LuaJIT FFI to test Crypt(Un)protectData Function to Diagnose Genshin Impact Logged Out Problem

testcrypt.lua

local ffi = require("ffi")
local Crypt32 = ffi.load("Crypt32")

local TEST_TEXT = [[
struct DATA_BLOB {
	uint32_t size;
	void *data;
};

uint32_t GetLastError();
void *__stdcall LocalFree(void*);
bool __stdcall CryptProtectData(struct DATA_BLOB*, const wchar_t*, struct DATA_BLOB*, void*, void*, uint32_t, struct DATA_BLOB*);
bool __stdcall CryptUnprotectData(struct DATA_BLOB*, wchar_t*, struct DATA_BLOB*, void*, void*, uint32_t, struct DATA_BLOB*);
]]
ffi.cdef(TEST_TEXT)

local f = io.open("testcrypt-data.txt", "rb")
local s = ffi.new("struct DATA_BLOB[2]")

local function toHex(s)
	return string.format("%02X", s:byte())
end

local function encryptText()
	s[0].size = #TEST_TEXT
	s[0].data = ffi.cast("void*", TEST_TEXT)
	if not Crypt32.CryptProtectData(s, nil, nil, nil, nil, 0, s+1) then
		error("CryptProtectData error "..ffi.C.GetLastError())
	end

	local str = ffi.string(s[1].data, s[1].size)
	assert(ffi.C.LocalFree(s[1].data) == nil)
	return str
end

if not f then
	local enc = encryptText()
	f = assert(io.open("testcrypt-data.txt", "wb+"))
	f:write(enc)
	f:flush()
	f:seek("set", 0)
end

local encrypted = f:read("*a")
s[0].data = ffi.cast("void*", encrypted)
s[0].size = #encrypted

if not Crypt32.CryptUnprotectData(s, nil, nil, nil, nil, 0, s+1) then
	error("CryptUnprotectData error "..ffi.C.GetLastError())
end

local decrypted = ffi.string(s[1].data, s[1].size)
assert(ffi.C.LocalFree(s[1].data) == nil)

if decrypted ~= TEST_TEXT then
	print("Text mismatch")

	print("Actual text")
	print(string.gsub(TEST_TEXT, ".", toHex), "\n")
	print("Encrypted text from file")
	print(string.gsub(encrypted, ".", toHex), "\n")
	print("Decrypted text from file")
	print(string.gsub(decrypted, ".", toHex), "\n")
	print("Re-encrypted text for now")
	print(string.gsub(encryptText(), ".", toHex), "\n")
end