Kerberos with Java

Question

i am try to login kerberos kdc from Java. But Java is throwing exception. Seems like login is successful but something is stops login. I dont know why ? Someone have solution for this problem? Here is my java system output:

Debug is  true storeKey false useTicketCache true useKeyTab false doNotPrompt false ticketCache is null isInitiator true KeyTab is null refreshKrb5Config is true principal is null tryFirstPass is false useFirstPass is false storePass is false clearPass is false
Refreshing Kerberos configuration
Acquire TGT from Cache
Principal is null
null credentials from Ticket Cache
                [Krb5LoginModule] user entered username: kadirb

principal is [email protected]
Commit Succeeded

Exception in thread "main" java.lang.Error: GSSException: No valid credentials provided (Mechanism level: Server not found in Kerberos database (7) - LOOKING_UP_SERVER)
        at KerberosTicketRetriever$TicketCreatorAction.run(KerberosTicketRetriever.java:76)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAsPrivileged(Subject.java:473)
        at KerberosTicketRetriever.retrieveTicket(KerberosTicketRetriever.java:179)
        at KerberosTicketRetriever.main(KerberosTicketRetriever.java:188)
Caused by: GSSException: No valid credentials provided (Mechanism level: Server not found in Kerberos database (7) - LOOKING_UP_SERVER)
        at sun.security.jgss.krb5.Krb5Context.initSecContext(Krb5Context.java:710)
        at sun.security.jgss.GSSContextImpl.initSecContext(GSSContextImpl.java:248)
        at sun.security.jgss.GSSContextImpl.initSecContext(GSSContextImpl.java:179)
        at KerberosTicketRetriever$TicketCreatorAction.createTicket(KerberosTicketRetriever.java:105)
        at KerberosTicketRetriever$TicketCreatorAction.run(KerberosTicketRetriever.java:72)
        ... 4 more
Caused by: KrbException: Server not found in Kerberos database (7) - LOOKING_UP_SERVER
        at sun.security.krb5.KrbTgsRep.<init>(KrbTgsRep.java:73)
        at sun.security.krb5.KrbTgsReq.getReply(KrbTgsReq.java:192)
        at sun.security.krb5.KrbTgsReq.sendAndGetCreds(KrbTgsReq.java:203)
        at sun.security.krb5.internal.CredentialsUtil.serviceCreds(CredentialsUtil.java:311)
        at sun.security.krb5.internal.CredentialsUtil.acquireServiceCreds(CredentialsUtil.java:115)
        at sun.security.krb5.Credentials.acquireServiceCreds(Credentials.java:442)
        at sun.security.jgss.krb5.Krb5Context.initSecContext(Krb5Context.java:641)
        ... 8 more
Caused by: KrbException: Identifier doesn't match expected value (906)
        at sun.security.krb5.internal.KDCRep.init(KDCRep.java:143)
        at sun.security.krb5.internal.TGSRep.init(TGSRep.java:66)
        at sun.security.krb5.internal.TGSRep.<init>(TGSRep.java:61)
        at sun.security.krb5.KrbTgsRep.<init>(KrbTgsRep.java:55)
        ... 14 more
Disconnected from the target VM, address: '127.0.0.1:51126', transport: 'socket'

Process finished with exit code 1

And my java code:

import com.sun.security.auth.callback.DialogCallbackHandler;
import org.ietf.jgss.*;
import sun.misc.BASE64Encoder;
import javax.security.auth.Subject;
import javax.security.auth.login.LoginContext;
import javax.security.auth.login.LoginException;
import java.io.*;
import java.security.Principal;
import java.security.PrivilegedAction;
import java.util.Set;

/**
 * Tool to retrieve a kerberos ticket. This one will not be stored in the windows ticket cache.
 */
public final class KerberosTicketRetriever
{
private final static Oid KERB_V5_OID;
private final static Oid KRB5_PRINCIPAL_NAME_OID;

static {
    try
    {
        KERB_V5_OID = new Oid("1.2.840.113554.1.2.2");
        KRB5_PRINCIPAL_NAME_OID = new Oid("1.2.840.113554.1.2.2.1");

    } catch (final GSSException ex)
    {
        throw new Error(ex);
    }
}

/**
 * Not to be instanciated
 */
private KerberosTicketRetriever() {};

/**
 *
 */
private static class TicketCreatorAction implements PrivilegedAction
{
    final String userPrincipal;
    final String applicationPrincipal;

    private StringBuffer outputBuffer;

    /**
     *
     * @param userPrincipal  p.ex. <tt>[email protected]</tt>
     * @param applicationPrincipal  p.ex. <tt>HTTP/webserver.myfirm.com</tt>
     */
    private TicketCreatorAction(final String userPrincipal, final String applicationPrincipal)
    {
        this.userPrincipal = userPrincipal;
        this.applicationPrincipal = applicationPrincipal;
    }

    private void setOutputBuffer(final StringBuffer newOutputBuffer)
    {
        outputBuffer = newOutputBuffer;
    }

    /**
     * Only calls {@link #createTicket()}
     * @return <tt>null</tt>
     */
    public Object run()
    {
        try
        {
            createTicket();
        }
        catch (final GSSException  ex)
        {
            throw new Error(ex);
        }

        return null;
    }

    /**
     *
     * @throws GSSException
     */
    private void createTicket () throws GSSException
    {
        final GSSManager manager = GSSManager.getInstance();
        final GSSName clientName = manager.createName(userPrincipal, KRB5_PRINCIPAL_NAME_OID);
        final GSSCredential clientCred = manager.createCredential(clientName,
                8 * 3600,
                KERB_V5_OID,
                GSSCredential.INITIATE_ONLY);

        final GSSName serverName = manager.createName(applicationPrincipal, KRB5_PRINCIPAL_NAME_OID);

        final GSSContext context = manager.createContext(serverName,
                KERB_V5_OID,
                clientCred,
                GSSContext.DEFAULT_LIFETIME);
        context.requestMutualAuth(true);
        context.requestConf(false);
        context.requestInteg(true);

        final byte[] outToken = context.initSecContext(new byte[0], 0, 0);

        if (outputBuffer !=null)
        {
            outputBuffer.append(String.format("Src Name: %s\n", context.getSrcName()));
            outputBuffer.append(String.format("Target  : %s\n", context.getTargName()));
            outputBuffer.append(new BASE64Encoder().encode(outToken));
            outputBuffer.append("\n");
        }

        context.dispose();
    }
}

/**
 *
 * @param realm p.ex. <tt>MYFIRM.COM</tt>
 * @param kdc p.ex. <tt>kerbserver.myfirm.com</tt>
 * @param applicationPrincipal   cf. {@link #TicketCreatorAction(String, String)}
 * @throws GSSException
 * @throws LoginException
 */
static public String retrieveTicket(
        final String realm,
        final String kdc,
        final String applicationPrincipal)
        throws GSSException, LoginException
{

    // create the jass-config-file
    final File jaasConfFile;
    try
    {
        jaasConfFile = File.createTempFile("jaas.conf", null);
        final PrintStream bos = new PrintStream(new FileOutputStream(jaasConfFile));
        bos.print(String.format(
                "Krb5LoginContext { com.sun.security.auth.module.Krb5LoginModule required refreshKrb5Config=true useTicketCache=true debug=true ; };"
        ));
        bos.close();
        jaasConfFile.deleteOnExit();
    }
    catch (final IOException ex)
    {
        throw new IOError(ex);
    }

    // set the properties
    System.setProperty("java.security.krb5.realm", realm);
    System.setProperty("java.security.krb5.kdc", kdc);
    System.setProperty("java.security.auth.login.config",jaasConfFile.getAbsolutePath());

    // get the Subject(), i.e. the current user under Windows
    final Subject subject = new Subject();
    final LoginContext lc = new LoginContext("Krb5LoginContext", subject, new DialogCallbackHandler());
    try {
        lc.login();
    } catch (LoginException e) {
        e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
        //e = Client not found in Kerberos database (6) - CLIENT_NOT_FOUND
        System.exit(0);
    }

    // extract our principal
    final Set<Principal> principalSet = subject.getPrincipals();
    if (principalSet.size() != 1)
        throw new AssertionError("No or several principals: " + principalSet);
    final Principal userPrincipal = principalSet.iterator().next();

    // now try to execute the SampleAction as the authenticated Subject
    // action.run() without doAsPrivileged leads to
    //   No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)
    final TicketCreatorAction action = new TicketCreatorAction(userPrincipal.getName(), applicationPrincipal);
    final StringBuffer outputBuffer = new StringBuffer();
    action.setOutputBuffer(outputBuffer);
    Subject.doAsPrivileged(lc.getSubject(), action, null);

    return outputBuffer.toString();
}

public static void main (final String args[]) throws Throwable
 {
    final String ticket = retrieveTicket("EXAMPLE.COM", "EXAMPLE.COM", "HTTP/webserver.myfirm.com");
    System.out.println(ticket);
 }
}

Chicanery

Doesn't answer the question, but isn't throwin an Error in TicketCreatorAction#run() a little violent? – Tadeas

final byte[] outToken = context.initSecContext(new byte[0], 0, 0); i got exception throw on this line. – Chicanery

Answer 1

I didn't test your code, but reading stacktrace I believe the problem is with KDC domain. As documentation says:

the default realm and the KDC for that realm are indicated in the Kerberos krb5.conf

Typically KDC realm in krb5.conf is kdc. Example from fedora default installation:

[realms]
EXAMPLE.COM = {
kdc = kerberos.example.com
admin_server = kerberos.example.com
}

I seems obvious that you should change your kdc domain with domain name, not Realm name:

final String ticket = retrieveTicket("EXAMPLE.COM", "localhost", "HTTP/webserver.myfirm.com");

You are using Kerberos on local machine, you might want to add option dns_lookup_kdc = false to your krb5.conf

Flashbulb

I changed String applicationPrincipal = "[email protected]"; final String ticket = retrieveTicket("EXAMPLE.COM","EXAMPLE.COM", applicationPrincipal); applicationPrincipal = "[email protected]" fixed the problem.Thanks – Chicanery

krb5.conf file may need an update. – Began