DLL injection

DLL injection

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In computer programming, DLL injection is a technique used to run code within the address space of another process by forcing it to load a dynamic-link library.^[1] DLL injection is often used by third-party developers to influence the behavior of a program in a way its authors did not anticipate or intend.^[1][2][3] For example, the injected code could trap system function calls,^[4][5] or read the contents of password textboxes, which cannot be done the usual way.^[6]

[edit] Approaches on Microsoft Windows

There are at least four ways to force a program to load a DLL on Microsoft Windows:

• DLLs listed under the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows\AppInit_DLLs will be loaded into every process that links to User32.dll as that DLL attaches itself to the process.^[5][7][8][9]
• Process manipulation functions such as CreateRemoteThread can be used to inject a DLL into a program after it has started.^{[5][6][10][11][12][13]}
  1. Get a handle to the target process. This can be done by spawning the process^[14][15] or by keying off something created by that process that is known to exist – for instance, a window with a predictable title,^[16] or by obtaining a list of running processes^[17] and scanning for the target executable's filename.^[18]
  2. Allocate some memory in the target process,^[19] and the name of the DLL to be injected is written to it.^[10][20]

     This step can be skipped if a suitable DLL name is already available in the target process. For example, if a process links to ‘User32.dll’, ‘GDI32.dll’, ‘Kernel32.dll’ or any other library whose name ends in ‘32.dll’, it would be possible to load a library named ‘32.dll’. This technique has in the past been demonstrated to be effective against a method of guarding processes against DLL injection. ^[21]

  3. Create a new thread in the target process^[22] with the thread's start address set to be the address of LoadLibrary and the argument set to the address of the string just uploaded into the target.^[10][23]

     Instead of writing the name of a DLL-to-load to the target and starting the new thread at LoadLibrary, one can write the code-to-be-executed to the target and start the thread at that code. ^[6]

  4. The operating system will now call DllMain in the injected DLL.^[10][24]

  Note that without precautions, this approach can be detected by the target process due to the DLL_THREAD_ATTACH notifications sent to every loaded module as a thread starts. ^[24]

• Windows hooking calls such as SetWindowsHookEx.^{[2][5][6][25][26][27]}
• Use the debugging functions to pause all threads, and then hijack an existing thread in the application to execute injected code, that in turn could load a DLL.^[4][28][29]

[edit] Approaches on Unix-like systems

On Unix-like operating systems with the dynamic linker based on ld.so (on BSD) and ld-linux.so (on Linux), arbitrary libraries can be linked to a new process by giving the library's pathname in the LD PRELOAD environment variable, that can be set globally or individually for a single process.^[30]

For example, in bash, this command launches the command "prog-help" with the shared library from file "test.so" linked into it at the launchtime:

LD_PRELOAD="./test.so" prog—help

Such a library can be created with GCC by compiling the source file containing the new globals to be linked, with the -fpic or -fPIC option,^[31] and linking with the -shared option.^[32] The library has access to external symbols declared in the program like any other library.

[edit] References

1. ^ ^{a b} James Shewmaker (2006). "Analyzing DLL Injection" (PDF). GSM Presentation. Bluenotch. http://bluenotch.com/files/Shewmaker-DLL-Injection.pdf. Retrieved 2008-08-31. 
2. ^ ^{a b} Iczelion (August 2002). "Tutorial 24: Windows Hooks". Iczelion's Win32 Assembly Homepage. http://win32assembly.online.fr/tut24.html. Retrieved 2008-08-31. 
3. ^ Rocky Pulley (2005-05-19). "Extending Task Manager with DLL Injection". CodeProject. CodeProject. http://secure.codeproject.com/KB/threads/taskex.aspx. Retrieved 2008-09-01. 
4. ^ ^{a b} Nasser R. Rowhani (2003-10-23). "DLL Injection and function interception tutorial". CodeProject. CodeProject. http://www.codeproject.com/KB/DLL/DLL_Injection_tutorial.aspx. Retrieved 2008-08-31. 
5. ^ ^{a b c d} Ivo Ivanov (2002-12-02). "API hooking revealed". CodeProject. CodeProject. http://www.codeproject.com/KB/system/hooksys.aspx. Retrieved 2008-08-31. 
6. ^ ^{a b c d} Robert Kuster (2003-08-20). "Three Ways to Inject Your Code into Another Process". CodeProject. CodeProject. http://www.codeproject.com/KB/threads/winspy.aspx. Retrieved 2008-08-31. 
7. ^ "Working with the AppInit_DLLs registry value". Microsoft Help and Support. Microsoft. 2006-11-21. http://support.microsoft.com/kb/197571. Retrieved 2008-08-31. 
8. ^ Raymond Chen (2007-12-13). "AppInit_DLLs should be renamed Deadlock_Or_Crash_Randomly_DLLs". The Old New Thing. Microsoft. http://blogs.msdn.com/oldnewthing/archive/2007/12/13/6648400.aspx. Retrieved 2008-08-31. 
9. ^ "dllmain.c". ReactOS. ReactOS Foundation. 2008-07-08. http://svn.reactos.org/svn/reactos/trunk/reactos/dll/win32/user32/misc/dllmain.c?view=markup. Retrieved 2008-08-31. 
10. ^ ^{a b c d} Trent Waddington. "InjectDLL". http://www.quantumg.net/injectdll.php. Retrieved 2008-08-31. 
11. ^ "Dll Injection". DreamInCode.net. MediaGroup1. 2006-05-04. http://www.dreamincode.net/code/snippet407.htm. Retrieved 2008-08-31. 
12. ^ Greg Jenkins (November 2007). "DLL Injection Framework". Ring3 Circus. WordPress. http://www.ring3circus.com/downloads/dll-injection-framework/. Retrieved 2008-08-31. 
13. ^ Drew Benton (2007-08-17). "A More Complete DLL Injection Solution Using CreateRemoteThread". CodeProject. CodeProject. http://69.10.233.10/KB/threads/completeinject.aspx. Retrieved 2008-09-01. 
14. ^ CreateProcess ms-help://MS.PSDKXPSP2.1033/dllproc/base/createprocess.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
15. ^ PROCESS_INFORMATION ms-help://MS.PSDKXPSP2.1033/dllproc/base/process_information_str.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
16. ^ GetWindowThreadProcessId Function ms-help://MS.PSDKXPSP2.1033/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/getwindowthreadprocessid.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
17. ^ EnumProcesses ms-help://MS.PSDKXPSP2.1033/perfmon/base/enumprocesses.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
18. ^ GetModuleBaseName ms-help://MS.PSDKXPSP2.1033/perfmon/base/getmodulebasename.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
19. ^ VirtualAllocEx ms-help://MS.PSDKXPSP2.1033/memory/base/virtualallocex.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
20. ^ WriteProcessMemory ms-help://MS.PSDKXPSP2.1033/debug/base/writeprocessmemory.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
21. ^ "Outpost Bypassing Self-Protection via Advanced DLL injection with handle stealing Vulnerability". Matousec. 2006-12-01. http://www.matousec.com/info/advisories/Outpost-Bypassing-Self-Protection-via-Advanced-DLL-injection-with-handle-stealing.php. Retrieved 2008-08-31. 
22. ^ CreateRemoteThread ms-help://MS.PSDKXPSP2.1033/dllproc/base/createremotethread.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
23. ^ LoadLibrary ms-help://MS.PSDKXPSP2.1033/dllproc/base/loadlibrary.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
24. ^ ^{a b} DllMain ms-help://MS.PSDKXPSP2.1033/dllproc/base/dllmain.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
25. ^ SetWindowsHookEx Function ms-help://MS.PSDKXPSP2.1033/winui/winui/windowsuserinterface/windowing/hooks/hookreference/hookfunctions/setwindowshookex.htm Platform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31.
26. ^ "AppInit_DLLs Registry Value and Windows 95". Microsoft Help and Support. Microsoft. 2005-03-01. http://support.microsoft.com/kb/134655. Retrieved 2008-08-31. 
27. ^ "Dll Injection using SetWindowsHookEx() Method". Game Reversal. 2008-04-03. http://www.gamereversal.com/index.php?option=com_content&view=article&id=56%3Adll-injection-using-setwindowshookex-method&catid=39%3Ac--c-core-concepts&Itemid=1. Retrieved 2008-09-01. 
28. ^ "SetThreadContext DLL Injection". 2007-01-16. http://nerd.egloos.com/2940083. Retrieved 2008-09-01. 
29. ^ Ben Botto (2008-09-06). "DLL Injector". http://busybin.com/busybin/C++/dll_injector/. Retrieved 2008-09-01. 
30. ^ Linus Torvalds; David Engel, Eric Youngdale, Peter MacDonald, Hongjiu Lu, Lars Wirzenius and Mitch D'Souza (1998-03-14). ld.so/ld-linux.so – dynamic linker/loader man ld.so UNIX man pages. Retrieved on 2008-08-31.
31. ^ "Code Gen Options". Using the GNU Compiler Collection (GCC). Free Software Foundation. http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Code-Gen-Options.html#Code-Gen-Options. Retrieved 2008-08-31. "-fpic Generate position-independent code (PIC) suitable for use in a shared library, if supported for the target machine. sqq." 
32. ^ "Link Options". Using the GNU Compiler Collection (GCC). Free Software Foundation. http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Link-Options.html#Link-Options. Retrieved 2008-08-31. "-shared Produce a shared object which can then be linked with other objects to form an executable. sqq."

转载：http://en.wikipedia.org/wiki/DLL_injection