How to override the cipherlist sent to the server by Android when using HttpsURLConnection?

Question

During TLS negotiation, clients send a list of supported ciphers to the server, the server picks one, and encryption starts. I want to change this cipherlist sent to the server by Android, when I'm using HttpsURLConnection for communication.

I know that I can use setSSLSocketFactory on the HttpsURLConnection object to set it up to use a SSLSocketFactory. This is useful when I want to change the trustmanager etc used by the SSLSocket returned by the SSLSocketFactory.

I know that in general this ciphersuite list can be edited using an SSLParameters object and passing it to SSlsocket or SSLEngine objects using the methods they provide.

BUT the SSLSocketFactory does not seem to expose such methods!

I cannot find a way to change the SSLParameters of the returned SSLSocket objects created by the SSLSocketFactory I pass to HttpsURLConnection.

What to do?

I guess this is also relevant to Java in general, not only Android. Maybe there's an OO way to do it (e.g. extend SSLSocketFactory and provide that to HttpsURLConnection?)

Solution 1

This piece of code is a bit raw. please use with care.

public class PreferredCipherSuiteSSLSocketFactory extends SSLSocketFactory {


private static final String PREFERRED_CIPHER_SUITE = "TLS_RSA_WITH_AES_128_CBC_SHA";

private final SSLSocketFactory delegate;

public PreferredCipherSuiteSSLSocketFactory(SSLSocketFactory delegate) {

    this.delegate = delegate;
}

@Override
public String[] getDefaultCipherSuites() {

    return setupPreferredDefaultCipherSuites(this.delegate);
}

@Override
public String[] getSupportedCipherSuites() {

    return setupPreferredSupportedCipherSuites(this.delegate);
}

@Override
public Socket createSocket(String arg0, int arg1) throws IOException,
        UnknownHostException {

    Socket socket = this.delegate.createSocket(arg0, arg1);
    String[] cipherSuites = setupPreferredDefaultCipherSuites(delegate);
    ((SSLSocket)socket).setEnabledCipherSuites(cipherSuites);

    return socket;
}

@Override
public Socket createSocket(InetAddress arg0, int arg1) throws IOException {

    Socket socket = this.delegate.createSocket(arg0, arg1);
    String[] cipherSuites = setupPreferredDefaultCipherSuites(delegate);
    ((SSLSocket)socket).setEnabledCipherSuites(cipherSuites);

    return socket;
}

@Override
public Socket createSocket(Socket arg0, String arg1, int arg2, boolean arg3)
        throws IOException {

    Socket socket = this.delegate.createSocket(arg0, arg1, arg2, arg3);
    String[] cipherSuites = setupPreferredDefaultCipherSuites(delegate);
    ((SSLSocket)socket).setEnabledCipherSuites(cipherSuites);

    return socket;
}

@Override
public Socket createSocket(String arg0, int arg1, InetAddress arg2, int arg3)
        throws IOException, UnknownHostException {

    Socket socket = this.delegate.createSocket(arg0, arg1, arg2, arg3);
    String[] cipherSuites = setupPreferredDefaultCipherSuites(delegate);
    ((SSLSocket)socket).setEnabledCipherSuites(cipherSuites);

    return socket;
}

@Override
public Socket createSocket(InetAddress arg0, int arg1, InetAddress arg2,
        int arg3) throws IOException {

    Socket socket = this.delegate.createSocket(arg0, arg1, arg2, arg3);
    String[] cipherSuites = setupPreferredDefaultCipherSuites(delegate);
    ((SSLSocket)socket).setEnabledCipherSuites(cipherSuites);

    return socket;
}

private static String[] setupPreferredDefaultCipherSuites(SSLSocketFactory sslSocketFactory) {

    String[] defaultCipherSuites = sslSocketFactory.getDefaultCipherSuites();

    ArrayList<String> suitesList = new ArrayList<String>(Arrays.asList(defaultCipherSuites));
    suitesList.remove(PREFERRED_CIPHER_SUITE);
    suitesList.add(0, PREFERRED_CIPHER_SUITE);

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

private static String[] setupPreferredSupportedCipherSuites(SSLSocketFactory sslSocketFactory) {

    String[] supportedCipherSuites = sslSocketFactory.getSupportedCipherSuites();

    ArrayList<String> suitesList = new ArrayList<String>(Arrays.asList(supportedCipherSuites));
    suitesList.remove(PREFERRED_CIPHER_SUITE);
    suitesList.add(0, PREFERRED_CIPHER_SUITE);

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

When you want to use it.

            HttpsURLConnection connection = (HttpsURLConnection) (new URL(url))
                .openConnection();
        SSLContext context = SSLContext.getInstance("TLS");
        TrustManager tm[] = {new SSLPinningTrustManager()};
        context.init(null, tm, null);
        SSLSocketFactory preferredCipherSuiteSSLSocketFactory = new PreferredCipherSuiteSSLSocketFactory(context.getSocketFactory());
        connection.setSSLSocketFactory(preferredCipherSuiteSSLSocketFactory);
                    connection.connect();

Thanks you.

Solution 2

I bundled the technique in @ThinkChris's answer1 into a dead simple method call. You can use the NetCipher library to get a modern TLS config when using Android's HttpsURLConnection. NetCipher configures the HttpsURLConnection instance to use the best supported TLS version, removes SSLv3 support, and configures the best suite of ciphers for that TLS version. First, add it to your build.gradle:

compile 'info.guardianproject.netcipher:netcipher:1.2'

Or you can download the netcipher-1.2.jar and include it directly in your app. Then instead of calling:

HttpURLConnection connection = (HttpURLConnection) sourceUrl.openConnection();

Call this:

HttpsURLConnection connection = NetCipher.getHttpsURLConnection(sourceUrl);

If you want to specifically customize that cipher list, you can check the code there. But most people should not have to think about the cipher list, instead it should use the common best practices by default.

Comments

[Sergey Vakulenko]

small precision: this is javax.net.ssl.SSLSocketFactory and not apatche SSLSocketFactory.

[Amritesh]

What is SSLPinningTrustManager here? is "SSLPinningTrustManager" is user defined class as Android Studio is not able to resolve, if yes, then what could be replacement?

[Roman Vottner]

@Amritesh maybe SSLPinningTrustManager refers to this implementation