1 /* $OpenBSD: dh_key.c,v 1.36 2018/11/12 17:39:17 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 67 static int generate_key(DH *dh); 68 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 69 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, 70 const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 71 static int dh_init(DH *dh); 72 static int dh_finish(DH *dh); 73 74 int 75 DH_generate_key(DH *dh) 76 { 77 return dh->meth->generate_key(dh); 78 } 79 80 int 81 DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 82 { 83 return dh->meth->compute_key(key, pub_key, dh); 84 } 85 86 static DH_METHOD dh_ossl = { 87 .name = "OpenSSL DH Method", 88 .generate_key = generate_key, 89 .compute_key = compute_key, 90 .bn_mod_exp = dh_bn_mod_exp, 91 .init = dh_init, 92 .finish = dh_finish, 93 }; 94 95 const DH_METHOD * 96 DH_OpenSSL(void) 97 { 98 return &dh_ossl; 99 } 100 101 static int 102 generate_key(DH *dh) 103 { 104 int ok = 0; 105 unsigned l; 106 BN_CTX *ctx; 107 BN_MONT_CTX *mont = NULL; 108 BIGNUM *pub_key = NULL, *priv_key = NULL, *two = NULL; 109 110 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 111 DHerror(DH_R_MODULUS_TOO_LARGE); 112 return 0; 113 } 114 115 ctx = BN_CTX_new(); 116 if (ctx == NULL) 117 goto err; 118 119 if ((priv_key = dh->priv_key) == NULL) { 120 if ((priv_key = BN_new()) == NULL) 121 goto err; 122 } 123 124 if ((pub_key = dh->pub_key) == NULL) { 125 if ((pub_key = BN_new()) == NULL) 126 goto err; 127 } 128 129 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 130 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 131 CRYPTO_LOCK_DH, dh->p, ctx); 132 if (!mont) 133 goto err; 134 } 135 136 if (dh->priv_key == NULL) { 137 if (dh->q) { 138 if ((two = BN_new()) == NULL) 139 goto err; 140 if (!BN_add(two, BN_value_one(), BN_value_one())) 141 goto err; 142 if (!bn_rand_interval(priv_key, two, dh->q)) 143 goto err; 144 } else { 145 /* secret exponent length */ 146 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 147 if (!BN_rand(priv_key, l, 0, 0)) 148 goto err; 149 } 150 } 151 152 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key, dh->p, ctx, 153 mont)) 154 goto err; 155 156 dh->pub_key = pub_key; 157 dh->priv_key = priv_key; 158 ok = 1; 159 err: 160 if (ok != 1) 161 DHerror(ERR_R_BN_LIB); 162 163 if (dh->pub_key == NULL) 164 BN_free(pub_key); 165 if (dh->priv_key == NULL) 166 BN_free(priv_key); 167 BN_CTX_free(ctx); 168 BN_free(two); 169 return ok; 170 } 171 172 static int 173 compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 174 { 175 BN_CTX *ctx = NULL; 176 BN_MONT_CTX *mont = NULL; 177 BIGNUM *tmp; 178 int ret = -1; 179 int check_result; 180 181 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 182 DHerror(DH_R_MODULUS_TOO_LARGE); 183 goto err; 184 } 185 186 ctx = BN_CTX_new(); 187 if (ctx == NULL) 188 goto err; 189 BN_CTX_start(ctx); 190 if ((tmp = BN_CTX_get(ctx)) == NULL) 191 goto err; 192 193 if (dh->priv_key == NULL) { 194 DHerror(DH_R_NO_PRIVATE_VALUE); 195 goto err; 196 } 197 198 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 199 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 200 CRYPTO_LOCK_DH, dh->p, ctx); 201 202 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 203 204 if (!mont) 205 goto err; 206 } 207 208 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 209 DHerror(DH_R_INVALID_PUBKEY); 210 goto err; 211 } 212 213 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, 214 mont)) { 215 DHerror(ERR_R_BN_LIB); 216 goto err; 217 } 218 219 ret = BN_bn2bin(tmp, key); 220 err: 221 if (ctx != NULL) { 222 BN_CTX_end(ctx); 223 BN_CTX_free(ctx); 224 } 225 return ret; 226 } 227 228 static int 229 dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 230 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 231 { 232 return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx); 233 } 234 235 static int 236 dh_init(DH *dh) 237 { 238 dh->flags |= DH_FLAG_CACHE_MONT_P; 239 return 1; 240 } 241 242 static int 243 dh_finish(DH *dh) 244 { 245 BN_MONT_CTX_free(dh->method_mont_p); 246 return 1; 247 } 248