NtLoadEnclaveData

Prototype

NTSTATUS NtLoadEnclaveData(
  HANDLE  ProcessHandle,
  PVOID   BaseAddress,
  PVOID   Buffer,
  SIZE_T  BufferSize,
  ULONG   Protect,
  PVOID   PageInformation,
  ULONG   PageInformationLength,
  PSIZE_T NumberOfBytesWritten,
  PULONG  EnclaveError
);

Arguments

Syscall IDs by Windows version

Syscall stub

4C 8B D1            mov r10, rcx
B8 0F 01 00 00      mov eax, 0x10F
F6 04 25 08 03 FE 7F 01   test byte ptr [0x7FFE0308], 1
75 03               jne short +3
0F 05               syscall
C3                  ret
CD 2E               int 2Eh
C3                  ret

Undocumented notes

`NtLoadEnclaveData` is the **page-by-page ingest** call that runs *between* `NtCreateEnclave` and `NtInitializeEnclave`. On SGX it lowers into an `EADD` for each source page; on VBS the Secure Kernel `IumLoadEnclaveData` copies the source buffer across the VTL boundary and stamps the destination page's measurement into the running enclave hash. The protection passed here is the *final* protection — the enclave cannot remap it later (no per-page `mprotect` exists in VTL1). For an enclave DLL, `vertdll.dll` makes one call per `IMAGE_SCN_*` section: one PAGE_READONLY for `.rdata`, one PAGE_EXECUTE_READ for `.text`, one PAGE_READWRITE for `.data`. All loads must happen before `NtInitializeEnclave`; afterwards the call returns `STATUS_ENCLAVE_NOT_TERMINATED`.

Common malware usage

From an offensive standpoint, this is the call that physically *places code into VTL1*. The barrier to abuse is that the loaded bytes will be measured into the enclave hash and that hash must match what `IMAGE_ENCLAVE_CONFIG` permits at init time. Two real-world levers: (1) **Microsoft-signed enclave with attacker-controlled data**: load benign data pages whose contents are interpreted as commands by the signed code — equivalent to ROP inside the enclave; (2) **research loader**: the Yuste / Soriano-Salvador work loads a signed *stub* enclave whose 'code' is actually a tiny dispatcher that accepts a shellcode pointer at `NtCallEnclave` time — the malicious payload is never measured into MRENCLAVE, only the dispatcher is. Defenders cannot inspect the loaded bytes after the fact — VTL1 memory is opaque to VTL0.

Detection opportunities

The pre-init load burst is highly characteristic: ten-to-hundreds of `NtLoadEnclaveData` calls in quick succession on the same enclave base address, followed by `NtInitializeEnclave`. The ETW provider `Microsoft-Windows-Kernel-Memory` emits an event per load. EDRs that hook on the host syscall pattern can flag the sequence trivially; the harder problem is attribution — which DLL is being loaded into the enclave. The defender's best lever is the *file source*: the host module performing the loads will have an `IMAGE_ENCLAVE_CONFIG` directory naming the enclave DLL by image hash. Sysmon Event ID 7 (ImageLoad) on the host will show the enclave DLL's PE mapping prior to the load syscalls — pair the two for retroactive identification.

Direct syscall examples

// Walk the PE sections of a signed enclave DLL and copy them into the enclave.
// (Helper for the create -> load -> initialize -> call sequence.)
#include <windows.h>

BOOL LoadEnclaveImage(PVOID enclaveBase, PVOID peImage, SIZE_T peSize) {
    PIMAGE_DOS_HEADER dos = (PIMAGE_DOS_HEADER)peImage;
    PIMAGE_NT_HEADERS nt = (PIMAGE_NT_HEADERS)((BYTE*)peImage + dos->e_lfanew);
    PIMAGE_SECTION_HEADER sec = IMAGE_FIRST_SECTION(nt);

    for (WORD i = 0; i < nt->FileHeader.NumberOfSections; i++, sec++) {
        ULONG prot = PAGE_READONLY;
        if (sec->Characteristics & IMAGE_SCN_MEM_EXECUTE) prot = PAGE_EXECUTE_READ;
        else if (sec->Characteristics & IMAGE_SCN_MEM_WRITE) prot = PAGE_READWRITE;

        PVOID dst = (BYTE*)enclaveBase + sec->VirtualAddress;
        PVOID src = (BYTE*)peImage      + sec->PointerToRawData;
        SIZE_T size = ((sec->SizeOfRawData + 0xFFF) & ~0xFFFu);

        if (!LoadEnclaveData(
                GetCurrentProcess(),
                dst, src, size, prot,
                NULL, 0,           // page info (VBS-specific, may be NULL)
                NULL,              // bytes written
                NULL)) {           // enclave error
            return FALSE;
        }
    }
    return TRUE;
}

; Direct syscall stub for NtLoadEnclaveData (SSN 0x10F on Win11 24H2 / Server 2025)
NtLoadEnclaveData PROC
    mov  r10, rcx          ; ProcessHandle
    mov  eax, 10Fh         ; SSN
    syscall
    ret
NtLoadEnclaveData ENDP

MITRE ATT&CK mappings

• T1620Reflective Code Loadingmitre ↗
• T1574Hijack Execution Flowmitre ↗
• T1106Native APImitre ↗