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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, 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 #include "crypt.h"
  31
  32 typedef struct tag_arc4_info {
  33     unsigned char state[256];
  34     unsigned char x, y;
  35 } arc4_info;
  36
  37 static void arc4_init(arc4_info *a4i, const BYTE *key, unsigned int keyLen)
  38 {
  39     unsigned int keyIndex = 0, stateIndex = 0;
  40     unsigned int i, a;
  41
  42     a4i->x = a4i->y = 0;
  43
  44     for (i=0; i<256; i++)
  45         a4i->state[i] = i;
  46
  47     for (i=0; i<256; i++)
  48     {
  49         a = a4i->state[i];
  50         stateIndex += key[keyIndex] + a;
  51         stateIndex &= 0xff;
  52         a4i->state[i] = a4i->state[stateIndex];
  53         a4i->state[stateIndex] = a;
  54         if (++keyIndex >= keyLen)
  55             keyIndex = 0;
  56     }
  57 }
  58
  59 static void arc4_ProcessString(arc4_info *a4i, BYTE *inoutString, unsigned int length)
  60 {
  61     BYTE *const s=a4i->state;
  62     unsigned int x = a4i->x;
  63     unsigned int y = a4i->y;
  64     unsigned int a, b;
  65
  66     while(length--)
  67     {
  68         x = (x+1) & 0xff;
  69         a = s[x];
  70         y = (y+a) & 0xff;
  71         b = s[y];
  72         s[x] = b;
  73         s[y] = a;
  74         *inoutString++ ^= s[(a+b) & 0xff];
  75     }
  76
  77     a4i->x = x;
  78     a4i->y = y;
  79 }
  80
  81 /******************************************************************************
  82  * SystemFunction032  [ADVAPI32.@]
  83  *
  84  * Encrypts a string data using ARC4
  85  *
  86  * PARAMS
  87  *   data    [I/O] data to encrypt
  88  *   key     [I] key data
  89  *
  90  * RETURNS
  91  *  Success: STATUS_SUCCESS
  92  *  Failure: STATUS_UNSUCCESSFUL
  93  *
  94  * NOTES
  95  *  see http://web.it.kth.se/~rom/ntsec.html#crypto-strongavail
  96  */
  97 NTSTATUS WINAPI SystemFunction032(struct ustring *data, const struct ustring *key)
  98 {
  99     arc4_info a4i;
 100
 101     arc4_init(&a4i, key->Buffer, key->Length);
 102     arc4_ProcessString(&a4i, data->Buffer, data->Length);
 103
 104     return STATUS_SUCCESS;
 105 }