When the Microsoft Authentication Library for iOS and macOS (MSAL) signs in a user, or refreshes a token, it tries to cache tokens in the keychain. Caching tokens in the keychain allows MSAL to provide silent single sign-on (SSO) between multiple apps that are distributed by the same Apple developer. SSO is achieved via the keychain access groups functionality. For more information, see Apple's Keychain Items documentation.
This article covers how to configure app entitlements so that MSAL can write cached tokens to iOS and macOS keychain.
Default keychain access group
MSAL on iOS uses the
com.microsoft.adalcache access group by default. This ensures the best SSO experience between multiple apps from the same publisher.
On iOS, add the
com.microsoft.adalcache keychain group to your app's entitlement in XCode under Project settings > Capabilities > Keychain sharing.
MSAL on macOS uses
com.microsoft.identity.universalstorage access group by default.
Due to macOS keychain limitations, MSAL's
access group doesn't directly translate to the keychain access group attribute (see kSecAttrAccessGroup) on macOS 10.14 and earlier. However, it behaves similarly from an SSO perspective by ensuring that multiple applications distributed by the same Apple developer can have silent SSO.
On macOS 10.15 onwards (macOS Catalina), MSAL uses keychain access group attribute to achieve silent SSO, similarly to iOS.
Custom keychain access group
If you'd like to use a different keychain access group, you can pass your custom group when creating
MSALPublicClientApplicationConfig before creating
MSALPublicClientApplication, like this:
MSALPublicClientApplicationConfig *config = [[MSALPublicClientApplicationConfig alloc] initWithClientId:@"your-client-id"
config.cacheConfig.keychainSharingGroup = @"custom-group";
MSALPublicClientApplication *application = [[MSALPublicClientApplication alloc] initWithConfiguration:config error:nil];
// Now call `acquiretoken`.
// Tokens will be saved into the "custom-group" access group
// and only shared with other applications declaring the same access group
Disable keychain sharing
If you don't want to share SSO state between multiple apps, or use any keychain access group, disable keychain sharing by passing the application bundle ID as your keychainGroup:
config.cacheConfig.keychainSharingGroup = [[NSBundle mainBundle] bundleIdentifier];
Handle -34018 error (failed to set item into keychain)
Error -34018 normally means that the keychain hasn't been configured correctly. Ensure the keychain access group that has been configured in MSAL matches the one configured in entitlements.
Ensure your application is properly signed
On macOS, applications can execute without being signed by the developer. While most of MSAL's functionality will continue to work, SSO through keychain access requires application to be signed. If you're experiencing multiple keychain prompts, make sure your application's signature is valid.
Learn more about keychain access groups in Apple's Sharing Access to Keychain Items Among a Collection of Apps article.