Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | { |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 76 | return dh->meth->generate_key(dh); |
| 77 | } |
| 78 | |
| 79 | int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) |
| 80 | { |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | { |
Alexandre Savard | 7541067 | 2012-08-08 09:50:01 -0400 | [diff] [blame] | 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; |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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_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_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 | } |