/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import com.sun.security.auth.module.Krb5LoginModule;

import java.security.Key;

import java.security.PrivilegedActionException;

import java.security.PrivilegedExceptionAction;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Map;

import javax.security.auth.Subject;

import javax.security.auth.kerberos.KerberosKey;

import javax.security.auth.kerberos.KerberosTicket;

import javax.security.auth.login.LoginContext;

import org.ietf.jgss.GSSContext;

import org.ietf.jgss.GSSCredential;

import org.ietf.jgss.GSSException;

import org.ietf.jgss.GSSManager;

import org.ietf.jgss.GSSName;

import org.ietf.jgss.MessageProp;

import org.ietf.jgss.Oid;

import com.sun.security.jgss.ExtendedGSSContext;

import com.sun.security.jgss.InquireType;

import com.sun.security.jgss.AuthorizationDataEntry;

import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

/**

 * Context of a JGSS subject, encapsulating Subject and GSSContext.

 *

 * Three "constructors", which acquire the (private) credentials and fill

 * it into the Subject:

 *

 * 1. static fromJAAS(): Creates a Context using a JAAS login config entry

 * 2. static fromUserPass(): Creates a Context using a username and a password

 * 3. delegated(): A new context which uses the delegated credentials from a

 *    previously established acceptor Context

 *

 * Two context initiators, which create the GSSContext object inside:

 *

 * 1. startAsClient()

 * 2. startAsServer()

 *

 * Privileged action:

 *    doAs(): Performs an action in the name of the Subject

 *

 * Handshake process:

 *    static handShake(initiator, acceptor)

 *

 * A four-phase typical data communication which includes all four GSS

 * actions (wrap, unwrap, getMic and veryfyMiC):

 *    static transmit(message, from, to)

 */

public class Context {

    private Subject s;

    private ExtendedGSSContext x;

    private boolean f;      // context established?

    private String name;

    private GSSCredential cred;     // see static method delegated().

    static boolean usingStream = false;

    private Context() {}

    /**

     * Using the delegated credentials from a previous acceptor

     * @param c

     */

    public Context delegated() throws Exception {

        Context out = new Context();

        out.s = s;

        out.cred = x.getDelegCred();

        out.name = name + " as " + out.cred.getName().toString();

        return out;

    }

    /**

     * Logins with a JAAS login config entry name

     */

    public static Context fromJAAS(final String name) throws Exception {

        Context out = new Context();

        out.name = name;

        LoginContext lc = new LoginContext(name);

        lc.login();

        out.s = lc.getSubject();

        return out;

    }

    /**

     * Logins with a username and a password, using Krb5LoginModule directly

     * @param storeKey true if key should be saved, used on acceptor side

     */

    public static Context fromUserPass(String user, char[] pass, boolean storeKey)

            throws Exception {

        Context out = new Context();

        out.name = user;

        out.s = new Subject();

        Krb5LoginModule krb5 = new Krb5LoginModule();

        Map<String, String> map = new HashMap<>();

        Map<String, Object> shared = new HashMap<>();

        if (pass != null) {

            map.put("useFirstPass", "true");

            shared.put("javax.security.auth.login.name", user);

            shared.put("javax.security.auth.login.password", pass);

        } else {

            map.put("doNotPrompt", "true");

            map.put("useTicketCache", "true");

            if (user != null) {

                map.put("principal", user);

            }

        }

        if (storeKey) {

            map.put("storeKey", "true");

        }

        krb5.initialize(out.s, null, shared, map);

        krb5.login();

        krb5.commit();

        return out;

    }

    /**

     * Logins with a username and a keytab, using Krb5LoginModule directly

     * @param storeKey true if key should be saved, used on acceptor side

     */

    public static Context fromUserKtab(String user, String ktab, boolean storeKey)

            throws Exception {

        Context out = new Context();

        out.name = user;

        out.s = new Subject();

        Krb5LoginModule krb5 = new Krb5LoginModule();

        Map<String, String> map = new HashMap<>();

        map.put("doNotPrompt", "true");

        map.put("useTicketCache", "false");

        map.put("useKeyTab", "true");

        map.put("keyTab", ktab);

        map.put("principal", user);

        if (storeKey) {

            map.put("storeKey", "true");

        }

        krb5.initialize(out.s, null, null, map);

        krb5.login();

        krb5.commit();

        return out;

    }

    /**

     * Starts as a client

     * @param target communication peer

     * @param mech GSS mech

     * @throws java.lang.Exception

     */

    public void startAsClient(final String target, final Oid mech) throws Exception {

        doAs(new Action() {

            @Override

            public byte[] run(Context me, byte[] dummy) throws Exception {

                GSSManager m = GSSManager.getInstance();

                me.x = (ExtendedGSSContext)m.createContext(

                          target.indexOf('@') < 0 ?

                            m.createName(target, null) :

                            m.createName(target, GSSName.NT_HOSTBASED_SERVICE),

                        mech,

                        cred,

                        GSSContext.DEFAULT_LIFETIME);

                return null;

            }

        }, null);

        f = false;

    }

    /**

     * Starts as a server

     * @param mech GSS mech

     * @throws java.lang.Exception

     */

    public void startAsServer(final Oid mech) throws Exception {

        doAs(new Action() {

            @Override

            public byte[] run(Context me, byte[] dummy) throws Exception {

                GSSManager m = GSSManager.getInstance();

                me.x = (ExtendedGSSContext)m.createContext(m.createCredential(

                        null,

                        GSSCredential.INDEFINITE_LIFETIME,

                        mech,

                        GSSCredential.ACCEPT_ONLY));

                return null;

            }

        }, null);

        f = false;

    }

    /**

     * Accesses the internal GSSContext object. Currently it's used for --

     *

     * 1. calling requestXXX() before handshake

     * 2. accessing source name

     *

     * Note: If the application needs to do any privileged call on this

     * object, please use doAs(). Otherwise, it can be done directly. The

     * methods listed above are all non-privileged calls.

     *

     * @return the GSSContext object

     */

    public ExtendedGSSContext x() {

        return x;

    }

    /**

     * Disposes the GSSContext within

     * @throws org.ietf.jgss.GSSException

     */

    public void dispose() throws GSSException {

        x.dispose();

    }

    /**

     * Does something using the Subject inside

     * @param action the action

     * @param in the input byte

     * @return the output byte

     * @throws java.lang.Exception

     */

    public byte[] doAs(final Action action, final byte[] in) throws Exception {

        try {

            return Subject.doAs(s, new PrivilegedExceptionAction<byte[]>() {

                @Override

                public byte[] run() throws Exception {

                    return action.run(Context.this, in);

                }

            });

        } catch (PrivilegedActionException pae) {

            throw pae.getException();

        }

    }

    /**

     * Prints status of GSSContext and Subject

     * @throws java.lang.Exception

     */

    public void status() throws Exception {

        System.out.println("STATUS OF " + name.toUpperCase());

        try {

            StringBuffer sb = new StringBuffer();

            if (x.getAnonymityState()) {

                sb.append("anon, ");

            }

            if (x.getConfState()) {

                sb.append("conf, ");

            }

            if (x.getCredDelegState()) {

                sb.append("deleg, ");

            }

            if (x.getIntegState()) {

                sb.append("integ, ");

            }

            if (x.getMutualAuthState()) {

                sb.append("mutual, ");

            }

            if (x.getReplayDetState()) {

                sb.append("rep det, ");

            }

            if (x.getSequenceDetState()) {

                sb.append("seq det, ");

            }

            if (x instanceof ExtendedGSSContext) {

                if (((ExtendedGSSContext)x).getDelegPolicyState()) {

                    sb.append("deleg policy, ");

                }

            }

            System.out.println("Context status of " + name + ": " + sb.toString());

            System.out.println(x.getSrcName() + " -> " + x.getTargName());

        } catch (Exception e) {

            ;// Don't care

        }

        System.out.println("=====================================");

        for (Object o : s.getPrivateCredentials()) {

            System.out.println("    " + o.getClass());

            if (o instanceof KerberosTicket) {

                KerberosTicket kt = (KerberosTicket) o;

                System.out.println("        " + kt.getServer() + " for " + kt.getClient());

            } else if (o instanceof KerberosKey) {

                KerberosKey kk = (KerberosKey) o;

                System.out.print("        " + kk.getKeyType() + " " + kk.getVersionNumber() + " " + kk.getAlgorithm() + " ");

                for (byte b : kk.getEncoded()) {

                    System.out.printf("%02X", b & 0xff);

                }

                System.out.println();

            } else if (o instanceof Map) {

                Map map = (Map) o;

                for (Object k : map.keySet()) {

                    System.out.println("        " + k + ": " + map.get(k));

                }

            }

        }

        if (x != null && x instanceof ExtendedGSSContext) {

            if (x.isEstablished()) {

                ExtendedGSSContext ex = (ExtendedGSSContext)x;

                Key k = (Key)ex.inquireSecContext(

                        InquireType.KRB5_GET_SESSION_KEY);

                if (k == null) {

                    throw new Exception("Session key cannot be null");

                }

                System.out.println("Session key is: " + k);

                boolean[] flags = (boolean[])ex.inquireSecContext(

                        InquireType.KRB5_GET_TKT_FLAGS);

                if (flags == null) {

                    throw new Exception("Ticket flags cannot be null");

                }

                System.out.println("Ticket flags is: " + Arrays.toString(flags));

                String authTime = (String)ex.inquireSecContext(

                        InquireType.KRB5_GET_AUTHTIME);

                if (authTime == null) {

                    throw new Exception("Auth time cannot be null");

                }

                System.out.println("AuthTime is: " + authTime);

                if (!x.isInitiator()) {

                    AuthorizationDataEntry[] ad = (AuthorizationDataEntry[])ex.inquireSecContext(

                            InquireType.KRB5_GET_AUTHZ_DATA);

                    System.out.println("AuthzData is: " + Arrays.toString(ad));

                }

            }

        }

    }

    /**

     * Transmits a message from one Context to another. The sender wraps the

     * message and sends it to the receiver. The receiver unwraps it, creates

     * a MIC of the clear text and sends it back to the sender. The sender

     * verifies the MIC against the message sent earlier.

     * @param message the message

     * @param s1 the sender

     * @param s2 the receiver

     * @throws java.lang.Exception If anything goes wrong

     */

    static public void transmit(final String message, final Context s1,

            final Context s2) throws Exception {

        final byte[] messageBytes = message.getBytes();

        System.out.printf("-------------------- TRANSMIT from %s to %s------------------------\n",

                s1.name, s2.name);

        byte[] t = s1.doAs(new Action() {

            @Override

            public byte[] run(Context me, byte[] dummy) throws Exception {

                System.out.println("wrap");

                MessageProp p1 = new MessageProp(0, true);

                byte[] out;

                if (usingStream) {

                    ByteArrayOutputStream os = new ByteArrayOutputStream();

                    me.x.wrap(new ByteArrayInputStream(messageBytes), os, p1);

                    out = os.toByteArray();

                } else {

                    out = me.x.wrap(messageBytes, 0, messageBytes.length, p1);

                }

                System.out.println(printProp(p1));

                return out;

            }

        }, null);

        t = s2.doAs(new Action() {

            @Override

            public byte[] run(Context me, byte[] input) throws Exception {

                MessageProp p1 = new MessageProp(0, true);

                byte[] bytes;

                if (usingStream) {

                    ByteArrayOutputStream os = new ByteArrayOutputStream();

                    me.x.unwrap(new ByteArrayInputStream(input), os, p1);

                    bytes = os.toByteArray();

                } else {

                    bytes = me.x.unwrap(input, 0, input.length, p1);

                }

                if (!Arrays.equals(messageBytes, bytes))

                    throw new Exception("wrap/unwrap mismatch");

                System.out.println("unwrap");

                System.out.println(printProp(p1));

                p1 = new MessageProp(0, true);

                System.out.println("getMIC");

                if (usingStream) {

                    ByteArrayOutputStream os = new ByteArrayOutputStream();

                    me.x.getMIC(new ByteArrayInputStream(messageBytes), os, p1);

                    bytes = os.toByteArray();

                } else {

                    bytes = me.x.getMIC(messageBytes, 0, messageBytes.length, p1);

                }

                System.out.println(printProp(p1));

                return bytes;

            }

        }, t);

        // Re-unwrap should make p2.isDuplicateToken() returns true

        s1.doAs(new Action() {

            @Override

            public byte[] run(Context me, byte[] input) throws Exception {

                MessageProp p1 = new MessageProp(0, true);

                System.out.println("verifyMIC");

                if (usingStream) {

                    me.x.verifyMIC(new ByteArrayInputStream(input),

                            new ByteArrayInputStream(messageBytes), p1);

                } else {

                    me.x.verifyMIC(input, 0, input.length,

                            messageBytes, 0, messageBytes.length,

                            p1);

                }

                System.out.println(printProp(p1));

                return null;

            }

        }, t);

    }

    /**

     * Returns a string description of a MessageProp object

     * @param prop the object

     * @return the description

     */

    static public String printProp(MessageProp prop) {

        StringBuffer sb = new StringBuffer();

        sb.append("MessagePop: ");

        sb.append("QOP="+ prop.getQOP() + ", ");

        sb.append(prop.getPrivacy()?"privacy, ":"");

        sb.append(prop.isDuplicateToken()?"dup, ":"");

        sb.append(prop.isGapToken()?"gap, ":"");

        sb.append(prop.isOldToken()?"old, ":"");

        sb.append(prop.isUnseqToken()?"unseq, ":"");

        if (prop.getMinorStatus() != 0) {

            sb.append(prop.getMinorString()+ "(" + prop.getMinorStatus()+")");

        }

        return sb.toString();

    }

    /**

     * Handshake (security context establishment process) between two Contexts

     * @param c the initiator

     * @param s the acceptor

     * @throws java.lang.Exception

     */

    static public void handshake(final Context c, final Context s) throws Exception {

        byte[] t = new byte[0];

        while (!c.f || !s.f) {

            t = c.doAs(new Action() {

                @Override

                public byte[] run(Context me, byte[] input) throws Exception {

                    if (me.x.isEstablished()) {

                        me.f = true;

                        System.out.println(c.name + " side established");

                        if (input != null) {

                            throw new Exception("Context established but " +

                                    "still receive token at " + c.name);

                        }

                        return null;

                    } else {

                        System.out.println(c.name + " call initSecContext");

                        if (usingStream) {

                            ByteArrayOutputStream os = new ByteArrayOutputStream();

                            me.x.initSecContext(new ByteArrayInputStream(input), os);

                            return os.size() == 0 ? null : os.toByteArray();

                        } else {

                            return me.x.initSecContext(input, 0, input.length);

                        }

                    }

                }

            }, t);

            t = s.doAs(new Action() {

                @Override

                public byte[] run(Context me, byte[] input) throws Exception {

                    if (me.x.isEstablished()) {

                        me.f = true;

                        System.out.println(s.name + " side established");

                        if (input != null) {

                            throw new Exception("Context established but " +

                                    "still receive token at " + s.name);

                        }

                        return null;

                    } else {

                        System.out.println(s.name + " called acceptSecContext");

                        if (usingStream) {

                            ByteArrayOutputStream os = new ByteArrayOutputStream();

                            me.x.acceptSecContext(new ByteArrayInputStream(input), os);

                            return os.size() == 0 ? null : os.toByteArray();

                        } else {

                            return me.x.acceptSecContext(input, 0, input.length);

                        }

                    }

                }

            }, t);

        }

    }

}