square/Valet

Valet lets you securely store data in the iOS, tvOS, or macOS Keychain without knowing a thing about how the Keychain works. It’s easy. We promise.


Keywords
crypto, face-id, ios, keychain, macos, security, touch-id, tvos, watchos
License
Apache-2.0

Documentation

Valet

CI Status Carthage Compatibility Version License Platform

Valet lets you securely store data in the iOS, tvOS, watchOS, or macOS Keychain without knowing a thing about how the Keychain works. It’s easy. We promise.

Getting Started

CocoaPods

Install with CocoaPods by adding the following to your Podfile:

on iOS:

platform :ios, '9.0'
use_frameworks!
pod 'Valet'

on tvOS:

platform :tvos, '9.0'
use_frameworks!
pod 'Valet'

on watchOS:

platform :watchos, '2.0'
use_frameworks!
pod 'Valet'

on macOS:

platform :osx, '10.11'
use_frameworks!
pod 'Valet'

Carthage

Install with Carthage by adding the following to your Cartfile:

github "Square/Valet"

Run carthage to build the framework and drag the built Valet.framework into your Xcode project.

Swift Package Manager

Install with Swift Package Manager by adding the following to your Package.swift:

dependencies: [
    .package(url: "https://github.com/Square/Valet", from: "4.0.0"),
],

Submodules

Or manually checkout the submodule with git submodule add git@github.com:Square/Valet.git, drag Valet.xcodeproj to your project, and add Valet as a build dependency.

Usage

Basic Initialization

let myValet = Valet.valet(with: Identifier(nonEmpty: "Druidia")!, accessibility: .whenUnlocked)
VALValet *const myValet = [VALValet valetWithIdentifier:@"Druidia" accessibility:VALAccessibilityWhenUnlocked];

To begin storing data securely using Valet, you need to create a Valet instance with:

  • An identifier – a non-empty string that is used to identify this Valet. The Swift API uses an Identifier wrapper class to enforce the non-empty constraint.
  • An accessibility value – an enum (Accessibility) that defines when you will be able to persist and retrieve data.

This myValet instance can be used to store and retrieve data securely on this device, but only when the device is unlocked.

Choosing the Best Identifier

The identifier you choose for your Valet is used to create a sandbox for the data your Valet writes to the keychain. Two Valets of the same type created via the same initializer, accessibility value, and identifier will be able to read and write the same key:value pairs; Valets with different identifiers each have their own sandbox. Choose an identifier that describes the kind of data your Valet will protect. You do not need to include your application name or bundle identifier in your Valet’s identifier.

Choosing a User-friendly Identifier on macOS

let myValet = Valet.valet(withExplicitlySet: Identifier(nonEmpty: "Druidia")!, accessibility: .whenUnlocked)
VALValet *const myValet = [VALValet valetWithExplicitlySetIdentifier:@"Druidia" accessibility:VALAccessibilityWhenUnlocked];

Mac apps signed with a developer ID may see their Valet’s identifier shown to their users. ⚠️⚠️ While it is possible to explicitly set a user-friendly identifier, note that doing so bypasses this project’s guarantee that one Valet type will not have access to one another type’s key:value pairs ⚠️⚠️. To maintain this guarantee, ensure that each Valet’s identifier is globally unique.

Choosing the Best Accessibility Value

The Accessibility enum is used to determine when your secrets can be accessed. It’s a good idea to use the strictest accessibility possible that will allow your app to function. For example, if your app does not run in the background you will want to ensure the secrets can only be read when the phone is unlocked by using .whenUnlocked or .whenUnlockedThisDeviceOnly.

Changing an Accessibility Value After Persisting Data

let myOldValet = Valet.valet(withExplicitlySet: Identifier(nonEmpty: "Druidia")!, accessibility: .whenUnlocked)
let myNewValet = Valet.valet(withExplicitlySet: Identifier(nonEmpty: "Druidia")!, accessibility: .afterFirstUnlock)
try? myNewValet.migrateObjects(from: myOldValet, removeOnCompletion: true)
VALValet *const myOldValet = [VALValet valetWithExplicitlySetIdentifier:@"Druidia" accessibility:VALAccessibilityWhenUnlocked];
VALValet *const myNewValet = [VALValet valetWithExplicitlySetIdentifier:@"Druidia" accessibility:VALAccessibilityAfterFirstUnlock];
[myNewValet migrateObjectsFrom:myOldValet removeOnCompletion:true error:nil];

The Valet type, identifier, accessibility value, and initializer chosen to create a Valet are combined to create a sandbox within the keychain. This behavior ensures that different Valets can not read or write one another's key:value pairs. If you change a Valet's accessibility after persisting key:value pairs, you must migrate the key:value pairs from the Valet with the no-longer-desired accessibility to the Valet with the desired accessibility to avoid data loss.

Reading and Writing

let username = "Skroob"
try? myValet.setString("12345", forKey: username)
let myLuggageCombination = myValet.string(forKey: username)
NSString *const username = @"Skroob";
[myValet setString:@"12345" forKey:username error:nil];
NSString *const myLuggageCombination = [myValet stringForKey:username error:nil];

In addition to allowing the storage of strings, Valet allows the storage of Data objects via setObject(_ object: Data, forKey key: Key) and object(forKey key: String). Valets created with a different class type, via a different initializer, or with a different accessibility attribute will not be able to read or modify values in myValet.

Sharing Secrets Among Multiple Applications Using a Keychain Sharing Entitlement

let mySharedValet = Valet.sharedGroupValet(with: SharedGroupIdentifier(appIDPrefix: "AppID12345", nonEmptyGroup: "Druidia")!, accessibility: .whenUnlocked)
VALValet *const mySharedValet = [VALValet sharedGroupValetWithAppIDPrefix:@"AppID12345" sharedGroupIdentifier:@"Druidia" accessibility:VALAccessibilityWhenUnlocked];

This instance can be used to store and retrieve data securely across any app written by the same developer that has AppID12345.Druidia (or $(AppIdentifierPrefix)Druidia) set as a value for the keychain-access-groups key in the app’s Entitlements, where AppID12345 is the application’s App ID prefix. This Valet is accessible when the device is unlocked. Note that myValet and mySharedValet can not read or modify one another’s values because the two Valets were created with different initializers. All Valet types can share secrets across applications written by the same developer by using the sharedGroupValet initializer.

Sharing Secrets Among Multiple Applications Using an App Groups Entitlement

let mySharedValet = Valet.sharedGroupValet(with: SharedGroupIdentifier(groupPrefix: "group", nonEmptyGroup: "Druidia")!, accessibility: .whenUnlocked)
VALValet *const mySharedValet = [VALValet sharedGroupValetWithGroupPrefix:@"group" sharedGroupIdentifier:@"Druidia" accessibility:VALAccessibilityWhenUnlocked];

This instance can be used to store and retrieve data securely across any app written by the same developer that has group.Druidia set as a value for the com.apple.security.application-groups key in the app’s Entitlements. This Valet is accessible when the device is unlocked. Note that myValet and mySharedValet cannot read or modify one another’s values because the two Valets were created with different initializers. All Valet types can share secrets across applications written by the same developer by using the sharedGroupValet initializer. Note that on macOS, the groupPrefix must be the App ID prefix.

Sharing Secrets Across Devices with iCloud

let myCloudValet = Valet.iCloudValet(with: Identifier(nonEmpty: "Druidia")!, accessibility: .whenUnlocked)
VALValet *const myCloudValet = [VALValet iCloudValetWithIdentifier:@"Druidia" accessibility:VALAccessibilityWhenUnlocked];

This instance can be used to store and retrieve data that can be retrieved by this app on other devices logged into the same iCloud account with iCloud Keychain enabled. If iCloud Keychain is not enabled on this device, secrets can still be read and written, but will not sync to other devices. Note that myCloudValet can not read or modify values in either myValet or mySharedValet because myCloudValet was created a different initializer.

Protecting Secrets with Face ID, Touch ID, or device Passcode

let mySecureEnclaveValet = SecureEnclaveValet.valet(with: Identifier(nonEmpty: "Druidia")!, accessControl: .userPresence)
VALSecureEnclaveValet *const mySecureEnclaveValet = [VALSecureEnclaveValet valetWithIdentifier:@"Druidia" accessControl:VALAccessControlUserPresence];

This instance can be used to store and retrieve data in the Secure Enclave. Each time data is retrieved from this Valet, the user will be prompted to confirm their presence via Face ID, Touch ID, or by entering their device passcode. If no passcode is set on the device, this instance will be unable to access or store data. Data is removed from the Secure Enclave when the user removes a passcode from the device. Storing data using SecureEnclaveValet is the most secure way to store data on iOS, tvOS, watchOS, and macOS.

let mySecureEnclaveValet = SinglePromptSecureEnclaveValet.valet(with: Identifier(nonEmpty: "Druidia")!, accessControl: .userPresence)
VALSinglePromptSecureEnclaveValet *const mySecureEnclaveValet = [VALSinglePromptSecureEnclaveValet valetWithIdentifier:@"Druidia" accessControl:VALAccessControlUserPresence];

This instance also stores and retrieves data in the Secure Enclave, but does not require the user to confirm their presence each time data is retrieved. Instead, the user will be prompted to confirm their presence only on the first data retrieval. A SinglePromptSecureEnclaveValet instance can be forced to prompt the user on the next data retrieval by calling the instance method requirePromptOnNextAccess().

In order for your customers not to receive a prompt that your app does not yet support Face ID, you must set a value for the Privacy - Face ID Usage Description (NSFaceIDUsageDescription) key in your app’s Info.plist.

Thread Safety

Valet is built to be thread safe: it is possible to use a Valet instance on any queue or thread. Valet instances ensure that code that talks to the Keychain is atomic – it is impossible to corrupt data in Valet by reading and writing on multiple queues simultaneously.

However, because the Keychain is effectively disk storage, there is no guarantee that reading and writing items is fast - accessing a Valet instance from the main queue can result in choppy animations or blocked UI. As a result, we recommend utilizing your Valet instance on a background queue; treat Valet like you treat other code that reads from and writes to disk.

Migrating Existing Keychain Values into Valet

Already using the Keychain and no longer want to maintain your own Keychain code? We feel you. That’s why we wrote migrateObjects(matching query: [String : AnyHashable], removeOnCompletion: Bool). This method allows you to migrate all your existing Keychain entries to a Valet instance in one line. Just pass in a Dictionary with the kSecClass, kSecAttrService, and any other kSecAttr* attributes you use – we’ll migrate the data for you. If you need more control over how your data is migrated, use migrateObjects(matching query: [String : AnyHashable], compactMap: (MigratableKeyValuePair<AnyHashable>) throws -> MigratableKeyValuePair<String>?) to filter or remap key:value pairs as part of your migration.

Integrating Valet into a macOS application

Your macOS application must have the Keychain Sharing entitlement in order to use Valet, even if your application does not intend to share keychain data between applications. For instructions on how to add a Keychain Sharing entitlement to your application, read Apple's documentation on the subject. For more information on why this requirement exists, see issue #213.

If your macOS application supports macOS 10.14 or prior, you must run myValet.migrateObjectsFromPreCatalina() before reading values from a Valet. macOS Catalina introduced a breaking change to the macOS keychain, requiring that macOS keychain items that utilize kSecAttrAccessible or kSecAttrAccessGroup set kSecUseDataProtectionKeychain to true when writing or accessing these items. Valet’s migrateObjectsFromPreCatalina() upgrades items entered into the keychain on older macOS devices or other operating systems to include the key:value pair kSecUseDataProtectionKeychain:true. Note that Valets that share keychain items between devices with iCloud are exempt from this requirement. Similarly, SecureEnclaveValet and SinglePromptSecureEnclaveValet are exempt from this requirement.

Debugging

Valet guarantees it will never fail to write to or read from the keychain unless canAccessKeychain() returns false. There are only a few cases that can lead to the keychain being inaccessible:

  1. Using the wrong Accessibility for your use case. Examples of improper use include using .whenPasscodeSetThisDeviceOnly when there is no passcode set on the device, or using .whenUnlocked when running in the background.
  2. Initializing a Valet with shared access group Valet when the shared access group identifier is not in your entitlements file.
  3. Using SecureEnclaveValet on an iOS device that doesn’t have a Secure Enclave. The Secure Enclave was introduced with the A7 chip, which first appeared in the iPhone 5S, iPad Air, and iPad Mini 2.
  4. Running your app in DEBUG from Xcode. Xcode sometimes does not properly sign your app, which causes a failure to access keychain due to entitlements. If you run into this issue, just hit Run in Xcode again. This signing issue will not occur in properly signed (not DEBUG) builds.
  5. Running your app on device or in the simulator with a debugger attached may also cause an entitlements error to be returned when reading from or writing to the keychain. To work around this issue on device, run the app without the debugger attached. After running once without the debugger attached the keychain will usually behave properly for a few runs with the debugger attached before the process needs to be repeated.
  6. Running your app or unit tests without the application-identifier entitlement. Xcode 8 introduced a requirement that all schemes must be signed with the application-identifier entitlement to access the keychain. To satisfy this requirement when running unit tests, your unit tests must be run inside of a host application.

Requirements

  • Xcode 11.0 or later. Xcode 10 and Xcode 9 require Valet version 3.2.8. Earlier versions of Xcode require Valet version 2.4.2.
  • iOS 9 or later.
  • tvOS 9 or later.
  • watchOS 2 or later.
  • macOS 10.11 or later.

Migrating from prior Valet versions

The good news: most Valet configurations do not have to migrate keychain data when upgrading from an older version of Valet. All Valet objects are backwards compatible with their counterparts from prior versions. We have exhaustive unit tests to prove it (search for test_backwardsCompatibility). Valets that have had their configurations deprecated by Apple will need to migrate stored data.

The bad news: there are multiple source-breaking API changes from prior versions.

Both guides below explain the changes required to upgrade to Valet 4.

Migrating from Valet 2

  1. Initializers have changed in both Swift and Objective-C - both languages use class methods now, which felt more semantically honest (a lot of the time you’re not instantiating a new Valet, you’re re-accessing one you’ve already created). See example usage above.
  2. VALSynchronizableValet (which allowed keychains to be synced to iCloud) has been replaced by a Valet.iCloudValet(with:accessibility:) (or +[VALValet iCloudValetWithIdentifier:accessibility:] in Objective-C). See examples above.
  3. VALAccessControl has been renamed to SecureEnclaveAccessControl (VALSecureEnclaveAccessControl in Objective-C). This enum no longer references TouchID; instead it refers to unlocking with biometric due to the introduction of Face ID.
  4. Valet, SecureEnclaveValet, and SinglePromptSecureEnclaveValet are no longer in the same inheritance tree. All three now inherit directly from NSObject and use composition to share code. If you were relying on the subclass hierarchy before, 1) that might be a code smell 2) consider declaring a protocol for the shared behavior you were expecting to make your migration to Valet 3 easier.

You'll also need to continue reading through the migration from Valet 3 section below.

Migrating from Valet 3

  1. The accessibility values always and alwaysThisDeviceOnly have been removed from Valet, because Apple has deprecated their counterparts (see the documentation for kSecAttrAccessibleAlways and kSecAttrAccessibleAlwaysThisDeviceOnly). To migrate values stored with always accessibility, use the method migrateObjectsFromAlwaysAccessibleValet(removeOnCompletion:) on a Valet with your new preferred accessibility. To migrate values stored with alwaysThisDeviceOnly accessibility, use the method migrateObjectsFromAlwaysAccessibleThisDeviceOnlyValet(removeOnCompletion:) on a Valet with your new preferred accessibility.
  2. Most APIs that returned optionals or Bool values have been migrated to returning a nonoptional and throwing if an error is encountered. Ignoring the error that can be thrown by each API will keep your code flow behaving the same as it did before. Walking through one example: in Swift, let secret: String? = myValet.string(forKey: myKey) becomes let secret: String? = try? myValet.string(forKey: myKey). In Objective-C, NSString *const secret = [myValet stringForKey:myKey]; becomes NSString *const secret = [myValet stringForKey:myKey error:nil];. If you're interested in the reason data wasn't returned, use a do-catch statement in Swift, or pass in an NSError to each API call and inspect the output in Objective-C. Each method clearly documents the Error type it can throw. See examples above.
  3. The class method used to create a Valet that can share secrets between applications using keychain shared access groups has changed. In order to prevent the incorrect detection of the App ID prefix in rare circumstances, the App ID prefix must now be explicitly passed into these methods. See examples above.

Contributing

We’re glad you’re interested in Valet, and we’d love to see where you take it. Please read our contributing guidelines prior to submitting a Pull Request.

Thanks, and please do take it for a joyride!