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dh_check.c
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1 /* crypto/dh/dh_check.c */
2 /* Copyright (C) 1995-1998 Eric Young ([email protected])
3  * All rights reserved.
4  *
5  * This package is an SSL implementation written
6  * by Eric Young ([email protected]).
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 ([email protected]).
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 ([email protected])"
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 ([email protected])"
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))
103  }
104  else
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))
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)
133  BN_copy(q,dh->p);
134  BN_sub_word(q,1);
135  if (BN_cmp(pub_key,q)>=0)
137 
138  ok = 1;
139 err:
140  if (q != NULL) BN_free(q);
141  return(ok);
142  }