/*
 * Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package sun.security.jgss.krb5;

import org.ietf.jgss.*;
import sun.security.jgss.GSSCaller;
import sun.security.jgss.spi.*;

import java.io.IOException;

import sun.security.krb5.Credentials;
import sun.security.krb5.KrbException;
import sun.security.krb5.internal.Ticket;

import javax.security.auth.kerberos.KerberosTicket;

/**
 * Implements the krb5 proxy credential element used in constrained
 * delegation. It is used in both impersonation (where there is no Kerberos 5
 * communication between the middle server and the client) and normal
 * constrained delegation (where there is, but client has not called
 * requestCredDeleg(true)).
 * @since 1.8
 */

public class Krb5ProxyCredential
    implements Krb5CredElement {

    public final Krb5InitCredential self;   // the middle server
    private final Krb5NameElement client;     // the client

    // The ticket with cname=client and sname=self. This can be a normal
    // service ticket or an S4U2self ticket.
    public final Ticket tkt;

    Krb5ProxyCredential(Krb5InitCredential self, Krb5NameElement client,
            Ticket tkt) {
        this.self = self;
        this.tkt = tkt;
        this.client = client;
    }

    // The client name behind the proxy
    @Override
    public final Krb5NameElement getName() throws GSSException {
        return client;
    }

    @Override
    public int getInitLifetime() throws GSSException {
        // endTime of tkt is not used by KDC, and it's also not
        // available in the case of kerberos constr deleg
        return self.getInitLifetime();
    }

    @Override
    public int getAcceptLifetime() throws GSSException {
        return 0;
    }

    @Override
    public boolean isInitiatorCredential() throws GSSException {
        return true;
    }

    @Override
    public boolean isAcceptorCredential() throws GSSException {
        return false;
    }

    @Override
    public final Oid getMechanism() {
        return Krb5MechFactory.GSS_KRB5_MECH_OID;
    }

    @Override
    public final java.security.Provider getProvider() {
        return Krb5MechFactory.PROVIDER;
    }

    @Override
    public void dispose() throws GSSException {
        try {
            self.destroy();
        } catch (javax.security.auth.DestroyFailedException e) {
            GSSException gssException =
                new GSSException(GSSException.FAILURE, -1,
                 "Could not destroy credentials - " + e.getMessage());
            gssException.initCause(e);
        }
    }

    @Override
    public GSSCredentialSpi impersonate(GSSNameSpi name) throws GSSException {
        // Cannot impersonate multiple levels without the impersonatee's TGT.
        throw new GSSException(GSSException.FAILURE, -1,
                "Only an initiate credentials can impersonate");
    }

    // Try to see if a default credential should act as an impersonator.
    static Krb5CredElement tryImpersonation(GSSCaller caller,
            Krb5InitCredential initiator) throws GSSException {

        try {
            KerberosTicket proxy = initiator.proxyTicket;
            if (proxy != null) {
                Credentials proxyCreds = Krb5Util.ticketToCreds(proxy);
                return new Krb5ProxyCredential(initiator,
                        Krb5NameElement.getInstance(proxyCreds.getClient()),
                        proxyCreds.getTicket());
            } else {
                return initiator;
            }
        } catch (KrbException | IOException e) {
            throw new GSSException(GSSException.DEFECTIVE_CREDENTIAL, -1,
                    "Cannot create proxy credential");
        }
    }
}
