3819813 MTL |
152 | { |
153 | int ok = 0; | |
62f0afa2 MTL |
154 | BIGNUM *tmp = NULL; |
155 | BN_CTX *ctx = NULL; | |
3e575651 | 156 | |
d3819813 | 157 | *ret = 0; |
62f0afa2 MTL |
158 | ctx = BN_CTX_new(); |
159 | if (ctx == NULL) | |
d3819813 | 160 | goto err; |
62f0afa2 MTL |
161 | BN_CTX_start(ctx); |
162 | tmp = BN_CTX_get(ctx); | |
163 | if (tmp == NULL || !BN_set_word(tmp, 1)) | |
164 | goto err; | |
165 | if (BN_cmp(pub_key, tmp) <= 0) | |
d3819813 | 166 | *ret |= DH_CHECK_PUBKEY_TOO_SMALL; |
62f0afa2 MTL |
167 | if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1)) |
168 | goto err; | |
169 | if (BN_cmp(pub_key, tmp) >= 0) | |
d3819813 | 170 | *ret |= DH_CHECK_PUBKEY_TOO_LARGE; |
3e575651 | 171 | |
62f0afa2 MTL |
172 | if (dh->q != NULL) { |
173 | /* Check pub_key^q == 1 mod p */ | |
174 | if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx)) | |
175 | goto err; | |
176 | if (!BN_is_one(tmp)) | |
177 | *ret |= DH_CHECK_PUBKEY_INVALID; | |
178 | } | |
179 | ||
d3819813 MTL |
180 | ok = 1; |
181 | err: | |
62f0afa2 MTL |
182 | if (ctx != NULL) { |
183 | BN_CTX_end(ctx); | |
184 | BN_CTX_free(ctx); | |
185 | } | |
d3819813 MTL |
186 | return (ok); |
187 | } |