Improve Notepad++ UAC operations largely

This native implementation of UAC (User Account Control) operations in Notepad++ is designed not only to substitute the deprecated & problematic NppSaveAsAdminPlugin - which interferes with the FlushFileBuffers WINAPI used by Notepad++ - but also to support any future Notepad++ feature which may require elevated privileges.

When a user attempts an operation that fails due to indufficient rights, the system performs only that specific requested action with elevated privileges. After completing it, the elevated Notepad++ instance immediately exits, returning the user to his/her original Notepad++ instance seamlessly, as if nothing unusual occured.

This mechanism is independent of any Notepad++ features such as backup-snapshot or multi-instance mode. All UAC-related operations are executed at the very beginning of the wWinMain function, ensuring they are not affected by mutex handling, or other internal logic.

Importantly, this approach eliminates the need for a separate signed helper executable like NppAdminAcess.exe. Everything is handled within the main Notepad++ project, just as before.

In this commit, the NPP_UAC_SAVE, NPP_UAC_SETFILEATTRIBUTES & NPP_UAC_MOVEFILE are implemented.

Summary of the changes:

added last _dwErrorCode in:
.\PowerEditor\src\MISC\Common\FileInterface.h
.\PowerEditor\src\MISC\Common\FileInterface.cpp

FileManager::saveBuffer adjustment for the NPP_UAC_SAVE_SIGN in:
.\PowerEditor\src\ScintillaComponent\Buffer.cpp

N++ UAC ops signatures definitions & new invokeNppUacOp common func, toggleReadOnlyFlagFromFileAttributes func adjustment for the NPP_UAC_SETFILEATTRIBUTES_SIGN in:
.\PowerEditor\src\MISC\Common\Common.h
.\PowerEditor\src\MISC\Common\Common.cpp

only to fix Notepad_plus::doSave for isEndSessionCritical() in:
.\PowerEditor\src\NppIO.cpp

added getLastFileErrorState() & m_dwLastFileError in:
.\PowerEditor\src\Utf8_16.h
.\PowerEditor\src\Utf8_16.cpp

UAC ops handling at the very start of wWinMain + added new NPP_UAC_ handling nppUacSave and nppUacSetFileAttributes funcs in:
.\PowerEditor\src\winmain.cpp

Fix notepad-plus-plus#886, fix notepad-plus-plus#8655, fix notepad-plus-plus#9561, fix notepad-plus-plus#10302, fix notepad-plus-plus#14990, fix notepad-plus-plus#15008, fix notepad-plus-plus#15137, fix notepad-plus-plus#15323, close notepad-plus-plus#16933

Author: xomx

PowerEditor/src/MISC/Common/Common.cpp

@@ -1537,7 +1537,25 @@ bool toggleReadOnlyFlagFromFileAttributes(const wchar_t* fileFullPath, bool& isC
 	}
 	else
 	{
-		// probably the ERROR_ACCESS_DENIED (5) (TODO: UAC-prompt candidate)
+		if (::GetLastError() == ERROR_ACCESS_DENIED)
+		{
+			// try to set elevated
+			// (notepad++.exe #UAC-SETFILEATTRIBUTES# attrib_flags_number_str dest_file_path)
+			wstring strCmdLineParams = NPP_UAC_SETFILEATTRIBUTES_SIGN;
+			strCmdLineParams += L" \"" + to_wstring(dwFileAttribs) + L"\" \"";
+			strCmdLineParams += fileFullPath;
+			strCmdLineParams += L"\"";
+			DWORD dwNppUacOpError = invokeNppUacOp(strCmdLineParams);
+			if (dwNppUacOpError == NO_ERROR)
+			{
+				isChangedToReadOnly = (dwFileAttribs & FILE_ATTRIBUTE_READONLY) != 0;
+				return true;
+			}
+			else
+			{
+				::SetLastError(dwNppUacOpError); // set that as our current thread one for a possible reporting later
+			}
+		}
 		return false;
 	}
 }
@@ -2154,3 +2172,40 @@ void ControlInfoTip::hide()
 }
 
 #pragma warning(default:4996)
+
+DWORD invokeNppUacOp(std::wstring& strCmdLineParams)
+{
+	if ((strCmdLineParams.length() == 0) || (strCmdLineParams.length() > (USHRT_MAX / sizeof(WCHAR))))
+	{
+		// no cmdline or it exceeds the current max WinOS 32767 WCHARs
+		return ERROR_INVALID_PARAMETER;
+	}
+
+	wchar_t wszNppFullPath[MAX_PATH]{};
+	::SetLastError(NO_ERROR);
+	if (!::GetModuleFileName(NULL, wszNppFullPath, MAX_PATH) || (::GetLastError() == ERROR_INSUFFICIENT_BUFFER))
+	{
+		return ::GetLastError();
+	}
+
+	SHELLEXECUTEINFOW sei{};
+	sei.cbSize = sizeof(SHELLEXECUTEINFOW);
+	sei.lpVerb = L"runas"; // UAC prompt
+	sei.nShow = SW_SHOWNORMAL;
+	sei.fMask = SEE_MASK_NOCLOSEPROCESS; // sei.hProcess member receives the launched process handle
+	sei.lpFile = wszNppFullPath;
+	sei.lpParameters = strCmdLineParams.c_str();
+	if (!::ShellExecuteExW(&sei))
+		return ::GetLastError();
+
+	// wait for the elevated Notepad++ process to finish
+	DWORD dwError = NO_ERROR;
+	if (sei.hProcess) // beware - do not check here for the INVALID_HANDLE_VALUE (valid GetCurrentProcess() pseudohandle)
+	{
+		::WaitForSingleObject(sei.hProcess, INFINITE);
+		::GetExitCodeProcess(sei.hProcess, &dwError);
+		::CloseHandle(sei.hProcess);
+	}
+
+	return dwError;
+}

PowerEditor/src/MISC/Common/Common.h

@@ -331,3 +331,9 @@ class ControlInfoTip final
 	ControlInfoTip(const ControlInfoTip&) = delete;
 	ControlInfoTip& operator=(const ControlInfoTip&) = delete;
 };
+
+
+#define NPP_UAC_SAVE_SIGN L"#UAC-SAVE#"
+#define NPP_UAC_SETFILEATTRIBUTES_SIGN L"#UAC-SETFILEATTRIBUTES#"
+#define NPP_UAC_MOVEFILE_SIGN L"#UAC-MOVEFILE#"
+DWORD invokeNppUacOp(std::wstring& strCmdLineParams);

PowerEditor/src/MISC/Common/FileInterface.cpp

@@ -54,7 +54,10 @@ Win32_IO_File::Win32_IO_File(const wchar_t *fname)
 		{
 			bool isFromNetwork = PathIsNetworkPath(fname);
 			if (isFromNetwork && isTimeoutReached) // The file doesn't exist, and the file is a network file, plus the network problem has been detected due to timeout
-				return;                             // In this case, we don't call createFile to prevent hanging
+			{
+				_dwErrorCode = ERROR_FILE_NOT_FOUND; // store
+				return;                              // In this case, we don't call createFile to prevent hanging
+			}
 		}
 
 		_hFile = ::CreateFileW(fname, _accessParam, _shareParam, NULL, dispParam, _attribParam, NULL);
@@ -68,6 +71,9 @@ Win32_IO_File::Win32_IO_File(const wchar_t *fname)
 			_hFile = ::CreateFileW(fname, _accessParam, _shareParam, NULL, dispParam, _attribParam, NULL);
 		}
 
+		if (_hFile == INVALID_HANDLE_VALUE)
+			_dwErrorCode = ::GetLastError(); // store
+
 		if (fileExists && (dispParam == CREATE_ALWAYS) && (_hFile != INVALID_HANDLE_VALUE))
 		{
 			// restore back the original creation date & attributes
@@ -91,7 +97,7 @@ Win32_IO_File::Win32_IO_File(const wchar_t *fname)
 			else
 			{
 				msg += " failed to open, CreateFileW ErrorCode: ";
-				msg += std::to_string(::GetLastError());
+				msg += std::to_string(_dwErrorCode);
 			}
 			writeLog(nppIssueLog.c_str(), msg.c_str());
 		}
@@ -100,11 +106,13 @@ Win32_IO_File::Win32_IO_File(const wchar_t *fname)
 
 void Win32_IO_File::close()
 {
+	_dwErrorCode = NO_ERROR; // reset
+
 	if (isOpened())
 	{
 		NppParameters& nppParam = NppParameters::getInstance();
 
-		DWORD flushError = NOERROR;
+		DWORD flushError = NO_ERROR;
 		if (_written)
 		{
 			if (!::FlushFileBuffers(_hFile))
@@ -159,7 +167,14 @@ Please try using another storage and also check if your saved data is not corrup
 				}
 			}
 		}
-		::CloseHandle(_hFile);
+
+		_dwErrorCode = flushError; // store possible flushing error 1st
+
+		if (!::CloseHandle(_hFile))
+		{
+			if (!flushError)
+				_dwErrorCode = ::GetLastError(); // store
+		}
 
 		_hFile = INVALID_HANDLE_VALUE;
 
@@ -194,6 +209,8 @@ Please try using another storage and also check if your saved data is not corrup
 
 bool Win32_IO_File::write(const void *wbuf, size_t buf_size)
 {
+	_dwErrorCode = NO_ERROR; // reset
+
 	if (!isOpened() || (wbuf == nullptr))
 		return false;
 
@@ -203,6 +220,7 @@ bool Win32_IO_File::write(const void *wbuf, size_t buf_size)
 	size_t bytes_left_to_write = buf_size;
 
 	BOOL success = FALSE;
+	DWORD writeError = NO_ERROR; // use also a local var here to be 100% thread-safe
 
 	do
 	{
@@ -219,6 +237,10 @@ bool Win32_IO_File::write(const void *wbuf, size_t buf_size)
 			bytes_left_to_write -= static_cast<size_t>(bytes_written);
 			total_bytes_written += static_cast<size_t>(bytes_written);
 		}
+		else
+		{
+			writeError = ::GetLastError();
+		}
 	} while (success && bytes_left_to_write);
 
 	NppParameters& nppParam = NppParameters::getInstance();
@@ -234,11 +256,11 @@ bool Win32_IO_File::write(const void *wbuf, size_t buf_size)
 
 			std::string msg = _path;
 			msg += " written failed: ";
-			std::wstring lastErrorMsg = GetLastErrorAsString(::GetLastError());
+			std::wstring lastErrorMsg = GetLastErrorAsString(writeError);
 			msg += wstring2string(lastErrorMsg, CP_UTF8);
 			writeLog(nppIssueLog.c_str(), msg.c_str());
 		}
-
+		_dwErrorCode = writeError; // store
 		return false;
 	}
 	else

PowerEditor/src/MISC/Common/FileInterface.h

@@ -48,6 +48,10 @@ class Win32_IO_File final
 		return write(str.c_str(), str.length());
 	};
 
+	DWORD getLastErrorCode() {
+		return _dwErrorCode;
+	};
+
 private:
 	HANDLE	_hFile		{INVALID_HANDLE_VALUE};
 	bool	_written	{false};
@@ -56,4 +60,6 @@ class Win32_IO_File final
 	const DWORD _accessParam  { GENERIC_READ | GENERIC_WRITE };
 	const DWORD _shareParam   { FILE_SHARE_READ | FILE_SHARE_WRITE };
 	const DWORD _attribParam  { FILE_ATTRIBUTE_NORMAL };
+
+	DWORD _dwErrorCode{ NO_ERROR };
 };

PowerEditor/src/NppIO.cpp

@@ -683,8 +683,11 @@ bool Notepad_plus::doSave(BufferID id, const wchar_t * filename, bool isCopy)
 	}
 	else if (res == SavingStatus::SaveWritingFailed)
 	{
-		wstring errorMessage = GetLastErrorAsString(GetLastError());
-		::MessageBox(_pPublicInterface->getHSelf(), errorMessage.c_str(), L"Save failed", MB_OK | MB_ICONWARNING);
+		if (!(NppParameters::getInstance()).isEndSessionCritical()) // can we report to the user?
+		{
+			wstring errorMessage = GetLastErrorAsString(::GetLastError());
+			::MessageBox(_pPublicInterface->getHSelf(), errorMessage.c_str(), L"Save failed", MB_OK | MB_ICONWARNING);
+		}
 	}
 	else if (res == SavingStatus::SaveOpenFailed)
 	{