Protect Timeless Jewel cache integrity

spec/System/TestDataJewelFileLoader_spec.lua

@@ -0,0 +1,154 @@
+describe("Data jewel file loader", function()
+	local originalConPrintf
+	local originalGetScriptPath
+	local originalInflate
+	local originalNewFileSearch
+	local originalOpen
+	local originalRemove
+	local originalRename
+	local files, modifiedTimeByPath
+	local writePath
+	local renameFile
+	local renameOverride
+	local loadJewelFile
+	local cachePath
+	local compressedFilePath
+
+	local function setInputs(cacheData, cacheModified, inflatedData)
+		files[cachePath] = cacheData
+		modifiedTimeByPath[cachePath] = cacheModified
+		files[compressedFilePath] = "compressed data"
+		modifiedTimeByPath[compressedFilePath] = 10
+		_G.Inflate = function() return inflatedData end
+	end
+
+	before_each(function()
+		originalConPrintf = _G.ConPrintf
+		originalGetScriptPath = _G.GetScriptPath
+		originalInflate = _G.Inflate
+		originalNewFileSearch = _G.NewFileSearch
+		originalOpen = io.open
+		originalRemove = os.remove
+		originalRename = os.rename
+		files = { }
+		modifiedTimeByPath = { }
+		writePath = nil
+		cachePath = "./Data/TimelessJewelData/TestJewel.bin"
+		compressedFilePath = "./Data/TimelessJewelData/TestJewel.zip"
+
+		_G.ConPrintf = function() end
+		_G.GetScriptPath = function() return "." end
+		_G.NewFileSearch = function(path)
+			if modifiedTimeByPath[path] == nil then
+				return
+			end
+			return {
+				GetFileName = function() return path end,
+				GetFileModifiedTime = function() return modifiedTimeByPath[path] end,
+			}
+		end
+		io.open = function(path, mode)
+			if mode == "rb" then
+				if files[path] == nil then
+					return
+				end
+				return {
+					read = function() return files[path] end,
+					close = function() return true end,
+				}
+			end
+			if mode == "wb" then
+				writePath = path
+				local pendingData
+				local file = { }
+				function file:write(data)
+					pendingData = data
+					return self
+				end
+				function file:close()
+					files[path] = pendingData or ""
+					return true
+				end
+				return file
+			end
+		end
+		renameFile = function(sourcePath, destinationPath)
+			if files[sourcePath] == nil then
+				return nil, "source does not exist"
+			end
+			files[destinationPath] = files[sourcePath]
+			files[sourcePath] = nil
+			return true
+		end
+		os.rename = function(sourcePath, destinationPath)
+			if renameOverride then
+				local handled, renameResult, renameError = renameOverride(sourcePath, destinationPath)
+				if handled then
+					return renameResult, renameError
+				end
+			end
+			return renameFile(sourcePath, destinationPath)
+		end
+		os.remove = function(path)
+			if files[path] == nil then
+				return nil, "file does not exist"
+			end
+			files[path] = nil
+			return true
+		end
+
+		loadJewelFile = LoadModule("Modules/DataJewelFileLoader")
+	end)
+
+	after_each(function()
+		_G.ConPrintf = originalConPrintf
+		_G.GetScriptPath = originalGetScriptPath
+		_G.Inflate = originalInflate
+		_G.NewFileSearch = originalNewFileSearch
+		io.open = originalOpen
+		os.remove = originalRemove
+		os.rename = originalRename
+	end)
+
+	it("falls back from a newer zero-byte cache", function()
+		setInputs("", 20, "fresh jewel data")
+
+		local jewelData = loadJewelFile("TestJewel")
+
+		assert.are.equal("fresh jewel data", jewelData)
+		assert.are.equal("fresh jewel data", files[cachePath])
+		assert.is_truthy(writePath:find(cachePath .. ".tmp.", 1, true))
+	end)
+
+	it("rejects empty inflation without opening the cache for writing", function()
+		setInputs("previous jewel data", 5, "")
+
+		local jewelData = loadJewelFile("TestJewel")
+
+		assert.is_nil(jewelData)
+		assert.are.equal("previous jewel data", files[cachePath])
+		assert.is_nil(writePath)
+	end)
+
+	it("restores the previous cache when promotion fails", function()
+		setInputs("previous jewel data", 5, "fresh jewel data")
+		local promotionAttempts = 0
+		renameOverride = function(sourcePath, destinationPath)
+			if destinationPath == cachePath and sourcePath:find(cachePath .. ".tmp.", 1, true) == 1 then
+				promotionAttempts = promotionAttempts + 1
+				return true, nil, "promotion failed"
+			end
+			return false
+		end
+
+		local jewelData = loadJewelFile("TestJewel")
+
+		assert.are.equal("fresh jewel data", jewelData)
+		assert.are.equal("previous jewel data", files[cachePath])
+		assert.are.equal(2, promotionAttempts)
+		for path in pairs(files) do
+			assert.is_falsy(path:find(cachePath .. ".tmp.", 1, true))
+			assert.is_falsy(path:find(cachePath .. ".backup.", 1, true))
+		end
+	end)
+end)

src/Modules/DataJewelFileLoader.lua

@@ -5,6 +5,63 @@
 --
 local t_concat = table.concat
 
+-- Keep temporary and backup paths beside the cache so renames stay on one
+-- volume. A per-write suffix reduces collisions between concurrent writes.
+local function makeSiblingPaths(cachePath)
+	local allocationAddressToken = tostring({ }):match("0x(%x+)") or "unknown"
+	local suffix = os.time() .. "." .. allocationAddressToken
+	return cachePath .. ".tmp." .. suffix, cachePath .. ".backup." .. suffix
+end
+
+local function promoteCache(cachePath, temporaryPath, backupPath)
+	local promoted, promoteError = os.rename(temporaryPath, cachePath)
+	if promoted then
+		return true
+	end
+
+	-- Windows cannot rename over an existing file. Move the current cache aside
+	-- before retrying so a failed replacement can restore the previous data.
+	local backedUp, backupError = os.rename(cachePath, backupPath)
+	if not backedUp then
+		os.remove(temporaryPath)
+		return nil, promoteError or backupError
+	end
+
+	promoted, promoteError = os.rename(temporaryPath, cachePath)
+	if promoted then
+		local removed, removeError = os.remove(backupPath)
+		if not removed then
+			ConPrintf("Failed to remove jewel data cache backup " .. backupPath .. ": " .. tostring(removeError))
+		end
+		return true
+	end
+
+	local restored, restoreError = os.rename(backupPath, cachePath)
+	os.remove(temporaryPath)
+	if not restored then
+		return nil, tostring(promoteError) .. "; cache backup remains at " .. backupPath
+			.. " after restore failed: " .. tostring(restoreError)
+	end
+	return nil, promoteError
+end
+
+local function writeCache(cachePath, jewelData)
+	local temporaryPath, backupPath = makeSiblingPaths(cachePath)
+	local temporaryFile, openError = io.open(temporaryPath, "wb")
+	if not temporaryFile then
+		return nil, openError
+	end
+
+	local written, writeError = temporaryFile:write(jewelData)
+	local closed, closeError = temporaryFile:close()
+	if not written or not closed then
+		os.remove(temporaryPath)
+		return nil, writeError or closeError
+	end
+
+	return promoteCache(cachePath, temporaryPath, backupPath)
+end
+
 local function loadJewelFile(jewelTypeName, cacheUncompressed)
 	local jewelPath = "/Data/TimelessJewelData/" .. jewelTypeName
 	local scriptPath = GetScriptPath()
@@ -42,12 +99,12 @@ local function loadJewelFile(jewelTypeName, cacheUncompressed)
 	end
 
 	if uncompressedFileAttr.modified and uncompressedFileAttr.modified > (compressedFileAttr.modified or 0) then
-		ConPrintf("Uncompressed jewel data is up-to-date, loading " .. uncompressedFileAttr.fileName)
 		local uncompressedFile = io.open(scriptPath .. jewelPath .. ".bin", "rb")
 		if uncompressedFile then
 			local jewelData = uncompressedFile:read("*a")
 			uncompressedFile:close()
-			if jewelData then
+			if jewelData and jewelData ~= "" then
+				ConPrintf("Uncompressed jewel data is up-to-date, loading " .. uncompressedFileAttr.fileName)
 				return jewelData
 			end
 		end
@@ -82,11 +139,14 @@ local function loadJewelFile(jewelTypeName, cacheUncompressed)
 	end
 
 	local jewelData = Inflate(compressedData)
+	if not jewelData or jewelData == "" then
+		ConPrintf("Failed to inflate jewel data: " .. jewelTypeName)
+		return
+	end
 	if cacheUncompressed then
-		local uncompressedFile = io.open(scriptPath .. jewelPath .. ".bin", "wb+")
-		if uncompressedFile then
-			uncompressedFile:write(jewelData)
-			uncompressedFile:close()
+		local cached, cacheError = writeCache(scriptPath .. jewelPath .. ".bin", jewelData)
+		if not cached then
+			ConPrintf("Failed to cache jewel data " .. jewelTypeName .. ": " .. tostring(cacheError))
 		end
 	end
 	return jewelData