/*

 * Copyright (c) 1996, 2019, 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

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

 * questions.

 */

package sun.rmi.server;

import java.io.IOException;

import java.io.ObjectInput;

import java.io.ObjectInputFilter;

import java.io.ObjectInputStream;

import java.io.ObjectOutput;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.rmi.AccessException;

import java.rmi.MarshalException;

import java.rmi.Remote;

import java.rmi.RemoteException;

import java.rmi.ServerError;

import java.rmi.ServerException;

import java.rmi.UnmarshalException;

import java.rmi.server.ExportException;

import java.rmi.server.Operation;

import java.rmi.server.RemoteCall;

import java.rmi.server.RemoteRef;

import java.rmi.server.RemoteStub;

import java.rmi.server.ServerNotActiveException;

import java.rmi.server.ServerRef;

import java.rmi.server.Skeleton;

import java.rmi.server.SkeletonNotFoundException;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Collections;

import java.util.Date;

import java.util.HashMap;

import java.util.Map;

import java.util.WeakHashMap;

import java.util.concurrent.atomic.AtomicInteger;

import sun.rmi.runtime.Log;

import sun.rmi.transport.LiveRef;

import sun.rmi.transport.StreamRemoteCall;

import sun.rmi.transport.Target;

import sun.rmi.transport.tcp.TCPTransport;

/**

 * UnicastServerRef implements the remote reference layer server-side

 * behavior for remote objects exported with the "UnicastRef" reference

 * type.

 * If an {@link ObjectInputFilter ObjectInputFilter} is supplied it is

 * invoked during deserialization to filter the arguments,

 * otherwise the default filter of {@link ObjectInputStream ObjectInputStream}

 * applies.

 *

 * @author  Ann Wollrath

 * @author  Roger Riggs

 * @author  Peter Jones

 */

@SuppressWarnings("deprecation")

public class UnicastServerRef extends UnicastRef

    implements ServerRef, Dispatcher

{

    /** value of server call log property */

    public static final boolean logCalls = AccessController.doPrivileged(

        (PrivilegedAction<Boolean>) () -> Boolean.getBoolean("java.rmi.server.logCalls"));

    /** server call log */

    public static final Log callLog =

        Log.getLog("sun.rmi.server.call", "RMI", logCalls);

    // use serialVersionUID from JDK 1.2.2 for interoperability

    private static final long serialVersionUID = -7384275867073752268L;

    /** flag to enable writing exceptions to System.err */

    private static final boolean wantExceptionLog =

        AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->

            Boolean.getBoolean("sun.rmi.server.exceptionTrace"));

    private boolean forceStubUse = false;

    /**

     * flag to remove server-side stack traces before marshalling

     * exceptions thrown by remote invocations to this VM

     */

    private static final boolean suppressStackTraces =

        AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->

            Boolean.getBoolean("sun.rmi.server.suppressStackTraces"));

    /**

     * skeleton to dispatch remote calls through, for 1.1 stub protocol

     * (may be null if stub class only uses 1.2 stub protocol)

     */

    private transient Skeleton skel;

    // The ObjectInputFilter for checking the invocation arguments

    private final transient ObjectInputFilter filter;

    /** maps method hash to Method object for each remote method */

    private transient Map<Long,Method> hashToMethod_Map = null;

    /**

     * A weak hash map, mapping classes to hash maps that map method

     * hashes to method objects.

     **/

    private static final WeakClassHashMap<Map<Long,Method>> hashToMethod_Maps =

        new HashToMethod_Maps();

    /** cache of impl classes that have no corresponding skeleton class */

    private static final Map<Class<?>,?> withoutSkeletons =

        Collections.synchronizedMap(new WeakHashMap<Class<?>,Void>());

    private final AtomicInteger methodCallIDCount = new AtomicInteger(0);

    /**

     * Create a new (empty) Unicast server remote reference.

     * The filter is null to defer to the  default ObjectInputStream filter, if any.

     */

    public UnicastServerRef() {

        this.filter = null;

    }

    /**

     * Construct a Unicast server remote reference for a specified

     * liveRef.

     * The filter is null to defer to the  default ObjectInputStream filter, if any.

     */

    public UnicastServerRef(LiveRef ref) {

        super(ref);

        this.filter = null;

    }

    /**

     * Construct a Unicast server remote reference for a specified

     * liveRef and filter.

     */

    public UnicastServerRef(LiveRef ref, ObjectInputFilter filter) {

        super(ref);

        this.filter = filter;

    }

    /**

     * Construct a Unicast server remote reference to be exported

     * on the specified port.

     */

    public UnicastServerRef(int port) {

        super(new LiveRef(port));

        this.filter = null;

    }

    /**

     * Constructs a UnicastServerRef to be exported on an

     * anonymous port (i.e., 0) and that uses a pregenerated stub class

     * (NOT a dynamic proxy instance) if 'forceStubUse' is 'true'.

     *

     * This constructor is only called by the method

     * UnicastRemoteObject.exportObject(Remote) passing 'true' for

     * 'forceStubUse'.  The UnicastRemoteObject.exportObject(Remote) method

     * returns RemoteStub, so it must ensure that the stub for the

     * exported object is an instance of a pregenerated stub class that

     * extends RemoteStub (instead of an instance of a dynamic proxy class

     * which is not an instance of RemoteStub).

     **/

    public UnicastServerRef(boolean forceStubUse) {

        this(0);

        this.forceStubUse = forceStubUse;

    }

    /**

     * With the addition of support for dynamic proxies as stubs, this

     * method is obsolete because it returns RemoteStub instead of the more

     * general Remote.  It should not be called.  It sets the

     * 'forceStubUse' flag to true so that the stub for the exported object

     * is forced to be an instance of the pregenerated stub class, which

     * extends RemoteStub.

     *

     * Export this object, create the skeleton and stubs for this

     * dispatcher.  Create a stub based on the type of the impl,

     * initialize it with the appropriate remote reference. Create the

     * target defined by the impl, dispatcher (this) and stub.

     * Export that target via the Ref.

     **/

    public RemoteStub exportObject(Remote impl, Object data)

        throws RemoteException

    {

        forceStubUse = true;

        return (RemoteStub) exportObject(impl, data, false);

    }

    /**

     * Export this object, create the skeleton and stubs for this

     * dispatcher.  Create a stub based on the type of the impl,

     * initialize it with the appropriate remote reference. Create the

     * target defined by the impl, dispatcher (this) and stub.

     * Export that target via the Ref.

     */

    public Remote exportObject(Remote impl, Object data,

                               boolean permanent)

        throws RemoteException

    {

        Class<?> implClass = impl.getClass();

        Remote stub;

        try {

            stub = Util.createProxy(implClass, getClientRef(), forceStubUse);

        } catch (IllegalArgumentException e) {

            throw new ExportException(

                "remote object implements illegal remote interface", e);

        }

        if (stub instanceof RemoteStub) {

            setSkeleton(impl);

        }

        Target target =

            new Target(impl, this, stub, ref.getObjID(), permanent);

        ref.exportObject(target);

        hashToMethod_Map = hashToMethod_Maps.get(implClass);

        return stub;

    }

    /**

     * Return the hostname of the current client.  When called from a

     * thread actively handling a remote method invocation the

     * hostname of the client is returned.

     * @exception ServerNotActiveException If called outside of servicing

     * a remote method invocation.

     */

    public String getClientHost() throws ServerNotActiveException {

        return TCPTransport.getClientHost();

    }

    /**

     * Discovers and sets the appropriate skeleton for the impl.

     */

    public void setSkeleton(Remote impl) throws RemoteException {

        if (!withoutSkeletons.containsKey(impl.getClass())) {

            try {

                skel = Util.createSkeleton(impl);

            } catch (SkeletonNotFoundException e) {

                /*

                 * Ignore exception for skeleton class not found, because a

                 * skeleton class is not necessary with the 1.2 stub protocol.

                 * Remember that this impl's class does not have a skeleton

                 * class so we don't waste time searching for it again.

                 */

                withoutSkeletons.put(impl.getClass(), null);

            }

        }

    }

    /**

     * Call to dispatch to the remote object (on the server side).

     * The up-call to the server and the marshalling of return result

     * (or exception) should be handled before returning from this

     * method.

     * @param obj the target remote object for the call

     * @param call the "remote call" from which operation and

     * method arguments can be obtained.

     * @exception IOException If unable to marshal return result or

     * release input or output streams

     */

    public void dispatch(Remote obj, RemoteCall call) throws IOException {

        // positive operation number in 1.1 stubs;

        // negative version number in 1.2 stubs and beyond...

        int num;

        long op;

        try {

            // read remote call header

            ObjectInput in;

            try {

                in = call.getInputStream();

                num = in.readInt();

            } catch (Exception readEx) {

                throw new UnmarshalException("error unmarshalling call header",

                                             readEx);

            }

            if (skel != null) {

                // If there is a skeleton, use it

                    oldDispatch(obj, call, num);

                    return;

            } else if (num >= 0){

                throw new UnmarshalException(

                        "skeleton class not found but required for client version");

            }

            try {

                op = in.readLong();

            } catch (Exception readEx) {

                throw new UnmarshalException("error unmarshalling call header",

                        readEx);

            }

            /*

             * Since only system classes (with null class loaders) will be on

             * the execution stack during parameter unmarshalling for the 1.2

             * stub protocol, tell the MarshalInputStream not to bother trying

             * to resolve classes using its superclasses's default method of

             * consulting the first non-null class loader on the stack.

             */

            MarshalInputStream marshalStream = (MarshalInputStream) in;

            marshalStream.skipDefaultResolveClass();

            Method method = hashToMethod_Map.get(op);

            if (method == null) {

                throw new UnmarshalException("unrecognized method hash: " +

                    "method not supported by remote object");

            }

            // if calls are being logged, write out object id and operation

            logCall(obj, method);

            // unmarshal parameters

            Class<?>[] types = method.getParameterTypes();

            Object[] params = new Object[types.length];

            try {

                unmarshalCustomCallData(in);

                // Unmarshal the parameters

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

                    params[i] = unmarshalValue(types[i], in);

                }

            } catch (AccessException aex) {

                // For compatibility, AccessException is not wrapped in UnmarshalException

                // disable saving any refs in the inputStream for GC

                ((StreamRemoteCall) call).discardPendingRefs();

                throw aex;

            } catch (java.io.IOException | ClassNotFoundException e) {

                // disable saving any refs in the inputStream for GC

                ((StreamRemoteCall) call).discardPendingRefs();

                throw new UnmarshalException(

                    "error unmarshalling arguments", e);

            } finally {

                call.releaseInputStream();

            }

            // make upcall on remote object

            Object result;

            try {

                result = method.invoke(obj, params);

            } catch (InvocationTargetException e) {

                throw e.getTargetException();

            }

            // marshal return value

            try {

                ObjectOutput out = call.getResultStream(true);

                Class<?> rtype = method.getReturnType();

                if (rtype != void.class) {

                    marshalValue(rtype, result, out);

                }

            } catch (IOException ex) {

                throw new MarshalException("error marshalling return", ex);

                /*

                 * This throw is problematic because when it is caught below,

                 * we attempt to marshal it back to the client, but at this

                 * point, a "normal return" has already been indicated,

                 * so marshalling an exception will corrupt the stream.

                 * This was the case with skeletons as well; there is no

                 * immediately obvious solution without a protocol change.

                 */

            }

        } catch (Throwable e) {

            Throwable origEx = e;

            logCallException(e);

            ObjectOutput out = call.getResultStream(false);

            if (e instanceof Error) {

                e = new ServerError(

                    "Error occurred in server thread", (Error) e);

            } else if (e instanceof RemoteException) {

                e = new ServerException(

                    "RemoteException occurred in server thread",

                    (Exception) e);

            }

            if (suppressStackTraces) {

                clearStackTraces(e);

            }

            out.writeObject(e);

            // AccessExceptions should cause Transport.serviceCall

            // to flag the connection as unusable.

            if (origEx instanceof AccessException) {

                throw new IOException("Connection is not reusable", origEx);

            }

        } finally {

            call.releaseInputStream(); // in case skeleton doesn't

            call.releaseOutputStream();

        }

    }

    /**

     * Sets a filter for invocation arguments, if a filter has been set.

     * Called by dispatch before the arguments are read.

     */

    protected void unmarshalCustomCallData(ObjectInput in)

            throws IOException, ClassNotFoundException {

        if (filter != null &&

                in instanceof ObjectInputStream) {

            // Set the filter on the stream

            ObjectInputStream ois = (ObjectInputStream) in;

            AccessController.doPrivileged((PrivilegedAction<Void>)() -> {

                ois.setObjectInputFilter(filter);

                return null;

            });

        }

    }

    /**

     * Handle server-side dispatch using the RMI 1.1 stub/skeleton

     * protocol, given a non-negative operation number or negative method hash

     * that has already been read from the call stream.

     * Exceptions are handled by the caller to be sent to the remote client.

     *

     * @param obj the target remote object for the call

     * @param call the "remote call" from which operation and

     * method arguments can be obtained.

     * @param op the operation number

     * @throws Exception if unable to marshal return result or

     * release input or output streams

     */

    private void oldDispatch(Remote obj, RemoteCall call, int op)

        throws Exception

    {

        long hash;              // hash for matching stub with skeleton

        // read remote call header

        ObjectInput in;

        in = call.getInputStream();

        try {

            Class<?> clazz = Class.forName("sun.rmi.transport.DGCImpl_Skel");

            if (clazz.isAssignableFrom(skel.getClass())) {

                ((MarshalInputStream)in).useCodebaseOnly();

            }

        } catch (ClassNotFoundException ignore) { }

        try {

            hash = in.readLong();

        } catch (Exception ioe) {

            throw new UnmarshalException("error unmarshalling call header", ioe);

        }

        // if calls are being logged, write out object id and operation

        Operation[] operations = skel.getOperations();

        logCall(obj, op >= 0 && op < operations.length ?  operations[op] : "op: " + op);

        unmarshalCustomCallData(in);

        // dispatch to skeleton for remote object

        skel.dispatch(obj, call, op, hash);

    }

    /**

     * Clear the stack trace of the given Throwable by replacing it with

     * an empty StackTraceElement array, and do the same for all of its

     * chained causative exceptions.

     */

    public static void clearStackTraces(Throwable t) {

        StackTraceElement[] empty = new StackTraceElement[0];

        while (t != null) {

            t.setStackTrace(empty);

            t = t.getCause();

        }

    }

    /**

     * Log the details of an incoming call.  The method parameter is either of

     * type java.lang.reflect.Method or java.rmi.server.Operation.

     */

    private void logCall(Remote obj, Object method) {

        if (callLog.isLoggable(Log.VERBOSE)) {

            String clientHost;

            try {

                clientHost = getClientHost();

            } catch (ServerNotActiveException snae) {

                clientHost = "(local)"; // shouldn't happen

            }

            callLog.log(Log.VERBOSE, "[" + clientHost + ": " +

                              obj.getClass().getName() +

                              ref.getObjID().toString() + ": " +

                              method + "]");

        }

    }

    /**

     * Log the exception detail of an incoming call.

     */

    private void logCallException(Throwable e) {

        // if calls are being logged, log them

        if (callLog.isLoggable(Log.BRIEF)) {

            String clientHost = "";

            try {

                clientHost = "[" + getClientHost() + "] ";

            } catch (ServerNotActiveException snae) {

            }

            callLog.log(Log.BRIEF, clientHost + "exception: ", e);

        }