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https://git.tartarus.org/simon/putty.git
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44 lines
1.6 KiB
C
44 lines
1.6 KiB
C
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/*
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* If the OS provides it, call SetDefaultDllDirectories() to prevent
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* DLLs from being loaded from the directory containing our own
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* binary, and instead only load from system32.
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*
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* This is a protection against hijacking attacks, if someone runs
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* PuTTY directly from their web browser's download directory having
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* previously been enticed into clicking on an unwise link that
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* downloaded a malicious DLL to the same directory under one of
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* various magic names that seem to be things that standard Windows
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* DLLs delegate to.
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*
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* It shouldn't break deliberate loading of user-provided DLLs such as
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* GSSAPI providers, because those are specified by their full
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* pathname by the user-provided configuration.
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*/
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#include "putty.h"
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void dll_hijacking_protection(void)
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{
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static HMODULE kernel32_module;
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DECL_WINDOWS_FUNCTION(static, BOOL, SetDefaultDllDirectories, (DWORD));
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if (!kernel32_module) {
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kernel32_module = load_system32_dll("kernel32.dll");
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#if !HAVE_SETDEFAULTDLLDIRECTORIES
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/* For older Visual Studio, this function isn't available in
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* the header files to type-check */
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GET_WINDOWS_FUNCTION_NO_TYPECHECK(
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kernel32_module, SetDefaultDllDirectories);
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#else
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GET_WINDOWS_FUNCTION(kernel32_module, SetDefaultDllDirectories);
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#endif
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}
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if (p_SetDefaultDllDirectories) {
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/* LOAD_LIBRARY_SEARCH_SYSTEM32 and explicitly specified
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* directories only */
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p_SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_SYSTEM32 |
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LOAD_LIBRARY_SEARCH_USER_DIRS);
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}
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}
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