lib/libtelnet/pk.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      Dave Safford.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  */
  30
  31 #include <sys/cdefs.h>
  32
  33 #ifdef notdef
  34 __FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/pk.c,v 1.10 2002/08/22 06:19:07 nsayer Exp $");
  35 #else
  36 __RCSID("$NetBSD: pk.c,v 1.3 2005/02/19 22:47:51 christos Exp $");
  37 #endif
  38
  39 /* public key routines */
  40 /* functions:
  41         genkeys(char *public, char *secret)
  42         common_key(char *secret, char *public, desData *deskey)
  43         pk_encode(char *in, *out, DesData *deskey);
  44         pk_decode(char *in, *out, DesData *deskey);
  45       where
  46         char public[HEXKEYBYTES + 1];
  47         char secret[HEXKEYBYTES + 1];
  48  */
  49
  50 #include <sys/time.h>
  51 #include <des.h>
  52 #include <openssl/bn.h>
  53 #include <fcntl.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57
  58 #include "pk.h"
  59
  60 static void adjust(char *, const char *);
  61
  62 /*
  63  * Choose top 128 bits of the common key to use as our idea key.
  64  */
  65 static void
  66 extractideakey(BIGNUM *ck, IdeaData *ideakey)
  67 {
  68         BIGNUM *a = BN_new();
  69         BIGNUM *z = BN_new();
  70         BIGNUM *base = BN_new();
  71         BN_CTX *ctx = BN_CTX_new();
  72         size_t i;
  73         char *k;
  74
  75         (void)BN_zero(a);
  76         (void)BN_zero(z);
  77         (void)BN_set_word(base, 1 << 8);
  78         BN_add(a, ck, z);
  79
  80         for (i = 0; i < ((KEYSIZE - 128) / 8); i++)
  81                 BN_div(a, z, a, base, ctx);
  82
  83         k = (char *)(void *)ideakey;
  84         for (i = 0; i < 16; i++) {
  85                 BN_div(a, z, a, base, ctx);
  86                 *k++ = (char)BN_get_word(z);
  87         }
  88
  89         BN_CTX_free(ctx);
  90         BN_free(base);
  91         BN_free(z);
  92         BN_free(a);
  93 }
  94
  95 /*
  96  * Choose middle 64 bits of the common key to use as our des key, possibly
  97  * overwriting the lower order bits by setting parity.
  98  */
  99 static void
 100 extractdeskey(BIGNUM *ck, DesData *deskey)
 101 {
 102         BIGNUM *a = BN_new();
 103         BIGNUM *z = BN_new();
 104         BIGNUM *base = BN_new();
 105         BN_CTX *ctx = BN_CTX_new();
 106         size_t i;
 107         char *k;
 108
 109         (void)BN_zero(z);
 110         (void)BN_zero(a);
 111         (void)BN_set_word(base, 1 << 8);
 112         BN_add(a, ck, z);
 113
 114         for (i = 0; i < ((KEYSIZE - 64) / 2) / 8; i++)
 115                 BN_div(a, z, a, base, ctx);
 116
 117         k = (char *)deskey;
 118         for (i = 0; i < 8; i++) {
 119                 BN_div(a, z, a, base, ctx);
 120                 *k++ = (char)BN_get_word(z);
 121         }
 122
 123         BN_CTX_free(ctx);
 124         BN_free(base);
 125         BN_free(z);
 126         BN_free(a);
 127 }
 128
 129 /*
 130  * get common key from my secret key and his public key
 131  */
 132 void
 133 common_key(char *xsecret, char *xpublic, IdeaData *ideakey, DesData *deskey)
 134 {
 135         BIGNUM *public = BN_new();
 136         BIGNUM *secret = BN_new();
 137         BIGNUM *common = BN_new();
 138         BIGNUM *modulus  = BN_new();
 139         BN_CTX *ctx = BN_CTX_new();
 140
 141         (void)BN_hex2bn(&modulus, HEXMODULUS);
 142         (void)BN_hex2bn(&public, xpublic);
 143         (void)BN_hex2bn(&secret, xsecret);
 144         (void)BN_zero(common);
 145
 146         BN_mod_exp(common, public, secret, modulus, ctx);
 147         extractdeskey(common, deskey);
 148         extractideakey(common, ideakey);
 149         des_set_odd_parity(deskey);
 150
 151         BN_CTX_free(ctx);
 152         BN_free(common);
 153         BN_free(secret);
 154         BN_free(public);
 155         BN_free(modulus);
 156 }
 157
 158 /*
 159  * Generate a seed
 160  */
 161 static void
 162 getseed(char *seed, size_t seedsize)
 163 {
 164         size_t i;
 165
 166         for (i = 0; i < seedsize; i++)
 167                 seed[i] = arc4random() & 0xff;
 168 }
 169
 170 /*
 171  * Generate a random public/secret key pair
 172  */
 173 void
 174 genkeys(char *public, char *secret)
 175 {
 176         size_t i;
 177
 178 #       define BASEBITS (8 * sizeof(short) - 1)
 179 #       define BASE (1 << BASEBITS)
 180
 181         BIGNUM *pk = BN_new();
 182         BIGNUM *sk = BN_new();
 183         BIGNUM *tmp = BN_new();
 184         BIGNUM *base = BN_new();
 185         BIGNUM *root = BN_new();
 186         BIGNUM *modulus = BN_new();
 187         BN_CTX *ctx = BN_CTX_new();
 188         short r;
 189         unsigned short seed[KEYSIZE/BASEBITS + 1];
 190         char *xkey;
 191
 192         (void)BN_zero(pk);
 193         (void)BN_zero(sk);
 194         (void)BN_set_word(base, BASE);
 195         (void)BN_set_word(root, PROOT);
 196         (void)BN_hex2bn(&modulus, HEXMODULUS);
 197
 198         getseed((char *)seed, sizeof(seed));
 199         for (i = 0; i < KEYSIZE/BASEBITS + 1; i++) {
 200                 r = seed[i] % BASE;
 201                 (void)BN_set_word(tmp, r);
 202                 BN_mul(sk, tmp, sk, ctx);
 203                 BN_add(sk, tmp, sk);
 204         }
 205
 206         (void)BN_zero(tmp);
 207         BN_div(tmp, sk, sk, modulus, ctx);
 208         BN_mod_exp(pk, root, sk, modulus, ctx);
 209
 210         xkey = BN_bn2hex(sk);
 211         adjust(secret, xkey);
 212         xkey = BN_bn2hex(pk);
 213         adjust(public, xkey);
 214
 215         BN_CTX_free(ctx);
 216         BN_free(sk);
 217         BN_free(base);
 218         BN_free(pk);
 219         BN_free(tmp);
 220         BN_free(root);
 221         BN_free(modulus);
 222 }
 223
 224 /*
 225  * Adjust the input key so that it is 0-filled on the left
 226  */
 227 static void
 228 adjust(char *keyout, const char *keyin)
 229 {
 230         const char *p;
 231         char *s;
 232
 233         for (p = keyin; *p; p++)
 234                 continue;
 235         for (s = keyout + HEXKEYBYTES; p >= keyin; p--, s--)
 236                 *s = *p;
 237         while (s >= keyout)
 238                 *s-- = '0';
 239 }
 240
 241 static const char hextab[] = "0123456789ABCDEF";
 242
 243 /* given a DES key, cbc encrypt and translate input to terminated hex */
 244 void
 245 pk_encode(const char *in, char *out, DesData *key)
 246 {
 247         char buf[256];
 248         DesData i;
 249         des_key_schedule k;
 250         size_t l, op, deslen;
 251
 252         (void)memset(&i, 0, sizeof(i));
 253         (void)memset(buf, 0, sizeof(buf));
 254         deslen = ((strlen(in) + 7) / 8) * 8;
 255         des_key_sched(key, k);
 256         des_cbc_encrypt(in, buf, deslen, k, &i, DES_ENCRYPT);
 257         for (l = 0, op = 0; l < deslen; l++) {
 258                 out[op++] = hextab[(buf[l] & 0xf0) >> 4];
 259                 out[op++] = hextab[(buf[l] & 0x0f)];
 260         }
 261         out[op] = '\0';
 262 }
 263
 264 /* given a DES key, translate input from hex and decrypt */
 265 void
 266 pk_decode(const char *in, char *out, DesData *key)
 267 {
 268         char buf[256];
 269         DesData i;
 270         des_key_schedule k;
 271         int n1, n2, op;
 272         size_t l;
 273         size_t len = strlen(in) / 2;
 274
 275         (void)memset(&i, 0, sizeof(i));
 276         (void)memset(buf, 0, sizeof(buf));
 277
 278         for (l = 0, op = 0; l < len; l++, op += 2) {
 279                 if (in[op] > '9')
 280                         n1 = in[op] - 'A' + 10;
 281                 else
 282                         n1 = in[op] - '0';
 283                 if (in[op + 1] > '9')
 284                         n2 = in[op + 1] - 'A' + 10;
 285                 else
 286                         n2 = in[op + 1] - '0';
 287                 buf[l] = (char)(n1 * 16 + n2);
 288         }
 289         des_key_sched(key, k);
 290         des_cbc_encrypt(buf, out, len, k, &i, DES_DECRYPT);
 291         out[len] = '\0';
 292 }