packet.cpp

来自「从国外网站上下载的关于 逆向工程和协议分析练习 的一个分析文档 对你的加密与解密」· C++ 代码 · 共 101 行

/**
 * 包构造模块
 */
#include "stdafx.h"
#include <stdio.h>
#include "crypt.h"
#include "md5.h"
#include <stdlib.h>
#include <string.h>
#include "options.h"


/**
 *	在数据流当前位置(p)开始增加一个 (type,len,data) 三元组
 *
 *	返回指向下一个位置的指针
 */
static inline unsigned char *add_item(unsigned char *p,unsigned char type,void *buf,int len)
{
	*p++ = type;
	*p++ = 2 + len;
	memcpy(p,buf,len);
	p+=len;

	return p;
}


/**
 *	构造一个 ping 协议报文
 *
 *	@param size packet 缓冲区长度
 *	@return 返回构造出的报文长度
 *	@note 未检查是否构造越过 packet 边界
 */
int packet_ping(unsigned char *packet,int size)
{
	unsigned char *p;

	p = packet;
	*p++ = 3;
	p += 16 + 1;


	p = add_item(p,7,g_options.my_mac,sizeof(g_options.my_mac));

	p = add_item(p,8,g_options.session,g_options.sesslen);

	p = add_item(p,9,(void*)g_options.my_ip,strlen(g_options.my_ip));


	size = p - packet;
	p = packet + 1;
	*p++ = size;
	memset(p,0,16);
	MD5(p,packet,size);
	encrypt(packet,size);
	
	return size;
}


/**
 *	构造一个 login 协议报文
 *
 *	@param size packet 缓冲区长度
 *	@return 返回构造出的报文长度
 *	@note 未检查是否构造越过 packet 边界
 */
int packet_login(unsigned char *packet,int size)
{
	unsigned char c = 1;
	unsigned char *p;

	p = packet;
	*p++ = 1;
	p += 16 + 1;

	p = add_item(p,1,(void*)g_options.username,strlen(g_options.username));

	p = add_item(p,2,(void*)g_options.password,strlen(g_options.password));

	p = add_item(p,7,(void*)g_options.my_mac,sizeof(g_options.my_mac));

	p = add_item(p,9,(void*)g_options.my_ip,strlen(g_options.my_ip));

	p = add_item(p,0x0A,(void*)g_options.services,strlen(g_options.services));

	p = add_item(p,0x1F,(void*)g_options.version,strlen(g_options.version));

	p = add_item(p,0x20,(void*)&c,1);
	
	size = p - packet;
	p = packet + 1;
	*p++ = size;
	memset(p,0,16);
	MD5(p,packet,size);
	encrypt(packet,size);
	
	return size;	
}