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/* crypto/dh/dh_check.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/dh.h>
/* Check that p is a safe prime and
* if g is 2, 3 or 5, check that it is a suitable generator
* where
* for 2, p mod 24 == 11
* for 3, p mod 12 == 5
* for 5, p mod 10 == 3 or 7
* should hold.
*/
int DH_check(const DH *dh, int *ret)
{
int ok=0;
BN_CTX *ctx=NULL;
BN_ULONG l;
BIGNUM *q=NULL;
*ret=0;
ctx=BN_CTX_new();
if (ctx == NULL) goto err;
q=BN_new();
if (q == NULL) goto err;
if (BN_is_word(dh->g,DH_GENERATOR_2))
{
l=BN_mod_word(dh->p,24);
if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR;
}
#if 0
else if (BN_is_word(dh->g,DH_GENERATOR_3))
{
l=BN_mod_word(dh->p,12);
if (l != 5) *ret|=DH_NOT_SUITABLE_GENERATOR;
}
#endif
else if (BN_is_word(dh->g,DH_GENERATOR_5))
{
l=BN_mod_word(dh->p,10);
if ((l != 3) && (l != 7))
*ret|=DH_NOT_SUITABLE_GENERATOR;
}
else
*ret|=DH_UNABLE_TO_CHECK_GENERATOR;
if (!BN_is_prime_ex(dh->p,BN_prime_checks,ctx,NULL))
*ret|=DH_CHECK_P_NOT_PRIME;
else
{
if (!BN_rshift1(q,dh->p)) goto err;
if (!BN_is_prime_ex(q,BN_prime_checks,ctx,NULL))
*ret|=DH_CHECK_P_NOT_SAFE_PRIME;
}
ok=1;
err:
if (ctx != NULL) BN_CTX_free(ctx);
if (q != NULL) BN_free(q);
return(ok);
}
int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
{
int ok=0;
BIGNUM *q=NULL;
*ret=0;
q=BN_new();
if (q == NULL) goto err;
BN_set_word(q,1);
if (BN_cmp(pub_key,q)<=0)
*ret|=DH_CHECK_PUBKEY_TOO_SMALL;
BN_copy(q,dh->p);
BN_sub_word(q,1);
if (BN_cmp(pub_key,q)>=0)
*ret|=DH_CHECK_PUBKEY_TOO_LARGE;
ok = 1;
err:
if (q != NULL) BN_free(q);
return(ok);
}