1 /* $OpenBSD: dh_key.c,v 1.37 2022/01/07 09:27:13 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_lcl.h" 66 #include "dh_local.h" 67 68 static int generate_key(DH *dh); 69 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 70 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, 71 const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 72 static int dh_init(DH *dh); 73 static int dh_finish(DH *dh); 74 75 int 76 DH_generate_key(DH *dh) 77 { 78 return dh->meth->generate_key(dh); 79 } 80 81 int 82 DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 83 { 84 return dh->meth->compute_key(key, pub_key, dh); 85 } 86 87 static DH_METHOD dh_ossl = { 88 .name = "OpenSSL DH Method", 89 .generate_key = generate_key, 90 .compute_key = compute_key, 91 .bn_mod_exp = dh_bn_mod_exp, 92 .init = dh_init, 93 .finish = dh_finish, 94 }; 95 96 const DH_METHOD * 97 DH_OpenSSL(void) 98 { 99 return &dh_ossl; 100 } 101 102 static int 103 generate_key(DH *dh) 104 { 105 int ok = 0; 106 unsigned l; 107 BN_CTX *ctx; 108 BN_MONT_CTX *mont = NULL; 109 BIGNUM *pub_key = NULL, *priv_key = NULL, *two = NULL; 110 111 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 112 DHerror(DH_R_MODULUS_TOO_LARGE); 113 return 0; 114 } 115 116 ctx = BN_CTX_new(); 117 if (ctx == NULL) 118 goto err; 119 120 if ((priv_key = dh->priv_key) == NULL) { 121 if ((priv_key = BN_new()) == NULL) 122 goto err; 123 } 124 125 if ((pub_key = dh->pub_key) == NULL) { 126 if ((pub_key = BN_new()) == NULL) 127 goto err; 128 } 129 130 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 131 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 132 CRYPTO_LOCK_DH, dh->p, ctx); 133 if (!mont) 134 goto err; 135 } 136 137 if (dh->priv_key == NULL) { 138 if (dh->q) { 139 if ((two = BN_new()) == NULL) 140 goto err; 141 if (!BN_add(two, BN_value_one(), BN_value_one())) 142 goto err; 143 if (!bn_rand_interval(priv_key, two, dh->q)) 144 goto err; 145 } else { 146 /* secret exponent length */ 147 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 148 if (!BN_rand(priv_key, l, 0, 0)) 149 goto err; 150 } 151 } 152 153 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key, dh->p, ctx, 154 mont)) 155 goto err; 156 157 dh->pub_key = pub_key; 158 dh->priv_key = priv_key; 159 ok = 1; 160 err: 161 if (ok != 1) 162 DHerror(ERR_R_BN_LIB); 163 164 if (dh->pub_key == NULL) 165 BN_free(pub_key); 166 if (dh->priv_key == NULL) 167 BN_free(priv_key); 168 BN_CTX_free(ctx); 169 BN_free(two); 170 return ok; 171 } 172 173 static int 174 compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 175 { 176 BN_CTX *ctx = NULL; 177 BN_MONT_CTX *mont = NULL; 178 BIGNUM *tmp; 179 int ret = -1; 180 int check_result; 181 182 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 183 DHerror(DH_R_MODULUS_TOO_LARGE); 184 goto err; 185 } 186 187 ctx = BN_CTX_new(); 188 if (ctx == NULL) 189 goto err; 190 BN_CTX_start(ctx); 191 if ((tmp = BN_CTX_get(ctx)) == NULL) 192 goto err; 193 194 if (dh->priv_key == NULL) { 195 DHerror(DH_R_NO_PRIVATE_VALUE); 196 goto err; 197 } 198 199 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 200 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 201 CRYPTO_LOCK_DH, dh->p, ctx); 202 203 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 204 205 if (!mont) 206 goto err; 207 } 208 209 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 210 DHerror(DH_R_INVALID_PUBKEY); 211 goto err; 212 } 213 214 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, 215 mont)) { 216 DHerror(ERR_R_BN_LIB); 217 goto err; 218 } 219 220 ret = BN_bn2bin(tmp, key); 221 err: 222 if (ctx != NULL) { 223 BN_CTX_end(ctx); 224 BN_CTX_free(ctx); 225 } 226 return ret; 227 } 228 229 static int 230 dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 231 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 232 { 233 return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx); 234 } 235 236 static int 237 dh_init(DH *dh) 238 { 239 dh->flags |= DH_FLAG_CACHE_MONT_P; 240 return 1; 241 } 242 243 static int 244 dh_finish(DH *dh) 245 { 246 BN_MONT_CTX_free(dh->method_mont_p); 247 return 1; 248 } 249