Kerberos (v6.1)

pac4j allows you to login using the Keberos authentication mechanism (also known as SPNEGO or Microsoft HTTP Negotiate).

The Kerberos clients require to define an Authenticator to handle the credentials validation. Most likely all you need is to use the existing KerberosAuthenticator with a SunJaasKerberosTicketValidator which will do all the heavy-lifting of the Kerberos ticket validation.

1) Dependency

You need to use the following module: pac4j-kerberos.

Example (Maven dependency):

<dependency>
    <groupId>org.pac4j</groupId>
    <artifactId>pac4j-kerberos</artifactId>
    <version>${pac4j.version}</version>
</dependency>

2) Clients

You can use the following clients depending on how they are passed in the HTTP request:

Behaviour wanted	Client
Web Browser (Firefox/Safari/IE) after ticket validation, it stores user profile in the session	`IndirectKerberosClient` (upon failure it sends a `HTTP 401` with a `WWW-Authenticate: Negotiate` header asking the browser to provide the Kerberos/SPNEGO credentials)
Stateless Web service	`DirectKerberosClient` credentials are expected to be already provided as a request’s HTTP header: `Authentication: Negotiate SomeBase64EncKerberosTicket` (it will not send any headers to indicate expected mechanism)

Example:

import org.pac4j.kerberos.client.indirect.DirectKerberosClient;
import org.pac4j.kerberos.client.indirect.IndirectKerberosClient;
import org.pac4j.kerberos.credentials.KerberosCredentials;
import org.pac4j.kerberos.credentials.authenticator.KerberosAuthenticator;
import org.pac4j.kerberos.credentials.authenticator.SunJaasKerberosTicketValidator;
import org.pac4j.kerberos.profile.KerberosProfile;
import org.springframework.core.io.FileSystemResource;

SunJaasKerberosTicketValidator validator = new SunJaasKerberosTicketValidator();
// HTTP/fully-qualified-domain-name@DOMAIN
validator.setServicePrincipal("HTTP/[email protected]");
// the keytab file must contain the keys for the service principal, and should be protected
validator.setKeyTabLocation(new FileSystemResource("/private/security/http-keytab"));
// validator.setDebug(true);

IndirectKerberosClient client = new IndirectKerberosClient(new KerberosAuthenticator(validator));
client.setCallbackUrl("/force-kerberos-login"); // required only for indirect client

3) Common caveats with Kerberos (in JVM)

Some common problems/caveats:

make sure the keytab file contains the service principal, and the name matches exactly
- for web the HTTP/ prefix is mandatory and must be uppercase
Likely you need an Oracle Java (JDK/ Java SE etc) here.
- Most encryption mechanisms need the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files to be downloaded and copied over in a proper dir of your Java installation.
the browser URL must match the fully-qualified-domain-name as specified in setServicePrincipal.
- client needs to run kinit
- P.S. to test your app when developing locally, one can add a fake domain name in /etc/hosts pointing to localhost:
```
127.0.0.1 www.mydomain.myrealm.lt
```