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_DLLswill 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]
- 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]
- 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]
- 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]
- 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
- ^ a b James Shewmaker (2006). "Analyzing DLL Injection" (PDF). GSM Presentation. Bluenotch. http://bluenotch.com/files/Shewmaker-DLL-Injection.pdf. Retrieved 2008-08-31.
- ^ a b Iczelion (August 2002). "Tutorial 24: Windows Hooks". Iczelion's Win32 Assembly Homepage. http://win32assembly.online.fr/tut24.html. Retrieved 2008-08-31.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ "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.
- ^ 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.
- ^ "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.
- ^ a b c d Trent Waddington. "InjectDLL". http://www.quantumg.net/injectdll.php. Retrieved 2008-08-31.
- ^ "Dll Injection". DreamInCode.net. MediaGroup1. 2006-05-04. http://www.dreamincode.net/code/snippet407.htm. Retrieved 2008-08-31.
- ^ Greg Jenkins (November 2007). "DLL Injection Framework". Ring3 Circus. WordPress. http://www.ring3circus.com/downloads/dll-injection-framework/. Retrieved 2008-08-31.
- ^ 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.
- ^ CreateProcess
ms-help://MS.PSDKXPSP2.1033/dllproc/base/createprocess.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ PROCESS_INFORMATION
ms-help://MS.PSDKXPSP2.1033/dllproc/base/process_information_str.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ GetWindowThreadProcessId Function
ms-help://MS.PSDKXPSP2.1033/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/getwindowthreadprocessid.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ EnumProcesses
ms-help://MS.PSDKXPSP2.1033/perfmon/base/enumprocesses.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ GetModuleBaseName
ms-help://MS.PSDKXPSP2.1033/perfmon/base/getmodulebasename.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ VirtualAllocEx
ms-help://MS.PSDKXPSP2.1033/memory/base/virtualallocex.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ WriteProcessMemory
ms-help://MS.PSDKXPSP2.1033/debug/base/writeprocessmemory.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ "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.
- ^ CreateRemoteThread
ms-help://MS.PSDKXPSP2.1033/dllproc/base/createremotethread.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ LoadLibrary
ms-help://MS.PSDKXPSP2.1033/dllproc/base/loadlibrary.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ a b DllMain
ms-help://MS.PSDKXPSP2.1033/dllproc/base/dllmain.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ SetWindowsHookEx Function
ms-help://MS.PSDKXPSP2.1033/winui/winui/windowsuserinterface/windowing/hooks/hookreference/hookfunctions/setwindowshookex.htmPlatform SDK for Windows XP SP2. Microsoft. Retrieved on 2008-08-31. - ^ "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.
- ^ "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.
- ^ "SetThreadContext DLL Injection". 2007-01-16. http://nerd.egloos.com/2940083. Retrieved 2008-09-01.
- ^ Ben Botto (2008-09-06). "DLL Injector". http://busybin.com/busybin/C++/dll_injector/. Retrieved 2008-09-01.
- ^ 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.soUNIX man pages. Retrieved on 2008-08-31. - ^ "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. "
-fpicGenerate position-independent code (PIC) suitable for use in a shared library, if supported for the target machine. sqq." - ^ "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. "
-sharedProduce a shared object which can then be linked with other objects to form an executable. sqq."