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Load handler DLL with load dir on the path #63773

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Sep 23, 2025
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Load handler DLL with load dir on the path #63773

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2 changes: 1 addition & 1 deletion src/Servers/IIS/AspNetCoreModuleV2/AspNetCore/HandlerResolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -110,7 +110,7 @@ HandlerResolver::LoadRequestHandlerAssembly(const IHttpApplication &pApplication

LOG_INFOF(L"Loading request handler: '%ls'", handlerDllPath.c_str());

hRequestHandlerDll = LoadLibrary(handlerDllPath.c_str());
hRequestHandlerDll = LoadLibraryEx(handlerDllPath.c_str(), nullptr, LOAD_LIBRARY_SEARCH_DEFAULT_DIRS | LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR);
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this will search 4 places -- current dll, app, System32 and any AddDllDirectory/SetDllDirectory. Do we need all those places?

I see in the code of this dll we may SetDllDirectory to the current directory. Is that relevant?

aspnetcore/src/Servers/IIS/AspNetCoreModuleV2/InProcessRequestHandler/inprocessapplication.cpp

Line 297 in bb2d778

LOG_LAST_ERROR_IF(!SetDllDirectory(currentDirectory.c_str()));

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I'm wondering whether it's well defined exactly where it should look and that's something more limited than this range. As far as security goes, I guess we trust app directory/dll directory. We do not necessarily trust current directory, in general.

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I believe the only behavioral difference introduced here is that we now search the directory where the handler DLL is as well. The other places (app dir, system32, etc.) are already being searched with the current LoadLibrary code.

The inprocessapplication.cpp code you linked to is not yet relevant at this point; that comes later.

RETURN_LAST_ERROR_IF_NULL(hRequestHandlerDll);

if (preventUnload)
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