1 /* $OpenBSD: dh_key.c,v 1.18 2014/06/12 15:49:28 deraadt 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 #include "cryptlib.h" 61 #include <openssl/bn.h> 62 #include <openssl/rand.h> 63 #include <openssl/dh.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, 68 const BIGNUM *a, const BIGNUM *p, 69 const BIGNUM *m, BN_CTX *ctx, 70 BN_MONT_CTX *m_ctx); 71 static int dh_init(DH *dh); 72 static int dh_finish(DH *dh); 73 74 int DH_generate_key(DH *dh) 75 { 76 return dh->meth->generate_key(dh); 77 } 78 79 int 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 *DH_OpenSSL(void) 94 { 95 return &dh_ossl; 96 } 97 98 static int generate_key(DH *dh) 99 { 100 int ok=0; 101 int generate_new_key=0; 102 unsigned l; 103 BN_CTX *ctx; 104 BN_MONT_CTX *mont=NULL; 105 BIGNUM *pub_key=NULL,*priv_key=NULL; 106 107 ctx = BN_CTX_new(); 108 if (ctx == NULL) goto err; 109 110 if (dh->priv_key == NULL) 111 { 112 priv_key=BN_new(); 113 if (priv_key == NULL) goto err; 114 generate_new_key=1; 115 } 116 else 117 priv_key=dh->priv_key; 118 119 if (dh->pub_key == NULL) 120 { 121 pub_key=BN_new(); 122 if (pub_key == NULL) goto err; 123 } 124 else 125 pub_key=dh->pub_key; 126 127 128 if (dh->flags & DH_FLAG_CACHE_MONT_P) 129 { 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 { 138 if (dh->q) 139 { 140 do 141 { 142 if (!BN_rand_range(priv_key, dh->q)) 143 goto err; 144 } 145 while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 146 } 147 else 148 { 149 /* secret exponent length */ 150 l = dh->length ? dh->length : BN_num_bits(dh->p)-1; 151 if (!BN_rand(priv_key, l, 0, 0)) goto err; 152 } 153 } 154 155 { 156 BIGNUM local_prk; 157 BIGNUM *prk; 158 159 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) 160 { 161 BN_init(&local_prk); 162 prk = &local_prk; 163 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); 164 } 165 else 166 prk = priv_key; 167 168 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) goto err; 169 } 170 171 dh->pub_key=pub_key; 172 dh->priv_key=priv_key; 173 ok=1; 174 err: 175 if (ok != 1) 176 DHerr(DH_F_GENERATE_KEY,ERR_R_BN_LIB); 177 178 if ((pub_key != NULL) && (dh->pub_key == NULL)) BN_free(pub_key); 179 if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key); 180 BN_CTX_free(ctx); 181 return(ok); 182 } 183 184 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 185 { 186 BN_CTX *ctx=NULL; 187 BN_MONT_CTX *mont=NULL; 188 BIGNUM *tmp; 189 int ret= -1; 190 int check_result; 191 192 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) 193 { 194 DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE); 195 goto err; 196 } 197 198 ctx = BN_CTX_new(); 199 if (ctx == NULL) goto err; 200 BN_CTX_start(ctx); 201 tmp = BN_CTX_get(ctx); 202 203 if (dh->priv_key == NULL) 204 { 205 DHerr(DH_F_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE); 206 goto err; 207 } 208 209 if (dh->flags & DH_FLAG_CACHE_MONT_P) 210 { 211 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 212 CRYPTO_LOCK_DH, dh->p, ctx); 213 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) 214 { 215 /* XXX */ 216 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 217 } 218 if (!mont) 219 goto err; 220 } 221 222 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) 223 { 224 DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY); 225 goto err; 226 } 227 228 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont)) 229 { 230 DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB); 231 goto err; 232 } 233 234 ret=BN_bn2bin(tmp,key); 235 err: 236 if (ctx != NULL) 237 { 238 BN_CTX_end(ctx); 239 BN_CTX_free(ctx); 240 } 241 return(ret); 242 } 243 244 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 245 const BIGNUM *a, const BIGNUM *p, 246 const BIGNUM *m, BN_CTX *ctx, 247 BN_MONT_CTX *m_ctx) 248 { 249 /* If a is only one word long and constant time is false, use the faster 250 * exponenentiation function. 251 */ 252 if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) 253 { 254 BN_ULONG A = a->d[0]; 255 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx); 256 } 257 else 258 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx); 259 } 260 261 262 static int dh_init(DH *dh) 263 { 264 dh->flags |= DH_FLAG_CACHE_MONT_P; 265 return(1); 266 } 267 268 static int dh_finish(DH *dh) 269 { 270 if(dh->method_mont_p) 271 BN_MONT_CTX_free(dh->method_mont_p); 272 return(1); 273 } 274