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  * $FreeBSD: src/crypto/telnet/libtelnet/pk.c,v 1.2.2.4 2002/08/24 07:28:35 nsayer Exp $
  31  * $DragonFly: src/crypto/telnet/libtelnet/pk.c,v 1.5 2005/07/18 16:43:26 joerg Exp $
  32  */
  33
  34 /* public key routines */
  35 /* functions:
  36         genkeys(char *public, char *secret)
  37         common_key(char *secret, char *public, desData *deskey)
  38         pk_encode(char *in, *out, DesData *deskey);
  39         pk_decode(char *in, *out, DesData *deskey);
  40       where
  41         char public[HEXKEYBYTES + 1];
  42         char secret[HEXKEYBYTES + 1];
  43  */
  44
  45 #include <sys/time.h>
  46 #include <err.h>
  47 #include <fcntl.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51
  52 #include <openssl/bn.h>
  53 #include <openssl/crypto.h>
  54 #include <openssl/des.h>
  55 #include <openssl/err.h>
  56
  57 #include "pk.h"
  58
  59 static void adjust(char keyout[HEXKEYBYTES+1], char *keyin);
  60
  61 /*
  62  * Choose top 128 bits of the common key to use as our idea key.
  63  */
  64 static void
  65 extractideakey(BIGNUM *ck, IdeaData *ideakey)
  66 {
  67         BIGNUM *a, *z;
  68         int i;
  69         BN_ULONG r, base = (1 << 8);
  70         char *k;
  71
  72         if ((z = BN_new()) == NULL)
  73                 errx(1, "could not create BIGNUM");
  74         BN_zero(z);
  75         if ((a = BN_new()) == NULL)
  76                 errx(1, "could not create BIGNUM");
  77         BN_zero(a);
  78         BN_add(a, ck, z);
  79         for (i = 0; i < ((KEYSIZE - 128) / 8); i++) {
  80                 r = BN_div_word(a, base);
  81         }
  82         k = (char *)ideakey;
  83         for (i = 0; i < 16; i++) {
  84                 r = BN_div_word(a, base);
  85                 *k++ = r;
  86         }
  87         BN_free(z);
  88         BN_free(a);
  89 }
  90
  91 /*
  92  * Choose middle 64 bits of the common key to use as our des key, possibly
  93  * overwriting the lower order bits by setting parity.
  94  */
  95 static void
  96 extractdeskey(BIGNUM *ck, DesData *deskey)
  97 {
  98         BIGNUM *a, *z;
  99         int i;
 100         BN_ULONG r, base = (1 << 8);
 101         char *k;
 102
 103         if ((z = BN_new()) == NULL)
 104                 errx(1, "could not create BIGNUM");
 105         BN_zero(z);
 106         if ((a = BN_new()) == NULL)
 107                 errx(1, "could not create BIGNUM");
 108         BN_zero(a);
 109         BN_add(a, ck, z);
 110         for (i = 0; i < ((KEYSIZE - 64) / 2) / 8; i++) {
 111                 r = BN_div_word(a, base);
 112         }
 113         k = (char *)deskey;
 114         for (i = 0; i < 8; i++) {
 115                 r = BN_div_word(a, base);
 116                 *k++ = r;
 117         }
 118         BN_free(z);
 119         BN_free(a);
 120 }
 121
 122 /*
 123  * get common key from my secret key and his public key
 124  */
 125 void
 126 common_key(char *xsecret, char *xpublic, IdeaData *ideakey, DesData *deskey)
 127 {
 128         BIGNUM *public, *secret, *common, *modulus;
 129         BN_CTX *ctx;
 130
 131         if ((ctx = BN_CTX_new()) == NULL)
 132                 errx(1, "could not create BN_CTX");
 133         modulus = NULL;
 134         if (BN_hex2bn(&modulus, HEXMODULUS) == NULL)
 135                 errx(1, "could not convert modulus");
 136         public = NULL;
 137         if (BN_hex2bn(&public, xpublic) == NULL)
 138                 errx(1, "could not convert public");
 139         secret = NULL;
 140         if (BN_hex2bn(&secret, xsecret) == NULL)
 141                 errx(1, "could not convert secret");
 142
 143         if ((common = BN_new()) == NULL)
 144                 errx(1, "could not create BIGNUM");
 145         BN_zero(common);
 146         BN_mod_exp(common, public, secret, modulus, ctx);
 147         extractdeskey(common, deskey);
 148         extractideakey(common, ideakey);
 149         des_set_odd_parity(deskey);
 150         BN_free(common);
 151         BN_free(secret);
 152         BN_free(public);
 153         BN_free(modulus);
 154         BN_CTX_free(ctx);
 155 }
 156
 157 /*
 158  * Generate a seed
 159  */
 160 static void
 161 getseed(char *seed, int seedsize)
 162 {
 163         int i;
 164
 165         for (i = 0; i < seedsize; i++) {
 166                 seed[i] = arc4random() & 0xff;
 167         }
 168 }
 169
 170 static BIGNUM *
 171 itobn(long i)
 172 {
 173         BIGNUM *n = 0;
 174
 175         if ((n = BN_new()) == NULL)
 176                 errx(1, "could not create BIGNUM: %s",
 177                      ERR_error_string(ERR_get_error(), 0));
 178         BN_init(n);
 179         if (i > 0)
 180                 BN_add_word(n, (u_long)i);
 181         else
 182                 BN_sub_word(n, (u_long)(-i));
 183         return(n);
 184 }
 185
 186 /*
 187  * Generate a random public/secret key pair
 188  */
 189 void
 190 genkeys(char *public, char *secret)
 191 {
 192 #define BASEBITS (8*sizeof (short) - 1)
 193 #define BASE (short)(1 << BASEBITS)
 194
 195         unsigned int i;
 196         short r;
 197         unsigned short seed[KEYSIZE/BASEBITS + 1];
 198         char *xkey;
 199
 200         BN_CTX *ctx;
 201         BIGNUM *pk, *sk, *tmp, *base, *root, *modulus;
 202
 203         pk = itobn(0);
 204         sk = itobn(0);
 205         tmp = itobn(0);
 206         base = itobn(BASE);
 207         root = itobn(PROOT);
 208         modulus = NULL;
 209         if (BN_hex2bn(&modulus, HEXMODULUS) == NULL)
 210                 errx(1, "could not convert modulus to BIGNUM: %s",
 211                      ERR_error_string(ERR_get_error(), 0));
 212
 213         if ((ctx = BN_CTX_new()) == NULL)
 214                 errx(1, "could not create BN_CTX: %s",
 215                      ERR_error_string(ERR_get_error(), 0));
 216
 217         getseed((char *)seed, sizeof (seed));
 218         for (i = 0; i < KEYSIZE/BASEBITS + 1; i++) {
 219                 r = seed[i] % BASE;
 220                 BN_zero(tmp);
 221                 BN_add_word(tmp, r);
 222                 BN_mul(sk, base, sk, ctx);
 223                 BN_add(sk, tmp, sk);
 224         }
 225         BN_zero(tmp);
 226         BN_div(tmp, sk, sk, modulus, ctx);
 227         BN_mod_exp(pk, root, sk, modulus, ctx);
 228
 229         if ((xkey = BN_bn2hex(sk)) == NULL)
 230                 errx(1, "could convert sk to hex: %s",
 231                      ERR_error_string(ERR_get_error(), 0));
 232         adjust(secret, xkey);
 233         OPENSSL_free(xkey);
 234
 235         if ((xkey = BN_bn2hex(pk)) == NULL)
 236                 errx(1, "could convert pk to hex: %s",
 237                      ERR_error_string(ERR_get_error(), 0));
 238         adjust(public, xkey);
 239         OPENSSL_free(xkey);
 240
 241         BN_free(base);
 242         BN_free(modulus);
 243         BN_free(pk);
 244         BN_free(sk);
 245         BN_free(root);
 246         BN_free(tmp);
 247 }
 248
 249 /*
 250  * Adjust the input key so that it is 0-filled on the left
 251  */
 252 static void
 253 adjust(char keyout[HEXKEYBYTES+1], char *keyin)
 254 {
 255         char *p;
 256         char *s;
 257
 258         for (p = keyin; *p; p++)
 259                 ;
 260         for (s = keyout + HEXKEYBYTES; p >= keyin; p--, s--) {
 261                 *s = *p;
 262         }
 263         while (s >= keyout) {
 264                 *s-- = '0';
 265         }
 266 }
 267
 268 static char hextab[17] = "0123456789ABCDEF";
 269
 270 /* given a DES key, cbc encrypt and translate input to terminated hex */
 271 void
 272 pk_encode(char *in, char *out, DesData *key)
 273 {
 274         char buf[256];
 275         DesData i;
 276         des_key_schedule k;
 277         int l,op,deslen;
 278
 279         memset(&i,0,sizeof(i));
 280         memset(buf,0,sizeof(buf));
 281         deslen = ((strlen(in) + 7)/8)*8;
 282         des_key_sched(key, k);
 283         des_cbc_encrypt(in,buf,deslen, k,&i,DES_ENCRYPT);
 284         for (l=0,op=0;l<deslen;l++) {
 285                 out[op++] = hextab[(buf[l] & 0xf0) >> 4];
 286                 out[op++] = hextab[(buf[l] & 0x0f)];
 287         }
 288         out[op] = '\0';
 289 }
 290
 291 /* given a DES key, translate input from hex and decrypt */
 292 void
 293 pk_decode(char *in, char *out, DesData *key)
 294 {
 295         char buf[256];
 296         DesData i;
 297         des_key_schedule k;
 298         int n1,n2,op;
 299         size_t l;
 300
 301         memset(&i,0,sizeof(i));
 302         memset(buf,0,sizeof(buf));
 303         for (l=0,op=0;l<strlen(in)/2;l++,op+=2) {
 304                 if (in[op] > '9')
 305                         n1 = in[op] - 'A' + 10;
 306                 else
 307                         n1 = in[op] - '0';
 308                 if (in[op+1] > '9')
 309                         n2 = in[op+1] - 'A' + 10;
 310                 else
 311                         n2 = in[op+1] - '0';
 312                 buf[l] = n1*16 +n2;
 313         }
 314         des_key_sched(key, k);
 315         des_cbc_encrypt(buf,out,strlen(in)/2, k,&i,DES_DECRYPT);
 316         out[strlen(in)/2] = '\0';
 317 }