1/* $OpenBSD: dh_key.c,v 1.42 2024/05/09 20:43:36 tb Exp $ */ 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59#include <stdio.h> 60 61#include <openssl/bn.h> 62#include <openssl/dh.h> 63#include <openssl/err.h> 64 65#include "bn_local.h" 66#include "dh_local.h" 67 68static int 69generate_key(DH *dh) 70{ 71 int ok = 0; 72 unsigned l; 73 BN_CTX *ctx; 74 BN_MONT_CTX *mont = NULL; 75 BIGNUM *pub_key = NULL, *priv_key = NULL; 76 77 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 78 DHerror(DH_R_MODULUS_TOO_LARGE); 79 return 0; 80 } 81 82 ctx = BN_CTX_new(); 83 if (ctx == NULL) 84 goto err; 85 86 if ((priv_key = dh->priv_key) == NULL) { 87 if ((priv_key = BN_new()) == NULL) 88 goto err; 89 } 90 91 if ((pub_key = dh->pub_key) == NULL) { 92 if ((pub_key = BN_new()) == NULL) 93 goto err; 94 } 95 96 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 97 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 98 CRYPTO_LOCK_DH, dh->p, ctx); 99 if (!mont) 100 goto err; 101 } 102 103 if (dh->priv_key == NULL) { 104 if (dh->q) { 105 if (!bn_rand_interval(priv_key, 2, dh->q)) 106 goto err; 107 } else { 108 /* secret exponent length */ 109 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 110 if (!BN_rand(priv_key, l, 0, 0)) 111 goto err; 112 } 113 } 114 115 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key, dh->p, ctx, 116 mont)) 117 goto err; 118 119 dh->pub_key = pub_key; 120 dh->priv_key = priv_key; 121 ok = 1; 122 err: 123 if (ok != 1) 124 DHerror(ERR_R_BN_LIB); 125 126 if (dh->pub_key == NULL) 127 BN_free(pub_key); 128 if (dh->priv_key == NULL) 129 BN_free(priv_key); 130 BN_CTX_free(ctx); 131 132 return ok; 133} 134 135static int 136compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 137{ 138 BN_CTX *ctx = NULL; 139 BN_MONT_CTX *mont = NULL; 140 BIGNUM *tmp; 141 int ret = -1; 142 int check_result; 143 144 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 145 DHerror(DH_R_MODULUS_TOO_LARGE); 146 goto err; 147 } 148 149 ctx = BN_CTX_new(); 150 if (ctx == NULL) 151 goto err; 152 BN_CTX_start(ctx); 153 if ((tmp = BN_CTX_get(ctx)) == NULL) 154 goto err; 155 156 if (dh->priv_key == NULL) { 157 DHerror(DH_R_NO_PRIVATE_VALUE); 158 goto err; 159 } 160 161 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 162 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 163 CRYPTO_LOCK_DH, dh->p, ctx); 164 165 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 166 167 if (!mont) 168 goto err; 169 } 170 171 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 172 DHerror(DH_R_INVALID_PUBKEY); 173 goto err; 174 } 175 176 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, 177 mont)) { 178 DHerror(ERR_R_BN_LIB); 179 goto err; 180 } 181 182 ret = BN_bn2bin(tmp, key); 183 err: 184 if (ctx != NULL) { 185 BN_CTX_end(ctx); 186 BN_CTX_free(ctx); 187 } 188 return ret; 189} 190 191static int 192dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 193 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 194{ 195 return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx); 196} 197 198static int 199dh_init(DH *dh) 200{ 201 dh->flags |= DH_FLAG_CACHE_MONT_P; 202 return 1; 203} 204 205static int 206dh_finish(DH *dh) 207{ 208 BN_MONT_CTX_free(dh->method_mont_p); 209 return 1; 210} 211 212int 213DH_generate_key(DH *dh) 214{ 215 return dh->meth->generate_key(dh); 216} 217LCRYPTO_ALIAS(DH_generate_key); 218 219int 220DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 221{ 222 return dh->meth->compute_key(key, pub_key, dh); 223} 224LCRYPTO_ALIAS(DH_compute_key); 225 226static const DH_METHOD dh_ossl = { 227 .name = "OpenSSL DH Method", 228 .generate_key = generate_key, 229 .compute_key = compute_key, 230 .bn_mod_exp = dh_bn_mod_exp, 231 .init = dh_init, 232 .finish = dh_finish, 233}; 234 235const DH_METHOD * 236DH_OpenSSL(void) 237{ 238 return &dh_ossl; 239} 240LCRYPTO_ALIAS(DH_OpenSSL); 241