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 is 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#ifndef OPENSSL_FIPS
74
75int DH_check(const DH *dh, int *ret)
76	{
77	int ok=0;
78	BN_CTX *ctx=NULL;
79	BN_ULONG l;
80	BIGNUM *q=NULL;
81
82	*ret=0;
83	ctx=BN_CTX_new();
84	if (ctx == NULL) goto err;
85	q=BN_new();
86	if (q == NULL) goto err;
87
88	if (BN_is_word(dh->g,DH_GENERATOR_2))
89		{
90		l=BN_mod_word(dh->p,24);
91		if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR;
92		}
93#if 0
94	else if (BN_is_word(dh->g,DH_GENERATOR_3))
95		{
96		l=BN_mod_word(dh->p,12);
97		if (l != 5) *ret|=DH_NOT_SUITABLE_GENERATOR;
98		}
99#endif
100	else if (BN_is_word(dh->g,DH_GENERATOR_5))
101		{
102		l=BN_mod_word(dh->p,10);
103		if ((l != 3) && (l != 7))
104			*ret|=DH_NOT_SUITABLE_GENERATOR;
105		}
106	else
107		*ret|=DH_UNABLE_TO_CHECK_GENERATOR;
108
109	if (!BN_is_prime(dh->p,BN_prime_checks,NULL,ctx,NULL))
110		*ret|=DH_CHECK_P_NOT_PRIME;
111	else
112		{
113		if (!BN_rshift1(q,dh->p)) goto err;
114		if (!BN_is_prime(q,BN_prime_checks,NULL,ctx,NULL))
115			*ret|=DH_CHECK_P_NOT_SAFE_PRIME;
116		}
117	ok=1;
118err:
119	if (ctx != NULL) BN_CTX_free(ctx);
120	if (q != NULL) BN_free(q);
121	return(ok);
122	}
123
124#endif
125