1 /* $OpenBSD: dh_key.c,v 1.21 2014/07/12 16:03:37 miod 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 #include <openssl/rand.h> 65 66 static int generate_key(DH *dh); 67 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 68 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, 69 const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 70 static int dh_init(DH *dh); 71 static int dh_finish(DH *dh); 72 73 int 74 DH_generate_key(DH *dh) 75 { 76 return dh->meth->generate_key(dh); 77 } 78 79 int 80 DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 81 { 82 return dh->meth->compute_key(key, pub_key, dh); 83 } 84 85 static DH_METHOD dh_ossl = { 86 .name = "OpenSSL DH Method", 87 .generate_key = generate_key, 88 .compute_key = compute_key, 89 .bn_mod_exp = dh_bn_mod_exp, 90 .init = dh_init, 91 .finish = dh_finish, 92 }; 93 94 const DH_METHOD * 95 DH_OpenSSL(void) 96 { 97 return &dh_ossl; 98 } 99 100 static int 101 generate_key(DH *dh) 102 { 103 int ok = 0; 104 int generate_new_key = 0; 105 unsigned l; 106 BN_CTX *ctx; 107 BN_MONT_CTX *mont = NULL; 108 BIGNUM *pub_key = NULL, *priv_key = NULL; 109 110 ctx = BN_CTX_new(); 111 if (ctx == NULL) 112 goto err; 113 114 if (dh->priv_key == NULL) { 115 priv_key = BN_new(); 116 if (priv_key == NULL) 117 goto err; 118 generate_new_key = 1; 119 } else 120 priv_key = dh->priv_key; 121 122 if (dh->pub_key == NULL) { 123 pub_key = BN_new(); 124 if (pub_key == NULL) 125 goto err; 126 } else 127 pub_key = dh->pub_key; 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 (generate_new_key) { 137 if (dh->q) { 138 do { 139 if (!BN_rand_range(priv_key, dh->q)) 140 goto err; 141 } while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 142 } else { 143 /* secret exponent length */ 144 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 145 if (!BN_rand(priv_key, l, 0, 0)) 146 goto err; 147 } 148 } 149 150 { 151 BIGNUM local_prk; 152 BIGNUM *prk; 153 154 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 155 BN_init(&local_prk); 156 prk = &local_prk; 157 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); 158 } else 159 prk = priv_key; 160 161 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, 162 mont)) 163 goto err; 164 } 165 166 dh->pub_key = pub_key; 167 dh->priv_key = priv_key; 168 ok = 1; 169 err: 170 if (ok != 1) 171 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); 172 173 if (pub_key != NULL && dh->pub_key == NULL) 174 BN_free(pub_key); 175 if (priv_key != NULL && dh->priv_key == NULL) 176 BN_free(priv_key); 177 BN_CTX_free(ctx); 178 return ok; 179 } 180 181 static int 182 compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 183 { 184 BN_CTX *ctx = NULL; 185 BN_MONT_CTX *mont = NULL; 186 BIGNUM *tmp; 187 int ret = -1; 188 int check_result; 189 190 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 191 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); 192 goto err; 193 } 194 195 ctx = BN_CTX_new(); 196 if (ctx == NULL) 197 goto err; 198 BN_CTX_start(ctx); 199 tmp = BN_CTX_get(ctx); 200 201 if (dh->priv_key == NULL) { 202 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); 203 goto err; 204 } 205 206 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 207 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 208 CRYPTO_LOCK_DH, dh->p, ctx); 209 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 210 /* XXX */ 211 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 212 } 213 if (!mont) 214 goto err; 215 } 216 217 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 218 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); 219 goto err; 220 } 221 222 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, 223 mont)) { 224 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); 225 goto err; 226 } 227 228 ret = BN_bn2bin(tmp, key); 229 err: 230 if (ctx != NULL) { 231 BN_CTX_end(ctx); 232 BN_CTX_free(ctx); 233 } 234 return ret; 235 } 236 237 static int 238 dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 239 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 240 { 241 /* 242 * If a is only one word long and constant time is false, use the faster 243 * exponenentiation function. 244 */ 245 if (a->top == 1 && (dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0) { 246 BN_ULONG A = a->d[0]; 247 248 return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx); 249 } else 250 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 251 } 252 253 static int 254 dh_init(DH *dh) 255 { 256 dh->flags |= DH_FLAG_CACHE_MONT_P; 257 return 1; 258 } 259 260 static int 261 dh_finish(DH *dh) 262 { 263 BN_MONT_CTX_free(dh->method_mont_p); 264 return 1; 265 } 266