基于RawSocket的嗅探器设计与实现选座题目及资料.doc

基于Raw Socket的嗅探器设计与实现

功能：
基于Raw Socket实现IP 层以上原始数据包的发送和接受。

一. 摘要
Raw Socket: 原始套接字，可以用它来发送和接受 IP 层以上的原始数据包, 如 ICMP, TCP, UDP...
int sockRaw = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
Sniffer（嗅探器）基本原理与实现过程
1. 把网卡置于混杂模式;
2. 捕获数据包;
3. 分析数据包.

二. 把网卡置于混杂模式
在正常的情况下，一个网络接口应当只响应两种数据帧：
l 与自己硬件地址相匹配的数据帧
l 发向所有机器的广播数据帧
假如要网卡接受发向所有机器的广播数据帧，就必须把网卡置于混杂模式。
用 Raw Socket 实现代码如下:
//设立 IP 头操作选项
setsockopt(sock, IPPROTO_IP, IP_HDRINCL, (char*)&flag, sizeof(flag);
//把 sockRaw 绑定到本地网卡上
bind(sockRaw, (PSOCKADDR)&addrLocal, sizeof(addrLocal);
//让 sockRaw 接受所有的数据
ioctlsocket(sockRaw, SIO_RCVALL, &dwValue);
flag 标志是用来设立 IP 头操作的, 也就是说要亲自解决 IP 头: bool flag = ture;
addrLocal 为本地地址: SOCKADDR_IN addrLocal;
dwValue 为输入输出参数, 为 1 时执行, 0 时取消: DWORD dwValue = 1;
三. 捕获数据包
#define BUFFER_SIZE 65535
char RecvBuf[BUFFER_SIZE];

//接受任意数据包
recv(sockRaw, RecvBuf, BUFFER_SIZE, 0);

四. 分析数据包
用 recv()接受到的数据包中包含IP、TCP 等原始信息。要分析它一方面得知道这些结构.
数据包的总体结构:
----------------------------------------------
| ip header | tcp header(or x header) | data |
----------------------------------------------

IP header structure:
4 8 16 32 bit
|--------|--------|----------------|--------------------------------|
| Ver | IHL |Typeofservice| Total length |
|--------|--------|----------------|--------------------------------|
| Identification | Flags | Fragment offset |
|--------|--------|----------------|--------------------------------|
| Time to live | Protocol | Header checksum |
|--------|--------|----------------|--------------------------------|
| Source address |
|--------|--------|----------------|--------------------------------|
| Destination address |
|--------|--------|----------------|--------------------------------|
| Option + Padding |
|--------|--------|----------------|--------------------------------|
| Data |
|--------|--------|----------------|--------------------------------|

TCP header structure:
16 32 bit
|--------------------------------|--------------------------------|
| Source port | Destination port |
|--------------------------------|--------------------------------|
| Sequence number |
|--------------------------------|--------------------------------|
| Acknowledgement number |
|--------------------------------|--------------------------------|
| Offset | Resrvd |U|A|P|R|S|F| Window |
|--------------------------------|--------------------------------|
| Checksum | Urgent pointer |
|--------------------------------|--------------------------------|
| Option + Padding |
|--------------------------------|--------------------------------|
| Data |
|--------------------------------|--------------------------------|

五. 实现 Sniffer
用 BCB6 写的一个 Simple Sniffer 的代码, 仅供参考.
（需要在工程文献里加入WS2_32.LIB这个文献）
//*************************************************************************//
//* CPP File: WMain.cpp
//* Simple Sniffer by shadowstar
//*
//*************************************************************************//
#include <vcl.h>
#pragma hdrstop

#include <winsock2.h>
#include <ws2tcpip.h>
#include <mstcpip.h>
#include <netmon.h>
#include "WMain.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TMainForm *MainForm;
//---------------------------------------------------------------------------
__fastcall TMainForm::TMainForm(TComponent* Owner)
: TForm(Owner)
{
WSADATA WSAData;
BOOL flag = true;
int nTimeout = 1000;
char LocalName[16];
struct hostent *pHost;

//检查 Winsock 版本号
if (WSAStartup(MAKEWORD(2, 2), &WSAData) != 0)
throw Exception("WSAStartup error!");

//初始化 Raw Socket
if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) == INVALID_SOCKET)
throw Exception("socket setup error!");

//设立IP头操作选项
if (setsockopt(sock, IPPROTO_IP, IP_HDRINCL, (char*)&flag, sizeof(flag)) == SOCKET_ERROR)
throw Exception("setsockopt IP_HDRINCL error!");

//获取本机名
if (gethostname((char*)LocalName, sizeof(LocalName)-1) == SOCKET_ERROR)
throw Exception("gethostname error!");

//获取本地 IP 地址
if ((pHost = gethostbyname((char*)LocalName)) == NULL)
throw Exception("gethostbyname error!");

addr_in.sin_addr = *(in_addr *)pHost->h_addr_list[0]; //IP
addr_in.sin_family = AF_INET;
addr_in.sin_port = htons(57274);

//把 sock 绑定到本地地址上
if (bind(sock, (PSOCKADDR)&addr_in, sizeof(addr_in)) == SOCKET_ERROR)
throw Exception("bind error!");

iSortDirection = 1;
}
//---------------------------------------------------------------------------
__fastcall TMainForm::~TMainForm()
{
WSACleanup();
}
//---------------------------------------------------------------------------

void __fastcall TMainForm::btnCtrlClick(TObject *Sender)
{
TListItem *Item;
DWORD dwValue;
int nIndex = 0;

if (btnCtrl->Caption == "&Start")
{
dwValue = 1;
//设立 SOCK_RAW 为SIO_RCVALL，以便接受所有的IP包
if (ioctlsocket(sock, SIO_RCVALL, &dwValue) != 0)
throw Exception("ioctlsocket SIO_RCVALL error!");
bStop = false;
btnCtrl->Caption = "&Stop";
lsvPacket->Items->Clear();
}
else
{
dwValue = 0;
bStop = true;
btnCtrl->Caption = "&Start";
//设立SOCK_RAW为SIO_RCVALL，停止接受
if (ioctlsocket(sock, SIO_RCVALL, &dwValue) != 0)
throw Exception("WSAIoctl SIO_RCVALL error!");
}

while (!bStop)
{
if (recv(sock, RecvBuf, BUFFER_SIZE, 0) > 0)
{
nIndex++;

ip = *(IP*)RecvBuf;
tcp = *(TCP*)(RecvBuf + (ip.HdrLen & IP_HDRLEN_MASK));

Item = lsvPacket->Items->Add();
Item->Caption = nIndex;
Item->SubItems->Add(GetProtocolTxt(ip.Protocol));
Item->SubItems->Add(inet_ntoa(*(in_addr*)&ip.SrcAddr));
Item->SubItems->Add(inet_ntoa(*(in_addr*)&ip.DstAddr));
Item->SubItems->Add(tcp.SrcPort);
Item->SubItems->Add(tcp.DstPort);
Item->SubItems->Add(ntohs(ip.TotalLen));
}
Application->ProcessMessages();
}
}
//---------------------------------------------------------------------------

AnsiString __fastcall TMainForm::GetProtocolTxt(int Protocol)
{
switch (Protocol)
{
case IPPROTO_ICMP : //1 /* control message protocol */
return PROTOCOL_STRING_ICMP_TXT;
case IPPROTO_TCP : //6 /* tcp */
return PROTOCOL_STRING_TCP_TXT;
case IPPROTO_UDP : //17 /* user datagram protocol */
return PROTOCOL_STRING_UDP_TXT;
default :
return PROTOCOL_STRING_UNKNOWN_TXT;
}
}
//---------------------------------------------------------------------------

//*************************************************************************//
//* Header File: WMain.h for WMain.cpp class TMainForm
//*************************************************************************//
//---------------------------------------------------------------------------

#ifndef WMainH
#define WMainH
//---------------------------------------------------------------------------
#define BUFFER_SIZE 65535

#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
#include <ComCtrls.hpp>
#include <ExtCtrls.hpp>
#include <winsock2.h>
#include "netmon.h"

//---------------------------------------------------------------------------
class TMainForm : public TForm
{
__published: // IDE-managed Components
TPanel *Panel1;
TButton *btnCtrl;
TListView *lsvPacket;
TLabel *Label1;
void __fastcall btnCtrlClick(TObject *Sender);
void __fastcall lsvPacketColumnClick(TObject *Sender,
TListColumn *Column);
void __fastcall lsvPacketCompare(TObject *Sender, TListItem *Item1,
TListItem *Item2, int Data, int &Compare);
void __fastcall Label1Click(TObject *Sender);
private: // User declarations
AnsiString __fastcall GetProtocolTxt(int Protocol);
public: // User declarations
SOCKET sock;
SOCKADDR_IN addr_in;
IP ip;
TCP tcp;
PSUHDR psdHeader;
char RecvBuf[BUFFER_SIZE];
bool bStop;

int iSortDirection;
int iColumnToSort;

__fastcall TMainForm(TComponent* Owner);
__fastcall ~TMainForm();
};
//---------------------------------------------------------------------------
extern PACKAGE TMainForm *MainForm;
//---------------------------------------------------------------------------
#endif

IP, TCP 头及一些宏定义用了 netmon.h 的头, 这个文献在 BCB6 的 include 目录下可以找得到, 其中与本程序相关内容如下:
//*************************************************************************//
//* Header File: netmon.h
//*************************************************************************//
//
// IP Packet Structure
//
typedef struct _IP
{
union
{
BYTE Version;
BYTE HdrLen;
};
BYTE ServiceType;
WORD TotalLen;
WORD ID;
union
{
WORD Flags;
WORD FragOff;
};
BYTE TimeToLive;
BYTE Protocol;
WORD HdrChksum;
DWORD SrcAddr;
DWORD DstAddr;
BYTE Options[0];
} IP;

typedef IP * LPIP;
typedef IP UNALIGNED * ULPIP;

//
// TCP Packet Structure
//
typedef struct _TCP
{
WORD SrcPort;
WORD DstPort;
DWORD SeqNum;
DWORD AckNum;
BYTE DataOff;
BYTE Flags;
WORD Window;
WORD Chksum;
WORD UrgPtr;
} TCP;

typedef TCP *LPTCP;
typedef TCP UNALIGNED * ULPTCP;

// upper protocols
#define PROTOCOL_STRING_ICMP_TXT "ICMP"
#define PROTOCOL_STRING_TCP_TXT "TCP"
#define PROTOCOL_STRING_UDP_TXT "UDP"
#define PROTOCOL_STRING_SPX_TXT "SPX"
#define PROTOCOL_STRING_NCP_TXT "NCP"

#define PROTOCOL_STRING_UNKNOW_TXT "UNKNOW"

这个文献也有人声称没有.
//*************************************************************************//
//* Header File: mstcpip.h
//*************************************************************************//
// Copyright (c) Microsoft Corporation. All rights reserved.
#if _MSC_VER > 1000
#pragma once
#endif

/* Argument structure for SIO_KEEPALIVE_VALS */

struct tcp_keepalive {
u_long onoff;
u_long keepalivetime;
u_long keepaliveinterval;
};

// New WSAIoctl Options

#define SIO_RCVALL _WSAIOW(IOC_VENDOR,1)
#define SIO_RCVALL_MCAST _WSAIOW(IOC_VENDOR,2)
#define SIO_RCVALL_IGMPMCAST _WSAIOW(IOC_VENDOR,3)
#define SIO_KEEPALIVE_VALS _WSAIOW(IOC_VENDOR,4)
#define SIO_ABSORB_RTRALERT _WSAIOW(IOC_VENDOR,5)
#define SIO_UCAST_IF _WSAIOW(IOC_VENDOR,6)
#define SIO_LIMIT_BROADCASTS _WSAIOW(IOC_VENDOR,7)
#define SIO_INDEX_BIND _WSAIOW(IOC_VENDOR,8)
#define SIO_INDEX_MCASTIF _WSAIOW(IOC_VENDOR,9)
#define SIO_INDEX_ADD_MCAST _WSAIOW(IOC_VENDOR,10)
#define SIO_INDEX_DEL_MCAST _WSAIOW(IOC_VENDOR,11)

// Values for use with SIO_RCVALL* options
#define RCVALL_OFF 0
#define RCVALL_ON 1
#define RCVALL_SOCKETLEVELONLY 2

六. 小结
优点: 实现简朴, 不需要做驱动程序就可实现抓包.
缺陷: 数据包头不含帧信息, 不能接受到与 IP 同层的其它数据包, 如 ARP, RARP；没有对数据包进行进一步的分析。