1 /* $OpenBSD: dh_key.c,v 1.24 2016/06/30 02:02:06 bcook 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 static int generate_key(DH *dh); 66 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 67 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, 68 const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 69 static int dh_init(DH *dh); 70 static int dh_finish(DH *dh); 71 72 int 73 DH_generate_key(DH *dh) 74 { 75 return dh->meth->generate_key(dh); 76 } 77 78 int 79 DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 80 { 81 return dh->meth->compute_key(key, pub_key, dh); 82 } 83 84 static DH_METHOD dh_ossl = { 85 .name = "OpenSSL DH Method", 86 .generate_key = generate_key, 87 .compute_key = compute_key, 88 .bn_mod_exp = dh_bn_mod_exp, 89 .init = dh_init, 90 .finish = dh_finish, 91 }; 92 93 const DH_METHOD * 94 DH_OpenSSL(void) 95 { 96 return &dh_ossl; 97 } 98 99 static int 100 generate_key(DH *dh) 101 { 102 int ok = 0; 103 int generate_new_key = 0; 104 unsigned l; 105 BN_CTX *ctx; 106 BN_MONT_CTX *mont = NULL; 107 BIGNUM *pub_key = NULL, *priv_key = NULL; 108 109 ctx = BN_CTX_new(); 110 if (ctx == NULL) 111 goto err; 112 113 if (dh->priv_key == NULL) { 114 priv_key = BN_new(); 115 if (priv_key == NULL) 116 goto err; 117 generate_new_key = 1; 118 } else 119 priv_key = dh->priv_key; 120 121 if (dh->pub_key == NULL) { 122 pub_key = BN_new(); 123 if (pub_key == NULL) 124 goto err; 125 } else 126 pub_key = dh->pub_key; 127 128 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 129 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 130 CRYPTO_LOCK_DH, dh->p, ctx); 131 if (!mont) 132 goto err; 133 } 134 135 if (generate_new_key) { 136 if (dh->q) { 137 do { 138 if (!BN_rand_range(priv_key, dh->q)) 139 goto err; 140 } while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 141 } else { 142 /* secret exponent length */ 143 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 144 if (!BN_rand(priv_key, l, 0, 0)) 145 goto err; 146 } 147 } 148 149 { 150 BIGNUM prk; 151 152 BN_init(&prk); 153 BN_with_flags(&prk, priv_key, BN_FLG_CONSTTIME); 154 155 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, &prk, dh->p, ctx, 156 mont)) { 157 goto err; 158 } 159 } 160 161 dh->pub_key = pub_key; 162 dh->priv_key = priv_key; 163 ok = 1; 164 err: 165 if (ok != 1) 166 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); 167 168 if (pub_key != NULL && dh->pub_key == NULL) 169 BN_free(pub_key); 170 if (priv_key != NULL && dh->priv_key == NULL) 171 BN_free(priv_key); 172 BN_CTX_free(ctx); 173 return ok; 174 } 175 176 static int 177 compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 178 { 179 BN_CTX *ctx = NULL; 180 BN_MONT_CTX *mont = NULL; 181 BIGNUM *tmp; 182 int ret = -1; 183 int check_result; 184 185 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 186 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); 187 goto err; 188 } 189 190 ctx = BN_CTX_new(); 191 if (ctx == NULL) 192 goto err; 193 BN_CTX_start(ctx); 194 if ((tmp = BN_CTX_get(ctx)) == NULL) 195 goto err; 196 197 if (dh->priv_key == NULL) { 198 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); 199 goto err; 200 } 201 202 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 203 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 204 CRYPTO_LOCK_DH, dh->p, ctx); 205 206 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 207 208 if (!mont) 209 goto err; 210 } 211 212 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 213 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); 214 goto err; 215 } 216 217 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, 218 mont)) { 219 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); 220 goto err; 221 } 222 223 ret = BN_bn2bin(tmp, key); 224 err: 225 if (ctx != NULL) { 226 BN_CTX_end(ctx); 227 BN_CTX_free(ctx); 228 } 229 return ret; 230 } 231 232 static int 233 dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 234 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 235 { 236 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 237 } 238 239 static int 240 dh_init(DH *dh) 241 { 242 dh->flags |= DH_FLAG_CACHE_MONT_P; 243 return 1; 244 } 245 246 static int 247 dh_finish(DH *dh) 248 { 249 BN_MONT_CTX_free(dh->method_mont_p); 250 return 1; 251 } 252