AppleCSP/open_ssl/dh/dh_gen.c

   1 /*
   2  * Copyright (c) 2000-2002 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18 /* crypto/dh/dh_gen.c */
  19 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  20  * All rights reserved.
  21  *
  22  * This package is an SSL implementation written
  23  * by Eric Young (eay@cryptsoft.com).
  24  * The implementation was written so as to conform with Netscapes SSL.
  25  *
  26  * This library is free for commercial and non-commercial use as long as
  27  * the following conditions are aheared to.  The following conditions
  28  * apply to all code found in this distribution, be it the RC4, RSA,
  29  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  30  * included with this distribution is covered by the same copyright terms
  31  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  32  *
  33  * Copyright remains Eric Young's, and as such any Copyright notices in
  34  * the code are not to be removed.
  35  * If this package is used in a product, Eric Young should be given attribution
  36  * as the author of the parts of the library used.
  37  * This can be in the form of a textual message at program startup or
  38  * in documentation (online or textual) provided with the package.
  39  *
  40  * Redistribution and use in source and binary forms, with or without
  41  * modification, are permitted provided that the following conditions
  42  * are met:
  43  * 1. Redistributions of source code must retain the copyright
  44  *    notice, this list of conditions and the following disclaimer.
  45  * 2. Redistributions in binary form must reproduce the above copyright
  46  *    notice, this list of conditions and the following disclaimer in the
  47  *    documentation and/or other materials provided with the distribution.
  48  * 3. All advertising materials mentioning features or use of this software
  49  *    must display the following acknowledgement:
  50  *    "This product includes cryptographic software written by
  51  *     Eric Young (eay@cryptsoft.com)"
  52  *    The word 'cryptographic' can be left out if the rouines from the library
  53  *    being used are not cryptographic related :-).
  54  * 4. If you include any Windows specific code (or a derivative thereof) from
  55  *    the apps directory (application code) you must include an acknowledgement:
  56  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  57  *
  58  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  59  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  60  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  61  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  62  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  63  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  64  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  65  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  66  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  67  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  68  * SUCH DAMAGE.
  69  *
  70  * The licence and distribution terms for any publically available version or
  71  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  72  * copied and put under another distribution licence
  73  * [including the GNU Public Licence.]
  74  */
  75
  76 #include <stdio.h>
  77 #include "cryptlib.h"
  78 #include <openssl/bn.h>
  79 #include <openssl/dh.h>
  80
  81 /* We generate DH parameters as follows
  82  * find a prime q which is prime_len/2 bits long.
  83  * p=(2*q)+1 or (p-1)/2 = q
  84  * For this case, g is a generator if
  85  * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1.
  86  * Since the factors of p-1 are q and 2, we just need to check
  87  * g^2 mod p != 1 and g^q mod p != 1.
  88  *
  89  * Having said all that,
  90  * there is another special case method for the generators 2, 3 and 5.
  91  * for 2, p mod 24 == 11
  92  * for 3, p mod 12 == 5  <<<<< does not work for safe primes.
  93  * for 5, p mod 10 == 3 or 7
  94  *
  95  * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the
  96  * special generators and for answering some of my questions.
  97  *
  98  * I've implemented the second simple method :-).
  99  * Since DH should be using a safe prime (both p and q are prime),
 100  * this generator function can take a very very long time to run.
 101  */
 102
 103 DH *DH_generate_parameters(int prime_len, int generator,
 104              void (*callback)(int,int,void *), void *cb_arg)
 105         {
 106         BIGNUM *p=NULL,*t1,*t2;
 107         DH *ret=NULL;
 108         int g,ok= -1;
 109         BN_CTX *ctx=NULL;
 110
 111         ret=DH_new();
 112         if (ret == NULL) goto err;
 113         ctx=BN_CTX_new();
 114         if (ctx == NULL) goto err;
 115         BN_CTX_start(ctx);
 116         t1 = BN_CTX_get(ctx);
 117         t2 = BN_CTX_get(ctx);
 118         if (t1 == NULL || t2 == NULL) goto err;
 119
 120         if (generator == DH_GENERATOR_2)
 121                 {
 122                 BN_set_word(t1,24);
 123                 BN_set_word(t2,11);
 124                 g=2;
 125                 }
 126 #ifdef undef  /* does not work for safe primes */
 127         else if (generator == DH_GENERATOR_3)
 128                 {
 129                 BN_set_word(t1,12);
 130                 BN_set_word(t2,5);
 131                 g=3;
 132                 }
 133 #endif
 134         else if (generator == DH_GENERATOR_5)
 135                 {
 136                 BN_set_word(t1,10);
 137                 BN_set_word(t2,3);
 138                 /* BN_set_word(t3,7); just have to miss
 139                  * out on these ones :-( */
 140                 g=5;
 141                 }
 142         else
 143                 g=generator;
 144
 145         p=BN_generate_prime(NULL,prime_len,1,t1,t2,callback,cb_arg);
 146         if (p == NULL) goto err;
 147         if (callback != NULL) callback(3,0,cb_arg);
 148         ret->p=p;
 149         ret->g=BN_new();
 150         if (!BN_set_word(ret->g,g)) goto err;
 151         ok=1;
 152 err:
 153         if (ok == -1)
 154                 {
 155                 DHerr(DH_F_DH_GENERATE_PARAMETERS,ERR_R_BN_LIB);
 156                 ok=0;
 157                 }
 158
 159         if (ctx != NULL)
 160                 {
 161                 BN_CTX_end(ctx);
 162                 BN_CTX_free(ctx);
 163                 }
 164         if (!ok && (ret != NULL))
 165                 {
 166                 DH_free(ret);
 167                 ret=NULL;
 168                 }
 169         return(ret);
 170         }