Harden the TLS connection cipher suites

src/main/java/eu/siacs/conversations/Config.java

@@ -29,6 +29,32 @@ public final class Config {
 	public static final long MAM_MAX_CATCHUP =  MILLISECONDS_IN_DAY / 2;
 	public static final int MAM_MAX_MESSAGES = 500;
 
+	public static final String ENABLED_CIPHERS[] = {
+		"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
+		"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA384",
+		"TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA256",
+		"TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
+		"TLS_ECDHE_RSA_AES_128_SHA",
+		"TLS_ECDHE_RSA_AES_256_SHA",
+
+		"TLS_DHE_RSA_WITH_AES_128_GCM_SHA256",
+		"TLS_DHE_RSA_WITH_AES_128_GCM_SHA384",
+		"TLS_DHE_RSA_WITH_AES_256_GCM_SHA256",
+		"TLS_DHE_RSA_WITH_AES_256_GCM_SHA384",
+
+		"TLS_DHE_RSA_WITH_CAMELLIA_256_SHA",
+
+		// Fallback.
+		"TLS_RSA_WITH_AES_128_GCM_SHA256",
+		"TLS_RSA_WITH_AES_128_GCM_SHA384",
+		"TLS_RSA_WITH_AES_256_GCM_SHA256",
+		"TLS_RSA_WITH_AES_256_GCM_SHA384",
+		"TLS_RSA_WITH_AES_128_CBC_SHA256",
+		"TLS_RSA_WITH_AES_128_CBC_SHA384",
+		"TLS_RSA_WITH_AES_256_CBC_SHA256",
+		"TLS_RSA_WITH_AES_256_CBC_SHA384"
+	};
+
 	private Config() {
 
 	}

src/main/java/eu/siacs/conversations/http/HttpConnection.java

@@ -20,6 +20,7 @@ import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.HttpsURLConnection;
 import javax.net.ssl.SSLContext;
 import javax.net.ssl.SSLHandshakeException;
+import javax.net.ssl.SSLSocketFactory;
 import javax.net.ssl.X509TrustManager;
 
 import eu.siacs.conversations.Config;
@@ -124,10 +125,10 @@ public class HttpConnection implements Downloadable {
 		mXmppConnectionService.updateConversationUi();
 	}
 
-	private void setupTrustManager(HttpsURLConnection connection,
+	private void setupTrustManager(final HttpsURLConnection connection,
-								   boolean interactive) {
+			final boolean interactive) {
-		X509TrustManager trustManager;
+		final X509TrustManager trustManager;
-		HostnameVerifier hostnameVerifier;
+		final HostnameVerifier hostnameVerifier;
 		if (interactive) {
 			trustManager = mXmppConnectionService.getMemorizingTrustManager();
 			hostnameVerifier = mXmppConnectionService
@@ -142,15 +143,21 @@ public class HttpConnection implements Downloadable {
 						new StrictHostnameVerifier());
 		}
 		try {
-			SSLContext sc = SSLContext.getInstance("TLS");
+			final SSLContext sc = SSLContext.getInstance("TLS");
 			sc.init(null, new X509TrustManager[]{trustManager},
 					mXmppConnectionService.getRNG());
-			connection.setSSLSocketFactory(sc.getSocketFactory());
+
+			final SSLSocketFactory sf = sc.getSocketFactory();
+			final String[] cipherSuites = CryptoHelper.getSupportedCipherSuites(
+					sf.getSupportedCipherSuites());
+			if (cipherSuites.length > 0) {
+				sc.getDefaultSSLParameters().setCipherSuites(cipherSuites);
+
+			}
+
+			connection.setSSLSocketFactory(sf);
 			connection.setHostnameVerifier(hostnameVerifier);
-		} catch (KeyManagementException e) {
+		} catch (final KeyManagementException | NoSuchAlgorithmException ignored) {
-			return;
-		} catch (NoSuchAlgorithmException e) {
-			return;
 		}
 	}
 

src/main/java/eu/siacs/conversations/utils/CryptoHelper.java

@@ -2,12 +2,17 @@ package eu.siacs.conversations.utils;
 
 import java.security.SecureRandom;
 import java.text.Normalizer;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.LinkedHashSet;
 
-public class CryptoHelper {
+import eu.siacs.conversations.Config;
+
+public final class CryptoHelper {
 	public static final String FILETRANSFER = "?FILETRANSFERv1:";
-	final protected static char[] hexArray = "0123456789abcdef".toCharArray();
+	private final static char[] hexArray = "0123456789abcdef".toCharArray();
-	final protected static char[] vowels = "aeiou".toCharArray();
+	private final static char[] vowels = "aeiou".toCharArray();
-	final protected static char[] consonants = "bcdfghjklmnpqrstvwxyz".toCharArray();
+	private final static char[] consonants = "bcdfghjklmnpqrstvwxyz".toCharArray();
 	final public static byte[] ONE = new byte[] { 0, 0, 0, 1 };
 
 	public static String bytesToHex(byte[] bytes) {
@@ -45,7 +50,7 @@ public class CryptoHelper {
 		return randomWord(3, random) + "." + randomWord(7, random);
 	}
 
-	protected static String randomWord(int lenght, SecureRandom random) {
+	private static String randomWord(int lenght, SecureRandom random) {
 		StringBuilder builder = new StringBuilder(lenght);
 		for (int i = 0; i < lenght; ++i) {
 			if (i % 2 == 0) {
@@ -91,4 +96,10 @@ public class CryptoHelper {
 		builder.insert(35, " ");
 		return builder.toString();
 	}
+
+	public static String[] getSupportedCipherSuites(final String[] platformSupportedCipherSuites) {
+		final Collection<String> cipherSuites = new LinkedHashSet<>(Arrays.asList(Config.ENABLED_CIPHERS));
+		cipherSuites.retainAll(Arrays.asList(platformSupportedCipherSuites));
+		return cipherSuites.toArray(new String[cipherSuites.size()]);
+	}
 }

src/main/java/eu/siacs/conversations/xmpp/XmppConnection.java

@@ -53,6 +53,7 @@ import eu.siacs.conversations.crypto.sasl.ScramSha1;
 import eu.siacs.conversations.entities.Account;
 import eu.siacs.conversations.generator.IqGenerator;
 import eu.siacs.conversations.services.XmppConnectionService;
+import eu.siacs.conversations.utils.CryptoHelper;
 import eu.siacs.conversations.utils.DNSHelper;
 import eu.siacs.conversations.utils.Xmlns;
 import eu.siacs.conversations.xml.Element;
@@ -514,6 +515,12 @@ public class XmppConnection implements Runnable {
 				supportedProtocols.remove("SSLv3");
 				supportProtocols = new String[supportedProtocols.size()];
 				supportedProtocols.toArray(supportProtocols);
+
+				final String[] cipherSuites = CryptoHelper.getSupportedCipherSuites(
+						sslSocket.getSupportedCipherSuites());
+				if (cipherSuites.length > 0) {
+					sslSocket.setEnabledCipherSuites(cipherSuites);
+				}
 			}
 			sslSocket.setEnabledProtocols(supportProtocols);
 

src/main/res/values/strings.xml

@@ -274,7 +274,7 @@
     <string name="pref_dont_save_encrypted">Don’t save encrypted messages</string>
     <string name="pref_dont_save_encrypted_summary">Warning: This could lead to message loss</string>
     <string name="pref_enable_legacy_ssl">Enable legacy SSL</string>
-    <string name="pref_enable_legacy_ssl_summary">Enables SSLv3 support for legacy servers. Warning: SSLv3 is considered insecure.</string>
+    <string name="pref_enable_legacy_ssl_summary">Enables legacy SSLv3 support and insecure SSL ciphers.</string>
     <string name="pref_expert_options">Expert options</string>
     <string name="pref_expert_options_summary">Please be careful with these</string>
     <string name="title_activity_about">About Conversations</string>