Merge pull request #1346 from p12tic/client-identity-verification

Implement client identity verification [SECURITY VULNERABILITIES CVE-2021-42072, CVE-2021-42073]

doc/newsfragments/client-certificate-checking.bugfix

@@ -0,0 +1,7 @@
+SECURITY ISSUE
+
+Barrier now supports client identity verification (fixes CVE-2021-42072, CVE-2021-42073).
+
+To support seamless upgrades from older versions of Barrier this is currently disabled by default.
+The feature can be enabled in the settings dialog. If enabled, older clients of Barrier will be
+rejected.

doc/newsfragments/client-send-certificate.feature

@@ -0,0 +1 @@
+Barrier client now sends certificate that the server can verify.

src/gui/CMakeLists.txt

@@ -29,6 +29,7 @@ set(GUI_SOURCE_FILES
     src/CommandProcess.cpp
     src/DataDownloader.cpp
     src/DisplayIsValid.cpp
+    src/FingerprintAcceptDialog.cpp
     src/HotkeyDialog.cpp
     src/IpcClient.cpp
     src/Ipc.cpp
@@ -104,6 +105,7 @@ set(GUI_UI_FILES
     src/AboutDialogBase.ui
     src/ActionDialogBase.ui
     src/AddClientDialogBase.ui
+    src/FingerprintAcceptDialog.ui
     src/HotkeyDialogBase.ui
     src/LogWindowBase.ui
     src/MainWindowBase.ui

src/gui/src/AppConfig.cpp

@@ -158,6 +158,8 @@ void AppConfig::loadSettings()
     m_ElevateMode = static_cast<ElevateMode>(elevateMode.toInt());
     m_AutoConfigPrompted = settings().value("autoConfigPrompted", false).toBool();
     m_CryptoEnabled = settings().value("cryptoEnabled", true).toBool();
+    // TODO: set default value of requireClientCertificate to true on Barrier 2.5.0
+    m_RequireClientCertificate = settings().value("requireClientCertificate", false).toBool();
     m_AutoHide = settings().value("autoHide", false).toBool();
     m_AutoStart = settings().value("autoStart", false).toBool();
     m_MinimizeToTray = settings().value("minimizeToTray", false).toBool();
@@ -181,6 +183,7 @@ void AppConfig::saveSettings()
     settings().setValue("elevateModeEnum", static_cast<int>(m_ElevateMode));
     settings().setValue("autoConfigPrompted", m_AutoConfigPrompted);
     settings().setValue("cryptoEnabled", m_CryptoEnabled);
+    settings().setValue("requireClientCertificate", m_RequireClientCertificate);
     settings().setValue("autoHide", m_AutoHide);
     settings().setValue("autoStart", m_AutoStart);
     settings().setValue("minimizeToTray", m_MinimizeToTray);
@@ -225,6 +228,10 @@ void AppConfig::setCryptoEnabled(bool e) { m_CryptoEnabled = e; }
 
 bool AppConfig::getCryptoEnabled() const { return m_CryptoEnabled; }
 
+void AppConfig::setRequireClientCertificate(bool e) { m_RequireClientCertificate = e; }
+
+bool AppConfig::getRequireClientCertificate() const { return m_RequireClientCertificate; }
+
 void AppConfig::setAutoHide(bool b) { m_AutoHide = b; }
 
 bool AppConfig::getAutoHide() { return m_AutoHide; }

src/gui/src/AppConfig.h

@@ -91,6 +91,9 @@ class AppConfig: public QObject
         void setCryptoEnabled(bool e);
         bool getCryptoEnabled() const;
 
+        void setRequireClientCertificate(bool e);
+        bool getRequireClientCertificate() const;
+
         void setAutoHide(bool b);
         bool getAutoHide();
 
@@ -132,6 +135,7 @@ protected:
         ElevateMode m_ElevateMode;
         bool m_AutoConfigPrompted;
         bool m_CryptoEnabled;
+        bool m_RequireClientCertificate = false;
         bool m_AutoHide;
         bool m_AutoStart;
         bool m_MinimizeToTray;

src/gui/src/FingerprintAcceptDialog.cpp

@@ -0,0 +1,65 @@
+/*
+    barrier -- mouse and keyboard sharing utility
+    Copyright (C) Barrier contributors
+
+    This package is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    found in the file LICENSE that should have accompanied this file.
+
+    This package 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 for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "FingerprintAcceptDialog.h"
+#include "ui_FingerprintAcceptDialog.h"
+#include "net/SecureUtils.h"
+
+FingerprintAcceptDialog::FingerprintAcceptDialog(QWidget *parent,
+                                                 BarrierType type,
+                                                 const barrier::FingerprintData& fingerprint_sha1,
+                                                 const barrier::FingerprintData& fingerprint_sha256) :
+    QDialog(parent),
+    ui_{std::make_unique<Ui::FingerprintAcceptDialog>()}
+{
+    ui_->setupUi(this);
+
+    if (type == BarrierType::Server) {
+        ui_->label_sha1->hide();
+        ui_->label_sha1_fingerprint_full->hide();
+    } else {
+        ui_->label_sha1_fingerprint_full->setText(
+                QString::fromStdString(barrier::format_ssl_fingerprint(fingerprint_sha1.data)));
+    }
+
+    ui_->label_sha256_fingerprint_full->setText(
+            QString::fromStdString(barrier::format_ssl_fingerprint_columns(fingerprint_sha256.data)));
+    ui_->label_sha256_fingerprint_randomart->setText(
+            QString::fromStdString(barrier::create_fingerprint_randomart(fingerprint_sha256.data)));
+
+    QString explanation;
+    if (type == BarrierType::Server) {
+        explanation = tr("This is a client fingerprint. You should compare this "
+                         "fingerprint to the one on your client's screen. If the "
+                         "two don't match exactly, then it's probably not the client "
+                         "you're expecting (it could be a malicious user).\n\n"
+                         "To automatically trust this fingerprint for future "
+                         "connections, click Yes. To reject this fingerprint and "
+                         "disconnect the client, click No.");
+    } else {
+        explanation = tr("This is a server fingerprint. You should compare this "
+                         "fingerprint to the one on your server's screen. If the "
+                         "two don't match exactly, then it's probably not the server "
+                         "you're expecting (it could be a malicious user).\n\n"
+                         "To automatically trust this fingerprint for future "
+                         "connections, click Yes. To reject this fingerprint and "
+                         "disconnect from the server, click No.");
+    }
+    ui_->label_explanation->setText(explanation);
+}
+
+FingerprintAcceptDialog::~FingerprintAcceptDialog() = default;

src/gui/src/FingerprintAcceptDialog.h

@@ -0,0 +1,45 @@
+/*
+    barrier -- mouse and keyboard sharing utility
+    Copyright (C) Barrier contributors
+
+    This package is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    found in the file LICENSE that should have accompanied this file.
+
+    This package 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 for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef BARRIER_GUI_FINGERPRINT_ACCEPT_DIALOG_H
+#define BARRIER_GUI_FINGERPRINT_ACCEPT_DIALOG_H
+
+#include "net/FingerprintData.h"
+#include "barrier/BarrierType.h"
+#include <QDialog>
+#include <memory>
+
+namespace Ui {
+class FingerprintAcceptDialog;
+}
+
+class FingerprintAcceptDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit FingerprintAcceptDialog(QWidget* parent,
+                                     BarrierType type,
+                                     const barrier::FingerprintData& fingerprint_sha1,
+                                     const barrier::FingerprintData& fingerprint_sha256);
+    ~FingerprintAcceptDialog() override;
+
+private:
+    std::unique_ptr<Ui::FingerprintAcceptDialog> ui_;
+};
+
+#endif // BARRIER_GUI_FINGERPRINT_ACCEPT_DIALOG_H

src/gui/src/FingerprintAcceptDialog.ui

@@ -0,0 +1,174 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>FingerprintAcceptDialog</class>
+ <widget class="QDialog" name="FingerprintAcceptDialog">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>600</width>
+    <height>400</height>
+   </rect>
+  </property>
+  <property name="sizePolicy">
+   <sizepolicy hsizetype="Ignored" vsizetype="Preferred">
+    <horstretch>0</horstretch>
+    <verstretch>0</verstretch>
+   </sizepolicy>
+  </property>
+  <property name="windowTitle">
+   <string>Security question</string>
+  </property>
+  <layout class="QGridLayout" name="gridLayout">
+   <property name="sizeConstraint">
+    <enum>QLayout::SetFixedSize</enum>
+   </property>
+   <item row="6" column="0" colspan="2">
+    <widget class="QDialogButtonBox" name="buttonBox">
+     <property name="orientation">
+      <enum>Qt::Horizontal</enum>
+     </property>
+     <property name="standardButtons">
+      <set>QDialogButtonBox::No|QDialogButtonBox::Yes</set>
+     </property>
+    </widget>
+   </item>
+   <item row="3" column="0" colspan="2">
+    <widget class="QLabel" name="label_sha1">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Preferred" vsizetype="Minimum">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="text">
+      <string>SHA1 (deprecated, compare to old servers only)</string>
+     </property>
+    </widget>
+   </item>
+   <item row="5" column="0" colspan="2">
+    <widget class="QLabel" name="label_explanation">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Preferred" vsizetype="Minimum">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="text">
+      <string/>
+     </property>
+     <property name="wordWrap">
+      <bool>true</bool>
+     </property>
+     <property name="margin">
+      <number>10</number>
+     </property>
+    </widget>
+   </item>
+   <item row="4" column="0" colspan="2">
+    <widget class="QLabel" name="label_sha1_fingerprint_full">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Preferred" vsizetype="Minimum">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="text">
+      <string/>
+     </property>
+     <property name="textInteractionFlags">
+      <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
+     </property>
+    </widget>
+   </item>
+   <item row="0" column="0" colspan="2">
+    <widget class="QLabel" name="label_title">
+     <property name="text">
+      <string>Do you trust this fingerprint?</string>
+     </property>
+    </widget>
+   </item>
+   <item row="2" column="1">
+    <widget class="QLabel" name="label_sha256_fingerprint_randomart">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Minimum" vsizetype="Minimum">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="font">
+      <font>
+       <family>Courier</family>
+       <weight>75</weight>
+       <bold>true</bold>
+      </font>
+     </property>
+     <property name="text">
+      <string/>
+     </property>
+     <property name="alignment">
+      <set>Qt::AlignCenter</set>
+     </property>
+     <property name="textInteractionFlags">
+      <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
+     </property>
+    </widget>
+   </item>
+   <item row="2" column="0">
+    <widget class="QLabel" name="label_sha256_fingerprint_full">
+     <property name="text">
+      <string/>
+     </property>
+     <property name="alignment">
+      <set>Qt::AlignCenter</set>
+     </property>
+     <property name="textInteractionFlags">
+      <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
+     </property>
+    </widget>
+   </item>
+   <item row="1" column="0" colspan="2">
+    <widget class="QLabel" name="label_sha256">
+     <property name="text">
+      <string>SHA256:</string>
+     </property>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>accepted()</signal>
+   <receiver>FingerprintAcceptDialog</receiver>
+   <slot>accept()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>248</x>
+     <y>254</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>157</x>
+     <y>274</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>rejected()</signal>
+   <receiver>FingerprintAcceptDialog</receiver>
+   <slot>reject()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>316</x>
+     <y>260</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>286</x>
+     <y>274</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+</ui>

src/gui/src/MainWindow.cpp

@@ -26,6 +26,7 @@
 #include "ZeroconfService.h"
 #include "DataDownloader.h"
 #include "CommandProcess.h"
+#include "FingerprintAcceptDialog.h"
 #include "QUtility.h"
 #include "ProcessorArch.h"
 #include "SslCertificate.h"
@@ -427,7 +428,7 @@ void MainWindow::checkConnected(const QString& line)
 
 void MainWindow::checkFingerprint(const QString& line)
 {
-    QRegExp fingerprintRegex(".*server fingerprint \\(SHA1\\): ([A-F0-9:]+) \\(SHA256\\): ([A-F0-9:]+)");
+    QRegExp fingerprintRegex(".*peer fingerprint \\(SHA1\\): ([A-F0-9:]+) \\(SHA256\\): ([A-F0-9:]+)");
     if (!fingerprintRegex.exactMatch(line)) {
         return;
     }
@@ -442,7 +443,16 @@ void MainWindow::checkFingerprint(const QString& line)
         barrier::string::from_hex(fingerprintRegex.cap(2).toStdString())
     };
 
-    auto db_path = barrier::DataDirectories::trusted_servers_ssl_fingerprints_path();
+    bool is_client = barrier_type() == BarrierType::Client;
+
+    auto db_path = is_client
+            ? barrier::DataDirectories::trusted_servers_ssl_fingerprints_path()
+            : barrier::DataDirectories::trusted_clients_ssl_fingerprints_path();
+
+    auto db_dir = db_path.parent_path();
+    if (!barrier::fs::exists(db_dir)) {
+        barrier::fs::create_directories(db_dir);
+    }
 
     // We compare only SHA256 fingerprints, but show both SHA1 and SHA256 so that the users can
     // still verify fingerprints on old Barrier servers. This way the only time when we are exposed
@@ -456,37 +466,20 @@ void MainWindow::checkFingerprint(const QString& line)
     static bool messageBoxAlreadyShown = false;
 
     if (!messageBoxAlreadyShown) {
+        if (is_client) {
             stopBarrier();
+        }
 
         messageBoxAlreadyShown = true;
-        QMessageBox::StandardButton fingerprintReply =
+        FingerprintAcceptDialog dialog{this, barrier_type(), fingerprint_sha1, fingerprint_sha256};
-            QMessageBox::information(
+        if (dialog.exec() == QDialog::Accepted) {
-            this, tr("Security question"),
-            tr("Do you trust this fingerprint?\n\n"
-               "SHA256:\n"
-               "%1\n"
-               "%2\n\n"
-               "SHA1 (obsolete, when using old Barrier server):\n"
-               "%3\n\n"
-               "This is a server fingerprint. You should compare this "
-               "fingerprint to the one on your server's screen. If the "
-               "two don't match exactly, then it's probably not the server "
-               "you're expecting (it could be a malicious user).\n\n"
-               "To automatically trust this fingerprint for future "
-               "connections, click Yes. To reject this fingerprint and "
-               "disconnect from the server, click No.")
-            .arg(QString::fromStdString(barrier::format_ssl_fingerprint(fingerprint_sha256.data)))
-            .arg(QString::fromStdString(
-                     barrier::create_fingerprint_randomart(fingerprint_sha256.data)))
-            .arg(QString::fromStdString(barrier::format_ssl_fingerprint(fingerprint_sha1.data))),
-            QMessageBox::Yes | QMessageBox::No);
-
-        if (fingerprintReply == QMessageBox::Yes) {
             // restart core process after trusting fingerprint.
             db.add_trusted(fingerprint_sha256);
             db.write(db_path);
+            if (is_client) {
                 startBarrier();
             }
+        }
 
         messageBoxAlreadyShown = false;
     }
@@ -567,8 +560,8 @@ void MainWindow::startBarrier()
     args << "--profile-dir" << QString::fromStdString("\"" + barrier::DataDirectories::profile().u8string() + "\"");
 #endif
 
-    if ((barrierType() == barrierClient && !clientArgs(args, app))
+    if ((barrier_type() == BarrierType::Client && !clientArgs(args, app))
-        || (barrierType() == barrierServer && !serverArgs(args, app)))
+        || (barrier_type() == BarrierType::Server && !serverArgs(args, app)))
     {
         stopBarrier();
         return;
@@ -583,7 +576,7 @@ void MainWindow::startBarrier()
 
     m_pLogWindow->startNewInstance();
 
-    appendLogInfo("starting " + QString(barrierType() == barrierServer ? "server" : "client"));
+    appendLogInfo("starting " + QString(barrier_type() == BarrierType::Server ? "server" : "client"));
 
     qDebug() << args;
 
@@ -693,6 +686,11 @@ QString MainWindow::configFilename()
     return filename;
 }
 
+BarrierType MainWindow::barrier_type() const
+{
+    return m_pGroupClient->isChecked() ? BarrierType::Client : BarrierType::Server;
+}
+
 QString MainWindow::address()
 {
     QString address = appConfig().networkInterface();
@@ -729,6 +727,10 @@ bool MainWindow::serverArgs(QStringList& args, QString& app)
         args << "--log" << appConfig().logFilenameCmd();
     }
 
+    if (!appConfig().getRequireClientCertificate()) {
+        args << "--disable-client-cert-checking";
+    }
+
     QString configFilename = this->configFilename();
 #if defined(Q_OS_WIN)
     // wrap in quotes in case username contains spaces.
@@ -983,7 +985,7 @@ void MainWindow::updateZeroconfService()
                 m_pZeroconfService = NULL;
             }
 
-            if (m_AppConfig->autoConfig() || barrierType() == barrierServer) {
+            if (m_AppConfig->autoConfig() || barrier_type() == BarrierType::Server) {
                 m_pZeroconfService = new ZeroconfService(this);
             }
         }

src/gui/src/MainWindow.h

@@ -20,6 +20,8 @@
 
 #define MAINWINDOW__H
 
+#include "barrier/BarrierType.h"
+
 #include <QMainWindow>
 #include <QSystemTrayIcon>
 #include <QSettings>
@@ -76,12 +78,6 @@ class MainWindow : public QMainWindow, public Ui::MainWindowBase
             barrierTransfering
         };
 
-        enum qBarrierType
-        {
-            barrierClient,
-            barrierServer
-        };
-
         enum qLevel {
             Error,
             Info
@@ -98,7 +94,7 @@ class MainWindow : public QMainWindow, public Ui::MainWindowBase
 
     public:
         void setVisible(bool visible);
-        int barrierType() const { return m_pGroupClient->isChecked() ? barrierClient : barrierServer; }
+        BarrierType barrier_type() const;
         int barrierState() const { return m_BarrierState; }
         QString hostname() const { return m_pLineEditHostname->text(); }
         QString configFilename();

src/gui/src/MainWindowBase.ui

@@ -55,107 +55,6 @@
          </item>
         </layout>
        </item>
-       <item>
-        <layout class="QHBoxLayout" name="horizontalLayout_3">
-         <item>
-          <widget class="QLabel" name="m_pLabelFingerprint">
-           <property name="sizePolicy">
-            <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
-             <horstretch>0</horstretch>
-             <verstretch>0</verstretch>
-            </sizepolicy>
-           </property>
-           <property name="text">
-            <string>SSL Fingerprint:</string>
-           </property>
-          </widget>
-         </item>
-         <item>
-          <widget class="QLabel" name="m_pLabelLocalFingerprint">
-           <property name="text">
-            <string/>
-           </property>
-           <property name="textFormat">
-            <enum>Qt::PlainText</enum>
-           </property>
-          </widget>
-         </item>
-         <item>
-          <widget class="QToolButton" name="toolbutton_show_fingerprint">
-           <property name="text">
-            <string>...</string>
-           </property>
-           <property name="arrowType">
-            <enum>Qt::DownArrow</enum>
-           </property>
-          </widget>
-         </item>
-        </layout>
-       </item>
-       <item>
-        <widget class="QFrame" name="frame_fingerprint_details">
-         <property name="frameShape">
-          <enum>QFrame::StyledPanel</enum>
-         </property>
-         <property name="frameShadow">
-          <enum>QFrame::Raised</enum>
-         </property>
-         <layout class="QGridLayout" name="gridLayout">
-          <property name="sizeConstraint">
-           <enum>QLayout::SetMinimumSize</enum>
-          </property>
-          <item row="1" column="1">
-           <widget class="QLabel" name="label_sha256_randomart">
-            <property name="font">
-             <font>
-              <family>Courier</family>
-             </font>
-            </property>
-            <property name="text">
-             <string/>
-            </property>
-            <property name="textInteractionFlags">
-             <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
-            </property>
-           </widget>
-          </item>
-          <item row="2" column="0" colspan="2">
-           <widget class="QLabel" name="label_sha1">
-            <property name="text">
-             <string>SHA1 (deprecated, compare to old clients only):</string>
-            </property>
-           </widget>
-          </item>
-          <item row="3" column="0" colspan="2">
-           <widget class="QLabel" name="label_sha1_fingerprint_full">
-            <property name="text">
-             <string/>
-            </property>
-            <property name="textInteractionFlags">
-             <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
-            </property>
-           </widget>
-          </item>
-          <item row="0" column="0" colspan="2">
-           <widget class="QLabel" name="label_sha256">
-            <property name="text">
-             <string>SHA256:</string>
-            </property>
-           </widget>
-          </item>
-          <item row="1" column="0">
-           <widget class="QLabel" name="label_sha256_fingerprint_full">
-            <property name="text">
-             <string/>
-            </property>
-            <property name="textInteractionFlags">
-             <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
-            </property>
-           </widget>
-          </item>
-         </layout>
-        </widget>
-       </item>
        <item>
         <widget class="QRadioButton" name="m_pRadioInternalConfig">
          <property name="text">
@@ -305,6 +204,107 @@
       </layout>
      </widget>
     </item>
+    <item>
+     <layout class="QHBoxLayout" name="horizontalLayout_3">
+      <item>
+       <widget class="QLabel" name="m_pLabelFingerprint">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>SSL Fingerprint:</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLabel" name="m_pLabelLocalFingerprint">
+        <property name="text">
+         <string/>
+        </property>
+        <property name="textFormat">
+         <enum>Qt::PlainText</enum>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QToolButton" name="toolbutton_show_fingerprint">
+        <property name="text">
+         <string>...</string>
+        </property>
+        <property name="arrowType">
+         <enum>Qt::DownArrow</enum>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </item>
+    <item>
+     <widget class="QFrame" name="frame_fingerprint_details">
+      <property name="frameShape">
+       <enum>QFrame::StyledPanel</enum>
+      </property>
+      <property name="frameShadow">
+       <enum>QFrame::Raised</enum>
+      </property>
+      <layout class="QGridLayout" name="gridLayout">
+       <property name="sizeConstraint">
+        <enum>QLayout::SetMinimumSize</enum>
+       </property>
+       <item row="1" column="1">
+        <widget class="QLabel" name="label_sha256_randomart">
+         <property name="font">
+          <font>
+           <family>Courier</family>
+          </font>
+         </property>
+         <property name="text">
+          <string/>
+         </property>
+         <property name="textInteractionFlags">
+          <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
+         </property>
+        </widget>
+       </item>
+       <item row="2" column="0" colspan="2">
+        <widget class="QLabel" name="label_sha1">
+         <property name="text">
+          <string>SHA1 (deprecated, compare to old clients and servers only):</string>
+         </property>
+        </widget>
+       </item>
+       <item row="3" column="0" colspan="2">
+        <widget class="QLabel" name="label_sha1_fingerprint_full">
+         <property name="text">
+          <string/>
+         </property>
+         <property name="textInteractionFlags">
+          <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
+         </property>
+        </widget>
+       </item>
+       <item row="0" column="0" colspan="2">
+        <widget class="QLabel" name="label_sha256">
+         <property name="text">
+          <string>SHA256:</string>
+         </property>
+        </widget>
+       </item>
+       <item row="1" column="0">
+        <widget class="QLabel" name="label_sha256_fingerprint_full">
+         <property name="text">
+          <string/>
+         </property>
+         <property name="textInteractionFlags">
+          <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByMouse</set>
+         </property>
+        </widget>
+       </item>
+      </layout>
+     </widget>
+    </item>
     <item>
      <layout class="QHBoxLayout" name="horizontalLayout">
       <property name="sizeConstraint">

src/gui/src/SettingsDialog.cpp

@@ -51,6 +51,7 @@ SettingsDialog::SettingsDialog(QWidget* parent, AppConfig& config) :
     m_pCheckBoxAutoStart->setChecked(appConfig().getAutoStart());
     m_pCheckBoxMinimizeToTray->setChecked(appConfig().getMinimizeToTray());
     m_pCheckBoxEnableCrypto->setChecked(m_appConfig.getCryptoEnabled());
+    checkbox_require_client_certificate->setChecked(m_appConfig.getRequireClientCertificate());
 
 #if defined(Q_OS_WIN)
     m_pComboElevate->setCurrentIndex(static_cast<int>(appConfig().elevateMode()));
@@ -67,6 +68,7 @@ void SettingsDialog::accept()
     m_appConfig.setPort(m_pSpinBoxPort->value());
     m_appConfig.setNetworkInterface(m_pLineEditInterface->text());
     m_appConfig.setCryptoEnabled(m_pCheckBoxEnableCrypto->isChecked());
+    m_appConfig.setRequireClientCertificate(checkbox_require_client_certificate->isChecked());
     m_appConfig.setLogLevel(m_pComboLogLevel->currentIndex());
     m_appConfig.setLogToFile(m_pCheckBoxLogToFile->isChecked());
     m_appConfig.setLogFilename(m_pLineEditLogFilename->text());

src/gui/src/SettingsDialogBase.ui

@@ -142,6 +142,16 @@
       <string>Networking</string>
      </property>
      <layout class="QGridLayout" name="gridLayout_3">
+      <item row="1" column="0">
+       <widget class="QLabel" name="m_pLabel_21">
+        <property name="text">
+         <string>&amp;Address:</string>
+        </property>
+        <property name="buddy">
+         <cstring>m_pLineEditInterface</cstring>
+        </property>
+       </widget>
+      </item>
       <item row="0" column="0">
        <widget class="QLabel" name="m_pLabel_20">
         <property name="text">
@@ -171,16 +181,6 @@
         </property>
        </widget>
       </item>
-      <item row="1" column="0">
-       <widget class="QLabel" name="m_pLabel_21">
-        <property name="text">
-         <string>&amp;Address:</string>
-        </property>
-        <property name="buddy">
-         <cstring>m_pLineEditInterface</cstring>
-        </property>
-       </widget>
-      </item>
       <item row="1" column="1">
        <widget class="QLineEdit" name="m_pLineEditInterface">
         <property name="enabled">
@@ -188,13 +188,20 @@
         </property>
        </widget>
       </item>
-      <item row="2" column="0">
+      <item row="2" column="0" colspan="2">
        <widget class="QCheckBox" name="m_pCheckBoxEnableCrypto">
         <property name="text">
          <string>Enable &amp;SSL</string>
         </property>
        </widget>
       </item>
+      <item row="3" column="0" colspan="2">
+       <widget class="QCheckBox" name="checkbox_require_client_certificate">
+        <property name="text">
+         <string>Require client certificate</string>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>
@@ -216,19 +223,20 @@
       <bool>false</bool>
      </property>
      <layout class="QGridLayout" name="gridLayout_2">
-      <item row="0" column="0">
+      <item row="1" column="0">
-       <widget class="QLabel" name="m_pLabel_3">
+       <widget class="QCheckBox" name="m_pCheckBoxLogToFile">
-        <property name="minimumSize">
+        <property name="text">
-         <size>
+         <string>Log to file:</string>
-          <width>75</width>
+        </property>
-          <height>0</height>
+       </widget>
-         </size>
+      </item>
+      <item row="1" column="2">
+       <widget class="QPushButton" name="m_pButtonBrowseLog">
+        <property name="enabled">
+         <bool>false</bool>
         </property>
         <property name="text">
-         <string>&amp;Logging level:</string>
+         <string>Browse...</string>
-        </property>
-        <property name="buddy">
-         <cstring>m_pComboLogLevel</cstring>
         </property>
        </widget>
       </item>
@@ -271,10 +279,19 @@
         </item>
        </widget>
       </item>
-      <item row="1" column="0">
+      <item row="0" column="0">
-       <widget class="QCheckBox" name="m_pCheckBoxLogToFile">
+       <widget class="QLabel" name="m_pLabel_3">
+        <property name="minimumSize">
+         <size>
+          <width>75</width>
+          <height>0</height>
+         </size>
+        </property>
         <property name="text">
-         <string>Log to file:</string>
+         <string>&amp;Logging level:</string>
+        </property>
+        <property name="buddy">
+         <cstring>m_pComboLogLevel</cstring>
         </property>
        </widget>
       </item>
@@ -285,16 +302,6 @@
         </property>
        </widget>
       </item>
-      <item row="1" column="2">
-       <widget class="QPushButton" name="m_pButtonBrowseLog">
-        <property name="enabled">
-         <bool>false</bool>
-        </property>
-        <property name="text">
-         <string>Browse...</string>
-        </property>
-       </widget>
-      </item>
      </layout>
     </widget>
    </item>

src/gui/src/SslCertificate.cpp

@@ -65,6 +65,11 @@ void SslCertificate::generate_fingerprint(const barrier::fs::path& cert_path)
 {
     try {
         auto local_path = barrier::DataDirectories::local_ssl_fingerprints_path();
+        auto local_dir = local_path.parent_path();
+        if (!barrier::fs::exists(local_dir)) {
+            barrier::fs::create_directories(local_dir);
+        }
+
         barrier::FingerprintDatabase db;
         db.add_trusted(barrier::get_pem_file_cert_fingerprint(cert_path.u8string(),
                                                               barrier::FingerprintType::SHA1));

src/gui/src/ZeroconfService.cpp

@@ -66,7 +66,7 @@ ZeroconfService::ZeroconfService(MainWindow* mainWindow) :
     m_ServiceRegistered(false)
 {
     silence_avahi_warning();
-    if (m_pMainWindow->barrierType() == MainWindow::barrierServer) {
+    if (m_pMainWindow->barrier_type() == BarrierType::Server) {
         if (registerService(true)) {
             m_pZeroconfBrowser = new ZeroconfBrowser(this);
             connect(m_pZeroconfBrowser, SIGNAL(

src/lib/barrier/ArgParser.cpp

@@ -65,7 +65,9 @@ ArgParser::parseServerArgs(ServerArgs& args, int argc, const char* const* argv)
             // save screen change script path
             args.m_screenChangeScript = argv[++i];
         }
-        else {
+        else if (isArg(i, argc, argv, nullptr, "--disable-client-cert-checking")) {
+            args.check_client_certificates = false;
+        } else {
             LOG((CLOG_PRINT "%s: unrecognized option `%s'" BYE, args.m_exename.c_str(), argv[i], args.m_exename.c_str()));
             return false;
         }

src/lib/barrier/BarrierType.h

@@ -0,0 +1,26 @@
+/*
+    barrier -- mouse and keyboard sharing utility
+    Copyright (C) Barrier contributors
+
+    This package is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    found in the file LICENSE that should have accompanied this file.
+
+    This package 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 for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef BARRIER_LIB_BARRIER_BARRIER_TYPE_H
+#define BARRIER_LIB_BARRIER_BARRIER_TYPE_H
+
+enum class BarrierType {
+    Server,
+    Client
+};
+
+#endif // BARRIER_LIB_BARRIER_BARRIER_TYPE_H

src/lib/barrier/ServerApp.cpp

@@ -148,7 +148,10 @@ ServerApp::help()
            << "Options:\n"
            << "  -a, --address <address>  listen for clients on the given address.\n"
            << "  -c, --config <pathname>  use the named configuration file instead.\n"
-           << HELP_COMMON_INFO_1 << WINAPI_INFO << HELP_SYS_INFO << HELP_COMMON_INFO_2 << "\n"
+           << HELP_COMMON_INFO_1
+           << "      --disable-client-cert-checking disable client SSL certificate \n"
+              "                                     checking (deprecated)\n"
+           << WINAPI_INFO << HELP_SYS_INFO << HELP_COMMON_INFO_2 << "\n"
            << "Default options are marked with a *\n"
            << "\n"
            << "The argument for --address is of the form: [<hostname>][:<port>].  The\n"
@@ -655,11 +658,18 @@ ServerApp::handleResume(const Event&, void*)
 ClientListener*
 ServerApp::openClientListener(const NetworkAddress& address)
 {
+    auto security_level = ConnectionSecurityLevel::PLAINTEXT;
+    if (args().m_enableCrypto) {
+        security_level = ConnectionSecurityLevel::ENCRYPTED;
+        if (args().check_client_certificates) {
+            security_level = ConnectionSecurityLevel::ENCRYPTED_AUTHENTICATED;
+        }
+    }
+
     ClientListener* listen = new ClientListener(
         address,
         new TCPSocketFactory(m_events, getSocketMultiplexer()),
-        m_events,
+        m_events, security_level);
-        args().m_enableCrypto);
 
     m_events->adoptHandler(
         m_events->forClientListener().connected(), listen,

src/lib/barrier/ServerArgs.h

@@ -30,4 +30,5 @@ public:
     String                m_configFile;
     Config*                m_config;
     String                m_screenChangeScript;
+    bool check_client_certificates = true;
 };

src/lib/client/Client.cpp

@@ -127,6 +127,12 @@ Client::connect()
         return;
     }
 
+    auto security_level = ConnectionSecurityLevel::PLAINTEXT;
+    if (m_useSecureNetwork) {
+        // client always authenticates server
+        security_level = ConnectionSecurityLevel::ENCRYPTED_AUTHENTICATED;
+    }
+
     try {
         // resolve the server hostname.  do this every time we connect
         // in case we couldn't resolve the address earlier or the address
@@ -145,9 +151,8 @@ Client::connect()
         }
 
         // create the socket
-        IDataSocket* socket = m_socketFactory->create(
+        IDataSocket* socket = m_socketFactory->create(ARCH->getAddrFamily(m_serverAddress.getAddress()),
-                ARCH->getAddrFamily(m_serverAddress.getAddress()),
+                                                      security_level);
-                m_useSecureNetwork);
         m_socket = dynamic_cast<TCPSocket*>(socket);
 
         // filter socket messages, including a packetizing filter

src/lib/net/ConnectionSecurityLevel.h

@@ -0,0 +1,27 @@
+/*
+    barrier -- mouse and keyboard sharing utility
+    Copyright (C) Barrier contributors
+
+    This package is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    found in the file LICENSE that should have accompanied this file.
+
+    This package 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 for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef BARRIER_LIB_NET_CONNECTION_SECURITY_LEVEL_H
+#define BARRIER_LIB_NET_CONNECTION_SECURITY_LEVEL_H
+
+enum class ConnectionSecurityLevel {
+    PLAINTEXT,
+    ENCRYPTED,
+    ENCRYPTED_AUTHENTICATED
+};
+
+#endif // BARRIER_LIB_NET_CONNECTION_SECURITY_LEVEL_H

src/lib/net/ISocketFactory.h

@@ -20,6 +20,7 @@
 
 #include "common/IInterface.h"
 #include "arch/IArchNetwork.h"
+#include "net/ConnectionSecurityLevel.h"
 
 class IDataSocket;
 class IListenSocket;
@@ -35,14 +36,12 @@ public:
     //@{
 
     //! Create data socket
-    virtual IDataSocket*    create(
+    virtual IDataSocket* create(IArchNetwork::EAddressFamily family,
-            IArchNetwork::EAddressFamily family,
+                                ConnectionSecurityLevel security_level) const = 0;
-            bool secure) const = 0;
 
     //! Create listen socket
-    virtual IListenSocket*    createListen(
+    virtual IListenSocket* createListen(IArchNetwork::EAddressFamily family,
-            IArchNetwork::EAddressFamily family,
+                                        ConnectionSecurityLevel security_level) const = 0;
-            bool secure) const = 0;
 
     //@}
 };

src/lib/net/SecureListenSocket.cpp

@@ -25,11 +25,11 @@
 #include "common/DataDirectories.h"
 #include "base/String.h"
 
-SecureListenSocket::SecureListenSocket(
+SecureListenSocket::SecureListenSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer,
-        IEventQueue* events,
+                                       IArchNetwork::EAddressFamily family,
-        SocketMultiplexer* socketMultiplexer,
+                                       ConnectionSecurityLevel security_level) :
-        IArchNetwork::EAddressFamily family) :
+    TCPListenSocket(events, socketMultiplexer, family),
-    TCPListenSocket(events, socketMultiplexer, family)
+    security_level_{security_level}
 {
 }
 
@@ -38,10 +38,8 @@ SecureListenSocket::accept()
 {
     SecureSocket* socket = NULL;
     try {
-        socket = new SecureSocket(
+        socket = new SecureSocket(m_events, m_socketMultiplexer,
-                        m_events,
+                                  ARCH->acceptSocket(m_socket, NULL), security_level_);
-                        m_socketMultiplexer,
-                        ARCH->acceptSocket(m_socket, NULL));
         socket->initSsl(true);
 
         if (socket != NULL) {

src/lib/net/SecureListenSocket.h

@@ -19,6 +19,7 @@
 
 #include "net/TCPListenSocket.h"
 #include "common/stdset.h"
+#include "ConnectionSecurityLevel.h"
 
 class IEventQueue;
 class SocketMultiplexer;
@@ -26,11 +27,13 @@ class IDataSocket;
 
 class SecureListenSocket : public TCPListenSocket {
 public:
-    SecureListenSocket(IEventQueue* events,
+    SecureListenSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer,
-        SocketMultiplexer* socketMultiplexer,
+                       IArchNetwork::EAddressFamily family,
-        IArchNetwork::EAddressFamily family);
+                       ConnectionSecurityLevel security_level);
 
     // IListenSocket overrides
     virtual IDataSocket*
                         accept();
+private:
+    ConnectionSecurityLevel security_level_;
 };

src/lib/net/SecureSocket.cpp

@@ -54,25 +54,24 @@ struct Ssl {
     SSL*        m_ssl;
 };
 
-SecureSocket::SecureSocket(
+SecureSocket::SecureSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer,
-        IEventQueue* events,
+                           IArchNetwork::EAddressFamily family,
-        SocketMultiplexer* socketMultiplexer,
+                           ConnectionSecurityLevel security_level) :
-        IArchNetwork::EAddressFamily family) :
     TCPSocket(events, socketMultiplexer, family),
     m_ssl(nullptr),
     m_secureReady(false),
-    m_fatal(false)
+    m_fatal(false),
+    security_level_{security_level}
 {
 }
 
-SecureSocket::SecureSocket(
+SecureSocket::SecureSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer,
-        IEventQueue* events,
+                           ArchSocket socket, ConnectionSecurityLevel security_level) :
-        SocketMultiplexer* socketMultiplexer,
-        ArchSocket socket) :
     TCPSocket(events, socketMultiplexer, socket),
     m_ssl(nullptr),
     m_secureReady(false),
-    m_fatal(false)
+    m_fatal(false),
+    security_level_{security_level}
 {
 }
 
@@ -362,6 +361,11 @@ bool SecureSocket::load_certificates(const barrier::fs::path& path)
     return true;
 }
 
+static int cert_verify_ignore_callback(X509_STORE_CTX*, void*)
+{
+    return 1;
+}
+
 void
 SecureSocket::initContext(bool server)
 {
@@ -397,6 +401,14 @@ SecureSocket::initContext(bool server)
     if (m_ssl->m_context == NULL) {
         showError("");
     }
+
+    if (security_level_ == ConnectionSecurityLevel::ENCRYPTED_AUTHENTICATED) {
+        // We want to ask for peer certificate, but not verify it. If we don't ask for peer
+        // certificate, e.g. client won't send it.
+        SSL_CTX_set_verify(m_ssl->m_context, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
+                           nullptr);
+        SSL_CTX_set_cert_verify_callback(m_ssl->m_context, cert_verify_ignore_callback, nullptr);
+    }
 }
 
 void
@@ -437,6 +449,24 @@ SecureSocket::secureAccept(int socket)
 
     // If not fatal and no retry, state is good
     if (retry == 0) {
+        if (security_level_ == ConnectionSecurityLevel::ENCRYPTED_AUTHENTICATED) {
+            if (verify_cert_fingerprint(
+                        barrier::DataDirectories::trusted_clients_ssl_fingerprints_path())) {
+                LOG((CLOG_INFO "accepted secure socket"));
+                if (!ensure_peer_certificate()) {
+                    retry = 0;
+                    disconnect();
+                    return -1;// Cert fail, error
+                }
+            }
+            else {
+                LOG((CLOG_ERR "failed to verify server certificate fingerprint"));
+                retry = 0;
+                disconnect();
+                return -1; // Fingerprint failed, error
+            }
+        }
+
         m_secureReady = true;
         LOG((CLOG_INFO "accepted secure socket"));
         if (CLOG->getFilter() >= kDEBUG1) {
@@ -462,6 +492,12 @@ SecureSocket::secureAccept(int socket)
 int
 SecureSocket::secureConnect(int socket)
 {
+    if (!load_certificates(barrier::DataDirectories::ssl_certificate_path())) {
+        LOG((CLOG_ERR "could not load client certificates"));
+        // FIXME: this is fatal error, but we current don't disconnect because whole logic in this
+        // function needs to be cleaned up
+    }
+
     createSSL();
 
     // attach the socket descriptor
@@ -491,9 +527,9 @@ SecureSocket::secureConnect(int socket)
     retry = 0;
     // No error, set ready, process and return ok
     m_secureReady = true;
-    if (verifyCertFingerprint()) {
+    if (verify_cert_fingerprint(barrier::DataDirectories::trusted_servers_ssl_fingerprints_path())) {
         LOG((CLOG_INFO "connected to secure socket"));
-        if (!showCertificate()) {
+        if (!ensure_peer_certificate()) {
             disconnect();
             return -1;// Cert fail, error
         }
@@ -512,7 +548,7 @@ SecureSocket::secureConnect(int socket)
 }
 
 bool
-SecureSocket::showCertificate()
+SecureSocket::ensure_peer_certificate()
 {
     X509* cert;
     char* line;
@@ -521,12 +557,12 @@ SecureSocket::showCertificate()
     cert = SSL_get_peer_certificate(m_ssl->m_ssl);
     if (cert != NULL) {
         line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);
-        LOG((CLOG_INFO "server ssl certificate info: %s", line));
+        LOG((CLOG_INFO "peer ssl certificate info: %s", line));
         OPENSSL_free(line);
         X509_free(cert);
     }
     else {
-        showError("server has no ssl certificate");
+        showError("peer has no ssl certificate");
         return false;
     }
 
@@ -649,8 +685,7 @@ SecureSocket::disconnect()
     sendEvent(getEvents()->forIStream().inputShutdown());
 }
 
-bool
+bool SecureSocket::verify_cert_fingerprint(const barrier::fs::path& fingerprint_db_path)
-SecureSocket::verifyCertFingerprint()
 {
     // calculate received certificate fingerprint
     barrier::FingerprintData fingerprint_sha1, fingerprint_sha256;
@@ -666,12 +701,10 @@ SecureSocket::verifyCertFingerprint()
     }
 
     // note: the GUI parses the following two lines of logs, don't change unnecessarily
-    LOG((CLOG_NOTE "server fingerprint (SHA1): %s (SHA256): %s",
+    LOG((CLOG_NOTE "peer fingerprint (SHA1): %s (SHA256): %s",
          barrier::format_ssl_fingerprint(fingerprint_sha1.data).c_str(),
          barrier::format_ssl_fingerprint(fingerprint_sha256.data).c_str()));
 
-    auto fingerprint_db_path = barrier::DataDirectories::trusted_servers_ssl_fingerprints_path();
-
     // Provide debug hint as to what file is being used to verify fingerprint trust
     LOG((CLOG_NOTE "fingerprint_db_path: %s", fingerprint_db_path.u8string().c_str()));
 

src/lib/net/SecureSocket.h

@@ -17,6 +17,7 @@
 
 #pragma once
 
+#include "ConnectionSecurityLevel.h"
 #include "net/TCPSocket.h"
 #include "net/XSocket.h"
 #include "io/filesystem.h"
@@ -33,10 +34,10 @@ A secure socket using SSL.
 */
 class SecureSocket : public TCPSocket {
 public:
-    SecureSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer, IArchNetwork::EAddressFamily family);
+    SecureSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer,
-    SecureSocket(IEventQueue* events,
+                 IArchNetwork::EAddressFamily family, ConnectionSecurityLevel security_level);
-        SocketMultiplexer* socketMultiplexer,
+    SecureSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer,
-        ArchSocket socket);
+                 ArchSocket socket, ConnectionSecurityLevel security_level);
     ~SecureSocket();
 
     // ISocket overrides
@@ -64,12 +65,12 @@ private:
     void                createSSL();
     int                    secureAccept(int s);
     int                    secureConnect(int s);
-    bool                showCertificate();
+    bool ensure_peer_certificate();
     void                checkResult(int n, int& retry);
     void                showError(const std::string& reason);
     std::string getError();
     void                disconnect();
-    bool                verifyCertFingerprint();
+    bool verify_cert_fingerprint(const barrier::fs::path& fingerprint_db_path);
 
     MultiplexerJobStatus serviceConnect(ISocketMultiplexerJob*, bool, bool, bool);
     MultiplexerJobStatus serviceAccept(ISocketMultiplexerJob*, bool, bool, bool);
@@ -86,4 +87,5 @@ private:
     Ssl*                m_ssl;
     bool                m_secureReady;
     bool                m_fatal;
+    ConnectionSecurityLevel security_level_ = ConnectionSecurityLevel::ENCRYPTED;
 };

src/lib/net/TCPSocketFactory.cpp

@@ -40,11 +40,12 @@ TCPSocketFactory::~TCPSocketFactory()
     // do nothing
 }
 
-IDataSocket*
+IDataSocket* TCPSocketFactory::create(IArchNetwork::EAddressFamily family,
-TCPSocketFactory::create(IArchNetwork::EAddressFamily family, bool secure) const
+                                      ConnectionSecurityLevel security_level) const
 {
-    if (secure) {
+    if (security_level != ConnectionSecurityLevel::PLAINTEXT) {
-        SecureSocket* secureSocket = new SecureSocket(m_events, m_socketMultiplexer, family);
+        SecureSocket* secureSocket = new SecureSocket(m_events, m_socketMultiplexer, family,
+                                                      security_level);
         secureSocket->initSsl (false);
         return secureSocket;
     }
@@ -53,12 +54,12 @@ TCPSocketFactory::create(IArchNetwork::EAddressFamily family, bool secure) const
     }
 }
 
-IListenSocket*
+IListenSocket* TCPSocketFactory::createListen(IArchNetwork::EAddressFamily family,
-TCPSocketFactory::createListen(IArchNetwork::EAddressFamily family, bool secure) const
+                                              ConnectionSecurityLevel security_level) const
 {
     IListenSocket* socket = NULL;
-    if (secure) {
+    if (security_level != ConnectionSecurityLevel::PLAINTEXT) {
-        socket = new SecureListenSocket(m_events, m_socketMultiplexer, family);
+        socket = new SecureListenSocket(m_events, m_socketMultiplexer, family, security_level);
     }
     else {
         socket = new TCPListenSocket(m_events, m_socketMultiplexer, family);

src/lib/net/TCPSocketFactory.h

@@ -31,12 +31,11 @@ public:
     virtual ~TCPSocketFactory();
 
     // ISocketFactory overrides
-    virtual IDataSocket* create(
+    virtual IDataSocket* create(IArchNetwork::EAddressFamily family,
-            IArchNetwork::EAddressFamily family,
+                                ConnectionSecurityLevel security_level) const;
-            bool secure) const;
+
-    virtual IListenSocket* createListen(
+    virtual IListenSocket* createListen(IArchNetwork::EAddressFamily family,
-            IArchNetwork::EAddressFamily family,
+                                        ConnectionSecurityLevel security_level) const;
-            bool secure) const;
 
 private:
     IEventQueue*        m_events;

src/lib/server/ClientListener.cpp

@@ -36,18 +36,17 @@
 ClientListener::ClientListener(const NetworkAddress& address,
                 ISocketFactory* socketFactory,
                 IEventQueue* events,
-                bool enableCrypto) :
+                               ConnectionSecurityLevel security_level) :
     m_socketFactory(socketFactory),
     m_server(NULL),
     m_events(events),
-    m_useSecureNetwork(enableCrypto)
+    security_level_{security_level}
 {
     assert(m_socketFactory != NULL);
 
     try {
-        m_listen = m_socketFactory->createListen(
+        m_listen = m_socketFactory->createListen(ARCH->getAddrFamily(address.getAddress()),
-                ARCH->getAddrFamily(address.getAddress()),
+                                                 security_level);
-                m_useSecureNetwork);
 
         // setup event handler
         m_events->adoptHandler(m_events->forIListenSocket().connecting(),
@@ -140,7 +139,7 @@ ClientListener::handleClientConnecting(const Event&, void*)
 
     // When using non SSL, server accepts clients immediately, while SSL
     // has to call secure accept which may require retry
-    if (!m_useSecureNetwork) {
+    if (security_level_ == ConnectionSecurityLevel::PLAINTEXT) {
         m_events->addEvent(Event(m_events->forClientListener().accepted(),
                                 socket->getEventTarget()));
     }

src/lib/server/ClientListener.h

@@ -23,6 +23,7 @@
 #include "base/Event.h"
 #include "common/stddeque.h"
 #include "common/stdset.h"
+#include "net/ConnectionSecurityLevel.h"
 
 class ClientProxy;
 class ClientProxyUnknown;
@@ -36,10 +37,8 @@ class IDataSocket;
 class ClientListener {
 public:
     // The factories are adopted.
-    ClientListener(const NetworkAddress&,
+    ClientListener(const NetworkAddress&, ISocketFactory*, IEventQueue* events,
-                            ISocketFactory*,
+                   ConnectionSecurityLevel security_level);
-                            IEventQueue* events,
-                            bool enableCrypto);
     ~ClientListener();
 
     //! @name manipulators
@@ -86,6 +85,6 @@ private:
     WaitingClients        m_waitingClients;
     Server*                m_server;
     IEventQueue*        m_events;
-    bool                m_useSecureNetwork;
+    ConnectionSecurityLevel security_level_;
     ClientSockets      m_clientSockets;
 };

src/test/integtests/net/NetworkTests.cpp

@@ -115,7 +115,8 @@ TEST_F(NetworkTests, sendToClient_mockData)
     // server
     SocketMultiplexer serverSocketMultiplexer;
     TCPSocketFactory* serverSocketFactory = new TCPSocketFactory(&m_events, &serverSocketMultiplexer);
-    ClientListener listener(serverAddress, serverSocketFactory, &m_events, false);
+    ClientListener listener(serverAddress, serverSocketFactory, &m_events,
+                            ConnectionSecurityLevel::PLAINTEXT);
     NiceMock<MockScreen> serverScreen;
     NiceMock<MockPrimaryClient> primaryClient;
     NiceMock<MockConfig> serverConfig;
@@ -173,7 +174,8 @@ TEST_F(NetworkTests, sendToClient_mockFile)
     // server
     SocketMultiplexer serverSocketMultiplexer;
     TCPSocketFactory* serverSocketFactory = new TCPSocketFactory(&m_events, &serverSocketMultiplexer);
-    ClientListener listener(serverAddress, serverSocketFactory, &m_events, false);
+    ClientListener listener(serverAddress, serverSocketFactory, &m_events,
+                            ConnectionSecurityLevel::PLAINTEXT);
     NiceMock<MockScreen> serverScreen;
     NiceMock<MockPrimaryClient> primaryClient;
     NiceMock<MockConfig> serverConfig;
@@ -230,7 +232,8 @@ TEST_F(NetworkTests, sendToServer_mockData)
     // server
     SocketMultiplexer serverSocketMultiplexer;
     TCPSocketFactory* serverSocketFactory = new TCPSocketFactory(&m_events, &serverSocketMultiplexer);
-    ClientListener listener(serverAddress, serverSocketFactory, &m_events, false);
+    ClientListener listener(serverAddress, serverSocketFactory, &m_events,
+                            ConnectionSecurityLevel::PLAINTEXT);
     NiceMock<MockScreen> serverScreen;
     NiceMock<MockPrimaryClient> primaryClient;
     NiceMock<MockConfig> serverConfig;
@@ -287,7 +290,8 @@ TEST_F(NetworkTests, sendToServer_mockFile)
     // server
     SocketMultiplexer serverSocketMultiplexer;
     TCPSocketFactory* serverSocketFactory = new TCPSocketFactory(&m_events, &serverSocketMultiplexer);
-    ClientListener listener(serverAddress, serverSocketFactory, &m_events, false);
+    ClientListener listener(serverAddress, serverSocketFactory, &m_events,
+                            ConnectionSecurityLevel::PLAINTEXT);
     NiceMock<MockScreen> serverScreen;
     NiceMock<MockPrimaryClient> primaryClient;
     NiceMock<MockConfig> serverConfig;