let focus_state = WellKnownStateName::FocusAssistMode; let mut buffer = [0u8; 4]; if let Ok(data) = focus_state.query_data(&mut buffer) { println!("Focus Assist status: {}", data); }
Traditional IPC systems like Named Pipes or COM require complex data marshaling, security checks across boundaries, and data serialization. WNF data, by contrast, is maintained in structured kernel-managed memory chunks. When a thread invokes NtQueryWnfStateData , ntdll.dll triggers a direct system transition ( sysenter / syscall ) into the kernel. The kernel directly copies the state payload from its memory pool to the user-mode buffer, ensuring rapid access. 2. The Power of Change Stamps
: It provides a more stable interface for developers. The raw ntquerywnfstatedata ntdlldll better
The function provides a WNF_CHANGE_STAMP output, a monotonically increasing integer that increments every time a state payload is modified.
NtQueryWnfStateData is the low-level system call used to retrieve the current payload data associated with one of these WNF State Names. Because it resides in ntdll.dll (the subsystem translation layer directly above the kernel boundary), it skips the overhead of the standard Win32 subsystem ( kernel32.dll or user32.dll ). Function Signature The kernel directly copies the state payload from
Because the function is not exposed in standard SDK headers like windows.h , developers must dynamically resolve its address from ntdll.dll using GetModuleHandleW and GetProcAddress .
: Accessing certain state names requires specific Security Identifiers (SIDs). If your process lacks the required privilege, the function will return STATUS_ACCESS_DENIED . Conclusion The raw The function provides a WNF_CHANGE_STAMP output,
when Windows changes its "Focus Assist" mode or when a driver is blocked by Code Integrity. Standard tools won't tell you; they only give you the result, not the live pulse of the system. You need a way to peek into the Windows Notification Facility (WNF)
: WNF is designed for high-performance kernel-to-user and inter-process communication. It often results in less system overhead than logging through standard event APIs.
: A 64-bit identifier representing the specific data category being queried.
#include #include // Manually define the return structure of NTSTATUS #define NT_SUCCESS(Status) (((NTSTATUS)(Status)) >= 0) typedef NTSTATUS(NTAPI* _NtQueryWnfStateData)( PULONG64 StateName, PVOID TypeId, PVOID ExplicitScope, PULONG ChangeSequenceNumber, PVOID Buffer, PULONG BufferLength ); int main() // 1. Get a handle to the native NT layer module HMODULE hNtdll = GetModuleHandleA("ntdll.dll"); if (!hNtdll) std::cerr << "[-] Failed to secure handle on ntdll.dll" << std::endl; return -1; // 2. Extract the procedure address dynamically _NtQueryWnfStateData NtQueryWnfStateData = (_NtQueryWnfStateData)GetProcAddress(hNtdll, "NtQueryWnfStateData"); if (!NtQueryWnfStateData) std::cerr << "[-] Failed to map NtQueryWnfStateData memory offset" << std::endl; return -1; // 3. Define a target WNF State Name (Example: Well-known Windows State Name) // Note: Replace with a real target State Name identifier hex for deployment ULONG64 TargetStateName = 0x41C64E6DA3BC1C75; ULONG ChangeSequenceNumber = 0; BYTE DataBuffer[256] = 0 ; ULONG BufferLength = sizeof(DataBuffer); // 4. Query the live kernel-backed WNF data block NTSTATUS status = NtQueryWnfStateData( &TargetStateName, NULL, NULL, &ChangeSequenceNumber, DataBuffer, &BufferLength ); // 5. Evaluate the Native API return status code if (NT_SUCCESS(status)) std::cout << "[+] Query Successful!" << std::endl; std::cout << "[+] Change Sequence: " << ChangeSequenceNumber << std::endl; std::cout << "[+] Data Bytes Returned: " << BufferLength << std::endl; else std::cerr << "[-] Native Call Failed with NTSTATUS Error: 0x" << std::hex << status << std::endl; return 0; Use code with caution. ⚠️ Stability Risks and Best Practices