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 3 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, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23
  24 /*****************************************************************
  25  Initialize state for an arc4 crypt/decrpyt.
  26  arc4 state is 258 bytes - last 2 bytes are the index bytes.
  27 *****************************************************************/
  28
  29 void smb_arc4_init(unsigned char arc4_state_out[258], const unsigned char *key, size_t keylen)
  30 {
  31         size_t ind;
  32         unsigned char j = 0;
  33
  34         for (ind = 0; ind < 256; ind++) {
  35                 arc4_state_out[ind] = (unsigned char)ind;
  36         }
  37
  38         for( ind = 0; ind < 256; ind++) {
  39                 unsigned char tc;
  40
  41                 j += (arc4_state_out[ind] + key[ind%keylen]);
  42
  43                 tc = arc4_state_out[ind];
  44                 arc4_state_out[ind] = arc4_state_out[j];
  45                 arc4_state_out[j] = tc;
  46         }
  47         arc4_state_out[256] = 0;
  48         arc4_state_out[257] = 0;
  49 }
  50
  51 /*****************************************************************
  52  Do the arc4 crypt/decrpyt.
  53  arc4 state is 258 bytes - last 2 bytes are the index bytes.
  54 *****************************************************************/
  55
  56 void smb_arc4_crypt(unsigned char arc4_state_inout[258], unsigned char *data, size_t len)
  57 {
  58         unsigned char index_i = arc4_state_inout[256];
  59         unsigned char index_j = arc4_state_inout[257];
  60         size_t ind;
  61
  62         for( ind = 0; ind < len; ind++) {
  63                 unsigned char tc;
  64                 unsigned char t;
  65
  66                 index_i++;
  67                 index_j += arc4_state_inout[index_i];
  68
  69                 tc = arc4_state_inout[index_i];
  70                 arc4_state_inout[index_i] = arc4_state_inout[index_j];
  71                 arc4_state_inout[index_j] = tc;
  72
  73                 t = arc4_state_inout[index_i] + arc4_state_inout[index_j];
  74                 data[ind] = data[ind] ^ arc4_state_inout[t];
  75         }
  76
  77         arc4_state_inout[256] = index_i;
  78         arc4_state_inout[257] = index_j;
  79 }