crypto/wvcountermode.cc

   1 /*
   2  * Worldvisions Tunnel Vision Software:
   3  *   Copyright (C) 1997-2002 Net Integration Technologies, Inc.
   4  *
   5  * A 'counter mode' cryptography engine abstraction.
   6  */
   7 #include "wvcountermode.h"
   8
   9
  10 WvCounterModeEncoder::WvCounterModeEncoder(WvEncoder *_keycrypt,
  11     const void *_counter, size_t _countersize) :
  12     keycrypt(_keycrypt), counter(NULL)
  13 {
  14     setcounter(_counter, _countersize);
  15 }
  16
  17
  18 WvCounterModeEncoder::~WvCounterModeEncoder()
  19 {
  20     delete keycrypt;
  21     deletev counter;
  22 }
  23
  24
  25 void WvCounterModeEncoder::setcounter(const void *_counter, size_t _countersize)
  26 {
  27     deletev counter;
  28     counter = new unsigned char[_countersize];
  29     countersize = _countersize;
  30     memcpy(counter, _counter, countersize);
  31 }
  32
  33
  34 void WvCounterModeEncoder::getcounter(void *_counter) const
  35 {
  36     memcpy(_counter, counter, countersize);
  37 }
  38
  39
  40 void WvCounterModeEncoder::incrcounter()
  41 {
  42     for (size_t i = 0; i < countersize && ! ++counter[i]; ++i);
  43 }
  44
  45
  46 bool WvCounterModeEncoder::_encode(WvBuf &inbuf, WvBuf &outbuf,
  47     bool flush)
  48 {
  49     bool success = true;
  50     size_t avail = inbuf.used();
  51     size_t offset = outbuf.used();
  52
  53     // generate a key stream
  54     size_t len;
  55     for (len = avail; len >= countersize; len -= countersize)
  56     {
  57         counterbuf.reset(counter, countersize);
  58         success = keycrypt->encode(counterbuf, outbuf, true);
  59         if (! success) break;
  60         incrcounter();
  61     }
  62     if (flush && len != 0 && success)
  63     {
  64         counterbuf.reset(counter, countersize);
  65         success = keycrypt->encode(counterbuf, outbuf, true);
  66         if (success)
  67         {
  68             outbuf.unalloc(countersize - len);
  69             len = 0;
  70             incrcounter();
  71         }
  72         else
  73             outbuf.unalloc(outbuf.used() - offset - avail);
  74     }
  75     avail -= len;
  76
  77     // XOR in the data
  78     while (avail > 0)
  79     {
  80         len = outbuf.optpeekable(offset);
  81         unsigned char *dataout = outbuf.mutablepeek(offset, len);
  82         size_t lenopt = inbuf.optgettable();
  83         if (len > lenopt)
  84             len = lenopt;
  85         const unsigned char *datain = inbuf.get(len);
  86
  87         if (len >= avail)
  88         {
  89             len = avail;
  90             avail = 0;
  91         }
  92         else
  93         {
  94             avail -= len;
  95             offset += len;
  96         }
  97         while (len-- > 0)
  98             *(dataout++) ^= *(datain++);
  99     }
 100     return success;
 101 }