1 /*
  2  * Copyright (c) 1996, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.  Oracle designates this
  8  * particular file as subject to the "Classpath" exception as provided
  9  * by Oracle in the LICENSE file that accompanied this code.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  */
 25 
 26 package sun.rmi.transport;
 27 
 28 import java.io.IOException;
 29 import java.io.ObjectOutput;
 30 import java.rmi.MarshalException;
 31 import java.rmi.NoSuchObjectException;
 32 import java.rmi.Remote;
 33 import java.rmi.RemoteException;
 34 import java.rmi.server.LogStream;
 35 import java.rmi.server.ObjID;
 36 import java.rmi.server.RemoteCall;
 37 import java.rmi.server.RemoteServer;
 38 import java.rmi.server.ServerNotActiveException;
 39 import java.security.AccessControlContext;
 40 import java.security.AccessController;
 41 import java.security.Permissions;
 42 import java.security.PrivilegedAction;
 43 import java.security.ProtectionDomain;
 44 import sun.rmi.runtime.Log;
 45 import sun.rmi.server.Dispatcher;
 46 import sun.rmi.server.UnicastServerRef;
 47 
 48 /**
 49  * Transport abstraction for enabling communication between different
 50  * VMs.
 51  *
 52  * @author Ann Wollrath
 53  */
 54 @SuppressWarnings({"removal","deprecation"})
 55 public abstract class Transport {
 56 
 57     /** "transport" package log level */
 58     static final int logLevel = LogStream.parseLevel(getLogLevel());
 59 
 60     private static String getLogLevel() {
 61         return java.security.AccessController.doPrivileged(
 62             (PrivilegedAction<String>) () -> System.getProperty("sun.rmi.transport.logLevel"));
 63     }
 64 
 65     /* transport package log */
 66     static final Log transportLog =
 67         Log.getLog("sun.rmi.transport.misc", "transport", Transport.logLevel);
 68 
 69     /** References the current transport when a call is being serviced */
 70     private static final ThreadLocal<Transport> currentTransport = new ThreadLocal<>();
 71 
 72     /** ObjID for DGCImpl */
 73     private static final ObjID dgcID = new ObjID(ObjID.DGC_ID);
 74 
 75     /** AccessControlContext for setting context ClassLoader */
 76     private static final AccessControlContext SETCCL_ACC;
 77     static {
 78         Permissions perms = new Permissions();
 79         perms.add(new RuntimePermission("setContextClassLoader"));
 80         ProtectionDomain[] pd = { new ProtectionDomain(null, perms) };
 81         SETCCL_ACC = new AccessControlContext(pd);
 82     }
 83 
 84     /**
 85      * Returns a <I>Channel</I> that generates connections to the
 86      * endpoint <I>ep</I>. A Channel is an object that creates and
 87      * manages connections of a particular type to some particular
 88      * address space.
 89      * @param ep the endpoint to which connections will be generated.
 90      * @return the channel or null if the transport cannot
 91      * generate connections to this endpoint
 92      */
 93     public abstract Channel getChannel(Endpoint ep);
 94 
 95     /**
 96      * Removes the <I>Channel</I> that generates connections to the
 97      * endpoint <I>ep</I>.
 98      */
 99     public abstract void free(Endpoint ep);
100 
101     /**
102      * Export the object so that it can accept incoming calls.
103      */
104     public void exportObject(Target target) throws RemoteException {
105         target.setExportedTransport(this);
106         ObjectTable.putTarget(target);
107     }
108 
109     /**
110      * Invoked when an object that was exported on this transport has
111      * become unexported, either by being garbage collected or by
112      * being explicitly unexported.
113      **/
114     protected void targetUnexported() { }
115 
116     /**
117      * Returns the current transport if a call is being serviced, otherwise
118      * returns null.
119      **/
120     static Transport currentTransport() {
121         return currentTransport.get();
122     }
123 
124     /**
125      * Verify that the current access control context has permission to accept
126      * the connection being dispatched by the current thread.  The current
127      * access control context is passed as a parameter to avoid the overhead of
128      * an additional call to AccessController.getContext.
129      */
130     protected abstract void checkAcceptPermission(AccessControlContext acc);
131 
132     /**
133      * Sets the context class loader for the current thread.
134      */
135     private static void setContextClassLoader(ClassLoader ccl) {
136         AccessController.doPrivileged((PrivilegedAction<Void>)() -> {
137                 Thread.currentThread().setContextClassLoader(ccl);
138                 return null;
139             }, SETCCL_ACC);
140     }
141 
142     /**
143      * Service an incoming remote call. When a message arrives on the
144      * connection indicating the beginning of a remote call, the
145      * threads are required to call the <I>serviceCall</I> method of
146      * their transport.  The default implementation of this method
147      * locates and calls the dispatcher object.  Ordinarily a
148      * transport implementation will not need to override this method.
149      * At the entry to <I>tr.serviceCall(conn)</I>, the connection's
150      * input stream is positioned at the start of the incoming
151      * message.  The <I>serviceCall</I> method processes the incoming
152      * remote invocation and sends the result on the connection's
153      * output stream.  If it returns "true", then the remote
154      * invocation was processed without error and the transport can
155      * cache the connection.  If it returns "false", a protocol error
156      * occurred during the call, and the transport should destroy the
157      * connection.
158      */
159     public boolean serviceCall(final RemoteCall call) {
160         try {
161             /* read object id */
162             final Remote impl;
163             ObjID id;
164 
165             try {
166                 id = ObjID.read(call.getInputStream());
167             } catch (java.io.IOException e) {
168                 throw new MarshalException("unable to read objID", e);
169             }
170 
171             /* get the remote object */
172             Transport transport = id.equals(dgcID) ? null : this;
173             Target target =
174                 ObjectTable.getTarget(new ObjectEndpoint(id, transport));
175 
176             if (target == null || (impl = target.getImpl()) == null) {
177                 throw new NoSuchObjectException("no such object in table");
178             }
179 
180             final Dispatcher disp = target.getDispatcher();
181             target.incrementCallCount();
182             try {
183                 /* call the dispatcher */
184                 transportLog.log(Log.VERBOSE, "call dispatcher");
185 
186                 final AccessControlContext acc =
187                     target.getAccessControlContext();
188                 ClassLoader ccl = target.getContextClassLoader();
189 
190                 ClassLoader savedCcl = Thread.currentThread().getContextClassLoader();
191 
192                 try {
193                     if (ccl != savedCcl) setContextClassLoader(ccl);
194                     currentTransport.set(this);
195                     try {
196                         java.security.AccessController.doPrivileged(
197                             new java.security.PrivilegedExceptionAction<Void>() {
198                             public Void run() throws IOException {
199                                 checkAcceptPermission(acc);
200                                 disp.dispatch(impl, call);
201                                 return null;
202                             }
203                         }, acc);
204                     } catch (java.security.PrivilegedActionException pae) {
205                         throw (IOException) pae.getException();
206                     }
207                 } finally {
208                     if (ccl != savedCcl) setContextClassLoader(savedCcl);
209                     currentTransport.set(null);
210                 }
211 
212             } catch (IOException ex) {
213                 transportLog.log(Log.BRIEF,
214                                  "exception thrown by dispatcher: ", ex);
215                 return false;
216             } finally {
217                 target.decrementCallCount();
218             }
219 
220         } catch (RemoteException e) {
221 
222             // if calls are being logged, write out exception
223             if (UnicastServerRef.callLog.isLoggable(Log.BRIEF)) {
224                 // include client host name if possible
225                 String clientHost = "";
226                 try {
227                     clientHost = "[" +
228                         RemoteServer.getClientHost() + "] ";
229                 } catch (ServerNotActiveException ex) {
230                 }
231                 String message = clientHost + "exception: ";
232                 UnicastServerRef.callLog.log(Log.BRIEF, message, e);
233             }
234 
235             /* We will get a RemoteException if either a) the objID is
236              * not readable, b) the target is not in the object table, or
237              * c) the object is in the midst of being unexported (note:
238              * NoSuchObjectException is thrown by the incrementCallCount
239              * method if the object is being unexported).  Here it is
240              * relatively safe to marshal an exception to the client
241              * since the client will not have seen a return value yet.
242              */
243             try {
244                 ObjectOutput out = call.getResultStream(false);
245                 UnicastServerRef.clearStackTraces(e);
246                 out.writeObject(e);
247                 call.releaseOutputStream();
248 
249             } catch (IOException ie) {
250                 transportLog.log(Log.BRIEF,
251                     "exception thrown marshalling exception: ", ie);
252                 return false;
253             }
254         }
255 
256         return true;
257     }
258 }
--- EOF ---