j0urney1-RemoteSamDecrypt/RemoteSamDecrypt/rc4.cpp

#include <Windows.h>
#include "md5.h"
typedef struct _RC4_CONTEXT
{
	unsigned char state[256];
	unsigned char x, y;
} RC4_CONTEXT;

void rc4_init(RC4_CONTEXT *a4i, const unsigned char *key, unsigned int keyLen);

void rc4_crypt(RC4_CONTEXT *a4i, unsigned char *inoutString, unsigned int length);
void rc4_init(RC4_CONTEXT *a4i, const unsigned char *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;
	}
}

void rc4_crypt(RC4_CONTEXT *a4i, unsigned char *inoutString, unsigned int length)
{
	unsigned char *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;
}
void rc4Decrypt(CRYPTO_BUFFER *data, CRYPTO_BUFFER *key)
{
	RC4_CONTEXT a4i;

	rc4_init(&a4i, key->Buffer, key->Length);
	rc4_crypt(&a4i, data->Buffer, data->Length);

}