<chapter id="auth_spi">
<title>Custom Authentication, Registration, and Required Actions</title>
<para>
Keycloak comes out of the box with a bunch of different authentication mechanisms: kerberos, password, and otp.
These mechanisms may not meet all of your requirements and you may want to plug in your own custom ones. Keycloak
provides an authentication SPI that you can use to write new plugins. The admin console supports applying, ordering,
and configuring these new mechanisms.
</para>
<para>
Keycloak also supports a simple registration form. Different aspects of this form can be enabled and disabled i.e.
Recaptcha support can be turned off and on. The same authentication SPI can be used to add another page to the
registration flow or reimplement it entirely. There's also an additional fine-grain SPI you can use to add
specific validations and user extensions to the built in registration form.
</para>
<para>
A required action in Keycloak is an action that a user has to perform after he authenticates. After the action
is performed successfully, the user doesn't have to perform the action again. Keycloak comes with some built in
required actions like "reset password". This action forces the user to change their password after they have logged in.
You can write and plug in your own required actions.
</para>
<section>
<title>Terms</title>
<para>
To first learn about the Authentication SPI, let's go over some of the terms used to describe it.
<variablelist>
<varlistentry>
<term>Authentication Flow</term>
<listitem>
<para>
A flow is a container for all authentications that must happen during login or registration. If you
go to the admin console authentication page, you can view all the defined flows in the system and
what authenticators they are made up of. Flows can contain other flows. You can also bind a new
different flow for browser login, direct granta access, and registration.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Authenticator</term>
<listitem>
<para>
An authenticator is a pluggable component that hold the logic for performing the authentication
or action within a flow. It is usually a singleton.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Execution</term>
<listitem>
<para>
An execution is an object that binds the authenticator to the flow and the authenticator
to the configuration of the authenticator. Flows contain execution entries.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Execution Requirement</term>
<listitem>
<para>
Each execution defines how an authenticator behaves in a flow. The requirement defines
whether the authenticator is enabled, disabled, optional, required, or an alternative. An
alternative requirement means that the authentiactor is optional unless no other alternative
authenticator is successful in the flow. For example, cookie authentication, kerberos,
and the set of all login forms are all alternative. If one of those is successful, none of
the others are executed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Authenticator Config</term>
<listitem>
<para>
This object defines the configuration for the Authenticator for a specific execution within
an authentication flow. Each execution can have a different config.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Required Action</term>
<listitem>
<para>
After authentication completes, the user might have one or more one-time actions he must
complete before he is allowed to login. The user might be required to set up an OTP token
generator or reset an expired password or even accept a Terms and Conditions document.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</section>
<section>
<title>Algorithm Overview</title>
<para>
Let's talk about how this all works for browser login. Let's assume the following flows, executions and sub flows.
<programlisting><![CDATA[
Cookie - ALTERNATIVE
Kerberos - ALTERNATIVE
Forms Subflow - ALTERNATIVE
Username/Password Form - REQUIRED
OTP Password Form - OPTIONAL
]]>
</programlisting>
</para>
<para>
In the top level of the form we have 3 executions of which all are alternatively required. This means that
if any of these are successful, then the others do not have to execute. The Username/Password form is not executed
if there is an SSO Cookie set or a successful Kerberos login. Let's walk through the steps from when a client
first redirects to keycloak to authenticate the user.
<orderedlist>
<listitem>
<para>
The OpenID Connect or SAML protocol provider unpacks relevent data, verifies the client and any signatures.
It creates a ClientSessionModel. It looks up what the browser flow should be, then starts executing the flow.
</para>
</listitem>
<listitem>
<para>
The flow looks at the cookie execution and sees that it is an alternative. It loads the cookie provider.
It checks to see if the cookie provider requires that a user already be associated with the client session.
Cookie provider does not require a user. If it did, the flow would abort and the user would see an error screen.
Cookie provider then executes. Its purpose is to see if there is an SSO cookie set. If there is one set, it is validated
and the UserSessionModel is verified and associated with the ClientSessionModel. The Cookie provider returns a
success() status if the SSO cookie exists and is validated. Since the cookie provider returned success and each execution
at this level of the flow is ALTERNATIVE, no other execution is executed and this results in a successful login.
If there is no SSO cookie, the cookie provider returns with a status of attempted(). This means there was no error condition,
but no success either. The provider tried, but the request just wasn't set up to handle this authenticator.
</para>
</listitem>
<listitem>
<para>
Next the flow looks at the Kerberos execution. This is also an alternative. The kerberos provider also does not
require a user to be already set up and associated with the ClientSessionModel so this provider is executed.
Kerberos uses the SPNEGO browser protocol. This requires a series of challenge/responses between the server and client
exchanging negotiation headers. The kerberos provider does not see any negotiate header, so it assumes that this is the
first interaction between the server and client. It therefore creates an HTTP challenge response to the client and sets a
forceChallenge() status. A forceChallenge() means that this HTTP response cannot be ignored by the flow and must be returned to the
client. If instead the provider returned a challenge() status, the flow would hold the challenge response until all other alternatives
are attempted. So, in this initial phase, the flow would stop and the challenge response would be sent back to the browser. If the browser
then responds with a successful negotiate header, the provider associates the user with the ClientSession and the flow ends because
the rest of the executions on this level of the flow are all alternatives. Otherwise, again, the kerberos provider
sets an attempted() status and the flow continues.
</para>
</listitem>
<listitem>
<para>
The next execution is a subflow called Forms. The executions for this subflow are loaded and
the same processing logic occurs
</para>
</listitem>
<listitem>
<para>
The first execution in the Forms subflow is the UsernamePassword provider. This provider also does not require for a user
to already be associated with the flow. This provider creates challenge HTTP response and sets its status to challenge().
This execution is required, so the flow honors this challenge and sends the HTTP response back to the browser. This
response is a rendering of the Username/Password HTML page. The user enters in their username and password and clicks submit.
This HTTP request is directed to the UsernamePassword provider. If the user entered an invalid username or password, a new
challenge response is created and a status of failureChallenge() is set for this execution. A failureChallenge() means that
there is a challenge, but that the flow should log this as an error in the error log. This error log can be used to lock accounts
or IP Addresses that have had too many login failures. If the username and password is valid, the provider associated the
UserModel with the ClientSessionModel and returns a status of success()
</para>
</listitem>
<listitem>
<para>
The next execution is the OTP Form. This provider requires that a user has been associated with the flow. This requirement is satisfied
because the UsernamePassword provider already associated the user with the flow. Since a user is required for this provider, the provider
is also asked if the user is configured to use this provider. If user is not configured, and this execution is required, then the flow will
then set up a required action that the user must perform after authentication is complete. For OTP, this means the OTP setup page.
If the execution was optional, then this execution is skipped.
</para>
</listitem>
<listitem>
<para>
After the flow is complete, the authentication processor creates a UserSEssionModel and associates it with the ClientSEssionModel.
It then checks to see if the user is required to complete any required actions before logging in.
</para>
</listitem>
<listitem>
<para>
First, each required action's evaluateTriggers() method is called. This allows the required action provider to figure out if
there is some state that might trigger the action to be fired. For example, if your realm has a password expiration policy,
it might be triggered by this method.
</para>
</listitem>
<listitem>
<para>
Each required action associated with the user that has its requiredActionChallenge() method called. Here the provider
sets up an HTTP response which renders the page for the required action. This is done by setting a challenge status.
</para>
</listitem>
<listitem>
<para>
If the required action is ultimately successful, then the required action is removed from the user's require actions list.
</para>
</listitem>
<listitem>
<para>
After all required actions have been resolved, the user is finally logged in.
</para>
</listitem>
</orderedlist>
</para>
</section>
<section>
<title>Authenticator SPI Walk Through</title>
<para>
In this section, we'll take a look at the Authenticator interface. For this, we are going to implement an authenticator
that requires that a user enter in the answer to a secret question like "What is your mother's maiden name?". This example
is fully implemented and contained in the examples/providers/authenticator directory of the demo distribution of Keycloak.
</para>
<para>
The classes you must implement are the org.keycloak.authentication.AuthenticatorFactory and Authenticator interfaces. The Authenticator
interface defines the logic. The AuthenticatorFactory is responsible for creating instances of an Authenticator. They both extend
a more generic Provider and ProviderFactory set of interfaces that other Keycloak components like User Federation do.
</para>
<section>
<title>Packaging Classes and Deployment</title>
<para>
You will package your classes within a single jar. This jar must contain a file named <literal>org.keycloak.authentication.AuthenticatorFactory</literal>
and must be contained in the <literal>META-INF/services/</literal> directory of your jar. This file must list the fully qualified classname
of each AuthenticatorFactory implementation you have in the jar. For example:
<programlisting>
org.keycloak.examples.authenticator.SecretQuestionAuthenticatorFactory
org.keycloak.examples.authenticator.AnotherProviderFactory
</programlisting>
</para>
<para>
This services/ file is used by Keycloak to scan the providers it has to load into the system.
</para>
<para>
To deploy this jar, just copy it to the standalone/configuration/providers directory.
</para>
</section>
<section>
<title>Implementing an Authenticator</title>
<para>
When implementing the Authenticator interface, the first method that needs to be implemented is the
requiresUser() method. For our example, this method must return true as we need to validate the secret question
associated with the user. A provider like kerberos would return false from this method as it can
resolve a user from the negotiate header. This example however is validating a specific credential of a specific
user.
</para>
<para>
The next method to implement is the configuredFor() method. This method is responsible for determining if the
user is configured for this particular authenticator. For this example, we need to check of the answer to the
secret question is been set up by the user or not. In our case we are storing this information, hashed, within
a UserCredentialValueModel within the UserModel (just like passwords are stored). Here's how we do this
very simple check:
<programlisting>
@Override
public boolean configuredFor(KeycloakSession session, RealmModel realm, UserModel user) {
return session.users().configuredForCredentialType("secret_question", realm, user);
}
</programlisting>
</para>
<para>
The configuredForCredentialType() call queries the user to see if it supports that credential type.
</para>
<para>
The next method to implement on the Authenticator is setRequiredActions(). If configuredFor() returns fales
and our example authenticator is required within the flow, this method will be called. It is response for
registering any required actions that must be performed by the user. In our example, we need to register
a required action that will force the user to set up the answer to the secret question. We will implement
this required action provider later in this chapter. Here is the implementation of the setRequiredActions()
method.
<programlisting>
@Override
public void setRequiredActions(KeycloakSession session, RealmModel realm, UserModel user) {
user.addRequiredAction("SECRET_QUESTION_CONFIG");
}
</programlisting>
</para>
<para>
Now we are getting into the meat of the Authenticator implementation. The next method to implement is
authenticate(). This is the initial method the flow invokes when the execution is first visited. What we
want is that if a user has answered the secret question already on their browser's machine, that the
user doesn't have to answer the question again. Basically making that machine "trusted". The authenticate()
method isn't responsible for processing the secret question form. Its sole purpose is to render the page
or to continue the flow.
<programlisting>
@Override
public void authenticate(AuthenticationFlowContext context) {
if (hasCookie(context)) {
context.success();
return;
}
Response challenge = loginForm(context).createForm("secret_question.ftl");
context.challenge(challenge);
}
</programlisting>
</para>
<para>
If the hasCookie() method checks to see if there is already a cookie set on the browser which indicates
that the secret question has already been answered. If that returns true, we just mark this execution's
status as SUCCESS using the AuthenticationFlowContext.success() method and returning from the authentication()
method.
</para>
<para>
If the hasCookie() method returns false, we must return a response that renders the secret question HTML
form. AuthenticationFlowContext has a form() method that initializes a Freemarker page builder with appropriate base information needed
to build the form. This page builder is called <literal>org.keycloak.login.LoginFormsProvider</literal>.
the LoginFormsProvider.createForm() method loads a Freemarker template file from your login theme. Additionally
you can call the LoginFormsProvider.setAttribute() method if you want to pass additional information to the
Freemarker template. We'll go over this later.
</para>
<para>
Calling LoginFormsProvider.createForm() returns a JAX-RS Response object. We then call AuthenticationFlowContext.challenge()
passing in this response. This sets the status of the execution as CHALLENGE and if the execution is Required, this
JAX-RS Response object will be sent to the browser.
</para>
<para>
So, the HTML page asking for the answer to a secret question is displayed to the user and the user
enteres in the answer and clicks submit. The action URL of the HTML form will send an HTTP request to the
flow. The flow will end up invoking the action() method of our Authenticator implementation.
<programlisting>
@Override
public void action(AuthenticationFlowContext context) {
boolean validated = validateAnswer(context);
if (!validated) {
Response challenge = context.form()
.setError("badSecret")
.createForm("secret-question.ftl");
context.failureChallenge(AuthenticationFlowError.INVALID_CREDENTIALS, challenge);
return;
}
setCookie(context);
context.success();
}
</programlisting>
</para>
<para>
If the answer is not valid, we rebuild the HTML Form with an additional error message. We then call
AuthenticationFlowContext.failureChallenge() passing in the reason for the value and the JAX-RS response.
failureChallenge() works the same as challenge(), but it also records the failure so it can be analyzed
by any attack detection service.
</para>
<para>
If validation is successful, then we set a cookie to remember that the secret question has been answered
and we call AuthenticationFlowContext.success().
</para>
<para>
The last thing I want to go over is the setCookie() method. This is an example of providing configuration
for the Authenticator. In this case we want the max age of the cookie to be configurable.
<programlisting>
protected void setCookie(AuthenticationFlowContext context) {
AuthenticatorConfigModel config = context.getAuthenticatorConfig();
int maxCookieAge = 60 * 60 * 24 * 30; // 30 days
if (config != null) {
maxCookieAge = Integer.valueOf(config.getConfig().get("cookie.max.age"));
}
... set the cookie ...
}
</programlisting>
</para>
<para>
We obtain an AuthenticatorConfigModel from the AuthenticationFlowContext.getAuthenticatorConfig() method.
If configuration exists we pull the max age config out of it. We will see how we can define what should
be configured when we talk about the AuthenticatorFactory implementation. The config values can be
defined within the admin console if you set up config definitions in your AuthenticatorFactory implementation.
</para>
</section>
<section>
<title>Implementing an AuthenticatorFactory</title>
<para>
The next step in this process is to implement an AuthenticatorFactory. This factory is responsible
for instantiating an Authenticator. It also provides deployment and configuration metadata about
the Authenticator.
</para>
<para>
The getId() method is just the unique name of the component. The create() methods should also
be self explanatory. The create(KeycloakSession) method will actually never be called. It is just
an artifact of the more generic ProviderFactory interface.
<programlisting>
public class SecretQuestionAuthenticatorFactory implements AuthenticatorFactory, ConfigurableAuthenticatorFactory {
public static final String PROVIDER_ID = "secret-question-authenticator";
private static final SecretQuestionAuthenticator SINGLETON = new SecretQuestionAuthenticator();
@Override
public String getId() {
return PROVIDER_ID;
}
@Override
public Authenticator create() {
return SINGLETON;
}
@Override
public Authenticator create(KeycloakSession session) {
return SINGLETON;
}
</programlisting>
</para>
<para>
The next thing the factory is responsible for is specify the allowed requirement switches. While there
are four different requirement types: ALTERNATIVE, REQUIRED, OPTIONAL, DISABLED, AuthenticatorFactory
implementations can limit which requirement options are shown in the admin console when defining
a flow. In our example, we're going to limit our requirement options to REQUIRED and DISABLED.
<programlisting>
private static AuthenticationExecutionModel.Requirement[] REQUIREMENT_CHOICES = {
AuthenticationExecutionModel.Requirement.REQUIRED,
AuthenticationExecutionModel.Requirement.DISABLED
};
@Override
public AuthenticationExecutionModel.Requirement[] getRequirementChoices() {
return REQUIREMENT_CHOICES;
}
</programlisting>
</para>
<para>
The AuthenticatorFactory.isUserSetupAllowed() is a flag that tells the flow manager whether or not
Authenticator.setRequiredActions() method will be called. If an Authenticator is not configured for a user,
the flow manager checks isUserSetupAllowed(). If it is false, then the flow aborts with an error. If it
returns true, then the flow manager will invoke Authenticator.setRequiredActions().
<programlisting>
@Override
public boolean isUserSetupAllowed() {
return true;
}
</programlisting>
</para>
<para>
The next few methods define how the Authenticator can be configured. The isConfigurable() method
is a flag which specifies to the admin console on whether the Authenticator can be configured within
a flow. The getConfigProperties() method returns a list of ProviderConfigProperty objects. These
objects define a specific configuration attribute.
<programlisting><![CDATA[
@Override
public List<ProviderConfigProperty> getConfigProperties() {
return configProperties;
}
private static final List<ProviderConfigProperty> configProperties = new ArrayList<ProviderConfigProperty>();
static {
ProviderConfigProperty property;
property = new ProviderConfigProperty();
property.setName("cookie.max.age");
property.setLabel("Cookie Max Age");
property.setType(ProviderConfigProperty.STRING_TYPE);
property.setHelpText("Max age in seconds of the SECRET_QUESTION_COOKIE.");
configProperties.add(property);
}
]]></programlisting>
</para>
<para>
Each ProviderConfigProperty defines the name of the config property. This is the key used in the config
map stored in AuthenticatorConfigModel. The label defines how the config option will be displayed in the
admin console. The type defines if it is a String, Boolean, or other type. The admin console
will display different UI inputs depending on the type. The help text is what will be shown in the
tooltip for the config attribute in the admin console. Read the javadoc of ProviderConfigProperty
for more detail.
</para>
<para>
The rest of the methods are for the admin console. getHelpText() is the tooltip text that will be
shown when you are picking the Authenticator you want to bind to an execution. getDisplayType()
is what text that will be shown in the admin console when listing the Authenticator. getReferenceCategory()
is just a category the Authenticator belongs to.
</para>
</section>
<section>
<title>Adding Authenticator Form</title>
<para>
Keycloak comes with a Freemarker <link linkend="themes">theme and template engine</link>. The createForm()
method you called within authenticate() of your Authenticator class, builds an HTML page from a file within
your login them: secret-question.ftl. This file should be placed in the login theme with all the other
.ftl files you see for login.
</para>
<para>
Let's take a bigger look at secret-question.ftl Here's a small code snippet:
<programlisting><![CDATA[
<form id="kc-totp-login-form" class="${properties.kcFormClass!}" action="${url.loginAction}" method="post">
<div class="${properties.kcFormGroupClass!}">
<div class="${properties.kcLabelWrapperClass!}">
<label for="totp" class="${properties.kcLabelClass!}">${msg("loginSecretQuestion")}</label>
</div>
<div class="${properties.kcInputWrapperClass!}">
<input id="totp" name="secret_answer" type="text" class="${properties.kcInputClass!}" />
</div>
</div>
]]></programlisting>
</para>
<para>
Any piece of text enclosed in <literal>${}</literal> corresponds to an attribute or template funtion.
If you see the form's action, you see it points to <literal>${url.loginAction}</literal>. This value
is automatically generated when you invoke the AuthenticationFlowContext.form() method. You can also obtain
this value by calling the AuthenticationFlowContext.getActionURL() method in Java code.
</para>
<para>
You'll also see <literal>${properties.someValue}</literal>. These correspond to properties defined
in your theme.properties file of our theme. <literal>${msg("someValue")}</literal> corresponds to the
internationalized message bundles (.properties files) included with the login theme messages/ directory.
If you're just using english, you can just add the value of the <literal>loginSecretQuestion</literal>
value. This should be the question you want to ask the user.
</para>
<para>
When you call AuthenticationFlowContext.form() this gives you a LoginFormsProvider instance. If you called,
<literal>LoginFormsProvider.setAttribute("foo", "bar")</literal>, the value of "foo" would be available
for reference in your form as <literal>${foo}</literal>. The value of an attribute can be any Java
bean as well.
</para>
</section>
<section>
<title>Adding Authenticator to a Flow</title>
<para>
Adding an Authenticator to a flow must be done in the admin console.
If you go to the Authentication menu item and go to the Flow tab, you will be able to view the currently
defined flows. You cannot modify an built in flows, so, to add the Authenticator we've created you
have to copy an existing flow or create your own. I'm hoping the UI is intuitive enough so that you
can figure out for yourself how to create a flow and add the Authenticator.
</para>
<para>
After you've created your flow, you have to bind it to the login action you want to bind it to. If you go
to the Authentication menu and go to the Bindings tab you will see options to bind a flow to
the browser, registration, or direct grant flow.
</para>
</section>
</section>
</chapter>