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 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

 * 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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

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package sun.security.krb5.internal.ssl;

import sun.security.ssl.ClientKeyExchange;

import sun.security.ssl.Debug;

import sun.security.ssl.ClientKeyExchangeService;

import sun.security.ssl.HandshakeOutStream;

import sun.security.jgss.GSSCaller;

import sun.security.jgss.krb5.Krb5Util;

import sun.security.jgss.krb5.ServiceCreds;

import sun.security.krb5.EncryptedData;

import sun.security.krb5.EncryptionKey;

import sun.security.krb5.KrbException;

import sun.security.krb5.PrincipalName;

import sun.security.krb5.internal.EncTicketPart;

import sun.security.krb5.internal.Ticket;

import sun.security.krb5.internal.crypto.KeyUsage;

import sun.security.ssl.ProtocolVersion;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

import javax.security.auth.Subject;

import javax.security.auth.kerberos.KerberosKey;

import javax.security.auth.kerberos.KerberosPrincipal;

import javax.security.auth.kerberos.KerberosTicket;

import javax.security.auth.kerberos.KeyTab;

import javax.security.auth.kerberos.ServicePermission;

import java.io.IOException;

import java.io.PrintStream;

import java.net.InetAddress;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.Principal;

import java.security.PrivilegedAction;

import java.security.PrivilegedActionException;

import java.security.PrivilegedExceptionAction;

import java.security.SecureRandom;

import java.util.Set;

/**

 * The provider for TLS_KRB_ cipher suites.

 *

 * @since 1.9

 */

public class Krb5KeyExchangeService implements ClientKeyExchangeService {

    public static final Debug debug = Debug.getInstance("ssl");

    @Override

    public String[] supported() {

        return new String[] { "KRB5", "KRB5_EXPORT" };

    }

    @Override

    public Object getServiceCreds(AccessControlContext acc) {

        try {

            ServiceCreds serviceCreds = AccessController.doPrivileged(

                    (PrivilegedExceptionAction<ServiceCreds>)

                            () -> Krb5Util.getServiceCreds(

                                    GSSCaller.CALLER_SSL_SERVER, null, acc));

            if (debug != null && Debug.isOn("handshake")) {

                System.out.println("Using Kerberos creds");

            }

            String serverPrincipal = serviceCreds.getName();

            if (serverPrincipal != null) {

                // When service is bound, we check ASAP. Otherwise,

                // will check after client request is received

                // in in Kerberos ClientKeyExchange

                SecurityManager sm = System.getSecurityManager();

                try {

                    if (sm != null) {

                        // Eliminate dependency on ServicePermission

                        sm.checkPermission(new ServicePermission(

                                serverPrincipal, "accept"), acc);

                    }

                } catch (SecurityException se) {

                    if (debug != null && Debug.isOn("handshake")) {

                        System.out.println("Permission to access Kerberos"

                                + " secret key denied");

                    }

                    return null;

                }

            }

            return serviceCreds;

        } catch (PrivilegedActionException e) {

            // Likely exception here is LoginException

            if (debug != null && Debug.isOn("handshake")) {

                System.out.println("Attempt to obtain Kerberos key failed: "

                        + e.toString());

            }

            return null;

        }

    }

    @Override

    public String getServiceHostName(Principal principal) {

        if (principal == null) {

            return null;

        }

        String hostName = null;

        try {

            PrincipalName princName =

                    new PrincipalName(principal.getName(),

                            PrincipalName.KRB_NT_SRV_HST);

            String[] nameParts = princName.getNameStrings();

            if (nameParts.length >= 2) {

                hostName = nameParts[1];

            }

        } catch (Exception e) {

            // ignore

        }

        return hostName;

    }

    @Override

    public boolean isRelated(boolean isClient,

            AccessControlContext acc, Principal p) {

        if (p == null) return false;

        try {

            Subject subject = AccessController.doPrivileged(

                    (PrivilegedExceptionAction<Subject>)

                            () -> Krb5Util.getSubject(

                                    isClient ? GSSCaller.CALLER_SSL_CLIENT

                                            : GSSCaller.CALLER_SSL_SERVER,

                                    acc));

            if (subject == null) {

                if (debug != null && Debug.isOn("session")) {

                    System.out.println("Kerberos credentials are" +

                            " not present in the current Subject;" +

                            " check if " +

                            " javax.security.auth.useSubjectAsCreds" +

                            " system property has been set to false");

                }

                return false;

            }

            Set<Principal> principals =

                    subject.getPrincipals(Principal.class);

            if (principals.contains(p)) {

                // bound to this principal

                return true;

            } else {

                if (isClient) {

                    return false;

                } else {

                    for (KeyTab pc : subject.getPrivateCredentials(KeyTab.class)) {

                        if (!pc.isBound()) {

                            return true;

                        }

                    }

                    return false;

                }

            }

        } catch (PrivilegedActionException pae) {

            if (debug != null && Debug.isOn("session")) {

                System.out.println("Attempt to obtain" +

                        " subject failed! " + pae);

            }

            return false;

        }

    }

    public ClientKeyExchange createClientExchange(

            String serverName, AccessControlContext acc,

            ProtocolVersion protocolVerson, SecureRandom rand) throws IOException {

        return new ExchangerImpl(serverName, acc, protocolVerson, rand);

    }

    public ClientKeyExchange createServerExchange(

            ProtocolVersion protocolVersion, ProtocolVersion clientVersion,

            SecureRandom rand, byte[] encodedTicket, byte[] encrypted,

            AccessControlContext acc, Object serviceCreds) throws IOException {

        return new ExchangerImpl(protocolVersion, clientVersion, rand,

                encodedTicket, encrypted, acc, serviceCreds);

    }

    static class ExchangerImpl extends ClientKeyExchange {

        final private KerberosPreMasterSecret preMaster;

        final private byte[] encodedTicket;

        final private KerberosPrincipal peerPrincipal;

        final private KerberosPrincipal localPrincipal;

        @Override

        public int messageLength() {

            return encodedTicket.length + preMaster.getEncrypted().length + 6;

        }

        @Override

        public void send(HandshakeOutStream s) throws IOException {

            s.putBytes16(encodedTicket);

            s.putBytes16(null);

            s.putBytes16(preMaster.getEncrypted());

        }

        @Override

        public 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());

            }

        }

        ExchangerImpl(String serverName, AccessControlContext acc,

                ProtocolVersion protocolVersion, SecureRandom rand) throws IOException {

            // Get service ticket

            KerberosTicket ticket = getServiceTicket(serverName, 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);

        }

        ExchangerImpl(

                ProtocolVersion protocolVersion, ProtocolVersion clientVersion, SecureRandom rand,

                byte[] encodedTicket, byte[] encrypted,

                AccessControlContext acc, Object serviceCreds) throws IOException {

            // Read ticket

            this.encodedTicket = encodedTicket;

            if (debug != null && Debug.isOn("verbose")) {

                Debug.println(System.out,

                        "encoded Kerberos service ticket", encodedTicket);

            }

            EncryptionKey sessionKey = null;

            KerberosPrincipal tmpPeer = null;

            KerberosPrincipal tmpLocal = null;

            try {

                Ticket t = new Ticket(encodedTicket);

                EncryptedData encPart = t.encPart;

                PrincipalName ticketSname = t.sname;

                final ServiceCreds creds = (ServiceCreds)serviceCreds;

                final KerberosPrincipal princ =

                        new KerberosPrincipal(ticketSname.toString());

                // For bound service, permission already checked at setup

                if (creds.getName() == null) {

                    SecurityManager sm = System.getSecurityManager();

                    try {

                        if (sm != null) {

                            // Eliminate dependency on ServicePermission

                            sm.checkPermission(new ServicePermission(

                                    ticketSname.toString(), "accept"), acc);

                        }

                    } catch (SecurityException se) {

                        serviceCreds = null;

                        // Do not destroy keys. Will affect Subject

                        if (debug != null && Debug.isOn("handshake")) {

                            System.out.println("Permission to access Kerberos"

                                    + " secret key denied");

                            se.printStackTrace(System.out);

                        }

                        throw new IOException("Kerberos service not allowedy");

                    }

                }

                KerberosKey[] serverKeys = AccessController.doPrivileged(

                        new PrivilegedAction<KerberosKey[]>() {

                            @Override

                            public KerberosKey[] run() {

                                return creds.getKKeys(princ);

                            }

                        });

                if (serverKeys.length == 0) {

                    throw new IOException("Found no key for " + princ +

                            (creds.getName() == null ? "" :

                                    (", this keytab is for " + creds.getName() + " only")));

                }

                /*

                 * 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

                 */

                // See if we have the right key to decrypt the ticket to get

                // the session key.

                int encPartKeyType = encPart.getEType();

                Integer encPartKeyVersion = encPart.getKeyVersionNumber();

                KerberosKey dkey = null;

                try {

                    dkey = findKey(encPartKeyType, encPartKeyVersion, serverKeys);

                } catch (KrbException ke) { // a kvno mismatch

                    throw new IOException(

                            "Cannot find key matching version number", ke);

                }

                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

                tmpPeer = new KerberosPrincipal(encTicketPart.cname.getName());

                tmpLocal = new KerberosPrincipal(ticketSname.getName());

                sessionKey = encTicketPart.key;

                if (debug != null && Debug.isOn("handshake")) {

                    System.out.println("server principal: " + ticketSname);

                    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, encrypted, sessionKey);

            } else {

                // Generate bogus premaster secret

                preMaster = new KerberosPreMasterSecret(clientVersion, rand);

            }

            peerPrincipal = tmpPeer;

            localPrincipal = tmpLocal;

        }

        // Similar to sun.security.jgss.krb5.Krb5InitCredenetial/Krb5Context

        private static KerberosTicket getServiceTicket(String serverName,

                final AccessControlContext acc) throws IOException {

            if ("localhost".equals(serverName) ||

                    "localhost.localdomain".equals(serverName)) {

                if (debug != null && Debug.isOn("handshake")) {

                    System.out.println("Get the local hostname");

                }

                String localHost = java.security.AccessController.doPrivileged(

                        new java.security.PrivilegedAction<String>() {

                            public String run() {

                                try {

                                    return InetAddress.getLocalHost().getHostName();

                                } catch (java.net.UnknownHostException e) {

                                    if (debug != null && Debug.isOn("handshake")) {

                                        System.out.println("Warning,"

                                                + " cannot get the local hostname: "

                                                + e.getMessage());

                                    }

                                    return null;

                                }

                            }

                        });

                if (localHost != null) {

                    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;

            }

        }

        @Override

        public SecretKey clientKeyExchange() {

            byte[] secretBytes = preMaster.getUnencrypted();

            return new SecretKeySpec(secretBytes, "TlsPremasterSecret");

        }

        @Override

        public Principal getPeerPrincipal() {

            return peerPrincipal;

        }

        @Override

        public Principal getLocalPrincipal() {

            return localPrincipal;

        }

        /**

         * Determines if a kvno matches another kvno. Used in the method

         * findKey(etype, version, keys). Always returns true if either input

         * is null or zero, in case any side does not have kvno info available.

         *

         * Note: zero is included because N/A is not a legal value for kvno

         * in javax.security.auth.kerberos.KerberosKey. Therefore, the info

         * that the kvno is N/A might be lost when converting between

         * EncryptionKey and KerberosKey.

         */

        private static boolean versionMatches(Integer v1, int v2) {

            if (v1 == null || v1 == 0 || v2 == 0) {

                return true;

            }

            return v1.equals(v2);

        }

        private static KerberosKey findKey(int etype, Integer version,

                KerberosKey[] keys) throws KrbException {

            int ktype;

            boolean etypeFound = false;

            // When no matched kvno is found, returns tke key of the same

            // etype with the highest kvno

            int kvno_found = 0;

            KerberosKey key_found = null;

            for (int i = 0; i < keys.length; i++) {

                ktype = keys[i].getKeyType();

                if (etype == ktype) {

                    int kv = keys[i].getVersionNumber();

                    etypeFound = true;

                    if (versionMatches(version, kv)) {

                        return keys[i];

                    } else if (kv > kvno_found) {

                        key_found = keys[i];

                        kvno_found = kv;

                    }

                }

            }

            // 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)) {