Here’s an explanation of each policy type:

There are two different algorithms to choose from for your OTP generators. Time Based (TOTP) and Counter Based (HOTP). For TOTP, your token generator will hash the current time and a shared secret. The server validates the OTP by comparing the all hashes within a certain window of time to the submitted value. So, TOTPs are valid only for a short window of time (usually 30 seconds). For HOTP a shared counter is used instead of the current time. The server increments the counter with each successful OTP login. So, valid OTPs only change after a successful login.

TOTP is considered a little more secure because the matchable OTP is only valid for a short window of time while the OTP for HOTP can be valid for an indeterminate amount of time. HOTP is much more user friendly as the user won’t have to hurry to enter in their OTP before the time interval is up. With the way Red Hat Single Sign-On has implemented TOTP this distinction becomes a little more blurry. HOTP requires a database update every time the server wants to increment the counter. This can be a performance drain on the authentication server when there is heavy load. So, to provide a more efficient alternative, TOTP does not remember passwords used. This bypasses the need to do any DB updates, but the downside is that TOTPs can be re-used in the valid time interval. For future versions of Red Hat Single Sign-On it is planned that you will be able to configure whether TOTP checks older OTPs in the time interval.

This is platform dependent. Exact steps depend on your OS and the Kerberos vendor you’re going to use. Consult Windows Active Directory, MIT Kerberos and your OS documentation for how exactly to setup and configure Kerberos server.

At least you will need to:

sudo kadmin.local

Then add HTTP principal and export his key to a keytab file with the commands like:

addprinc -randkey HTTP/www.mydomain.org@MYDOMAIN.ORG
ktadd -k /tmp/http.keytab HTTP/www.mydomain.org@MYDOMAIN.ORG

The Keytab file /tmp/http.keytab will need to be accessible on the host where Red Hat Single Sign-On server will be running.

You need to install a kerberos client on your machine. This is also platform dependent. If you are on Fedora, Ubuntu or RHEL, you can install the package freeipa-client, which contains a Kerberos client and several other utilities. Configure the kerberos client (on linux it’s in file /etc/krb5.conf ). You need to put your Kerberos realm and at least configure the HTTP domains your server will be running on. For the example realm MYDOMAIN.ORG you may configure the domain_realm section like this:

[domain_realm]
  .mydomain.org = MYDOMAIN.ORG
  mydomain.org = MYDOMAIN.ORG

Next you need to export the keytab file with the HTTP principal and make sure the file is accessible to the process under which Red Hat Single Sign-On server is running. For production, it’s ideal if it’s readable just by this process and not by someone else. For the MIT Kerberos example above, we already exported keytab to /tmp/http.keytab . If your KDC and Red Hat Single Sign-On are running on same host, you have that file already available.

Clients need to install kerberos client and setup krb5.conf as described above. Additionally they need to enable SPNEGO login support in their browser. See configuring Firefox for Kerberos if you are using that browser. URI .mydomain.org must be allowed in the network.negotiate-auth.trusted-uris config option.

In a Windows domain, clients usually don’t need to configure anything special as IE is already able to participate in SPNEGO authentication for the Windows domain.

Kerberos 5 supports the concept of credential delegation. In this scenario, your applications may want access to the Kerberos ticket so that they can re-use it to interact with other services secured by Kerberos. Since the SPNEGO protocol is processed in the Red Hat Single Sign-On server, you have to propagate the GSS credential to your application within the OpenID Connect token claim or a SAML assertion attribute that is transmitted to your application from the Red Hat Single Sign-On server. To have this claim inserted into the token or assertion, each application will need to enable the built-in protocol mapper called gss delegation credential. This is enabled in the Mappers tab of the application’s client page. See Protocol Mappers chapter for more details.

Applications will need to deserialize the claim it receives from Red Hat Single Sign-On before it can use it to make GSS calls against other services. Once you deserialize the credential from the access token to the GSSCredential object, the GSSContext will need to be created with this credential passed to the method GSSManager.createContext for example like this:

// Obtain accessToken in your application.
KeycloakPrincipal keycloakPrincipal = (KeycloakPrincipal) servletReq.getUserPrincipal();
AccessToken accessToken = keycloakPrincipal.getKeycloakSecurityContext().getToken();

// Retrieve kerberos credential from accessToken and deserialize it
String serializedGssCredential = (String) accessToken.getOtherClaims().
    get(org.keycloak.common.constants.KerberosConstants.GSS_DELEGATION_CREDENTIAL);

GSSCredential deserializedGssCredential = org.keycloak.common.util.KerberosSerializationUtils.
    deserializeCredential(serializedGssCredential);

// Create GSSContext to call other kerberos-secured services
GSSContext context = gssManager.createContext(serviceName, krb5Oid,
    deserializedGssCredential, GSSContext.DEFAULT_LIFETIME);

Note that you also need to configure forwardable kerberos tickets in krb5.conf file and add support for delegated credentials to your browser.

In the Kerberos V5 protocol, the realm is a set of Kerberos principals defined in the Kerberos database (typically LDAP server). The Kerberos protocol has a concept of cross-realm trust. For example, if there are 2 kerberos realms A and B, the cross-realm trust will allow the users from realm A to access resources (services) of realm B. This means that realm B trusts the realm A.

The Red Hat Single Sign-On server has support for cross-realm trust. There are few things which need to be done to achieve this:

If you have issues, we recommend that you enable additional logging to debug the problem:

emailAddress=(.*?)(?:,|$)

The regular expression filtering is applicable only if the Identity Source is set to either Match SubjectDN using regular expression or Match IssuerDN using regular expression.

The following sections describe how to configure Wildfly/Undertow and the Red Hat Single Sign-On Server to enable X.509 client certificate authentication.

<security-realms>
    <security-realm name="ssl-realm">
        <server-identities>
            <ssl>
                <keystore path="servercert.jks"
                          relative-to="jboss.server.config.dir"
                          keystore-password="servercert password"/>
            </ssl>
        </server-identities>
        <authentication>
            <truststore path="truststore.jks"
                        relative-to="jboss.server.config.dir"
                        keystore-password="truststore password"/>
        </authentication>
    </security-realm>
</security-realms>

<subsystem xmlns="urn:jboss:domain:undertow:4.0">
	....
    <server name="default-server">
	    <https-listener name="default"
                        socket-binding="https"
                        security-realm="ssl-realm"
                        verify-client="REQUESTED"/>
    </server>
</subsystem>

When an HTTP request is sent directly to Red Hat Single Sign-On server, the JBoss EAP undertow subsystem will establish an SSL handshake and extract the client certificate. The client certificate will be then saved to the attribute javax.servlet.request.X509Certificate of the HTTP request, as specified in the servlet specification. The Red Hat Single Sign-On X509 authenticator will be then able to lookup the certificate from this attribute.

However, when the Red Hat Single Sign-On server listens to HTTP requests behind a load balancer or reverse proxy, it may be the proxy server which extracts the client certificate and establishes the mutual SSL connection. A reverse proxy usually puts the authenticated client certificate in the HTTP header of the underlying request and forwards it to the back end Red Hat Single Sign-On server. In this case, Red Hat Single Sign-On must be able to look up the X.509 certificate chain from the HTTP headers instead of from the attribute of HTTP request, as is done for Undertow.

If Red Hat Single Sign-On is behind a reverse proxy, you usually need to configure alternative provider of the x509cert-lookup SPI in RHSSO_HOME/standalone/configuration/standalone.xml. Along with the default provider, which looks up the certificate from the HTTP header, we also have two additional built-in providers: haproxy and apache, which are described next.

<spi name="x509cert-lookup">
    <default-provider>haproxy</default-provider>
    <provider name="haproxy" enabled="true">
        <properties>
            <property name="sslClientCert" value="SSL_CLIENT_CERT"/>
            <property name="sslCertChainPrefix" value="CERT_CHAIN"/>
            <property name="certificateChainLength" value="10"/>
        </properties>
    </provider>
</spi>

<spi name="x509cert-lookup">
    <default-provider>apache</default-provider>
    <provider name="apache" enabled="true">
        <properties>
            <property name="sslClientCert" value="SSL_CLIENT_CERT"/>
            <property name="sslCertChainPrefix" value="CERT_CHAIN"/>
            <property name="certificateChainLength" value="10"/>
        </properties>
    </provider>
</spi>

$ curl https://[host][:port]/auth/realms/master/protocol/openid-connect/token \
       --insecure \
       --data "grant_type=password&scope=openid profile&username=&password=&client_id=CLIENT_ID&client_secret=CLIENT_SECRET" \
       -E /path/to/client_cert.crt \
       --key /path/to/client_cert.key