lib/hcrypto/dh-ltm.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 #include <roken.h>
  38
  39 #include <dh.h>
  40
  41 #include "tommath.h"
  42
  43 static void
  44 BN2mpz(mp_int *s, const BIGNUM *bn)
  45 {
  46     size_t len;
  47     void *p;
  48
  49     len = BN_num_bytes(bn);
  50     p = malloc(len);
  51     BN_bn2bin(bn, p);
  52     mp_read_unsigned_bin(s, p, len);
  53     free(p);
  54 }
  55
  56
  57 static BIGNUM *
  58 mpz2BN(mp_int *s)
  59 {
  60     size_t size;
  61     BIGNUM *bn;
  62     void *p;
  63
  64     size = mp_unsigned_bin_size(s);
  65     p = malloc(size);
  66     if (p == NULL && size != 0)
  67         return NULL;
  68     mp_to_unsigned_bin(s, p);
  69
  70     bn = BN_bin2bn(p, size, NULL);
  71     free(p);
  72     return bn;
  73 }
  74
  75 /*
  76  *
  77  */
  78
  79 #define DH_NUM_TRIES 10
  80
  81 static int
  82 ltm_dh_generate_key(DH *dh)
  83 {
  84     mp_int pub, priv_key, g, p;
  85     int have_private_key = (dh->priv_key != NULL);
  86     int codes, times = 0;
  87     int res;
  88
  89     if (dh->p == NULL || dh->g == NULL)
  90         return 0;
  91
  92     while (times++ < DH_NUM_TRIES) {
  93         if (!have_private_key) {
  94             size_t bits = BN_num_bits(dh->p);
  95
  96             if (dh->priv_key)
  97                 BN_free(dh->priv_key);
  98
  99             dh->priv_key = BN_new();
 100             if (dh->priv_key == NULL)
 101                 return 0;
 102             if (!BN_rand(dh->priv_key, bits - 1, 0, 0)) {
 103                 BN_clear_free(dh->priv_key);
 104                 dh->priv_key = NULL;
 105                 return 0;
 106             }
 107         }
 108         if (dh->pub_key) {
 109             BN_free(dh->pub_key);
 110             dh->pub_key = NULL;
 111         }
 112
 113         mp_init_multi(&pub, &priv_key, &g, &p, NULL);
 114
 115         BN2mpz(&priv_key, dh->priv_key);
 116         BN2mpz(&g, dh->g);
 117         BN2mpz(&p, dh->p);
 118
 119         res = mp_exptmod(&g, &priv_key, &p, &pub);
 120
 121         mp_clear_multi(&priv_key, &g, &p, NULL);
 122         if (res != 0)
 123             continue;
 124
 125         dh->pub_key = mpz2BN(&pub);
 126         mp_clear(&pub);
 127         if (dh->pub_key == NULL)
 128             return 0;
 129
 130         if (DH_check_pubkey(dh, dh->pub_key, &codes) && codes == 0)
 131             break;
 132         if (have_private_key)
 133             return 0;
 134     }
 135
 136     if (times >= DH_NUM_TRIES) {
 137         if (!have_private_key && dh->priv_key) {
 138             BN_free(dh->priv_key);
 139             dh->priv_key = NULL;
 140         }
 141         if (dh->pub_key) {
 142             BN_free(dh->pub_key);
 143             dh->pub_key = NULL;
 144         }
 145         return 0;
 146     }
 147
 148     return 1;
 149 }
 150
 151 static int
 152 ltm_dh_compute_key(unsigned char *shared, const BIGNUM * pub, DH *dh)
 153 {
 154     mp_int s, priv_key, p, peer_pub;
 155     int ret;
 156
 157     if (dh->pub_key == NULL || dh->g == NULL || dh->priv_key == NULL)
 158         return -1;
 159
 160     mp_init_multi(&s, &priv_key, &p, &peer_pub, NULL);
 161     BN2mpz(&p, dh->p);
 162     BN2mpz(&peer_pub, pub);
 163
 164     /* check if peers pubkey is reasonable */
 165     if (mp_isneg(&peer_pub)
 166         || mp_cmp(&peer_pub, &p) >= 0
 167         || mp_cmp_d(&peer_pub, 1) <= 0)
 168     {
 169         ret = -1;
 170         goto out;
 171     }
 172
 173     BN2mpz(&priv_key, dh->priv_key);
 174
 175     ret = mp_exptmod(&peer_pub, &priv_key, &p, &s);
 176
 177     if (ret != 0) {
 178         ret = -1;
 179         goto out;
 180     }
 181
 182     ret = mp_unsigned_bin_size(&s);
 183     mp_to_unsigned_bin(&s, shared);
 184
 185  out:
 186     mp_clear_multi(&s, &priv_key, &p, &peer_pub, NULL);
 187
 188     return ret;
 189 }
 190
 191 static int
 192 ltm_dh_generate_params(DH *dh, int a, int b, BN_GENCB *callback)
 193 {
 194     /* groups should already be known, we don't care about this */
 195     return 0;
 196 }
 197
 198 static int
 199 ltm_dh_init(DH *dh)
 200 {
 201     return 1;
 202 }
 203
 204 static int
 205 ltm_dh_finish(DH *dh)
 206 {
 207     return 1;
 208 }
 209
 210
 211 /*
 212  *
 213  */
 214
 215 const DH_METHOD _hc_dh_ltm_method = {
 216     "hcrypto ltm DH",
 217     ltm_dh_generate_key,
 218     ltm_dh_compute_key,
 219     NULL,
 220     ltm_dh_init,
 221     ltm_dh_finish,
 222     0,
 223     NULL,
 224     ltm_dh_generate_params
 225 };
 226
 227 /**
 228  * DH implementation using libtommath.
 229  *
 230  * @return the DH_METHOD for the DH implementation using libtommath.
 231  *
 232  * @ingroup hcrypto_dh
 233  */
 234
 235 const DH_METHOD *
 236 DH_ltm_method(void)
 237 {
 238     return &_hc_dh_ltm_method;
 239 }