116 lines
4.6 KiB
Swift
116 lines
4.6 KiB
Swift
//
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// MigrationManager.swift
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// MullvadVPN
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//
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// Created by Marco Nikic on 2023-08-08.
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// Copyright © 2025 Mullvad VPN AB. All rights reserved.
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//
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import Foundation
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import MullvadLogging
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import MullvadTypes
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public enum SettingsMigrationResult: Sendable {
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/// Nothing to migrate.
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case nothing
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/// Successfully performed migration.
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case success
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/// Failure when migrating store.
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case failure(Error)
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}
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public struct MigrationManager {
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private let logger = Logger(label: "MigrationManager")
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private let cacheDirectory: URL
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public init(cacheDirectory: URL) {
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self.cacheDirectory = cacheDirectory.appendingPathComponent("migrationState.json")
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}
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/// Migrate settings store if needed.
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///
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/// Reads the current settings, upgrades them to the latest version if needed
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/// and writes back to `store` when settings are updated.
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///
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/// In order to avoid migration happening from both the VPN and the host processes at the same time,
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/// a non existent file path is used as a lock to synchronize access between the processes.
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/// This file is accessed by `NSFileCoordinator` in order to prevent multiple processes accessing at the same time.
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/// - Parameters:
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/// - store: The store to from which settings are read and written to.
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/// - migrationCompleted: Completion handler called with a migration result.
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public func migrateSettings(
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store: SettingsStore,
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migrationCompleted: @escaping @Sendable (SettingsMigrationResult) -> Void
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) {
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let fileCoordinator = NSFileCoordinator(filePresenter: nil)
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var error: NSError?
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// This will block the calling thread if another process is currently running the same code.
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// This is intentional to avoid TOCTOU issues, and guaranteeing settings cannot be read
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// in a half written state.
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// The resulting effect is that only one process at a time can do settings migrations.
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// The other process will be blocked, and will have nothing to do as long as settings were successfully upgraded.
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fileCoordinator.coordinate(writingItemAt: cacheDirectory, error: &error) { _ in
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let resetStoreHandler = { (result: SettingsMigrationResult) in
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// Reset store upon failure to migrate settings.
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if case .failure = result {
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SettingsManager.resetStore()
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}
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migrationCompleted(result)
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}
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do {
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try upgradeSettingsToLatestVersion(
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store: store,
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migrationCompleted: migrationCompleted
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)
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} catch .itemNotFound as KeychainError {
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migrationCompleted(.nothing)
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} catch let couldNotReadKeychainError as KeychainError
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where couldNotReadKeychainError == .interactionNotAllowed {
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migrationCompleted(.failure(couldNotReadKeychainError))
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} catch {
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resetStoreHandler(.failure(error))
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}
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}
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}
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private func upgradeSettingsToLatestVersion(
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store: SettingsStore,
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migrationCompleted: @escaping @Sendable (SettingsMigrationResult) -> Void
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) throws {
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let parser = SettingsParser(decoder: JSONDecoder(), encoder: JSONEncoder())
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let settingsData = try store.read(key: SettingsKey.settings)
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let settingsVersion = try parser.parseVersion(data: settingsData)
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guard settingsVersion != SchemaVersion.current.rawValue else {
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migrationCompleted(.nothing)
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return
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}
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// Corrupted settings version (i.e. negative values, or downgrade from a future version) should fail
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guard var savedSchema = SchemaVersion(rawValue: settingsVersion) else {
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migrationCompleted(.failure(UnsupportedSettingsVersionError(
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storedVersion: settingsVersion,
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currentVersion: SchemaVersion.current
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)))
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return
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}
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var savedSettings = try parser.parsePayload(as: savedSchema.settingsType, from: settingsData)
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repeat {
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let upgradedVersion = savedSettings.upgradeToNextVersion()
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savedSchema = savedSchema.nextVersion
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savedSettings = upgradedVersion
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} while savedSchema.rawValue < SchemaVersion.current.rawValue
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// Write the latest settings back to the store
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let latestVersionPayload = try parser.producePayload(savedSettings, version: SchemaVersion.current.rawValue)
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try store.write(latestVersionPayload, for: .settings)
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migrationCompleted(.success)
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}
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}
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