vde-2/src/vde_over_ns/encode.c

   1 /* ----------------------------------------------------------------------------
   2  *
   3     VDE_OVER_NS
   4         (C) 2007 Daniele Lacamera
   5
   6     Derived from:
   7     NSTX -- tunneling network-packets over DNS
   8
   9      (C) 2000 by Florian Heinz and Julien Oster
  10
  11     This program is free software; you can redistribute it and/or modify
  12     it under the terms of the GNU General Public License version 2, as
  13     published by the Free Software Foundation.
  14
  15     This program is distributed in the hope that it will be useful,
  16     but WITHOUT ANY WARRANTY; without even the implied warranty of
  17     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18     GNU General Public License for more details.
  19
  20     You should have received a copy of the GNU General Public License
  21     along with this program; if not, write to the Free Software
  22     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24   -------------------------------------------------------------------------- */
  25
  26 #include <string.h>
  27 #include <stdlib.h>
  28
  29 #include <config.h>
  30 #include <vde.h>
  31 #include <vdecommon.h>
  32
  33 unsigned char map[] =
  34             "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_1234567890";
  35 unsigned char *revmap = NULL;
  36
  37 void init_revmap (void)
  38 {
  39    unsigned int i;
  40
  41    revmap = malloc(256);
  42
  43    for (i = 0; i < strlen((char*)map); i++)
  44      revmap[map[i]] = i;
  45 }
  46
  47 const unsigned char *
  48 nstx_encode(const unsigned char *data, int len) {
  49    int i = 0, off = 1, cut = 0;
  50    static unsigned char *buf = NULL;
  51
  52    if (len % 3)
  53      cut = 3 - len%3;
  54
  55    buf = realloc(buf, ((len+2)/3)*4+2);
  56    buf[0] = map[cut];
  57    while (i < len) {
  58       buf[off + 0] = map[(data[i] & 252) >> 2];
  59       buf[off + 1] = map[((data[i] & 3) << 4) | ((data[i+1] & 240) >> 4)];
  60       buf[off + 2] = map[((data[i+1] & 15) << 2 ) | ((data[i+2] & 192) >> 6)];
  61       buf[off + 3] = map[(data[i+2] & 63)];
  62       i += 3;
  63       off += 4;
  64    }
  65    buf[off] = '\0';
  66
  67    return buf;
  68 }
  69
  70 const unsigned char *
  71 nstx_decode(const unsigned char *data, int *rlen) {
  72    int i = 0, off = 1;
  73    int len;
  74    static unsigned char *buf = NULL;
  75
  76    if (!revmap)
  77      init_revmap();
  78
  79    len = strlen((char*)data);
  80
  81    buf = realloc(buf, ((len+3)/4)*3);
  82
  83    while (off+3 < len) {
  84       buf[i+0] = (revmap[data[off]]<<2)|((revmap[data[off+1]]&48)>>4);
  85       buf[i+1] = ((revmap[data[off+1]]&15)<<4)|((revmap[data[off+2]]&60)>>2);
  86       buf[i+2] = ((revmap[data[off+2]]&3)<<6)|(revmap[data[off+3]]);
  87       i += 3;
  88       off += 4;
  89    }
  90    *rlen = i - revmap[data[0]];
  91
  92    return buf;
  93 }