Try to send HTTP error messages over sideband

When a client POSTs to /git-{upload,receive}-pack, the first line
includes their client capabilities. As soon as the C git client sends
side-band(-64k), it goes into a state where it chokes on data not sent
in a valid sideband channel.

GitSmartHttpTools.sendError() is called early in the request, likely
before a {Upload,Receive}Pack handler is assigned or, even so, before it
has read the request. In some cases we must read the first line manually
within sendError() to tell whether sideband is needed.

Change-Id: I8277fd45a4ec3b71fa8f87404b4f5d1a09e0f384

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/GitSmartHttpTools.java

@@ -43,6 +43,12 @@
 
 package org.eclipse.jgit.http.server;
 
+import static org.eclipse.jgit.http.server.ServletUtils.ATTRIBUTE_HANDLER;
+import static org.eclipse.jgit.transport.BasePackFetchConnection.OPTION_SIDE_BAND;
+import static org.eclipse.jgit.transport.BasePackFetchConnection.OPTION_SIDE_BAND_64K;
+import static org.eclipse.jgit.transport.BasePackPushConnection.CAPABILITY_SIDE_BAND_64K;
+import static org.eclipse.jgit.transport.SideBandOutputStream.CH_ERROR;
+import static org.eclipse.jgit.transport.SideBandOutputStream.SMALL_BUF;
 import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
 import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
@@ -58,7 +64,12 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.transport.PacketLineIn;
 import org.eclipse.jgit.transport.PacketLineOut;
+import org.eclipse.jgit.transport.ReceivePack;
+import org.eclipse.jgit.transport.RequestNotYetReadException;
+import org.eclipse.jgit.transport.SideBandOutputStream;
+import org.eclipse.jgit.transport.UploadPack;
 
 /**
  * Utility functions for handling the Git-over-HTTP protocol.
@@ -141,6 +152,11 @@ public class GitSmartHttpTools {
 	 * to a Git protocol client using an HTTP 200 OK response with the error
 	 * embedded in the payload. If the request was not issued by a Git client,
 	 * an HTTP response code is returned instead.
+	 * <p>
+	 * This method may only be called before handing off the request to
+	 * {@link UploadPack#upload(java.io.InputStream, OutputStream, OutputStream)}
+	 * or
+	 * {@link ReceivePack#receive(java.io.InputStream, OutputStream, OutputStream)}.
 	 *
 	 * @param req
 	 *            current request.
@@ -176,21 +192,12 @@ public class GitSmartHttpTools {
 			}
 		}
 
-		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
-		PacketLineOut pck = new PacketLineOut(buf);
-
 		if (isInfoRefs(req)) {
-			String svc = req.getParameter("service");
-			pck.writeString("# service=" + svc + "\n");
-			pck.end();
-			pck.writeString("ERR " + textForGit);
-			send(req, res, infoRefsResultType(svc), buf.toByteArray());
+			sendInfoRefsError(req, res, textForGit);
 		} else if (isUploadPack(req)) {
-			pck.writeString("ERR " + textForGit);
-			send(req, res, UPLOAD_PACK_RESULT_TYPE, buf.toByteArray());
+			sendUploadPackError(req, res, textForGit);
 		} else if (isReceivePack(req)) {
-			pck.writeString("ERR " + textForGit);
-			send(req, res, RECEIVE_PACK_RESULT_TYPE, buf.toByteArray());
+			sendReceivePackError(req, res, textForGit);
 		} else {
 			if (httpStatus < 400)
 				ServletUtils.consumeRequestBody(req);
@@ -198,6 +205,108 @@ public class GitSmartHttpTools {
 		}
 	}
 
+	private static void sendInfoRefsError(HttpServletRequest req,
+			HttpServletResponse res, String textForGit) throws IOException {
+		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
+		PacketLineOut pck = new PacketLineOut(buf);
+		String svc = req.getParameter("service");
+		pck.writeString("# service=" + svc + "\n");
+		pck.end();
+		pck.writeString("ERR " + textForGit);
+		send(req, res, infoRefsResultType(svc), buf.toByteArray());
+	}
+
+	private static void sendUploadPackError(HttpServletRequest req,
+			HttpServletResponse res, String textForGit) throws IOException {
+		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
+		PacketLineOut pckOut = new PacketLineOut(buf);
+
+		boolean sideband;
+		UploadPack up = (UploadPack) req.getAttribute(ATTRIBUTE_HANDLER);
+		if (up != null) {
+			try {
+				sideband = up.isSideBand();
+			} catch (RequestNotYetReadException e) {
+				sideband = isUploadPackSideBand(req);
+			}
+		} else
+			sideband = isUploadPackSideBand(req);
+
+		if (sideband)
+			writeSideBand(buf, textForGit);
+		else
+			writePacket(pckOut, textForGit);
+		send(req, res, UPLOAD_PACK_RESULT_TYPE, buf.toByteArray());
+	}
+
+	private static boolean isUploadPackSideBand(HttpServletRequest req) {
+		try {
+			// The client may be in a state where they have sent the sideband
+			// capability and are expecting a response in the sideband, but we might
+			// not have an UploadPack, or it might not have read any of the request.
+			// So, cheat and read the first line.
+			String line = new PacketLineIn(req.getInputStream()).readStringRaw();
+			UploadPack.FirstLine parsed = new UploadPack.FirstLine(line);
+			return (parsed.getOptions().contains(OPTION_SIDE_BAND)
+					|| parsed.getOptions().contains(OPTION_SIDE_BAND_64K));
+		} catch (IOException e) {
+			// Probably the connection is closed and a subsequent write will fail, but
+			// try it just in case.
+			return false;
+		}
+	}
+
+	private static void sendReceivePackError(HttpServletRequest req,
+			HttpServletResponse res, String textForGit) throws IOException {
+		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
+		PacketLineOut pckOut = new PacketLineOut(buf);
+
+		boolean sideband;
+		ReceivePack rp = (ReceivePack) req.getAttribute(ATTRIBUTE_HANDLER);
+		if (rp != null) {
+			try {
+				sideband = rp.isSideBand();
+			} catch (RequestNotYetReadException e) {
+				sideband = isReceivePackSideBand(req);
+			}
+		} else
+			sideband = isReceivePackSideBand(req);
+
+		if (sideband)
+			writeSideBand(buf, textForGit);
+		else
+			writePacket(pckOut, textForGit);
+		send(req, res, RECEIVE_PACK_RESULT_TYPE, buf.toByteArray());
+	}
+
+	private static boolean isReceivePackSideBand(HttpServletRequest req) {
+		try {
+			// The client may be in a state where they have sent the sideband
+			// capability and are expecting a response in the sideband, but we might
+			// not have a ReceivePack, or it might not have read any of the request.
+			// So, cheat and read the first line.
+			String line = new PacketLineIn(req.getInputStream()).readStringRaw();
+			ReceivePack.FirstLine parsed = new ReceivePack.FirstLine(line);
+			return parsed.getCapabilities().contains(CAPABILITY_SIDE_BAND_64K);
+		} catch (IOException e) {
+			// Probably the connection is closed and a subsequent write will fail, but
+			// try it just in case.
+			return false;
+		}
+	}
+
+	private static void writeSideBand(OutputStream out, String textForGit)
+			throws IOException {
+		OutputStream msg = new SideBandOutputStream(CH_ERROR, SMALL_BUF, out);
+		msg.write(Constants.encode("error: " + textForGit));
+		msg.flush();
+	}
+
+	private static void writePacket(PacketLineOut pckOut, String textForGit)
+			throws IOException {
+		pckOut.writeString("error: " + textForGit);
+	}
+
 	private static void send(HttpServletRequest req, HttpServletResponse res,
 			String type, byte[] buf) throws IOException {
 		ServletUtils.consumeRequestBody(req);

org.eclipse.jgit/src/org/eclipse/jgit/transport/ReceivePack.java

@@ -649,6 +649,23 @@ public class ReceivePack {
 		maxObjectSizeLimit = limit;
 	}
 
+	/**
+	 * Check whether the client expects a side-band stream.
+	 *
+	 * @return true if the client has advertised a side-band capability, false
+	 *     otherwise.
+	 * @throws RequestNotYetReadException
+	 *             if the client's request has not yet been read from the wire, so
+	 *             we do not know if they expect side-band. Note that the client
+	 *             may have already written the request, it just has not been
+	 *             read.
+	 */
+	public boolean isSideBand() throws RequestNotYetReadException {
+		if (enabledCapabilities == null)
+			throw new RequestNotYetReadException();
+		return enabledCapabilities.contains(CAPABILITY_SIDE_BAND_64K);
+	}
+
 	/** @return all of the command received by the current request. */
 	public List<ReceiveCommand> getAllCommands() {
 		return Collections.unmodifiableList(commands);

org.eclipse.jgit/src/org/eclipse/jgit/transport/RequestNotYetReadException.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2012, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.transport;
+
+/** Indicates that a client request has not yet been read from the wire. */
+public class RequestNotYetReadException extends IllegalStateException {
+	private static final long serialVersionUID = 1L;
+
+	/** Initialize with no message. */
+	public RequestNotYetReadException() {
+		// Do not set a message.
+	}
+
+	/**
+	 * @param msg
+	 *            a message explaining the state. This message should not
+	 *            be shown to an end-user.
+	 */
+	public RequestNotYetReadException(String msg) {
+		super(msg);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/transport/SideBandOutputStream.java

@@ -55,16 +55,21 @@ import org.eclipse.jgit.JGitText;
  * This stream is buffered at packet sizes, so the caller doesn't need to wrap
  * it in yet another buffered stream.
  */
-class SideBandOutputStream extends OutputStream {
-	static final int CH_DATA = SideBandInputStream.CH_DATA;
+public class SideBandOutputStream extends OutputStream {
+	/** Channel used for pack data. */
+	public static final int CH_DATA = SideBandInputStream.CH_DATA;
 
-	static final int CH_PROGRESS = SideBandInputStream.CH_PROGRESS;
+	/** Channel used for progress messages. */
+	public static final int CH_PROGRESS = SideBandInputStream.CH_PROGRESS;
 
-	static final int CH_ERROR = SideBandInputStream.CH_ERROR;
+	/** Channel used for error messages. */
+	public static final int CH_ERROR = SideBandInputStream.CH_ERROR;
 
-	static final int SMALL_BUF = 1000;
+	/** Default buffer size for a small amount of data. */
+	public static final int SMALL_BUF = 1000;
 
-	static final int MAX_BUF = 65520;
+	/** Maximum buffer size for a single packet of sideband data. */
+	public static final int MAX_BUF = 65520;
 
 	static final int HDR_SIZE = 5;
 
@@ -95,7 +100,7 @@ class SideBandOutputStream extends OutputStream {
 	 *            stream that the packets are written onto. This stream should
 	 *            be attached to a SideBandInputStream on the remote side.
 	 */
-	SideBandOutputStream(final int chan, final int sz, final OutputStream os) {
+	public SideBandOutputStream(final int chan, final int sz, final OutputStream os) {
 		if (chan <= 0 || chan > 255)
 			throw new IllegalArgumentException(MessageFormat.format(JGitText.get().channelMustBeInRange0_255, chan));
 		if (sz <= HDR_SIZE)

org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java

@@ -464,6 +464,24 @@ public class UploadPack {
 		this.logger = logger;
 	}
 
+	/**
+	 * Check whether the client expects a side-band stream.
+	 *
+	 * @return true if the client has advertised a side-band capability, false
+	 *     otherwise.
+	 * @throws RequestNotYetReadException
+	 *             if the client's request has not yet been read from the wire, so
+	 *             we do not know if they expect side-band. Note that the client
+	 *             may have already written the request, it just has not been
+	 *             read.
+	 */
+	public boolean isSideBand() throws RequestNotYetReadException {
+		if (options == null)
+			throw new RequestNotYetReadException();
+		return (options.contains(OPTION_SIDE_BAND)
+				|| options.contains(OPTION_SIDE_BAND_64K));
+	}
+
 	/**
 	 * Execute the upload task on the socket.
 	 *