crypt_arc4.c 2.68 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
/*
 *  Copyright 2006 Mike McCormack
 *
 *  based on arc4.cpp - written and placed in the public domain by Wei Dai
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  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 22 23 24 25 26 27 28 29
 */

/* http://cryptopp.sourceforge.net/docs/ref521/arc4_8cpp-source.html */

#include <stdarg.h>

#include "ntstatus.h"
#define WIN32_NO_STATUS
#include "windef.h"
#include "winternl.h"

30 31
#include "crypt.h"

32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96
typedef struct tag_arc4_info {
    unsigned char state[256];
    unsigned char x, y;
} arc4_info;

static void arc4_init(arc4_info *a4i, const BYTE *key, unsigned int keyLen)
{
    unsigned int keyIndex = 0, stateIndex = 0;
    unsigned int i, a;

    a4i->x = a4i->y = 0;

    for (i=0; i<256; i++)
        a4i->state[i] = i;

    for (i=0; i<256; i++)
    {
        a = a4i->state[i];
        stateIndex += key[keyIndex] + a;
        stateIndex &= 0xff;
        a4i->state[i] = a4i->state[stateIndex];
        a4i->state[stateIndex] = a;
        if (++keyIndex >= keyLen)
            keyIndex = 0;
    }
}

static void arc4_ProcessString(arc4_info *a4i, BYTE *inoutString, unsigned int length)
{
    BYTE *const s=a4i->state;
    unsigned int x = a4i->x;
    unsigned int y = a4i->y;
    unsigned int a, b;

    while(length--)
    {
        x = (x+1) & 0xff;
        a = s[x];
        y = (y+a) & 0xff;
        b = s[y];
        s[x] = b;
        s[y] = a;
        *inoutString++ ^= s[(a+b) & 0xff];
    }

    a4i->x = x;
    a4i->y = y;
}

/******************************************************************************
 * SystemFunction032  [ADVAPI32.@]
 *
 * Encrypts a string data using ARC4
 *
 * PARAMS
 *   data    [I/O] data to encrypt
 *   key     [I] key data
 *
 * RETURNS
 *  Success: STATUS_SUCCESS
 *  Failure: STATUS_UNSUCCESSFUL
 *
 * NOTES
 *  see http://web.it.kth.se/~rom/ntsec.html#crypto-strongavail
 */
97
NTSTATUS WINAPI SystemFunction032(struct ustring *data, const struct ustring *key)
98 99 100 101
{
    arc4_info a4i;

    arc4_init(&a4i, key->Buffer, key->Length);
102
    arc4_ProcessString(&a4i, data->Buffer, data->Length);
103 104 105

    return STATUS_SUCCESS;
}