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