155714Skris/* crypto/dh/dh_gen.c */ 255714Skris/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 355714Skris * All rights reserved. 455714Skris * 555714Skris * This package is an SSL implementation written 655714Skris * by Eric Young (eay@cryptsoft.com). 755714Skris * The implementation was written so as to conform with Netscapes SSL. 8280304Sjkim * 955714Skris * This library is free for commercial and non-commercial use as long as 1055714Skris * the following conditions are aheared to. The following conditions 1155714Skris * apply to all code found in this distribution, be it the RC4, RSA, 1255714Skris * lhash, DES, etc., code; not just the SSL code. The SSL documentation 1355714Skris * included with this distribution is covered by the same copyright terms 1455714Skris * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15280304Sjkim * 1655714Skris * Copyright remains Eric Young's, and as such any Copyright notices in 1755714Skris * the code are not to be removed. 1855714Skris * If this package is used in a product, Eric Young should be given attribution 1955714Skris * as the author of the parts of the library used. 2055714Skris * This can be in the form of a textual message at program startup or 2155714Skris * in documentation (online or textual) provided with the package. 22280304Sjkim * 2355714Skris * Redistribution and use in source and binary forms, with or without 2455714Skris * modification, are permitted provided that the following conditions 2555714Skris * are met: 2655714Skris * 1. Redistributions of source code must retain the copyright 2755714Skris * notice, this list of conditions and the following disclaimer. 2855714Skris * 2. Redistributions in binary form must reproduce the above copyright 2955714Skris * notice, this list of conditions and the following disclaimer in the 3055714Skris * documentation and/or other materials provided with the distribution. 3155714Skris * 3. All advertising materials mentioning features or use of this software 3255714Skris * must display the following acknowledgement: 3355714Skris * "This product includes cryptographic software written by 3455714Skris * Eric Young (eay@cryptsoft.com)" 3555714Skris * The word 'cryptographic' can be left out if the rouines from the library 3655714Skris * being used are not cryptographic related :-). 37280304Sjkim * 4. If you include any Windows specific code (or a derivative thereof) from 3855714Skris * the apps directory (application code) you must include an acknowledgement: 3955714Skris * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40280304Sjkim * 4155714Skris * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 4255714Skris * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 4355714Skris * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 4455714Skris * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 4555714Skris * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 4655714Skris * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 4755714Skris * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 4855714Skris * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 4955714Skris * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 5055714Skris * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 5155714Skris * SUCH DAMAGE. 52280304Sjkim * 5355714Skris * The licence and distribution terms for any publically available version or 5455714Skris * derivative of this code cannot be changed. i.e. this code cannot simply be 5555714Skris * copied and put under another distribution licence 5655714Skris * [including the GNU Public Licence.] 5755714Skris */ 5855714Skris 59280304Sjkim/* 60280304Sjkim * NB: These functions have been upgraded - the previous prototypes are in 61280304Sjkim * dh_depr.c as wrappers to these ones. - Geoff 62160814Ssimon */ 63160814Ssimon 6455714Skris#include <stdio.h> 6555714Skris#include "cryptlib.h" 6655714Skris#include <openssl/bn.h> 6755714Skris#include <openssl/dh.h> 6855714Skris 69238405Sjkim#ifdef OPENSSL_FIPS 70280304Sjkim# include <openssl/fips.h> 71238405Sjkim#endif 72194206Ssimon 73280304Sjkimstatic int dh_builtin_genparams(DH *ret, int prime_len, int generator, 74280304Sjkim BN_GENCB *cb); 75160814Ssimon 76280304Sjkimint DH_generate_parameters_ex(DH *ret, int prime_len, int generator, 77280304Sjkim BN_GENCB *cb) 78280304Sjkim{ 79238405Sjkim#ifdef OPENSSL_FIPS 80280304Sjkim if (FIPS_mode() && !(ret->meth->flags & DH_FLAG_FIPS_METHOD) 81280304Sjkim && !(ret->flags & DH_FLAG_NON_FIPS_ALLOW)) { 82280304Sjkim DHerr(DH_F_DH_GENERATE_PARAMETERS_EX, DH_R_NON_FIPS_METHOD); 83280304Sjkim return 0; 84280304Sjkim } 85238405Sjkim#endif 86280304Sjkim if (ret->meth->generate_params) 87280304Sjkim return ret->meth->generate_params(ret, prime_len, generator, cb); 88238405Sjkim#ifdef OPENSSL_FIPS 89280304Sjkim if (FIPS_mode()) 90280304Sjkim return FIPS_dh_generate_parameters_ex(ret, prime_len, generator, cb); 91238405Sjkim#endif 92280304Sjkim return dh_builtin_genparams(ret, prime_len, generator, cb); 93280304Sjkim} 94160814Ssimon 95280304Sjkim/*- 96280304Sjkim * We generate DH parameters as follows 9755714Skris * find a prime q which is prime_len/2 bits long. 9855714Skris * p=(2*q)+1 or (p-1)/2 = q 9955714Skris * For this case, g is a generator if 10055714Skris * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. 10155714Skris * Since the factors of p-1 are q and 2, we just need to check 10255714Skris * g^2 mod p != 1 and g^q mod p != 1. 10355714Skris * 10455714Skris * Having said all that, 10555714Skris * there is another special case method for the generators 2, 3 and 5. 10655714Skris * for 2, p mod 24 == 11 10759191Skris * for 3, p mod 12 == 5 <<<<< does not work for safe primes. 10855714Skris * for 5, p mod 10 == 3 or 7 10955714Skris * 11055714Skris * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the 11155714Skris * special generators and for answering some of my questions. 11255714Skris * 11355714Skris * I've implemented the second simple method :-). 11459191Skris * Since DH should be using a safe prime (both p and q are prime), 11555714Skris * this generator function can take a very very long time to run. 11655714Skris */ 117280304Sjkim/* 118280304Sjkim * Actually there is no reason to insist that 'generator' be a generator. 119100928Snectar * It's just as OK (and in some sense better) to use a generator of the 120100928Snectar * order-q subgroup. 121100928Snectar */ 122280304Sjkimstatic int dh_builtin_genparams(DH *ret, int prime_len, int generator, 123280304Sjkim BN_GENCB *cb) 124280304Sjkim{ 125280304Sjkim BIGNUM *t1, *t2; 126280304Sjkim int g, ok = -1; 127280304Sjkim BN_CTX *ctx = NULL; 12855714Skris 129280304Sjkim ctx = BN_CTX_new(); 130280304Sjkim if (ctx == NULL) 131280304Sjkim goto err; 132280304Sjkim BN_CTX_start(ctx); 133280304Sjkim t1 = BN_CTX_get(ctx); 134280304Sjkim t2 = BN_CTX_get(ctx); 135280304Sjkim if (t1 == NULL || t2 == NULL) 136280304Sjkim goto err; 137160814Ssimon 138280304Sjkim /* Make sure 'ret' has the necessary elements */ 139280304Sjkim if (!ret->p && ((ret->p = BN_new()) == NULL)) 140280304Sjkim goto err; 141280304Sjkim if (!ret->g && ((ret->g = BN_new()) == NULL)) 142280304Sjkim goto err; 143280304Sjkim 144280304Sjkim if (generator <= 1) { 145280304Sjkim DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_BAD_GENERATOR); 146280304Sjkim goto err; 147280304Sjkim } 148280304Sjkim if (generator == DH_GENERATOR_2) { 149280304Sjkim if (!BN_set_word(t1, 24)) 150280304Sjkim goto err; 151280304Sjkim if (!BN_set_word(t2, 11)) 152280304Sjkim goto err; 153280304Sjkim g = 2; 154280304Sjkim } 155280304Sjkim#if 0 /* does not work for safe primes */ 156280304Sjkim else if (generator == DH_GENERATOR_3) { 157280304Sjkim if (!BN_set_word(t1, 12)) 158280304Sjkim goto err; 159280304Sjkim if (!BN_set_word(t2, 5)) 160280304Sjkim goto err; 161280304Sjkim g = 3; 162280304Sjkim } 16355714Skris#endif 164280304Sjkim else if (generator == DH_GENERATOR_5) { 165280304Sjkim if (!BN_set_word(t1, 10)) 166280304Sjkim goto err; 167280304Sjkim if (!BN_set_word(t2, 3)) 168280304Sjkim goto err; 169280304Sjkim /* 170280304Sjkim * BN_set_word(t3,7); just have to miss out on these ones :-( 171280304Sjkim */ 172280304Sjkim g = 5; 173280304Sjkim } else { 174280304Sjkim /* 175280304Sjkim * in the general case, don't worry if 'generator' is a generator or 176280304Sjkim * not: since we are using safe primes, it will generate either an 177280304Sjkim * order-q or an order-2q group, which both is OK 178280304Sjkim */ 179280304Sjkim if (!BN_set_word(t1, 2)) 180280304Sjkim goto err; 181280304Sjkim if (!BN_set_word(t2, 1)) 182280304Sjkim goto err; 183280304Sjkim g = generator; 184280304Sjkim } 18555714Skris 186280304Sjkim if (!BN_generate_prime_ex(ret->p, prime_len, 1, t1, t2, cb)) 187280304Sjkim goto err; 188280304Sjkim if (!BN_GENCB_call(cb, 3, 0)) 189280304Sjkim goto err; 190280304Sjkim if (!BN_set_word(ret->g, g)) 191280304Sjkim goto err; 192280304Sjkim ok = 1; 193280304Sjkim err: 194280304Sjkim if (ok == -1) { 195280304Sjkim DHerr(DH_F_DH_BUILTIN_GENPARAMS, ERR_R_BN_LIB); 196280304Sjkim ok = 0; 197280304Sjkim } 198280304Sjkim 199280304Sjkim if (ctx != NULL) { 200280304Sjkim BN_CTX_end(ctx); 201280304Sjkim BN_CTX_free(ctx); 202280304Sjkim } 203280304Sjkim return ok; 204280304Sjkim} 205