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package sun.security.ssl;

import java.io.IOException;
import java.io.PrintStream;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.PrivilegedExceptionAction;
import java.security.PrivilegedActionException;
import java.security.SecureRandom;
import java.net.InetAddress;

import javax.security.auth.kerberos.KerberosTicket;
import javax.security.auth.kerberos.KerberosKey;
import javax.security.auth.kerberos.KerberosPrincipal;
import javax.security.auth.kerberos.ServicePermission;
import sun.security.jgss.GSSCaller;

import sun.security.krb5.EncryptionKey;
import sun.security.krb5.EncryptedData;
import sun.security.krb5.PrincipalName;
import sun.security.krb5.Realm;
import sun.security.krb5.internal.Ticket;
import sun.security.krb5.internal.EncTicketPart;
import sun.security.krb5.internal.crypto.KeyUsage;

import sun.security.jgss.krb5.Krb5Util;

This is Kerberos option in the client key exchange message
(CLIENT -> SERVER). It holds the Kerberos ticket and the encrypted
premaster secret encrypted with the session key sealed in the ticket.
From RFC 2712:
 struct
 {
   opaque Ticket;
   opaque authenticator;            // optional
   opaque EncryptedPreMasterSecret; // encrypted with the session key
                                    // which is sealed in the ticket
 } KerberosWrapper;
Ticket and authenticator are encrypted as per RFC 1510 (in ASN.1)
Encrypted pre-master secret has the same structure as it does for RSA
except for Kerberos, the encryption key is the session key instead of
the RSA public key.
XXX authenticator currently ignored
/**
 * This is Kerberos option in the client key exchange message
 * (CLIENT -> SERVER). It holds the Kerberos ticket and the encrypted
 * premaster secret encrypted with the session key sealed in the ticket.
 * From RFC 2712:
 *  struct
 *  {
 *    opaque Ticket;
 *    opaque authenticator;            // optional
 *    opaque EncryptedPreMasterSecret; // encrypted with the session key
 *                                     // which is sealed in the ticket
 *  } KerberosWrapper;
 *
 *
 * Ticket and authenticator are encrypted as per RFC 1510 (in ASN.1)
 * Encrypted pre-master secret has the same structure as it does for RSA
 * except for Kerberos, the encryption key is the session key instead of
 * the RSA public key.
 *
 * XXX authenticator currently ignored
 *
 */
final class KerberosClientKeyExchange extends HandshakeMessage {

    private KerberosPreMasterSecret preMaster;
    private byte[] encodedTicket;
    private KerberosPrincipal peerPrincipal;
    private KerberosPrincipal localPrincipal;

    
Creates an instance of KerberosClientKeyExchange consisting of the
Kerberos service ticket, authenticator and encrypted premaster secret.
Called by client handshaker.
Params:
serverName – name of server with which to do handshake;
            this is used to get the Kerberos service ticket
protocolVersion – Maximum version supported by client (i.e,
         version it requested in client hello)
rand – random number generator to use for generating pre-master
         secret/**
     * Creates an instance of KerberosClientKeyExchange consisting of the
     * Kerberos service ticket, authenticator and encrypted premaster secret.
     * Called by client handshaker.
     *
     * @param serverName name of server with which to do handshake;
     *             this is used to get the Kerberos service ticket
     * @param protocolVersion Maximum version supported by client (i.e,
     *          version it requested in client hello)
     * @param rand random number generator to use for generating pre-master
     *          secret
     */
    KerberosClientKeyExchange(String serverName, boolean isLoopback,
        AccessControlContext acc, ProtocolVersion protocolVersion,
        SecureRandom rand) throws IOException {

         // Get service ticket
         KerberosTicket ticket = getServiceTicket(serverName, isLoopback, acc);
         encodedTicket = ticket.getEncoded();

         // Record the Kerberos principals
         peerPrincipal = ticket.getServer();
         localPrincipal = ticket.getClient();

         // Optional authenticator, encrypted using session key,
         // currently ignored

         // Generate premaster secret and encrypt it using session key
         EncryptionKey sessionKey = new EncryptionKey(
                                        ticket.getSessionKeyType(),
                                        ticket.getSessionKey().getEncoded());

         preMaster = new KerberosPreMasterSecret(protocolVersion,
             rand, sessionKey);
    }

    
Creates an instance of KerberosClientKeyExchange from its ASN.1 encoding.
Used by ServerHandshaker to verify and obtain premaster secret.
Params:
protocolVersion – current protocol version
clientVersion – version requested by client in its ClientHello;
         used by premaster secret version check
rand – random number generator used for generating random
         premaster secret if ticket and/or premaster verification fails
input – inputstream from which to get ASN.1-encoded KerberosWrapper
serverKey – server's master secret key/**
     * Creates an instance of KerberosClientKeyExchange from its ASN.1 encoding.
     * Used by ServerHandshaker to verify and obtain premaster secret.
     *
     * @param protocolVersion current protocol version
     * @param clientVersion version requested by client in its ClientHello;
     *          used by premaster secret version check
     * @param rand random number generator used for generating random
     *          premaster secret if ticket and/or premaster verification fails
     * @param input inputstream from which to get ASN.1-encoded KerberosWrapper
     * @param serverKey server's master secret key
     */
    KerberosClientKeyExchange(ProtocolVersion protocolVersion,
        ProtocolVersion clientVersion,
        SecureRandom rand, HandshakeInStream input, KerberosKey[] serverKeys)
        throws IOException {

        // Read ticket
        encodedTicket = input.getBytes16();

        if (debug != null && Debug.isOn("verbose")) {
            Debug.println(System.out,
                "encoded Kerberos service ticket", encodedTicket);
        }

        EncryptionKey sessionKey = null;

        try {
            Ticket t = new Ticket(encodedTicket);

            EncryptedData encPart = t.encPart;
            PrincipalName ticketSname = t.sname;
            Realm ticketRealm = t.sname.getRealm();

            String serverPrincipal = serverKeys[0].getPrincipal().getName();

            /*
             * permission to access and use the secret key of the Kerberized
             * "host" service is done in ServerHandshaker.getKerberosKeys()
             * to ensure server has the permission to use the secret key
             * before promising the client
             */

            // Check that ticket Sname matches serverPrincipal
            String ticketPrinc = ticketSname.toString();
            if (!ticketPrinc.equals(serverPrincipal)) {
                if (debug != null && Debug.isOn("handshake"))
                   System.out.println("Service principal in Ticket does not"
                        + " match associated principal in KerberosKey");
                throw new IOException("Server principal is " +
                    serverPrincipal + " but ticket is for " +
                    ticketPrinc);
            }

            // See if we have the right key to decrypt the ticket to get
            // the session key.
            int encPartKeyType = encPart.getEType();
            KerberosKey dkey = findKey(encPartKeyType, serverKeys);
            if (dkey == null) {
                // %%% Should print string repr of etype
                throw new IOException(
        "Cannot find key of appropriate type to decrypt ticket - need etype " +
                                   encPartKeyType);
            }

            EncryptionKey secretKey = new EncryptionKey(
                encPartKeyType,
                dkey.getEncoded());

            // Decrypt encPart using server's secret key
            byte[] bytes = encPart.decrypt(secretKey, KeyUsage.KU_TICKET);

            // Reset data stream after decryption, remove redundant bytes
            byte[] temp = encPart.reset(bytes);
            EncTicketPart encTicketPart = new EncTicketPart(temp);

            // Record the Kerberos Principals
            peerPrincipal =
                new KerberosPrincipal(encTicketPart.cname.getName());
            localPrincipal = new KerberosPrincipal(ticketSname.getName());

            sessionKey = encTicketPart.key;

            if (debug != null && Debug.isOn("handshake")) {
                System.out.println("server principal: " + serverPrincipal);
                System.out.println("cname: " + encTicketPart.cname.toString());
            }
        } catch (IOException e) {
            throw e;
        } catch (Exception e) {
            if (debug != null && Debug.isOn("handshake")) {
                System.out.println("KerberosWrapper error getting session key,"
                        + " generating random secret (" + e.getMessage() + ")");
            }
            sessionKey = null;
        }

        input.getBytes16();   // XXX Read and ignore authenticator

        if (sessionKey != null) {
            preMaster = new KerberosPreMasterSecret(protocolVersion,
                clientVersion, rand, input, sessionKey);
        } else {
            // Generate bogus premaster secret
            preMaster = new KerberosPreMasterSecret(clientVersion, rand);
        }
    }

    int messageType() {
        return ht_client_key_exchange;
    }

    int messageLength() {
        return (6 + encodedTicket.length + preMaster.getEncrypted().length);
    }

    void send(HandshakeOutStream s) throws IOException {
        s.putBytes16(encodedTicket);
        s.putBytes16(null); // XXX no authenticator
        s.putBytes16(preMaster.getEncrypted());
    }

    void print(PrintStream s) throws IOException {
        s.println("*** ClientKeyExchange, Kerberos");

        if (debug != null && Debug.isOn("verbose")) {
            Debug.println(s, "Kerberos service ticket", encodedTicket);
            Debug.println(s, "Random Secret", preMaster.getUnencrypted());
            Debug.println(s, "Encrypted random Secret",
                preMaster.getEncrypted());
        }
    }

    // Similar to sun.security.jgss.krb5.Krb5InitCredenetial/Krb5Context
    private static KerberosTicket getServiceTicket(String srvName,
        boolean isLoopback, final AccessControlContext acc) throws IOException {

        // get the local hostname if srvName is loopback address
        String serverName = srvName;
        if (isLoopback) {
            String localHost = java.security.AccessController.doPrivileged(
                new java.security.PrivilegedAction<String>() {
                public String run() {
                    String hostname;
                    try {
                        hostname = InetAddress.getLocalHost().getHostName();
                    } catch (java.net.UnknownHostException e) {
                        hostname = "localhost";
                    }
                    return hostname;
                }
            });
          serverName = localHost;
        }

        // Resolve serverName (possibly in IP addr form) to Kerberos principal
        // name for service with hostname
        String serviceName = "host/" + serverName;
        PrincipalName principal;
        try {
            principal = new PrincipalName(serviceName,
                                PrincipalName.KRB_NT_SRV_HST);
        } catch (SecurityException se) {
            throw se;
        } catch (Exception e) {
            IOException ioe = new IOException("Invalid service principal" +
                                " name: " + serviceName);
            ioe.initCause(e);
            throw ioe;
        }
        String realm = principal.getRealmAsString();

        final String serverPrincipal = principal.toString();
        final String tgsPrincipal = "krbtgt/" + realm + "@" + realm;
        final String clientPrincipal = null;  // use default


        // check permission to obtain a service ticket to initiate a
        // context with the "host" service
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
           sm.checkPermission(new ServicePermission(serverPrincipal,
                                "initiate"), acc);
        }

        try {
            KerberosTicket ticket = AccessController.doPrivileged(
                new PrivilegedExceptionAction<KerberosTicket>() {
                public KerberosTicket run() throws Exception {
                    return Krb5Util.getTicketFromSubjectAndTgs(
                        GSSCaller.CALLER_SSL_CLIENT,
                        clientPrincipal, serverPrincipal,
                        tgsPrincipal, acc);
                        }});

            if (ticket == null) {
                throw new IOException("Failed to find any kerberos service" +
                        " ticket for " + serverPrincipal);
            }
            return ticket;
        } catch (PrivilegedActionException e) {
            IOException ioe = new IOException(
                "Attempt to obtain kerberos service ticket for " +
                        serverPrincipal + " failed!");
            ioe.initCause(e);
            throw ioe;
        }
    }

    KerberosPreMasterSecret getPreMasterSecret() {
        return preMaster;
    }

    KerberosPrincipal getPeerPrincipal() {
        return peerPrincipal;
    }

    KerberosPrincipal getLocalPrincipal() {
        return localPrincipal;
    }

    private static KerberosKey findKey(int etype, KerberosKey[] keys) {
        int ktype;
        for (int i = 0; i < keys.length; i++) {
            ktype = keys[i].getKeyType();
            if (etype == ktype) {
                return keys[i];
            }
        }
        // Key not found.
        // %%% kludge to allow DES keys to be used for diff etypes
        if ((etype == EncryptedData.ETYPE_DES_CBC_CRC ||
            etype == EncryptedData.ETYPE_DES_CBC_MD5)) {
            for (int i = 0; i < keys.length; i++) {
                ktype = keys[i].getKeyType();
                if (ktype == EncryptedData.ETYPE_DES_CBC_CRC ||
                    ktype == EncryptedData.ETYPE_DES_CBC_MD5) {
                    return new KerberosKey(keys[i].getPrincipal(),
                        keys[i].getEncoded(),
                        etype,
                        keys[i].getVersionNumber());
                }
            }
        }
        return null;
    }
}