dh_check.c revision 296465 
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/*-
65 * Check that p is a safe prime and
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
74#ifndef OPENSSL_FIPS
75
76int DH_check(const DH *dh, int *ret)
77{
78    int ok = 0;
79    BN_CTX *ctx = NULL;
80    BN_ULONG l;
81    BIGNUM *q = NULL;
82
83    *ret = 0;
84    ctx = BN_CTX_new();
85    if (ctx == NULL)
86        goto err;
87    q = BN_new();
88    if (q == NULL)
89        goto err;
90
91    if (BN_is_word(dh->g, DH_GENERATOR_2)) {
92        l = BN_mod_word(dh->p, 24);
93        if (l != 11)
94            *ret |= DH_NOT_SUITABLE_GENERATOR;
95    }
96# if 0
97    else if (BN_is_word(dh->g, DH_GENERATOR_3)) {
98        l = BN_mod_word(dh->p, 12);
99        if (l != 5)
100            *ret |= DH_NOT_SUITABLE_GENERATOR;
101    }
102# endif
103    else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
104        l = BN_mod_word(dh->p, 10);
105        if ((l != 3) && (l != 7))
106            *ret |= DH_NOT_SUITABLE_GENERATOR;
107    } else
108        *ret |= DH_UNABLE_TO_CHECK_GENERATOR;
109
110    if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL))
111        *ret |= DH_CHECK_P_NOT_PRIME;
112    else {
113        if (!BN_rshift1(q, dh->p))
114            goto err;
115        if (!BN_is_prime_ex(q, BN_prime_checks, ctx, NULL))
116            *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
117    }
118    ok = 1;
119 err:
120    if (ctx != NULL)
121        BN_CTX_free(ctx);
122    if (q != NULL)
123        BN_free(q);
124    return (ok);
125}
126
127int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
128{
129    int ok = 0;
130    BIGNUM *q = NULL;
131
132    *ret = 0;
133    q = BN_new();
134    if (q == NULL)
135        goto err;
136    BN_set_word(q, 1);
137    if (BN_cmp(pub_key, q) <= 0)
138        *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
139    BN_copy(q, dh->p);
140    BN_sub_word(q, 1);
141    if (BN_cmp(pub_key, q) >= 0)
142        *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
143
144    ok = 1;
145 err:
146    if (q != NULL)
147        BN_free(q);
148    return (ok);
149}
150
151#endif
152