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package sun.security.jgss.krb5;

import org.ietf.jgss.*;

import sun.security.jgss.GSSUtil;

import sun.security.jgss.GSSCaller;

import sun.security.jgss.spi.*;

import javax.security.auth.kerberos.ServicePermission;

import java.security.Provider;

import java.util.Vector;

/**

 * Krb5 Mechanism plug in for JGSS

 * This is the properties object required by the JGSS framework.

 * All mechanism specific information is defined here.

 *

 * @author Mayank Upadhyay

 */

public final class Krb5MechFactory implements MechanismFactory {

    private static final boolean DEBUG = Krb5Util.DEBUG;

    static final Provider PROVIDER =

        new sun.security.jgss.SunProvider();

    static final Oid GSS_KRB5_MECH_OID =

        createOid("1.2.840.113554.1.2.2");

    static final Oid NT_GSS_KRB5_PRINCIPAL =

        createOid("1.2.840.113554.1.2.2.1");

    private static Oid[] nameTypes =

        new Oid[] { GSSName.NT_USER_NAME,

                        GSSName.NT_HOSTBASED_SERVICE,

                        GSSName.NT_EXPORT_NAME,

                        NT_GSS_KRB5_PRINCIPAL};

    final private GSSCaller caller;

    private static Krb5CredElement getCredFromSubject(GSSNameSpi name,

                                                      boolean initiate)

        throws GSSException {

        Vector<Krb5CredElement> creds =

            GSSUtil.searchSubject(name, GSS_KRB5_MECH_OID, initiate,

                                  (initiate ?

                                   Krb5InitCredential.class :

                                   Krb5AcceptCredential.class));

        Krb5CredElement result = ((creds == null || creds.isEmpty()) ?

                                  null : creds.firstElement());

        // Force permission check before returning the cred to caller

        if (result != null) {

            if (initiate) {

                checkInitCredPermission((Krb5NameElement) result.getName());

            } else {

                checkAcceptCredPermission

                    ((Krb5NameElement) result.getName(), name);

            }

        }

        return result;

    }

    public Krb5MechFactory() {

        this(GSSCaller.CALLER_UNKNOWN);

    }

    public Krb5MechFactory(GSSCaller caller) {

        this.caller = caller;

    }

    public GSSNameSpi getNameElement(String nameStr, Oid nameType)

        throws GSSException {

        return Krb5NameElement.getInstance(nameStr, nameType);

    }

    public GSSNameSpi getNameElement(byte[] name, Oid nameType)

        throws GSSException {

        // At this point, even an exported name is stripped down to safe

        // bytes only

        // XXX Use encoding here

        return Krb5NameElement.getInstance(new String(name), nameType);

    }

    public GSSCredentialSpi getCredentialElement(GSSNameSpi name,

           int initLifetime, int acceptLifetime,

           int usage) throws GSSException {

        if (name != null && !(name instanceof Krb5NameElement)) {

            name = Krb5NameElement.getInstance(name.toString(),

                                       name.getStringNameType());

        }

        Krb5CredElement credElement = getCredFromSubject

            (name, (usage != GSSCredential.ACCEPT_ONLY));

        if (credElement == null) {

            if (usage == GSSCredential.INITIATE_ONLY ||

                usage == GSSCredential.INITIATE_AND_ACCEPT) {

                credElement = Krb5InitCredential.getInstance

                    (caller, (Krb5NameElement) name, initLifetime);

                checkInitCredPermission

                    ((Krb5NameElement) credElement.getName());

            } else if (usage == GSSCredential.ACCEPT_ONLY) {

                credElement =

                    Krb5AcceptCredential.getInstance(caller,

                                                     (Krb5NameElement) name);

                checkAcceptCredPermission

                    ((Krb5NameElement) credElement.getName(), name);

            } else

                throw new GSSException(GSSException.FAILURE, -1,

                                       "Unknown usage mode requested");

        }

        return credElement;

    }

    public static void checkInitCredPermission(Krb5NameElement name) {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            String realm = (name.getKrb5PrincipalName()).getRealmAsString();

            String tgsPrincipal =

                new String("krbtgt/" + realm + '@' + realm);

            ServicePermission perm =

                new ServicePermission(tgsPrincipal, "initiate");

            try {

                sm.checkPermission(perm);

            } catch (SecurityException e) {

                if (DEBUG) {

                    System.out.println("Permission to initiate" +

                        "kerberos init credential" + e.getMessage());

                }

                throw e;

            }

        }

    }

    public static void checkAcceptCredPermission(Krb5NameElement name,

                                           GSSNameSpi originalName) {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null && name != null) {

            ServicePermission perm = new ServicePermission

                (name.getKrb5PrincipalName().getName(), "accept");

            try {

                sm.checkPermission(perm);

            } catch (SecurityException e) {

                if (originalName == null) {

                    // Don't disclose the name of the principal

                    e = new SecurityException("No permission to acquire "

                                      + "Kerberos accept credential");

                    // Don't call e.initCause() with caught exception

                }

                throw e;

            }

        }

    }

    public GSSContextSpi getMechanismContext(GSSNameSpi peer,

                             GSSCredentialSpi myInitiatorCred, int lifetime)

        throws GSSException {

        if (peer != null && !(peer instanceof Krb5NameElement)) {

            peer = Krb5NameElement.getInstance(peer.toString(),

                                       peer.getStringNameType());

        }

        // XXX Convert myInitiatorCred to Krb5CredElement

        if (myInitiatorCred == null) {

            myInitiatorCred = getCredentialElement(null, lifetime, 0,

                GSSCredential.INITIATE_ONLY);

        }

        return new Krb5Context(caller, (Krb5NameElement)peer,

                               (Krb5CredElement)myInitiatorCred, lifetime);

    }

    public GSSContextSpi getMechanismContext(GSSCredentialSpi myAcceptorCred)

        throws GSSException {

        // XXX Convert myAcceptorCred to Krb5CredElement

        if (myAcceptorCred == null) {

            myAcceptorCred = getCredentialElement(null, 0,

                GSSCredential.INDEFINITE_LIFETIME, GSSCredential.ACCEPT_ONLY);

        }

        return new Krb5Context(caller, (Krb5CredElement)myAcceptorCred);

    }

    public GSSContextSpi getMechanismContext(byte[] exportedContext)

        throws GSSException {

        return new Krb5Context(caller, exportedContext);

    }

    public final Oid getMechanismOid() {

        return GSS_KRB5_MECH_OID;

    }

    public Provider getProvider() {

        return PROVIDER;

    }

    public Oid[] getNameTypes() {

        // nameTypes is cloned in GSSManager.getNamesForMech

        return nameTypes;

    }

    private static Oid createOid(String oidStr) {

        Oid retVal = null;

        try {

            retVal = new Oid(oidStr);

        } catch (GSSException e) {

            // Should not happen!

        }

        return retVal;

    }

}