SSH: Implement X11 forwarding

Change-Id: Ia7b15e784cb098bc7c6c6be2748d772192187e97
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/ssh/ssh.pro

@@ -33,7 +33,9 @@ SOURCES = $$PWD/sshsendfacility.cpp \
     $$PWD/sshtcpipforwardserver.cpp \
     $$PWD/sshtcpiptunnel.cpp \
     $$PWD/sshforwardedtcpiptunnel.cpp \
-    $$PWD/sshagent.cpp
+    $$PWD/sshagent.cpp \
+    $$PWD/sshx11channel.cpp \
+    $$PWD/sshx11inforetriever.cpp
 
 HEADERS = $$PWD/sshsendfacility_p.h \
     $$PWD/sshremoteprocess.h \
@@ -76,7 +78,10 @@ HEADERS = $$PWD/sshsendfacility_p.h \
     $$PWD/sshtcpiptunnel_p.h \
     $$PWD/sshforwardedtcpiptunnel.h \
     $$PWD/sshforwardedtcpiptunnel_p.h \
-    $$PWD/sshagent_p.h
+    $$PWD/sshagent_p.h \
+    $$PWD/sshx11channel_p.h \
+    $$PWD/sshx11displayinfo_p.h \
+    $$PWD/sshx11inforetriever_p.h
 
 FORMS = $$PWD/sshkeycreationdialog.ui
 

src/libs/ssh/ssh.qbs

@@ -95,6 +95,11 @@ Project {
             "sshtcpipforwardserver_p.h",
             "sshtcpiptunnel.cpp",
             "sshtcpiptunnel_p.h",
+            "sshx11channel.cpp",
+            "sshx11channel_p.h",
+            "sshx11displayinfo_p.h",
+            "sshx11inforetriever.cpp",
+            "sshx11inforetriever_p.h",
         ]
 
         property var botanIncludes: qtc.useSystemBotan ? ["/usr/include/botan-2"] : []

src/libs/ssh/ssh_global.h

@@ -33,6 +33,12 @@
 #  define QSSH_EXPORT Q_DECL_IMPORT
 #endif
 
+#ifdef WITH_TESTS
+#  define QSSH_AUTOTEST_EXPORT QSSH_EXPORT
+#else
+#  define QSSH_AUTOTEST_EXPORT
+#endif
+
 #define QSSH_PRINT_WARNING qWarning("Soft assert at %s:%d", __FILE__, __LINE__)
 #define QSSH_ASSERT(cond) do { if (!(cond)) { QSSH_PRINT_WARNING; } } while (false)
 #define QSSH_ASSERT_AND_RETURN(cond) do { if (!(cond)) { QSSH_PRINT_WARNING; return; } } while (false)

src/libs/ssh/sshchannelmanager.cpp

@@ -38,6 +38,8 @@
 #include "sshsendfacility_p.h"
 #include "sshtcpipforwardserver.h"
 #include "sshtcpipforwardserver_p.h"
+#include "sshx11channel_p.h"
+#include "sshx11inforetriever_p.h"
 
 #include <QList>
 
@@ -63,6 +65,10 @@ void SshChannelManager::handleChannelOpen(const SshIncomingPacket &packet)
         handleChannelOpenForwardedTcpIp(channelOpen);
         return;
     }
+    if (channelOpen.channelType == "x11") {
+        handleChannelOpenX11(channelOpen);
+        return;
+    }
     try {
         m_sendFacility.sendChannelOpenFailurePacket(channelOpen.commonData.remoteChannel,
                                                     SSH_OPEN_UNKNOWN_CHANNEL_TYPE, QByteArray());
@@ -195,6 +201,43 @@ QSsh::SshRemoteProcess::Ptr SshChannelManager::createRemoteProcess(const QByteAr
 {
     SshRemoteProcess::Ptr proc(new SshRemoteProcess(command, m_nextLocalChannelId++, m_sendFacility));
     insertChannel(proc->d, proc);
+    connect(proc->d, &SshRemoteProcessPrivate::destroyed, this, [this] {
+        m_x11ForwardingRequests.removeOne(static_cast<SshRemoteProcessPrivate *>(sender()));
+    });
+    connect(proc->d, &SshRemoteProcessPrivate::x11ForwardingRequested, this,
+            [this, proc = proc->d](const QString &displayName) {
+        if (!x11DisplayName().isEmpty()) {
+            if (x11DisplayName() != displayName) {
+                proc->failToStart(tr("Cannot forward to display %1 on SSH connection that is "
+                                     "already forwarding to display %2.")
+                                  .arg(displayName, x11DisplayName()));
+                return;
+            }
+            if (!m_x11DisplayInfo.cookie.isEmpty())
+                proc->startProcess(m_x11DisplayInfo);
+            else
+                m_x11ForwardingRequests << proc;
+            return;
+        }
+        m_x11DisplayInfo.displayName = displayName;
+        m_x11ForwardingRequests << proc;
+        auto * const x11InfoRetriever = new SshX11InfoRetriever(displayName, this);
+        const auto failureHandler = [this](const QString &errorMessage) {
+            for (SshRemoteProcessPrivate * const proc : qAsConst(m_x11ForwardingRequests))
+                proc->failToStart(errorMessage);
+            m_x11ForwardingRequests.clear();
+        };
+        connect(x11InfoRetriever, &SshX11InfoRetriever::failure, this, failureHandler);
+        const auto successHandler = [this](const X11DisplayInfo &displayInfo) {
+            m_x11DisplayInfo = displayInfo;
+            for (SshRemoteProcessPrivate * const proc : qAsConst(m_x11ForwardingRequests))
+                proc->startProcess(displayInfo);
+            m_x11ForwardingRequests.clear();
+        };
+        connect(x11InfoRetriever, &SshX11InfoRetriever::success, this, successHandler);
+        qCDebug(sshLog) << "starting x11 info retriever";
+        x11InfoRetriever->start();
+    });
     return proc;
 }
 
@@ -303,6 +346,25 @@ void SshChannelManager::handleChannelOpenForwardedTcpIp(
     insertChannel(tunnel->d, tunnel);
 }
 
+void SshChannelManager::handleChannelOpenX11(const SshChannelOpenGeneric &channelOpenGeneric)
+{
+    qCDebug(sshLog) << "incoming X11 channel open request";
+    const SshChannelOpenX11 channelOpen
+            = SshIncomingPacket::extractChannelOpenX11(channelOpenGeneric);
+    if (m_x11DisplayInfo.cookie.isEmpty()) {
+        throw SSH_SERVER_EXCEPTION(SSH_DISCONNECT_PROTOCOL_ERROR,
+                                   "Server attempted to open an unrequested X11 channel.");
+    }
+    SshX11Channel * const x11Channel = new SshX11Channel(m_x11DisplayInfo,
+                                                         m_nextLocalChannelId++,
+                                                         m_sendFacility);
+    x11Channel->setParent(this);
+    x11Channel->handleOpenSuccess(channelOpen.common.remoteChannel,
+                                  channelOpen.common.remoteWindowSize,
+                                  channelOpen.common.remoteMaxPacketSize);
+    insertChannel(x11Channel, QSharedPointer<QObject>());
+}
+
 int SshChannelManager::closeAllChannels(CloseAllMode mode)
 {
     int count = 0;

src/libs/ssh/sshchannelmanager_p.h

@@ -25,6 +25,8 @@
 
 #pragma once
 
+#include "sshx11displayinfo_p.h"
+
 #include <QHash>
 #include <QObject>
 #include <QSharedPointer>
@@ -41,6 +43,7 @@ class AbstractSshChannel;
 struct SshChannelOpenGeneric;
 class SshIncomingPacket;
 class SshSendFacility;
+class SshRemoteProcessPrivate;
 
 class SshChannelManager : public QObject
 {
@@ -59,6 +62,7 @@ public:
     int channelCount() const;
     enum CloseAllMode { CloseAllRegular, CloseAllAndReset };
     int closeAllChannels(CloseAllMode mode);
+    QString x11DisplayName() const { return m_x11DisplayInfo.displayName; }
 
     void handleChannelRequest(const SshIncomingPacket &packet);
     void handleChannelOpen(const SshIncomingPacket &packet);
@@ -89,12 +93,16 @@ private:
         const QSharedPointer<QObject> &pub);
 
     void handleChannelOpenForwardedTcpIp(const SshChannelOpenGeneric &channelOpenGeneric);
+    void handleChannelOpenX11(const SshChannelOpenGeneric &channelOpenGeneric);
+
     SshSendFacility &m_sendFacility;
     QHash<quint32, AbstractSshChannel *> m_channels;
     QHash<AbstractSshChannel *, QSharedPointer<QObject> > m_sessions;
     quint32 m_nextLocalChannelId;
     QList<QSharedPointer<SshTcpIpForwardServer>> m_waitingForwardServers;
     QList<QSharedPointer<SshTcpIpForwardServer>> m_listeningForwardServers;
+    QList<SshRemoteProcessPrivate *> m_x11ForwardingRequests;
+    X11DisplayInfo m_x11DisplayInfo;
 };
 
 } // namespace Internal

src/libs/ssh/sshconnection.cpp

@@ -207,6 +207,11 @@ int SshConnection::channelCount() const
     return d->m_channelManager->channelCount();
 }
 
+QString SshConnection::x11DisplayName() const
+{
+    return d->m_channelManager->x11DisplayName();
+}
+
 namespace Internal {
 
 SshConnectionPrivate::SshConnectionPrivate(SshConnection *conn,

src/libs/ssh/sshconnection.h

@@ -142,6 +142,8 @@ public:
 
     int channelCount() const;
 
+    QString x11DisplayName() const;
+
 signals:
     void connected();
     void disconnected();

src/libs/ssh/sshincomingpacket.cpp

@@ -406,6 +406,23 @@ SshChannelOpenForwardedTcpIp SshIncomingPacket::extractChannelOpenForwardedTcpIp
     }
 }
 
+SshChannelOpenX11 SshIncomingPacket::extractChannelOpenX11(const SshChannelOpenGeneric &genericData)
+{
+    try {
+        SshChannelOpenX11 specificData;
+        specificData.common = genericData.commonData;
+        quint32 offset = 0;
+        specificData.originatorAddress = SshPacketParser::asString(genericData.typeSpecificData,
+                                                                   &offset);
+        specificData.originatorPort = SshPacketParser::asUint32(genericData.typeSpecificData,
+                                                                &offset);
+        return specificData;
+    } catch (const SshPacketParseException &) {
+        throw SSH_SERVER_EXCEPTION(SSH_DISCONNECT_PROTOCOL_ERROR,
+            "Server sent invalid SSH_MSG_CHANNEL_OPEN packet.");
+    }
+}
+
 SshChannelOpenFailure SshIncomingPacket::extractChannelOpenFailure() const
 {
     Q_ASSERT(isComplete());

src/libs/ssh/sshincomingpacket_p.h

@@ -131,6 +131,13 @@ struct SshChannelOpenForwardedTcpIp
     quint32 originatorPort;
 };
 
+struct SshChannelOpenX11
+{
+    SshChannelOpenCommon common;
+    QByteArray originatorAddress;
+    quint32 originatorPort;
+};
+
 struct SshChannelOpenFailure
 {
     quint32 localChannel;
@@ -204,6 +211,7 @@ public:
     SshChannelOpenGeneric extractChannelOpen() const;
     static SshChannelOpenForwardedTcpIp extractChannelOpenForwardedTcpIp(
             const SshChannelOpenGeneric &genericData);
+    static SshChannelOpenX11 extractChannelOpenX11(const SshChannelOpenGeneric &genericData);
     SshChannelOpenFailure extractChannelOpenFailure() const;
     SshChannelOpenConfirmation extractChannelOpenConfirmation() const;
     SshChannelWindowAdjust extractWindowAdjust() const;

src/libs/ssh/sshoutgoingpacket.cpp

@@ -225,6 +225,14 @@ void SshOutgoingPacket::generateEnvPacket(quint32 remoteChannel,
         .appendBool(false).appendString(var).appendString(value).finalize();
 }
 
+void SshOutgoingPacket::generateX11ForwardingPacket(quint32 remoteChannel,
+        const QByteArray &protocol, const QByteArray &cookie, quint32 screenNumber)
+{
+    init(SSH_MSG_CHANNEL_REQUEST).appendInt(remoteChannel).appendString("x11-req")
+            .appendBool(false).appendBool(false).appendString(protocol)
+            .appendString(cookie).appendInt(screenNumber).finalize();
+}
+
 void SshOutgoingPacket::generatePtyRequestPacket(quint32 remoteChannel,
     const SshPseudoTerminal &terminal)
 {

src/libs/ssh/sshoutgoingpacket_p.h

@@ -71,6 +71,8 @@ public:
     void generateCancelTcpIpForwardPacket(const QByteArray &bindAddress, quint32 bindPort);
     void generateEnvPacket(quint32 remoteChannel, const QByteArray &var,
         const QByteArray &value);
+    void generateX11ForwardingPacket(quint32 remoteChannel, const QByteArray &protocol,
+                                     const QByteArray &cookie, quint32 screenNumber);
     void generatePtyRequestPacket(quint32 remoteChannel,
         const SshPseudoTerminal &terminal);
     void generateExecPacket(quint32 remoteChannel, const QByteArray &command);

src/libs/ssh/sshremoteprocess.cpp

@@ -30,6 +30,7 @@
 #include "sshincomingpacket_p.h"
 #include "sshlogging_p.h"
 #include "sshsendfacility_p.h"
+#include "sshx11displayinfo_p.h"
 
 #include <QTimer>
 
@@ -186,6 +187,12 @@ void SshRemoteProcess::requestTerminal(const SshPseudoTerminal &terminal)
     d->m_terminal = terminal;
 }
 
+void SshRemoteProcess::requestX11Forwarding(const QString &displayName)
+{
+    QSSH_ASSERT_AND_RETURN(d->channelState() == Internal::SshRemoteProcessPrivate::Inactive);
+    d->m_x11DisplayName = displayName;
+}
+
 void SshRemoteProcess::start()
 {
     if (d->channelState() == Internal::SshRemoteProcessPrivate::Inactive) {
@@ -227,6 +234,14 @@ SshRemoteProcess::Signal SshRemoteProcess::exitSignal() const
 
 namespace Internal {
 
+void SshRemoteProcessPrivate::failToStart(const QString &reason)
+{
+    if (m_procState != NotYetStarted)
+        return;
+    m_proc->setErrorString(reason);
+    setProcState(StartFailed);
+}
+
 SshRemoteProcessPrivate::SshRemoteProcessPrivate(const QByteArray &command,
         quint32 channelId, SshSendFacility &sendFacility, SshRemoteProcess *proc)
     : AbstractSshChannel(channelId, sendFacility),
@@ -286,26 +301,41 @@ void SshRemoteProcessPrivate::closeHook()
 
 void SshRemoteProcessPrivate::handleOpenSuccessInternal()
 {
-   foreach (const EnvVar &envVar, m_env) {
-       m_sendFacility.sendEnvPacket(remoteChannel(), envVar.first,
-           envVar.second);
-   }
+    if (m_x11DisplayName.isEmpty())
+        startProcess(X11DisplayInfo());
+    else
+        emit x11ForwardingRequested(m_x11DisplayName);
+}
 
-   if (m_useTerminal)
-       m_sendFacility.sendPtyRequestPacket(remoteChannel(), m_terminal);
+void SshRemoteProcessPrivate::startProcess(const X11DisplayInfo &displayInfo)
+{
+    if (m_procState != NotYetStarted)
+        return;
 
-   if (m_isShell)
-       m_sendFacility.sendShellPacket(remoteChannel());
-   else
-       m_sendFacility.sendExecPacket(remoteChannel(), m_command);
-   setProcState(ExecRequested);
-   m_timeoutTimer.start(ReplyTimeout);
+    foreach (const EnvVar &envVar, m_env) {
+        m_sendFacility.sendEnvPacket(remoteChannel(), envVar.first,
+            envVar.second);
+    }
+
+    if (!m_x11DisplayName.isEmpty()) {
+        m_sendFacility.sendX11ForwardingPacket(remoteChannel(), displayInfo.protocol,
+                                               displayInfo.randomCookie.toHex(), 0);
+    }
+
+    if (m_useTerminal)
+        m_sendFacility.sendPtyRequestPacket(remoteChannel(), m_terminal);
+
+    if (m_isShell)
+        m_sendFacility.sendShellPacket(remoteChannel());
+    else
+        m_sendFacility.sendExecPacket(remoteChannel(), m_command);
+    setProcState(ExecRequested);
+    m_timeoutTimer.start(ReplyTimeout);
 }
 
 void SshRemoteProcessPrivate::handleOpenFailureInternal(const QString &reason)
 {
-   setProcState(StartFailed);
-   m_proc->setErrorString(reason);
+    failToStart(reason);
 }
 
 void SshRemoteProcessPrivate::handleChannelSuccess()

src/libs/ssh/sshremoteprocess.h

@@ -78,6 +78,7 @@ public:
     void clearEnvironment();
 
     void requestTerminal(const SshPseudoTerminal &terminal);
+    void requestX11Forwarding(const QString &displayName);
     void start();
 
     bool isRunning() const;

src/libs/ssh/sshremoteprocess_p.h

@@ -38,6 +38,7 @@ class SshRemoteProcess;
 
 namespace Internal {
 class SshSendFacility;
+class X11DisplayInfo;
 
 class SshRemoteProcessPrivate : public AbstractSshChannel
 {
@@ -48,12 +49,16 @@ public:
         NotYetStarted, ExecRequested, StartFailed, Running, Exited
     };
 
+    void failToStart(const QString &reason);
+    void startProcess(const X11DisplayInfo &displayInfo);
+
 signals:
     void started();
     void readyRead();
     void readyReadStandardOutput();
     void readyReadStandardError();
     void closed(int exitStatus);
+    void x11ForwardingRequested(const QString &display);
 
 private:
     SshRemoteProcessPrivate(const QByteArray &command, quint32 channelId,
@@ -93,6 +98,8 @@ private:
     bool m_useTerminal;
     SshPseudoTerminal m_terminal;
 
+    QString m_x11DisplayName;
+
     QByteArray m_stdout;
     QByteArray m_stderr;
 

src/libs/ssh/sshsendfacility.cpp

@@ -205,6 +205,13 @@ void SshSendFacility::sendEnvPacket(quint32 remoteChannel,
     sendPacket();
 }
 
+void SshSendFacility::sendX11ForwardingPacket(quint32 remoteChannel, const QByteArray &protocol,
+                                              const QByteArray &cookie, quint32 screenNumber)
+{
+    m_outgoingPacket.generateX11ForwardingPacket(remoteChannel, protocol, cookie, screenNumber);
+    sendPacket();
+}
+
 void SshSendFacility::sendExecPacket(quint32 remoteChannel,
     const QByteArray &command)
 {

src/libs/ssh/sshsendfacility_p.h

@@ -82,6 +82,8 @@ public:
         const SshPseudoTerminal &terminal);
     void sendEnvPacket(quint32 remoteChannel, const QByteArray &var,
         const QByteArray &value);
+    void sendX11ForwardingPacket(quint32 remoteChannel, const QByteArray &protocol,
+                                 const QByteArray &cookie, quint32 screenNumber);
     void sendExecPacket(quint32 remoteChannel, const QByteArray &command);
     void sendShellPacket(quint32 remoteChannel);
     void sendSftpPacket(quint32 remoteChannel);

src/libs/ssh/sshx11channel.cpp

@@ -0,0 +1,220 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include "sshx11channel_p.h"
+
+#include "sshincomingpacket_p.h"
+#include "sshlogging_p.h"
+#include "sshsendfacility_p.h"
+
+#include <QFileInfo>
+#include <QLocalSocket>
+#include <QTcpSocket>
+
+namespace QSsh {
+namespace Internal {
+
+class X11Socket : public QObject
+{
+    Q_OBJECT
+public:
+    X11Socket(QObject *parent) : QObject(parent) { }
+
+    void establishConnection(const X11DisplayInfo &displayInfo)
+    {
+        const bool hostNameIsPath = displayInfo.hostName.startsWith('/'); // macOS
+        const bool hasActualHostName = !displayInfo.hostName.isEmpty()
+                && displayInfo.hostName != "unix" && !displayInfo.hostName.endsWith("/unix")
+                && !hostNameIsPath;
+        if (hasActualHostName) {
+            QTcpSocket * const socket = new QTcpSocket(this);
+            connect(socket, &QTcpSocket::connected, this, &X11Socket::connected);
+            connect(socket,
+                    static_cast<void(QTcpSocket::*)(QTcpSocket::SocketError)>(&QTcpSocket::error),
+                    [this, socket] {
+                emit error(socket->errorString());
+            });
+            socket->connectToHost(displayInfo.hostName, 6000 + displayInfo.display);
+            m_socket = socket;
+        } else {
+            const QString serverBasePath = hostNameIsPath ? QString(displayInfo.hostName + ':')
+                                                          : "/tmp/.X11-unix/X";
+            QLocalSocket * const socket = new QLocalSocket(this);
+            connect(socket, &QLocalSocket::connected, this, &X11Socket::connected);
+            connect(socket,
+                    static_cast<void(QLocalSocket::*)(QLocalSocket::LocalSocketError)>(&QLocalSocket::error),
+                    [this, socket] {
+                emit error(socket->errorString());
+            });
+            socket->connectToServer(serverBasePath + QString::number(displayInfo.display));
+            m_socket = socket;
+        }
+        connect(m_socket, &QIODevice::readyRead,
+                [this] { emit dataAvailable(m_socket->readAll()); });
+    }
+
+    void closeConnection()
+    {
+        m_socket->disconnect();
+        if (localSocket())
+            localSocket()->disconnectFromServer();
+        else
+            tcpSocket()->disconnectFromHost();
+    }
+
+    void write(const QByteArray &data)
+    {
+        m_socket->write(data);
+    }
+
+    bool hasError() const
+    {
+        return (localSocket() && localSocket()->error() != QLocalSocket::UnknownSocketError)
+                || (tcpSocket() && tcpSocket()->error() != QTcpSocket::UnknownSocketError);
+    }
+
+    bool isConnected() const
+    {
+        return (localSocket() && localSocket()->state() == QLocalSocket::ConnectedState)
+                || (tcpSocket() && tcpSocket()->state() == QTcpSocket::ConnectedState);
+    }
+
+signals:
+    void connected();
+    void error(const QString &message);
+    void dataAvailable(const QByteArray &data);
+
+private:
+    QLocalSocket *localSocket() const { return qobject_cast<QLocalSocket *>(m_socket); }
+    QTcpSocket *tcpSocket() const { return qobject_cast<QTcpSocket *>(m_socket); }
+
+    QIODevice *m_socket = nullptr;
+};
+
+SshX11Channel::SshX11Channel(const X11DisplayInfo &displayInfo, quint32 channelId,
+                             SshSendFacility &sendFacility)
+    : AbstractSshChannel (channelId, sendFacility),
+      m_x11Socket(new X11Socket(this)),
+      m_displayInfo(displayInfo)
+{
+    setChannelState(SessionRequested); // Invariant for parent class.
+}
+
+void SshX11Channel::handleChannelSuccess()
+{
+    qCWarning(sshLog) << "unexpected channel success message for X11 channel";
+}
+
+void SshX11Channel::handleChannelFailure()
+{
+    qCWarning(sshLog) << "unexpected channel failure message for X11 channel";
+}
+
+void SshX11Channel::handleOpenSuccessInternal()
+{
+    m_sendFacility.sendChannelOpenConfirmationPacket(remoteChannel(), localChannelId(),
+                                                     initialWindowSize(), maxPacketSize());
+    connect(m_x11Socket, &X11Socket::connected, [this] {
+        qCDebug(sshLog) << "x11 socket connected for channel" << localChannelId();
+        if (!m_queuedRemoteData.isEmpty())
+            handleRemoteData(QByteArray());
+    });
+    connect(m_x11Socket, &X11Socket::error,
+            [this](const QString &msg) { emit error(tr("X11 socket error: %1").arg(msg)); });
+    connect(m_x11Socket, &X11Socket::dataAvailable, [this](const QByteArray &data) {
+        qCDebug(sshLog) << "sending " << data.size() << "bytes from x11 socket to remote side "
+                           "in channel" << localChannelId();
+        sendData(data);
+    });
+    m_x11Socket->establishConnection(m_displayInfo);
+}
+
+void SshX11Channel::handleOpenFailureInternal(const QString &reason)
+{
+    qCWarning(sshLog) << "unexpected channel open failure message for X11 channel:" << reason;
+}
+
+void SshX11Channel::handleChannelDataInternal(const QByteArray &data)
+{
+    handleRemoteData(data);
+}
+
+void SshX11Channel::handleChannelExtendedDataInternal(quint32 type, const QByteArray &data)
+{
+    qCWarning(sshLog) << "unexpected extended data for X11 channel" << type << data;
+}
+
+void SshX11Channel::handleExitStatus(const SshChannelExitStatus &exitStatus)
+{
+    qCWarning(sshLog) << "unexpected exit status message on X11 channel" << exitStatus.exitStatus;
+    closeChannel();
+}
+
+void SshX11Channel::handleExitSignal(const SshChannelExitSignal &signal)
+{
+    qCWarning(sshLog) << "unexpected exit signal message on X11 channel" << signal.error;
+    closeChannel();
+}
+
+void SshX11Channel::closeHook()
+{
+    m_x11Socket->disconnect();
+    m_x11Socket->closeConnection();
+}
+
+void SshX11Channel::handleRemoteData(const QByteArray &data)
+{
+    if (m_x11Socket->hasError())
+        return;
+    qCDebug(sshLog) << "received" << data.size() << "bytes from remote side in x11 channel"
+                    << localChannelId();
+    if (!m_x11Socket->isConnected()) {
+        qCDebug(sshLog) << "x11 socket not yet connected, queueing data";
+        m_queuedRemoteData += data;
+        return;
+    }
+    if (m_haveReplacedRandomCookie) {
+        qCDebug(sshLog) << "forwarding data to x11 socket";
+        m_x11Socket->write(data);
+        return;
+    }
+    m_queuedRemoteData += data;
+    const int randomCookieOffset = m_queuedRemoteData.indexOf(m_displayInfo.randomCookie);
+    if (randomCookieOffset == -1) {
+        qCDebug(sshLog) << "random cookie has not appeared in remote data yet, queueing data";
+        return;
+    }
+    m_queuedRemoteData.replace(randomCookieOffset, m_displayInfo.cookie.size(),
+                               m_displayInfo.cookie);
+    qCDebug(sshLog) << "found and replaced random cookie, forwarding data to x11 socket";
+    m_x11Socket->write(m_queuedRemoteData);
+    m_queuedRemoteData.clear();
+    m_haveReplacedRandomCookie = true;
+}
+
+} // namespace Internal
+} // namespace QSsh
+
+#include <sshx11channel.moc>

src/libs/ssh/sshx11channel_p.h

@@ -0,0 +1,73 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include "sshchannel_p.h"
+
+#include "sshx11displayinfo_p.h"
+
+#include <QByteArray>
+
+namespace QSsh {
+namespace Internal {
+class SshChannelManager;
+class SshSendFacility;
+class X11Socket;
+
+class SshX11Channel : public AbstractSshChannel
+{
+    Q_OBJECT
+
+    friend class Internal::SshChannelManager;
+
+signals:
+    void error(const QString &message);
+
+private:
+    SshX11Channel(const X11DisplayInfo &displayInfo, quint32 channelId,
+                  SshSendFacility &sendFacility);
+
+    void handleChannelSuccess() override;
+    void handleChannelFailure() override;
+
+    void handleOpenSuccessInternal() override;
+    void handleOpenFailureInternal(const QString &reason) override;
+    void handleChannelDataInternal(const QByteArray &data) override;
+    void handleChannelExtendedDataInternal(quint32 type, const QByteArray &data) override;
+    void handleExitStatus(const SshChannelExitStatus &exitStatus) override;
+    void handleExitSignal(const SshChannelExitSignal &signal) override;
+    void closeHook() override;
+
+    void handleRemoteData(const QByteArray &data);
+
+    X11Socket * const m_x11Socket;
+    const X11DisplayInfo m_displayInfo;
+    QByteArray m_queuedRemoteData;
+    bool m_haveReplacedRandomCookie = false;
+};
+
+} // namespace Internal
+} // namespace QSsh

src/libs/ssh/sshx11displayinfo_p.h

@@ -0,0 +1,49 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include "ssh_global.h"
+
+#include <QString>
+#include <QByteArray>
+
+namespace QSsh {
+namespace Internal {
+
+class QSSH_AUTOTEST_EXPORT X11DisplayInfo
+{
+public:
+    QString displayName;
+    QString hostName;
+    QByteArray protocol;
+    QByteArray cookie;
+    QByteArray randomCookie;
+    int display = 0;
+    int screen = 0;
+};
+
+} // namespace Internal
+} // namespace QSsh

src/libs/ssh/sshx11inforetriever.cpp

@@ -0,0 +1,150 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include "sshx11inforetriever_p.h"
+
+#include "sshlogging_p.h"
+#include "sshx11displayinfo_p.h"
+
+#include <QByteArrayList>
+#include <QProcess>
+#include <QTemporaryFile>
+
+#include <botan/auto_rng.h>
+
+namespace QSsh {
+namespace Internal {
+
+static QByteArray xauthProtocol() { return "MIT-MAGIC-COOKIE-1"; }
+
+SshX11InfoRetriever::SshX11InfoRetriever(const QString &displayName, QObject *parent)
+    : QObject(parent),
+      m_displayName(displayName),
+      m_xauthProc(new QProcess(this)),
+      m_xauthFile(new QTemporaryFile(this))
+{
+    connect(m_xauthProc, &QProcess::errorOccurred, [this] {
+        if (m_xauthProc->error() == QProcess::FailedToStart) {
+            emitFailure(tr("Could not start xauth: %1").arg(m_xauthProc->errorString()));
+        }
+    });
+    connect(m_xauthProc,
+            static_cast<void (QProcess::*)(int,QProcess::ExitStatus)>(&QProcess::finished),
+            [this] {
+        if (m_xauthProc->exitStatus() != QProcess::NormalExit) {
+            emitFailure(tr("xauth crashed: %1").arg(m_xauthProc->errorString()));
+            return;
+        }
+        if (m_xauthProc->exitCode() != 0) {
+            emitFailure(tr("xauth failed with exit code %1.").arg(m_xauthProc->exitCode()));
+            return;
+        }
+        switch (m_state) {
+        case State::RunningGenerate:
+            m_state = State::RunningList;
+            m_xauthProc->start("xauth", QStringList{"-f", m_xauthFile->fileName(), "list",
+                                                    m_displayName});
+            break;
+        case State::RunningList: {
+            const QByteArrayList outputLines = m_xauthProc->readAllStandardOutput().split('\n');
+            if (outputLines.empty()) {
+                emitFailure(tr("Unexpected xauth output."));
+                return;
+            }
+            const QByteArrayList data = outputLines.first().simplified().split(' ');
+            if (data.size() < 3 || data.at(1) != xauthProtocol() || data.at(2).isEmpty()) {
+                emitFailure(tr("Unexpected xauth output."));
+                return;
+            }
+            X11DisplayInfo displayInfo;
+            displayInfo.displayName = m_displayName;
+            const int colonIndex = m_displayName.indexOf(':');
+            if (colonIndex == -1) {
+                emitFailure(tr("Invalid display name \"%1\"").arg(m_displayName));
+                return;
+            }
+            displayInfo.hostName = m_displayName.mid(0, colonIndex);
+            const int dotIndex = m_displayName.indexOf('.', colonIndex + 1);
+            const QString display = m_displayName.mid(colonIndex + 1,
+                                                      dotIndex == -1 ? -1
+                                                                     : dotIndex - colonIndex - 1);
+            if (display.isEmpty()) {
+                emitFailure(tr("Invalid display name \"%1\"").arg(m_displayName));
+                return;
+            }
+            bool ok;
+            displayInfo.display = display.toInt(&ok);
+            if (!ok) {
+                emitFailure(tr("Invalid display name \"%1\"").arg(m_displayName));
+                return;
+            }
+            if (dotIndex != -1) {
+                displayInfo.screen = m_displayName.mid(dotIndex + 1).toInt(&ok);
+                if (!ok) {
+                    emitFailure(tr("Invalid display name \"%1\"").arg(m_displayName));
+                    return;
+                }
+            }
+            displayInfo.protocol = data.at(1);
+            displayInfo.cookie = QByteArray::fromHex(data.at(2));
+            displayInfo.randomCookie.resize(displayInfo.cookie.size());
+            try {
+                Botan::AutoSeeded_RNG rng;
+                rng.randomize(reinterpret_cast<Botan::uint8_t *>(displayInfo.randomCookie.data()),
+                              displayInfo.randomCookie.size());
+            } catch (const std::exception &ex) {
+                emitFailure(tr("Failed to generate random cookie: %1")
+                            .arg(QLatin1String(ex.what())));
+                return;
+            }
+            emit success(displayInfo);
+            deleteLater();
+            break;
+        }
+        default:
+            emitFailure(tr("Internal error"));
+        }
+    });
+}
+
+void SshX11InfoRetriever::start()
+{
+    if (!m_xauthFile->open()) {
+        emitFailure(tr("Could not create temporary file: %1").arg(m_xauthFile->errorString()));
+        return;
+    }
+    m_state = State::RunningGenerate;
+    m_xauthProc->start("xauth", QStringList{"-f", m_xauthFile->fileName(), "generate",
+                                            m_displayName, QString::fromLatin1(xauthProtocol())});
+}
+
+void SshX11InfoRetriever::emitFailure(const QString &reason)
+{
+    emit failure(tr("Could not retrieve X11 authentication cookie: %1").arg(reason));
+    deleteLater();
+}
+
+} // namespace Internal
+} // namespace QSsh

src/libs/ssh/sshx11inforetriever_p.h

@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include "ssh_global.h"
+
+#include <QObject>
+#include <QString>
+
+QT_BEGIN_NAMESPACE
+class QByteArray;
+class QProcess;
+class QTemporaryFile;
+QT_END_NAMESPACE
+
+namespace QSsh {
+namespace Internal {
+class X11DisplayInfo;
+
+class QSSH_AUTOTEST_EXPORT SshX11InfoRetriever : public QObject
+{
+    Q_OBJECT
+public:
+    SshX11InfoRetriever(const QString &displayName, QObject *parent = nullptr);
+    void start();
+
+signals:
+    void failure(const QString &message);
+    void success(const X11DisplayInfo &displayInfo);
+
+private:
+    void emitFailure(const QString &reason);
+
+    const QString m_displayName;
+    QProcess * const m_xauthProc;
+    QTemporaryFile * const m_xauthFile;
+
+    enum class State { Inactive, RunningGenerate, RunningList } m_state = State::Inactive;
+};
+
+} // namespace Internal
+} // namespace QSsh

tests/auto/ssh/ssh.pro

@@ -1,5 +1,5 @@
 QT = core network
-QTC_LIB_DEPENDS += ssh
+QTC_LIB_DEPENDS += ssh utils
 include(../qttest.pri)
 
 SOURCES += tst_ssh.cpp

tests/auto/ssh/ssh.qbs

@@ -3,5 +3,6 @@ import qbs
 QtcAutotest {
     name: "SSH autotest"
     Depends { name: "QtcSsh" }
+    Depends { name: "Utils" }
     files: "tst_ssh.cpp"
 }

tests/auto/ssh/tst_ssh.cpp

@@ -30,6 +30,9 @@
 #include <ssh/sshpseudoterminal.h>
 #include <ssh/sshremoteprocessrunner.h>
 #include <ssh/sshtcpipforwardserver.h>
+#include <ssh/sshx11displayinfo_p.h>
+#include <ssh/sshx11inforetriever_p.h>
+#include <utils/environment.h>
 
 #include <QDateTime>
 #include <QDir>
@@ -152,6 +155,8 @@ private slots:
     void remoteProcessChannels();
     void remoteProcessInput();
     void sftp();
+    void x11InfoRetriever_data();
+    void x11InfoRetriever();
 
 private:
     bool waitForConnection(SshConnection &connection);
@@ -826,6 +831,62 @@ void tst_Ssh::sftp()
     QCOMPARE(sftpChannel->state(), SftpChannel::Closed);
 }
 
+void tst_Ssh::x11InfoRetriever_data()
+{
+    QTest::addColumn<QString>("displayName");
+    QTest::addColumn<bool>("successExpected");
+
+    const Utils::FileName xauthCommand
+            = Utils::Environment::systemEnvironment().searchInPath("xauth");
+    const QString displayName = QLatin1String(qgetenv("DISPLAY"));
+    const bool canSucceed = xauthCommand.exists() && !displayName.isEmpty();
+    QTest::newRow(canSucceed ? "suitable host" : "unsuitable host") << displayName << canSucceed;
+    QTest::newRow("invalid display name") << QString("dummy") << false;
+}
+
+void tst_Ssh::x11InfoRetriever()
+{
+    QFETCH(QString, displayName);
+    QFETCH(bool, successExpected);
+    using namespace QSsh::Internal;
+    SshX11InfoRetriever x11InfoRetriever(displayName);
+    QEventLoop loop;
+    bool success;
+    X11DisplayInfo displayInfo;
+    QString errorMessage;
+    const auto successHandler = [&loop, &success, &displayInfo](const X11DisplayInfo &di) {
+        success = true;
+        displayInfo = di;
+        loop.quit();
+    };
+    connect(&x11InfoRetriever, &SshX11InfoRetriever::success, successHandler);
+    const auto failureHandler = [&loop, &success, &errorMessage](const QString &error) {
+        success = false;
+        errorMessage = error;
+        loop.quit();
+    };
+    connect(&x11InfoRetriever, &SshX11InfoRetriever::failure, failureHandler);
+    QTimer timer;
+    QObject::connect(&timer, &QTimer::timeout, &loop, &QEventLoop::quit);
+    timer.setSingleShot(true);
+    timer.setInterval(40000);
+    timer.start();
+    x11InfoRetriever.start();
+    loop.exec();
+    QVERIFY(timer.isActive());
+    timer.stop();
+    if (successExpected) {
+        QVERIFY2(success, qPrintable(errorMessage));
+        QVERIFY(!displayInfo.protocol.isEmpty());
+        QVERIFY(!displayInfo.cookie.isEmpty());
+        QCOMPARE(displayInfo.cookie.size(), displayInfo.randomCookie.size());
+        QCOMPARE(displayInfo.displayName, displayName);
+    } else {
+        QVERIFY(!success);
+        QVERIFY(!errorMessage.isEmpty());
+    }
+}
+
 bool tst_Ssh::waitForConnection(SshConnection &connection)
 {
     QEventLoop loop;