Change the way we harden SSL/TLS sockets (3fd7470d) · Commits · e / os / Mail

src/com/fsck/k9/net/ssl/TrustedSocketFactory.java

+69 −32

Original line number	Diff line number	Diff line
		@@ -13,46 +13,67 @@ import java.util.*;

		/**
		* Filter and reorder list of cipher suites and TLS versions.
		*
		* <p>
		* See: <a href="http://op-co.de/blog/posts/android_ssl_downgrade/">http://op-co.de/blog/posts/android_ssl_downgrade/</a>
		* </p>
		*/
		public class TrustedSocketFactory {
		protected static final String ENABLED_CIPHERS[];
		protected static final String ENABLED_PROTOCOLS[];

		static {
		String preferredCiphers[] = {
		"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
		"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
		// Order taken from OpenSSL 1.0.1c
		protected static final String ORDERED_KNOWN_CIPHERS[] = {
		"TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
		"TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
		"TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
		"TLS_DHE_RSA_WITH_AES_256_CBC_SHA",
		"TLS_DHE_DSS_WITH_AES_256_CBC_SHA",
		"TLS_ECDH_RSA_WITH_AES_256_CBC_SHA",
		"TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA",
		"TLS_RSA_WITH_AES_256_CBC_SHA",
		"TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
		"TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA",
		"TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA",
		"TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA",
		"SSL_RSA_WITH_3DES_EDE_CBC_SHA",
		"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
		"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
		"TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
		"TLS_DHE_DSS_WITH_AES_128_CBC_SHA",
		"TLS_ECDH_RSA_WITH_AES_128_CBC_SHA",
		"TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA",
		"TLS_RSA_WITH_AES_128_CBC_SHA",
		"TLS_ECDHE_RSA_WITH_RC4_128_SHA",
		"TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
		"TLS_RSA_WITH_AES_128_CBC_SHA",
		"TLS_RSA_WITH_AES_256_CBC_SHA",
		"SSL_RSA_WITH_3DES_EDE_CBC_SHA",
		"TLS_ECDH_RSA_WITH_RC4_128_SHA",
		"TLS_ECDH_ECDSA_WITH_RC4_128_SHA",
		"SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA",
		"SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA",
		"SSL_RSA_WITH_RC4_128_SHA",
		"SSL_RSA_WITH_RC4_128_MD5",
		};
		String preferredProtocols[] = {
		"TLSv1.2", "TLSv1.1", "TLSv1"

		protected static final String[] BLACKLISTED_CIPHERS = {
		"SSL_RSA_WITH_DES_CBC_SHA",
		"SSL_DHE_RSA_WITH_DES_CBC_SHA",
		"SSL_DHE_DSS_WITH_DES_CBC_SHA",
		"SSL_RSA_EXPORT_WITH_RC4_40_MD5",
		"SSL_RSA_EXPORT_WITH_DES40_CBC_SHA",
		"SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA",
		"SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA",
		};

		protected static final String ORDERED_KNOWN_PROTOCOLS[] = {
		"TLSv1.2", "TLSv1.1", "TLSv1", "SSLv3"
		};

		String[] supportedCiphers = null;
		String[] supportedProtocols = null;
		static {
		String[] enabledCiphers = null;
		String[] enabledProtocols = null;

		try {
		SSLContext sslContext = SSLContext.getInstance("TLS");
		sslContext.init(null, null, new SecureRandom());
		SSLSocketFactory sf = sslContext.getSocketFactory();
		supportedCiphers = sf.getSupportedCipherSuites();
		SSLSocket sock = (SSLSocket) sf.createSocket();
		supportedProtocols = sock.getSupportedProtocols();
		enabledCiphers = sock.getEnabledCipherSuites();
		enabledProtocols = sock.getEnabledProtocols();
		} catch (IOException ioe) {
		ioe.printStackTrace();
		} catch (KeyManagementException kme) {
		@@ -61,21 +82,37 @@ public class TrustedSocketFactory {
		nsae.printStackTrace();
		}

		ENABLED_CIPHERS = supportedCiphers == null ? null :
		filterBySupport(preferredCiphers, supportedCiphers);
		ENABLED_PROTOCOLS = supportedProtocols == null ? null :
		filterBySupport(preferredProtocols, supportedProtocols);
		ENABLED_CIPHERS = (enabledCiphers == null) ? null :
		reorder(enabledCiphers, ORDERED_KNOWN_CIPHERS, BLACKLISTED_CIPHERS);

		ENABLED_PROTOCOLS = (enabledProtocols == null) ? null :
		reorder(enabledProtocols, ORDERED_KNOWN_PROTOCOLS, null);
		}

		protected static String[] filterBySupport(String[] preferred, String[] supported) {
		List<String> enabled = new ArrayList<String>();
		Set<String> available = new HashSet<String>();
		Collections.addAll(available, supported);
		protected static String[] reorder(String[] enabled, String[] known, String[] blacklisted) {
		List<String> unknown = new ArrayList<String>();
		Collections.addAll(unknown, enabled);

		for (String item : preferred) {
		if (available.contains(item)) enabled.add(item);
		// Remove blacklisted items
		if (blacklisted != null) {
		for (String item : blacklisted) {
		unknown.remove(item);
		}
		return enabled.toArray(new String[enabled.size()]);
		}

		// Order known items
		List<String> result = new ArrayList<String>();
		for (String item : known) {
		if (unknown.remove(item)) {
		result.add(item);
		}
		}

		// Add unknown items at the end. This way security won't get worse when unknown ciphers
		// start showing up in the future.
		result.addAll(unknown);

		return result.toArray(new String[result.size()]);
		}

		public static Socket createSocket(SSLContext sslContext) throws IOException {