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cwindowsloadlibrarygetprocaddresspointer-address

GetProcAddress weird return address

Someone explain why the next code returns a pointer inside ntdll.dll?

GetProcAddress(LoadLibraryA("kernel32.dll"), "EncodePointer");
GetProcAddress(LoadLibraryA("kernel32.dll"), "DecodePointer");

PS: If call the function pointed by kernel32's export table a breakpoint is thrown.

Solution

  • This is a simple case of export forwarding, as described in one of Matt Pietrek's excellent MSDN magazine articles, An In-Depth Look into the Win32 Portable Executable File Format, Part 2.

    You can verify this yourself with a tool like Dependency Walker or dumpbin.

    dumpbin /exports kernel32.dll | grep codePointer

    205   CC          DecodePointer (forwarded to NTDLL.RtlDecodePointer)
    240   EF          EncodePointer (forwarded to NTDLL.RtlEncodePointer)