1 /* crypto/dh/dh_key.c */ 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 "OpenSSL DH Method", 86 generate_key, 87 compute_key, 88 dh_bn_mod_exp, 89 dh_init, 90 dh_finish, 91 0, 92 NULL, 93 NULL 94 }; 95 96 const DH_METHOD *DH_OpenSSL(void) 97 { 98 return &dh_ossl; 99 } 100 101 static int 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) goto err; 112 113 if (dh->priv_key == NULL) 114 { 115 priv_key=BN_new(); 116 if (priv_key == NULL) goto err; 117 generate_new_key=1; 118 } 119 else 120 priv_key=dh->priv_key; 121 122 if (dh->pub_key == NULL) 123 { 124 pub_key=BN_new(); 125 if (pub_key == NULL) goto err; 126 } 127 else 128 pub_key=dh->pub_key; 129 130 131 if (dh->flags & DH_FLAG_CACHE_MONT_P) 132 { 133 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 134 CRYPTO_LOCK_DH, dh->p, ctx); 135 if (!mont) 136 goto err; 137 } 138 139 if (generate_new_key) 140 { 141 l = dh->length ? dh->length : BN_num_bits(dh->p)-1; /* secret exponent length */ 142 if (!BN_rand(priv_key, l, 0, 0)) goto err; 143 } 144 145 { 146 BIGNUM local_prk; 147 BIGNUM *prk; 148 149 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) 150 { 151 BN_init(&local_prk); 152 prk = &local_prk; 153 BN_with_flags(prk, priv_key, BN_FLG_EXP_CONSTTIME); 154 } 155 else 156 prk = priv_key; 157 158 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) goto err; 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)) BN_free(pub_key); 169 if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key); 170 BN_CTX_free(ctx); 171 return(ok); 172 } 173 174 static int 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 { 184 DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE); 185 goto err; 186 } 187 188 ctx = BN_CTX_new(); 189 if (ctx == NULL) goto err; 190 BN_CTX_start(ctx); 191 tmp = BN_CTX_get(ctx); 192 193 if (dh->priv_key == NULL) 194 { 195 DHerr(DH_F_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE); 196 goto err; 197 } 198 199 if (dh->flags & DH_FLAG_CACHE_MONT_P) 200 { 201 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 202 CRYPTO_LOCK_DH, dh->p, ctx); 203 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) 204 { 205 /* XXX */ 206 BN_set_flags(dh->priv_key, BN_FLG_EXP_CONSTTIME); 207 } 208 if (!mont) 209 goto err; 210 } 211 212 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) 213 { 214 DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY); 215 goto err; 216 } 217 218 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont)) 219 { 220 DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB); 221 goto err; 222 } 223 224 ret=BN_bn2bin(tmp,key); 225 err: 226 if (ctx != NULL) 227 { 228 BN_CTX_end(ctx); 229 BN_CTX_free(ctx); 230 } 231 return(ret); 232 } 233 234 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 235 const BIGNUM *a, const BIGNUM *p, 236 const BIGNUM *m, BN_CTX *ctx, 237 BN_MONT_CTX *m_ctx) 238 { 239 /* If a is only one word long and constant time is false, use the faster 240 * exponenentiation function. 241 */ 242 if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) 243 { 244 BN_ULONG A = a->d[0]; 245 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx); 246 } 247 else 248 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx); 249 } 250 251 252 static int dh_init(DH *dh) 253 { 254 dh->flags |= DH_FLAG_CACHE_MONT_P; 255 return(1); 256 } 257 258 static int dh_finish(DH *dh) 259 { 260 if(dh->method_mont_p) 261 BN_MONT_CTX_free(dh->method_mont_p); 262 return(1); 263 } 264