1 /* crypto/dh/dh_check.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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.
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.]
57 */
58
59 #include <stdio.h>
60 #include "cryptlib.h"
61 #include <openssl/bn.h>
62 #include <openssl/dh.h>
63
64 /* Check that p is a safe prime and
65 * if g is 2, 3 or 5, check that it is a suitable generator
66 * where
67 * for 2, p mod 24 == 11
68 * for 3, p mod 12 == 5
69 * for 5, p mod 10 == 3 or 7
70 * should hold.
71 */
72
73 int DH_check(const DH *dh, int *ret)
74 {
75 int ok=0;
76 BN_CTX *ctx=NULL;
77 BN_ULONG l;
78 BIGNUM *q=NULL;
79
80 *ret=0;
81 ctx=BN_CTX_new();
82 if (ctx == NULL) goto err;
83 q=BN_new();
84 if (q == NULL) goto err;
85
86 if (BN_is_word(dh->g,DH_GENERATOR_2))
87 {
88 l=BN_mod_word(dh->p,24);
89 if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR;
90 }
91 #if 0
92 else if (BN_is_word(dh->g,DH_GENERATOR_3))
93 {
94 l=BN_mod_word(dh->p,12);
95 if (l != 5) *ret|=DH_NOT_SUITABLE_GENERATOR;
96 }
97 #endif
98 else if (BN_is_word(dh->g,DH_GENERATOR_5))
99 {
100 l=BN_mod_word(dh->p,10);
101 if ((l != 3) && (l != 7))
102 *ret|=DH_NOT_SUITABLE_GENERATOR;
103 }
104 else
105 *ret|=DH_UNABLE_TO_CHECK_GENERATOR;
106
107 if (!BN_is_prime_ex(dh->p,BN_prime_checks,ctx,NULL))
108 *ret|=DH_CHECK_P_NOT_PRIME;
109 else
110 {
111 if (!BN_rshift1(q,dh->p)) goto err;
112 if (!BN_is_prime_ex(q,BN_prime_checks,ctx,NULL))
113 *ret|=DH_CHECK_P_NOT_SAFE_PRIME;
114 }
115 ok=1;
116 err:
117 if (ctx != NULL) BN_CTX_free(ctx);
118 if (q != NULL) BN_free(q);
119 return(ok);
120 }
121
122 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
123 {
124 int ok=0;
125 BIGNUM *q=NULL;
126
127 *ret=0;
128 q=BN_new();
129 if (q == NULL) goto err;
130 BN_set_word(q,1);
131 if (BN_cmp(pub_key,q)<=0)
132 *ret|=DH_CHECK_PUBKEY_TOO_SMALL;
133 BN_copy(q,dh->p);
134 BN_sub_word(q,1);
135 if (BN_cmp(pub_key,q)>=0)
136 *ret|=DH_CHECK_PUBKEY_TOO_LARGE;
137
138 ok = 1;
139 err:
140 if (q != NULL) BN_free(q);
141 return(ok);
142 }