release/src/router/dropbear/gendss.c

   1 /*
   2  * Dropbear - a SSH2 server
   3  *
   4  * Copyright (c) 2002,2003 Matt Johnston
   5  * All rights reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE. */
  24
  25 #include "includes.h"
  26 #include "dbutil.h"
  27 #include "signkey.h"
  28 #include "bignum.h"
  29 #include "random.h"
  30 #include "buffer.h"
  31 #include "gendss.h"
  32 #include "dss.h"
  33
  34 #define QSIZE 20 /* 160 bit */
  35
  36 /* This is just a test */
  37
  38 #ifdef DROPBEAR_DSS
  39
  40 static void getq(dropbear_dss_key *key);
  41 static void getp(dropbear_dss_key *key, unsigned int size);
  42 static void getg(dropbear_dss_key *key);
  43 static void getx(dropbear_dss_key *key);
  44 static void gety(dropbear_dss_key *key);
  45
  46 dropbear_dss_key * gen_dss_priv_key(unsigned int size) {
  47
  48         dropbear_dss_key *key;
  49
  50         key = m_malloc(sizeof(*key));
  51
  52         key->p = (mp_int*)m_malloc(sizeof(mp_int));
  53         key->q = (mp_int*)m_malloc(sizeof(mp_int));
  54         key->g = (mp_int*)m_malloc(sizeof(mp_int));
  55         key->y = (mp_int*)m_malloc(sizeof(mp_int));
  56         key->x = (mp_int*)m_malloc(sizeof(mp_int));
  57         m_mp_init_multi(key->p, key->q, key->g, key->y, key->x, NULL);
  58
  59         seedrandom();
  60
  61         getq(key);
  62         getp(key, size);
  63         getg(key);
  64         getx(key);
  65         gety(key);
  66
  67         return key;
  68
  69 }
  70
  71 static void getq(dropbear_dss_key *key) {
  72
  73         char buf[QSIZE];
  74
  75         /* 160 bit prime */
  76         genrandom(buf, QSIZE);
  77         buf[0] |= 0x80; /* top bit high */
  78         buf[QSIZE-1] |= 0x01; /* bottom bit high */
  79
  80         bytes_to_mp(key->q, buf, QSIZE);
  81
  82         /* 18 rounds are required according to HAC */
  83         if (mp_prime_next_prime(key->q, 18, 0) != MP_OKAY) {
  84                 fprintf(stderr, "DSS key generation failed\n");
  85                 exit(1);
  86         }
  87 }
  88
  89 static void getp(dropbear_dss_key *key, unsigned int size) {
  90
  91         DEF_MP_INT(tempX);
  92         DEF_MP_INT(tempC);
  93         DEF_MP_INT(tempP);
  94         DEF_MP_INT(temp2q);
  95         int result;
  96         unsigned char *buf;
  97
  98         m_mp_init_multi(&tempX, &tempC, &tempP, &temp2q, NULL);
  99
 100
 101         /* 2*q */
 102         if (mp_mul_d(key->q, 2, &temp2q) != MP_OKAY) {
 103                 fprintf(stderr, "DSS key generation failed\n");
 104                 exit(1);
 105         }
 106
 107         buf = (unsigned char*)m_malloc(size);
 108
 109         result = 0;
 110         do {
 111
 112                 genrandom(buf, size);
 113                 buf[0] |= 0x80; /* set the top bit high */
 114
 115                 /* X is a random mp_int */
 116                 bytes_to_mp(&tempX, buf, size);
 117
 118                 /* C = X mod 2q */
 119                 if (mp_mod(&tempX, &temp2q, &tempC) != MP_OKAY) {
 120                         fprintf(stderr, "DSS key generation failed\n");
 121                         exit(1);
 122                 }
 123
 124                 /* P = X - (C - 1) = X - C + 1*/
 125                 if (mp_sub(&tempX, &tempC, &tempP) != MP_OKAY) {
 126                         fprintf(stderr, "DSS key generation failed\n");
 127                         exit(1);
 128                 }
 129
 130                 if (mp_add_d(&tempP, 1, key->p) != MP_OKAY) {
 131                         fprintf(stderr, "DSS key generation failed\n");
 132                         exit(1);
 133                 }
 134
 135                 /* now check for prime, 5 rounds is enough according to HAC */
 136                 /* result == 1  =>  p is prime */
 137                 if (mp_prime_is_prime(key->p, 5, &result) != MP_OKAY) {
 138                         fprintf(stderr, "DSS key generation failed\n");
 139                         exit(1);
 140                 }
 141         } while (!result);
 142
 143         mp_clear_multi(&tempX, &tempC, &tempP, &temp2q, NULL);
 144         m_burn(buf, size);
 145         m_free(buf);
 146 }
 147
 148 static void getg(dropbear_dss_key * key) {
 149
 150         DEF_MP_INT(div);
 151         DEF_MP_INT(h);
 152         DEF_MP_INT(val);
 153
 154         m_mp_init_multi(&div, &h, &val, NULL);
 155
 156         /* get div=(p-1)/q */
 157         if (mp_sub_d(key->p, 1, &val) != MP_OKAY) {
 158                 fprintf(stderr, "DSS key generation failed\n");
 159                 exit(1);
 160         }
 161         if (mp_div(&val, key->q, &div, NULL) != MP_OKAY) {
 162                 fprintf(stderr, "DSS key generation failed\n");
 163                 exit(1);
 164         }
 165
 166         /* initialise h=1 */
 167         mp_set(&h, 1);
 168         do {
 169                 /* now keep going with g=h^div mod p, until g > 1 */
 170                 if (mp_exptmod(&h, &div, key->p, key->g) != MP_OKAY) {
 171                         fprintf(stderr, "DSS key generation failed\n");
 172                         exit(1);
 173                 }
 174
 175                 if (mp_add_d(&h, 1, &h) != MP_OKAY) {
 176                         fprintf(stderr, "DSS key generation failed\n");
 177                         exit(1);
 178                 }
 179
 180         } while (mp_cmp_d(key->g, 1) != MP_GT);
 181
 182         mp_clear_multi(&div, &h, &val, NULL);
 183 }
 184
 185 static void getx(dropbear_dss_key *key) {
 186
 187         gen_random_mpint(key->q, key->x);
 188 }
 189
 190 static void gety(dropbear_dss_key *key) {
 191
 192         if (mp_exptmod(key->g, key->x, key->p, key->y) != MP_OKAY) {
 193                 fprintf(stderr, "DSS key generation failed\n");
 194                 exit(1);
 195         }
 196 }
 197
 198 #endif /* DROPBEAR_DSS */