I'm currently working on a new credential SPI that will replace existing methods on UserProvider and UserModel, as well as replacing UserCredentialModel, etc. This is a work in progress where we may see multiple iterations in master. I hope to remain backward compatible, but can't guarentee I won't break existing User Federation Providers. Here's an initial writeup to explain things. Credentials revolve around these 4 events that are initiated by authentication flows, the admin console, and the account service.

* Is the user configured for a specific credential type

* Is a credential valid

* What required actions must be taken for an unconfigured credential type

* update a credential

How each of these events is resolved will depend on the configuration of the system and these interfaces:

public interface CredentialInput {
    String getType();
}

public interface CredentialInputValidator {
    boolean supportsCredentialType(String credentialType);
    boolean isConfiguredFor(RealmModel realm, UserModel user, String credentialType);
    boolean isValid(RealmModel realm, UserModel user, CredentialInput input);

}

public interface CredentialInputUpdater {
    boolean supportsCredentialType(String credentialType);
    Set<String> requiredActionsFor(RealmModel realm, UserModel user, String credentialType);
    void updateCredential(RealmModel realm, UserModel user, CredentialInput input);
}

Two different types of components will be able to implement these interfaces. UserStorageProviders (user federation) and CredentialProviders. CredentialProviders are components configured at the realm level. CredentialProviders are responsible for managing one or more types of credential types and are the bridge between CredentialInput and where the credential is stored. UserStorageProvider is always asked first whether it can complete the requested action, then CredentialProviders are queried in order of their priority.

Each UserStorageProvider and/or CredentialProvider can implement the OnUserCache callback interface discussed in my previous custom caching email. This allows each credential type to decide whether it will be cached or not along with the user. For example, HOTP cannot be cached.

So, for example, there will be a KeycloakMobileOTPProvider. This deals with Google Authenticator and FreeOTP as well as storing these things within Keycloak storage, it also looks at the OTP policy of the realm to determine how to update and store the OTP secret and stuff. There is also a KeycloakPasswordProvider which hooks into Keycloak storage and the PasswordPolicies set up by the realm. When a user is cached, the KeycloakPasswordProvider will add the hashed password to the user cache, the KeycloakMobileOTPProvider will add the OTP secret to cache if its not HOTP and needs to maintain a counter.

Let's walk through an authentication flow, specificaly for OTP.

1. Authenticator calls KeycloakSession.users().isConfiguredFor(realm, user, "OTP"). If the user was loaded by a UserStorageProvider and that provider implements the CredentialInputValidator interface, isConfiguredFor() is called on that. If that returns false, each CredentialProvider is iterated on to call isConfiguredFor().

2. If OTP is required and not configured for the user, the Authenticator then calls KeycloakSession.users().requiredActionsFor(...). Again, UserStorageProvider is queried first, then the CredneitalProviders. The first provider that returns a non-empty set will end the query and the set of required actions will be returned.

3a. Let's say that in this particular example, the generic OTP Requried Action screen is invoked. In that case, this required action provider callsKeycloakSession.users().updateCredential. The first UserStorageProvider or CredentialProvider that can handle this credential type will save the credential.

3b. If OTP is configured for user, the OTP is obtained by the Authenticator and KeycloakSession.users().isValid() method is called. Again, UserStorageProvider first, then each CredentialProvider. Each provider is queried until one returns true or the list is exhausted. FYI, This algorithm allows for multiple OTP authenticators per user.

** Admin console and Account Service UIs **

Like we do for other components, the UserStorageProvider or CredentialProvider can optionally provide a list of ProviderConfigProperties for the admin console and/or account serviceso that it can create a credential for a specific user. There will be separate property lists for admin console and account service. If a specific custom screen is desired, I'm pretty sure we can just allow the develoepr to plug in their own $routeProvider for the admin console. We don't have a pluggable mechanism for the account service yet (or a way to generic render either). This will need to be developed eventually.