add ssl server certificate pinning

src/main/java/com/sparrowwallet/sparrow/AppController.java

@@ -76,6 +76,7 @@ public class AppController implements Initializable {
     public static final double TAB_LABEL_GRAPHIC_OPACITY_INACTIVE = 0.8;
     public static final double TAB_LABEL_GRAPHIC_OPACITY_ACTIVE = 0.95;
     public static final String LOADING_TRANSACTIONS_MESSAGE = "Loading wallet, select Transactions tab to view...";
+    public static final String CONNECTION_FAILED_PREFIX = "Connection failed: ";
 
     @FXML
     private MenuItem saveTransaction;
@@ -1451,8 +1452,7 @@ public class AppController implements Initializable {
 
     @Subscribe
     public void connectionFailed(ConnectionFailedEvent event) {
-        String reason = event.getException().getCause() != null ? event.getException().getCause().getMessage() : event.getException().getMessage();
+        String status = CONNECTION_FAILED_PREFIX + event.getMessage();
-        String status = "Connection failed: " + reason;
         statusUpdated(new StatusEvent(status));
     }
 
@@ -1465,7 +1465,7 @@ public class AppController implements Initializable {
     @Subscribe
     public void disconnection(DisconnectionEvent event) {
         serverToggle.setDisable(false);
-        if(!AppServices.isConnecting() && !AppServices.isConnected() && !statusBar.getText().startsWith("Connection error")) {
+        if(!AppServices.isConnecting() && !AppServices.isConnected() && !statusBar.getText().startsWith(CONNECTION_FAILED_PREFIX)) {
             statusUpdated(new StatusEvent("Disconnected"));
         }
         if(statusTimeline == null || statusTimeline.getStatus() != Animation.Status.RUNNING) {

src/main/java/com/sparrowwallet/sparrow/AppServices.java

@@ -208,6 +208,31 @@ public class AppServices {
                 connectionService.setRestartOnFailure(false);
             }
 
+            if(failEvent.getSource().getException() instanceof TlsServerException && failEvent.getSource().getException().getCause() != null) {
+                TlsServerException tlsServerException = (TlsServerException)failEvent.getSource().getException();
+                connectionService.setRestartOnFailure(false);
+                if(tlsServerException.getCause().getMessage().contains("PKIX path building failed")) {
+                    File crtFile = Config.get().getElectrumServerCert();
+                    if(crtFile != null) {
+                        AppServices.showErrorDialog("SSL Handshake Failed", "The configured server certificate at " + crtFile.getAbsolutePath() + " did not match the certificate provided by the server at " + tlsServerException.getServer().getHost() + "." +
+                                "\n\nThis may indicate a man-in-the-middle attack!" +
+                                "\n\nChange the configured server certificate if you would like to proceed.");
+                    } else {
+                        crtFile = Storage.getCertificateFile(tlsServerException.getServer().getHost());
+                        if(crtFile != null) {
+                            Optional<ButtonType> optButton = AppServices.showErrorDialog("SSL Handshake Failed", "The certificate provided by the server at " + tlsServerException.getServer().getHost() + " appears to have changed." +
+                                    "\n\nThis may indicate a man-in-the-middle attack!" +
+                                    "\n\nDo you still want to proceed?", ButtonType.NO, ButtonType.YES);
+                            if(optButton.isPresent() && optButton.get() == ButtonType.YES) {
+                                crtFile.delete();
+                                Platform.runLater(() -> restartService(connectionService));
+                                return;
+                            }
+                        }
+                    }
+                }
+            }
+
             onlineProperty.removeListener(onlineServicesListener);
             onlineProperty.setValue(false);
             onlineProperty.addListener(onlineServicesListener);

src/main/java/com/sparrowwallet/sparrow/event/ConnectionFailedEvent.java

@@ -1,5 +1,7 @@
 package com.sparrowwallet.sparrow.event;
 
+import com.sparrowwallet.sparrow.net.TlsServerException;
+
 public class ConnectionFailedEvent {
     private final Throwable exception;
 
@@ -10,4 +12,26 @@ public class ConnectionFailedEvent {
     public Throwable getException() {
         return exception;
     }
+
+    public String getMessage() {
+        if(exception instanceof TlsServerException) {
+            return exception.getMessage();
+        }
+
+        Throwable cause = (exception.getCause() != null ? exception.getCause() : exception);
+        cause = (cause.getCause() != null ? cause.getCause() : cause);
+        String message = splitCamelCase(cause.getClass().getSimpleName().replace("Exception", "Error"));
+        return message + " (" + cause.getMessage() + ")";
+    }
+
+    static String splitCamelCase(String s) {
+        return s.replaceAll(
+                String.format("%s|%s|%s",
+                        "(?<=[A-Z])(?=[A-Z][a-z])",
+                        "(?<=[^A-Z])(?=[A-Z])",
+                        "(?<=[A-Za-z])(?=[^A-Za-z])"
+                ),
+                " "
+        );
+    }
 }

src/main/java/com/sparrowwallet/sparrow/io/Storage.java

@@ -24,6 +24,8 @@ import java.lang.reflect.Type;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.security.SecureRandom;
+import java.security.cert.Certificate;
+import java.security.cert.CertificateEncodingException;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.*;
@@ -44,6 +46,7 @@ public class Storage {
     public static final String WINDOWS_SPARROW_DIR = "Sparrow";
     public static final String WALLETS_DIR = "wallets";
     public static final String WALLETS_BACKUP_DIR = "backup";
+    public static final String CERTS_DIR = "certs";
     public static final String HEADER_MAGIC_1 = "SPRW1";
     private static final int BINARY_HEADER_LENGTH = 28;
     public static final String TEMP_BACKUP_EXTENSION = "tmp";
@@ -384,6 +387,37 @@ public class Storage {
         return walletsDir;
     }
 
+    public static File getCertificateFile(String host) {
+        File certsDir = getCertsDir();
+        File[] certs = certsDir.listFiles((dir, name) -> name.equals(host));
+        if(certs.length > 0) {
+            return certs[0];
+        }
+
+        return null;
+    }
+
+    public static void saveCertificate(String host, Certificate cert) {
+        try(FileWriter writer = new FileWriter(new File(getCertsDir(), host))) {
+            writer.write("-----BEGIN CERTIFICATE-----\n");
+            writer.write(Base64.getEncoder().encodeToString(cert.getEncoded()).replaceAll("(.{64})", "$1\n"));
+            writer.write("\n-----END CERTIFICATE-----\n");
+        } catch(CertificateEncodingException e) {
+            log.error("Error encoding PEM certificate", e);
+        } catch(IOException e) {
+            log.error("Error writing PEM certificate", e);
+        }
+    }
+
+    static File getCertsDir() {
+        File certsDir = new File(getSparrowDir(), CERTS_DIR);
+        if(!certsDir.exists()) {
+            certsDir.mkdirs();
+        }
+
+        return certsDir;
+    }
+
     static File getSparrowDir() {
         if(Network.get() != Network.MAINNET) {
             return new File(getSparrowHome(), Network.get().getName());

src/main/java/com/sparrowwallet/sparrow/net/Protocol.java

@@ -39,7 +39,7 @@ public enum Protocol {
     },
     SSL {
         @Override
-        public Transport getTransport(HostAndPort server) throws KeyManagementException, NoSuchAlgorithmException {
+        public Transport getTransport(HostAndPort server) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
             if(isOnionAddress(server)) {
                 return new TorTcpOverTlsTransport(server);
             }
@@ -57,7 +57,7 @@ public enum Protocol {
         }
 
         @Override
-        public Transport getTransport(HostAndPort server, HostAndPort proxy) throws NoSuchAlgorithmException, KeyManagementException {
+        public Transport getTransport(HostAndPort server, HostAndPort proxy) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
             return new ProxyTcpOverTlsTransport(server, proxy);
         }
 
@@ -68,27 +68,27 @@ public enum Protocol {
     },
     HTTP {
         @Override
-        public Transport getTransport(HostAndPort server) throws KeyManagementException, NoSuchAlgorithmException {
+        public Transport getTransport(HostAndPort server) {
             throw new UnsupportedOperationException("No transport supported for HTTP");
         }
 
         @Override
-        public Transport getTransport(HostAndPort server, File serverCert) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
+        public Transport getTransport(HostAndPort server, File serverCert) {
             throw new UnsupportedOperationException("No transport supported for HTTP");
         }
 
         @Override
-        public Transport getTransport(HostAndPort server, HostAndPort proxy) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
+        public Transport getTransport(HostAndPort server, HostAndPort proxy) {
             throw new UnsupportedOperationException("No transport supported for HTTP");
         }
 
         @Override
-        public Transport getTransport(HostAndPort server, File serverCert, HostAndPort proxy) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
+        public Transport getTransport(HostAndPort server, File serverCert, HostAndPort proxy) {
             throw new UnsupportedOperationException("No transport supported for HTTP");
         }
     };
 
-    public abstract Transport getTransport(HostAndPort server) throws KeyManagementException, NoSuchAlgorithmException;
+    public abstract Transport getTransport(HostAndPort server) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException;
 
     public abstract Transport getTransport(HostAndPort server, File serverCert) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException;
 

src/main/java/com/sparrowwallet/sparrow/net/ProxyTcpOverTlsTransport.java

@@ -18,7 +18,7 @@ public class ProxyTcpOverTlsTransport extends TcpOverTlsTransport {
 
     private final HostAndPort proxy;
 
-    public ProxyTcpOverTlsTransport(HostAndPort server, HostAndPort proxy) throws KeyManagementException, NoSuchAlgorithmException {
+    public ProxyTcpOverTlsTransport(HostAndPort server, HostAndPort proxy) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
         super(server);
         this.proxy = proxy;
     }
@@ -34,7 +34,7 @@ public class ProxyTcpOverTlsTransport extends TcpOverTlsTransport {
         Socket underlying = new Socket(new Proxy(Proxy.Type.SOCKS, proxyAddr));
         underlying.connect(new InetSocketAddress(server.getHost(), server.getPortOrDefault(DEFAULT_PORT)));
         SSLSocket sslSocket = (SSLSocket) sslSocketFactory.createSocket(underlying, proxy.getHost(), proxy.getPortOrDefault(DEFAULT_PROXY_PORT), true);
-        sslSocket.startHandshake();
+        startHandshake(sslSocket);
 
         return sslSocket;
     }

src/main/java/com/sparrowwallet/sparrow/net/TcpOverTlsTransport.java

@@ -1,6 +1,9 @@
 package com.sparrowwallet.sparrow.net;
 
 import com.google.common.net.HostAndPort;
+import com.sparrowwallet.sparrow.io.Storage;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import javax.net.ssl.*;
 import java.io.File;
@@ -8,35 +11,23 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.net.Socket;
 import java.security.*;
+import java.security.cert.*;
 import java.security.cert.Certificate;
-import java.security.cert.CertificateException;
-import java.security.cert.CertificateFactory;
-import java.security.cert.X509Certificate;
 
 public class TcpOverTlsTransport extends TcpTransport {
+    private static final Logger log = LoggerFactory.getLogger(TcpOverTlsTransport.class);
+
     public static final int DEFAULT_PORT = 50002;
 
     protected final SSLSocketFactory sslSocketFactory;
 
-    public TcpOverTlsTransport(HostAndPort server) throws NoSuchAlgorithmException, KeyManagementException {
+    public TcpOverTlsTransport(HostAndPort server) throws NoSuchAlgorithmException, KeyManagementException, CertificateException, KeyStoreException, IOException {
         super(server);
 
-        TrustManager[] trustAllCerts = new TrustManager[]{
+        TrustManager[] trustManagers = getTrustManagers(Storage.getCertificateFile(server.getHost()));
-                new X509TrustManager() {
-                    public X509Certificate[] getAcceptedIssuers() {
-                        return new X509Certificate[0];
-                    }
-
-                    public void checkClientTrusted(X509Certificate[] certs, String authType) {
-                    }
-
-                    public void checkServerTrusted(X509Certificate[] certs, String authType) {
-                    }
-                }
-        };
 
         SSLContext sslContext = SSLContext.getInstance("TLS");
-        sslContext.init(null, trustAllCerts, new SecureRandom());
+        sslContext.init(null, trustManagers, new SecureRandom());
 
         this.sslSocketFactory = sslContext.getSocketFactory();
     }
@@ -44,25 +35,77 @@ public class TcpOverTlsTransport extends TcpTransport {
     public TcpOverTlsTransport(HostAndPort server, File crtFile) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
         super(server);
 
-        Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(new FileInputStream(crtFile));
+        TrustManager[] trustManagers = getTrustManagers(crtFile);
-
-        KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
-        keyStore.load(null, null);
-        keyStore.setCertificateEntry("electrumx", certificate);
-
-        TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
-        trustManagerFactory.init(keyStore);
 
         SSLContext sslContext = SSLContext.getInstance("TLS");
-        sslContext.init(null, trustManagerFactory.getTrustManagers(), null);
+        sslContext.init(null, trustManagers, null);
 
         sslSocketFactory = sslContext.getSocketFactory();
     }
 
+    private TrustManager[] getTrustManagers(File crtFile) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException {
+        if(crtFile == null) {
+            return new TrustManager[] {
+                    new X509TrustManager() {
+                        public X509Certificate[] getAcceptedIssuers() {
+                            return new X509Certificate[0];
+                        }
+
+                        public void checkClientTrusted(X509Certificate[] certs, String authType) throws CertificateException {
+                        }
+
+                        public void checkServerTrusted(X509Certificate[] certs, String authType) throws CertificateException {
+                            if(certs.length == 0) {
+                                throw new CertificateException("No server certificate provided");
+                            }
+
+                            certs[0].checkValidity();
+                        }
+                    }
+            };
+        }
+
+        Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(new FileInputStream(crtFile));
+        if(certificate instanceof X509Certificate) {
+            try {
+                X509Certificate x509Certificate = (X509Certificate)certificate;
+                x509Certificate.checkValidity();
+            } catch(CertificateException e) {
+                crtFile.delete();
+                return getTrustManagers(null);
+            }
+        }
+
+        KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
+        keyStore.load(null, null);
+        keyStore.setCertificateEntry("electrum-server", certificate);
+
+        TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
+        trustManagerFactory.init(keyStore);
+
+        return trustManagerFactory.getTrustManagers();
+    }
+
     protected Socket createSocket() throws IOException {
         SSLSocket sslSocket = (SSLSocket) sslSocketFactory.createSocket(server.getHost(), server.getPortOrDefault(DEFAULT_PORT));
-        sslSocket.startHandshake();
+        startHandshake(sslSocket);
-
         return sslSocket;
     }
+
+    protected void startHandshake(SSLSocket sslSocket) throws IOException {
+        sslSocket.addHandshakeCompletedListener(event -> {
+            if(Storage.getCertificateFile(server.getHost()) == null) {
+                try {
+                    Certificate[] certs = event.getPeerCertificates();
+                    if(certs.length > 0) {
+                        Storage.saveCertificate(server.getHost(), certs[0]);
+                    }
+                } catch(SSLPeerUnverifiedException e) {
+                    log.warn("Attempting to retrieve certificate for unverified peer", e);
+                }
+            }
+        });
+
+        sslSocket.startHandshake();
+    }
 }

src/main/java/com/sparrowwallet/sparrow/net/TcpTransport.java

@@ -10,6 +10,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.net.SocketFactory;
+import javax.net.ssl.SSLHandshakeException;
 import java.io.*;
 import java.net.Socket;
 import java.nio.charset.StandardCharsets;
@@ -192,6 +193,8 @@ public class TcpTransport implements Transport, Closeable {
         try {
             socket = createSocket();
             running = true;
+        } catch(SSLHandshakeException e) {
+            throw new TlsServerException(server, e);
         } catch(IOException e) {
             throw new ServerException(e);
         }

src/main/java/com/sparrowwallet/sparrow/net/TlsServerException.java

@@ -0,0 +1,59 @@
+package com.sparrowwallet.sparrow.net;
+
+import com.google.common.net.HostAndPort;
+import com.sparrowwallet.sparrow.io.Config;
+import com.sparrowwallet.sparrow.io.Storage;
+
+import java.io.File;
+import java.security.cert.CertificateExpiredException;
+import java.security.cert.CertificateNotYetValidException;
+
+public class TlsServerException extends ServerException {
+    private final HostAndPort server;
+
+    public TlsServerException(HostAndPort server) {
+        this.server = server;
+    }
+
+    public TlsServerException(HostAndPort server, String message) {
+        super(message);
+        this.server = server;
+    }
+
+    public TlsServerException(HostAndPort server, Throwable cause) {
+        this(server, getMessage(cause, server), cause);
+    }
+
+    public TlsServerException(HostAndPort server, String message, Throwable cause) {
+        super(message, cause);
+        this.server = server;
+    }
+
+    public HostAndPort getServer() {
+        return server;
+    }
+
+    private static String getMessage(Throwable cause, HostAndPort server) {
+        if(cause != null) {
+            if(cause.getMessage().contains("PKIX path building failed")) {
+                File configCrtFile = Config.get().getElectrumServerCert();
+                File savedCrtFile = Storage.getCertificateFile(server.getHost());
+                if(configCrtFile != null) {
+                    return "Provided server certificate from " + server.getHost() + " did not match configured certificate at " + configCrtFile.getAbsolutePath();
+                } else if(savedCrtFile != null) {
+                    return "Provided server certificate from " + server.getHost() + " did not match previously saved certificate at " + savedCrtFile.getAbsolutePath();
+                }
+
+                return "Provided server certificate from " + server.getHost() + " was invalid: " + (cause.getCause() != null ? cause.getCause().getMessage() : cause.getMessage());
+            } else if(cause.getCause() instanceof CertificateNotYetValidException) {
+                return cause.getMessage().replace("NotBefore:", "Certificate only valid from");
+            } else if(cause.getCause() instanceof CertificateExpiredException) {
+                return cause.getMessage().replace("NotAfter:", "Certificate expired at");
+            }
+
+            return cause.getMessage();
+        }
+
+        return "SSL Handshake Error";
+    }
+}

src/main/java/com/sparrowwallet/sparrow/net/TorTcpOverTlsTransport.java

@@ -17,7 +17,7 @@ import java.security.cert.CertificateException;
 public class TorTcpOverTlsTransport extends TcpOverTlsTransport {
     private static final Logger log = LoggerFactory.getLogger(TorTcpOverTlsTransport.class);
 
-    public TorTcpOverTlsTransport(HostAndPort server) throws NoSuchAlgorithmException, KeyManagementException {
+    public TorTcpOverTlsTransport(HostAndPort server) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
         super(server);
     }
 
@@ -42,7 +42,7 @@ public class TorTcpOverTlsTransport extends TcpOverTlsTransport {
         }
 
         SSLSocket sslSocket = (SSLSocket) sslSocketFactory.createSocket(socket, server.getHost(), server.getPortOrDefault(DEFAULT_PORT), true);
-        sslSocket.startHandshake();
+        startHandshake(sslSocket);
 
         return sslSocket;
     }

src/main/java/com/sparrowwallet/sparrow/preferences/ServerPreferencesController.java

@@ -11,6 +11,7 @@ import com.sparrowwallet.sparrow.control.UnlabeledToggleSwitch;
 import com.sparrowwallet.sparrow.event.*;
 import com.sparrowwallet.sparrow.glyphfont.FontAwesome5;
 import com.sparrowwallet.sparrow.io.Config;
+import com.sparrowwallet.sparrow.io.Storage;
 import com.sparrowwallet.sparrow.net.*;
 import javafx.application.Platform;
 import javafx.beans.value.ChangeListener;
@@ -35,13 +36,13 @@ import org.slf4j.LoggerFactory;
 import tornadofx.control.Field;
 import tornadofx.control.Form;
 
-import javax.net.ssl.SSLHandshakeException;
 import java.io.File;
 import java.io.FileInputStream;
 import java.security.cert.CertificateFactory;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.List;
+import java.util.Optional;
 import java.util.Random;
 
 public class ServerPreferencesController extends PreferencesDetailController {
@@ -545,10 +546,27 @@ public class ServerPreferencesController extends PreferencesDetailController {
     private void showConnectionFailure(Throwable exception) {
         log.error("Connection error", exception);
         String reason = exception.getCause() != null ? exception.getCause().getMessage() : exception.getMessage();
-        if(exception.getCause() != null && exception.getCause() instanceof SSLHandshakeException) {
+        if(exception instanceof TlsServerException && exception.getCause() != null) {
-            reason = "SSL Handshake Error\n" + reason;
+            TlsServerException tlsServerException = (TlsServerException)exception;
+            if(exception.getCause().getMessage().contains("PKIX path building failed")) {
+                File configCrtFile = Config.get().getElectrumServerCert();
+                File savedCrtFile = Storage.getCertificateFile(tlsServerException.getServer().getHost());
+                if(configCrtFile == null && savedCrtFile != null) {
+                    Optional<ButtonType> optButton = AppServices.showErrorDialog("SSL Handshake Failed", "The certificate provided by the server at " + tlsServerException.getServer().getHost() + " appears to have changed." +
+                            "\n\nThis may indicate a man-in-the-middle attack!" +
+                            "\n\nDo you still want to proceed?", ButtonType.NO, ButtonType.YES);
+                    if(optButton.isPresent()) {
+                        if(optButton.get() == ButtonType.YES) {
+                            savedCrtFile.delete();
+                            Platform.runLater(this::startElectrumConnection);
+                            return;
                         }
-        if(exception.getCause() != null && exception.getCause() instanceof TorControlError && exception.getCause().getMessage().contains("Failed to bind")) {
+                    }
+                }
+            }
+
+            reason = tlsServerException.getMessage() + "\n\n" + reason;
+        } else if(exception.getCause() != null && exception.getCause() instanceof TorControlError && exception.getCause().getMessage().contains("Failed to bind")) {
             reason += "\nIs a Tor proxy already running on port " + TorService.PROXY_PORT + "?";
         }