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