dlls/advapi32/crypt_arc4.c

   1 /*
   2  *  Copyright 2006 Mike McCormack
   3  *
   4  *  based on arc4.cpp - written and placed in the public domain by Wei Dai
   5  *
   6  *  This library is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU Lesser General Public
   8  *  License as published by the Free Software Foundation; either
   9  *  version 2.1 of the License, or (at your option) any later version.
  10  *
  11  *  This library is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  *  Lesser General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU Lesser General Public
  17  *  License along with this library; if not, write to the Free Software
  18  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 /* http://cryptopp.sourceforge.net/docs/ref521/arc4_8cpp-source.html */
  22
  23 #include <stdarg.h>
  24
  25 #include "ntstatus.h"
  26 #define WIN32_NO_STATUS
  27 #include "windef.h"
  28 #include "winternl.h"
  29
  30 typedef struct tag_arc4_info {
  31     unsigned char state[256];
  32     unsigned char x, y;
  33 } arc4_info;
  34
  35 static void arc4_init(arc4_info *a4i, const BYTE *key, unsigned int keyLen)
  36 {
  37     unsigned int keyIndex = 0, stateIndex = 0;
  38     unsigned int i, a;
  39
  40     a4i->x = a4i->y = 0;
  41
  42     for (i=0; i<256; i++)
  43         a4i->state[i] = i;
  44
  45     for (i=0; i<256; i++)
  46     {
  47         a = a4i->state[i];
  48         stateIndex += key[keyIndex] + a;
  49         stateIndex &= 0xff;
  50         a4i->state[i] = a4i->state[stateIndex];
  51         a4i->state[stateIndex] = a;
  52         if (++keyIndex >= keyLen)
  53             keyIndex = 0;
  54     }
  55 }
  56
  57 static void arc4_ProcessString(arc4_info *a4i, BYTE *inoutString, unsigned int length)
  58 {
  59     BYTE *const s=a4i->state;
  60     unsigned int x = a4i->x;
  61     unsigned int y = a4i->y;
  62     unsigned int a, b;
  63
  64     while(length--)
  65     {
  66         x = (x+1) & 0xff;
  67         a = s[x];
  68         y = (y+a) & 0xff;
  69         b = s[y];
  70         s[x] = b;
  71         s[y] = a;
  72         *inoutString++ ^= s[(a+b) & 0xff];
  73     }
  74
  75     a4i->x = x;
  76     a4i->y = y;
  77 }
  78
  79 struct ustring {
  80     DWORD Length;
  81     DWORD MaximumLength;
  82     unsigned char *Buffer;
  83 };
  84
  85 /******************************************************************************
  86  * SystemFunction032  [ADVAPI32.@]
  87  *
  88  * Encrypts a string data using ARC4
  89  *
  90  * PARAMS
  91  *   data    [I/O] data to encrypt
  92  *   key     [I] key data
  93  *
  94  * RETURNS
  95  *  Success: STATUS_SUCCESS
  96  *  Failure: STATUS_UNSUCCESSFUL
  97  *
  98  * NOTES
  99  *  see http://web.it.kth.se/~rom/ntsec.html#crypto-strongavail
 100  */
 101 NTSTATUS WINAPI SystemFunction032(struct ustring *data, struct ustring *key)
 102 {
 103     arc4_info a4i;
 104
 105     arc4_init(&a4i, key->Buffer, key->Length);
 106     arc4_ProcessString(&a4i, data->Buffer, data->Length);
 107
 108     return STATUS_SUCCESS;
 109 }