source/lib/arc4.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    An implementation of arc4.
   5
   6    Copyright (C) Jeremy Allison 2005.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 #include "includes.h"
  24
  25 /*****************************************************************
  26  Initialize state for an arc4 crypt/decrpyt.
  27  arc4 state is 258 bytes - last 2 bytes are the index bytes.
  28 *****************************************************************/
  29
  30 void smb_arc4_init(unsigned char arc4_state_out[258], const unsigned char *key, size_t keylen)
  31 {
  32         size_t ind;
  33         unsigned char j = 0;
  34
  35         for (ind = 0; ind < 256; ind++) {
  36                 arc4_state_out[ind] = (unsigned char)ind;
  37         }
  38
  39         for( ind = 0; ind < 256; ind++) {
  40                 unsigned char tc;
  41
  42                 j += (arc4_state_out[ind] + key[ind%keylen]);
  43
  44                 tc = arc4_state_out[ind];
  45                 arc4_state_out[ind] = arc4_state_out[j];
  46                 arc4_state_out[j] = tc;
  47         }
  48         arc4_state_out[256] = 0;
  49         arc4_state_out[257] = 0;
  50 }
  51
  52 /*****************************************************************
  53  Do the arc4 crypt/decrpyt.
  54  arc4 state is 258 bytes - last 2 bytes are the index bytes.
  55 *****************************************************************/
  56
  57 void smb_arc4_crypt(unsigned char arc4_state_inout[258], unsigned char *data, size_t len)
  58 {
  59         unsigned char index_i = arc4_state_inout[256];
  60         unsigned char index_j = arc4_state_inout[257];
  61         size_t ind;
  62
  63         for( ind = 0; ind < len; ind++) {
  64                 unsigned char tc;
  65                 unsigned char t;
  66
  67                 index_i++;
  68                 index_j += arc4_state_inout[index_i];
  69
  70                 tc = arc4_state_inout[index_i];
  71                 arc4_state_inout[index_i] = arc4_state_inout[index_j];
  72                 arc4_state_inout[index_j] = tc;
  73
  74                 t = arc4_state_inout[index_i] + arc4_state_inout[index_j];
  75                 data[ind] = data[ind] ^ arc4_state_inout[t];
  76         }
  77
  78         arc4_state_inout[256] = index_i;
  79         arc4_state_inout[257] = index_j;
  80 }