lib/hcrypto/dh-imath.c

   1 /*
   2  * Copyright (c) 2006 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #ifdef HAVE_CONFIG_H
  35 #include <config.h>
  36 #endif
  37
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <dh.h>
  41
  42 #include <roken.h>
  43
  44 #include "imath/imath.h"
  45
  46 static void
  47 BN2mpz(mpz_t *s, const BIGNUM *bn)
  48 {
  49     size_t len;
  50     void *p;
  51
  52     len = BN_num_bytes(bn);
  53     p = malloc(len);
  54     BN_bn2bin(bn, p);
  55     mp_int_read_unsigned(s, p, len);
  56     free(p);
  57 }
  58
  59
  60 static BIGNUM *
  61 mpz2BN(mpz_t *s)
  62 {
  63     size_t size;
  64     BIGNUM *bn;
  65     void *p;
  66
  67     size = mp_int_unsigned_len(s);
  68     p = malloc(size);
  69     if (p == NULL && size != 0)
  70         return NULL;
  71     mp_int_to_unsigned(s, p, size);
  72
  73     bn = BN_bin2bn(p, size, NULL);
  74     free(p);
  75     return bn;
  76 }
  77
  78 /*
  79  *
  80  */
  81
  82 #define DH_NUM_TRIES 10
  83
  84 static int
  85 dh_generate_key(DH *dh)
  86 {
  87     mpz_t pub, priv_key, g, p;
  88     int have_private_key = (dh->priv_key != NULL);
  89     int codes, times = 0;
  90     mp_result res;
  91
  92     if (dh->p == NULL || dh->g == NULL)
  93         return 0;
  94
  95     while (times++ < DH_NUM_TRIES) {
  96         if (!have_private_key) {
  97             size_t bits = BN_num_bits(dh->p);
  98
  99             if (dh->priv_key)
 100                 BN_free(dh->priv_key);
 101
 102             dh->priv_key = BN_new();
 103             if (dh->priv_key == NULL)
 104                 return 0;
 105             if (!BN_rand(dh->priv_key, bits - 1, 0, 0)) {
 106                 BN_clear_free(dh->priv_key);
 107                 dh->priv_key = NULL;
 108                 return 0;
 109             }
 110         }
 111         if (dh->pub_key)
 112             BN_free(dh->pub_key);
 113
 114         mp_int_init(&pub);
 115         mp_int_init(&priv_key);
 116         mp_int_init(&g);
 117         mp_int_init(&p);
 118
 119         BN2mpz(&priv_key, dh->priv_key);
 120         BN2mpz(&g, dh->g);
 121         BN2mpz(&p, dh->p);
 122
 123         res = mp_int_exptmod(&g, &priv_key, &p, &pub);
 124
 125         mp_int_clear(&priv_key);
 126         mp_int_clear(&g);
 127         mp_int_clear(&p);
 128         if (res != MP_OK)
 129             continue;
 130
 131         dh->pub_key = mpz2BN(&pub);
 132         mp_int_clear(&pub);
 133         if (dh->pub_key == NULL)
 134             return 0;
 135
 136         if (DH_check_pubkey(dh, dh->pub_key, &codes) && codes == 0)
 137             break;
 138         if (have_private_key)
 139             return 0;
 140     }
 141
 142     if (times >= DH_NUM_TRIES) {
 143         if (!have_private_key && dh->priv_key) {
 144             BN_free(dh->priv_key);
 145             dh->priv_key = NULL;
 146         }
 147         if (dh->pub_key) {
 148             BN_free(dh->pub_key);
 149             dh->pub_key = NULL;
 150         }
 151         return 0;
 152     }
 153
 154     return 1;
 155 }
 156
 157 static int
 158 dh_compute_key(unsigned char *shared, const BIGNUM * pub, DH *dh)
 159 {
 160     mpz_t s, priv_key, p, peer_pub;
 161     size_t size = 0;
 162     mp_result res;
 163
 164     if (dh->pub_key == NULL || dh->g == NULL || dh->priv_key == NULL)
 165         return -1;
 166
 167     mp_int_init(&p);
 168     BN2mpz(&p, dh->p);
 169
 170     mp_int_init(&peer_pub);
 171     BN2mpz(&peer_pub, pub);
 172
 173     /* check if peers pubkey is reasonable */
 174     if (MP_SIGN(&peer_pub) == MP_NEG
 175         || mp_int_compare(&peer_pub, &p) >= 0
 176         || mp_int_compare_value(&peer_pub, 1) <= 0)
 177     {
 178         mp_int_clear(&p);
 179         mp_int_clear(&peer_pub);
 180         return -1;
 181     }
 182
 183     mp_int_init(&priv_key);
 184     BN2mpz(&priv_key, dh->priv_key);
 185
 186     mp_int_init(&s);
 187
 188     mp_int_exptmod(&peer_pub, &priv_key, &p, &s);
 189
 190     mp_int_clear(&p);
 191     mp_int_clear(&peer_pub);
 192     mp_int_clear(&priv_key);
 193
 194     size = mp_int_unsigned_len(&s);
 195     res = mp_int_to_unsigned(&s, shared, size);
 196     mp_int_clear(&s);
 197
 198     return (res == MP_OK) ? size : -1;
 199 }
 200
 201 static int
 202 dh_generate_params(DH *dh, int a, int b, BN_GENCB *callback)
 203 {
 204     /* groups should already be known, we don't care about this */
 205     return 0;
 206 }
 207
 208 static int
 209 dh_init(DH *dh)
 210 {
 211     return 1;
 212 }
 213
 214 static int
 215 dh_finish(DH *dh)
 216 {
 217     return 1;
 218 }
 219
 220
 221 /*
 222  *
 223  */
 224
 225 const DH_METHOD _hc_dh_imath_method = {
 226     "hcrypto imath DH",
 227     dh_generate_key,
 228     dh_compute_key,
 229     NULL,
 230     dh_init,
 231     dh_finish,
 232     0,
 233     NULL,
 234     dh_generate_params
 235 };
 236
 237 /**
 238  * DH implementation using libimath.
 239  *
 240  * @return the DH_METHOD for the DH implementation using libimath.
 241  *
 242  * @ingroup hcrypto_dh
 243  */
 244
 245 const DH_METHOD *
 246 DH_imath_method(void)
 247 {
 248     return &_hc_dh_imath_method;
 249 }