SSL Pinning using Google Volley

SSL Pinning with Google Volley

SSL pinning is a security technique that ensures communication with a server is only allowed with a specific set of certificates. This helps prevent man-in-the-middle attacks where attackers intercept communication and present their own forged certificates.

Why use SSL Pinning?

SSL pinning adds an extra layer of security by restricting which certificates are trusted for a specific connection. This makes it harder for attackers to impersonate the legitimate server.

Implementing SSL Pinning with Google Volley

1. Obtaining the Certificate

The first step is to obtain the public key certificate from the server you’re communicating with. You can usually find this certificate in the server’s response, often in PEM format.

2. Creating the TrustManager

Next, create a custom TrustManager that trusts only the specified certificate. This TrustManager will be used to verify the server’s certificate.

import java.security.cert.X509Certificate;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;
import java.security.KeyStore;
import java.security.cert.CertificateException;
import java.io.InputStream;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateFactory;

public class CustomTrustManager implements X509TrustManager {

    private final X509Certificate[] trustedCertificates;

    public CustomTrustManager(X509Certificate... trustedCertificates) {
        this.trustedCertificates = trustedCertificates;
    }

    @Override
    public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
        // Not used in this case
    }

    @Override
    public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
        // Check if any of the trusted certificates are in the chain
        boolean found = false;
        for (X509Certificate trustedCert : trustedCertificates) {
            for (X509Certificate cert : chain) {
                if (cert.equals(trustedCert)) {
                    found = true;
                    break;
                }
            }
            if (found) {
                break;
            }
        }
        if (!found) {
            throw new CertificateException("Invalid certificate");
        }
    }

    @Override
    public X509Certificate[] getAcceptedIssuers() {
        return new X509Certificate[0];
    }

    // Helper method to load certificate from a resource
    public static X509Certificate loadCertificateFromResource(String resourceName) throws CertificateException, IOException {
        InputStream inputStream = CustomTrustManager.class.getResourceAsStream(resourceName);
        CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
        return (X509Certificate) certificateFactory.generateCertificate(inputStream);
    }
}

3. Setting Up the SSLContext

Create an SSLContext using the custom TrustManager to configure the SSL connection.

import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.security.NoSuchAlgorithmException;
import java.security.KeyManagementException;

public class SSLHelper {

    public static SSLContext getSSLContext(TrustManager[] trustManagers) throws NoSuchAlgorithmException, KeyManagementException {
        SSLContext sslContext = SSLContext.getInstance("TLS");
        sslContext.init(null, trustManagers, null);
        return sslContext;
    }
}

4. Configuring the Request Queue

Modify the Volley request queue to use the SSLContext created above.

import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;
import com.android.volley.toolbox.HurlStack;
import org.apache.http.conn.ssl.SSLSocketFactory;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;

public class MyRequestQueue {

    public static RequestQueue newRequestQueue(Context context) throws NoSuchAlgorithmException, KeyManagementException {
        // Create a custom TrustManager with your trusted certificate
        X509Certificate certificate = CustomTrustManager.loadCertificateFromResource("path/to/certificate.pem");
        CustomTrustManager trustManager = new CustomTrustManager(certificate);
        
        // Create an SSLContext with the custom TrustManager
        SSLContext sslContext = SSLHelper.getSSLContext(new TrustManager[] {trustManager});

        // Create an HurlStack that uses the custom SSLContext
        HurlStack hurlStack = new HurlStack(new SSLSocketFactory(sslContext.getSocketFactory()));

        // Create and return the request queue using the HurlStack
        return Volley.newRequestQueue(context.getApplicationContext(), hurlStack);
    }
}

5. Making Requests

Now, you can use your configured RequestQueue to make HTTPS requests with SSL pinning enabled.

import com.android.volley.RequestQueue;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.Response;
import android.widget.Toast;
import android.content.Context;

public class NetworkUtils {

    public void makeRequest(Context context, String url) throws NoSuchAlgorithmException, KeyManagementException {
        // Create the RequestQueue with SSL pinning
        RequestQueue requestQueue = MyRequestQueue.newRequestQueue(context);

        // Create a StringRequest
        StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener() {
            @Override
            public void onResponse(String response) {
                Toast.makeText(context, "Response: " + response, Toast.LENGTH_SHORT).show();
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(context, "Error: " + error.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });

        // Add the request to the queue
        requestQueue.add(request);
    }
}

Example:

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import androidx.appcompat.app.AppCompatActivity;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.Response;
import android.widget.Toast;
import java.security.NoSuchAlgorithmException;
import java.security.KeyManagementException;

public class MainActivity extends AppCompatActivity {

    private EditText editTextUrl;
    private Button buttonSend;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editTextUrl = findViewById(R.id.editTextUrl);
        buttonSend = findViewById(R.id.buttonSend);

        buttonSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String url = editTextUrl.getText().toString();
                try {
                    NetworkUtils.makeRequest(MainActivity.this, url);
                } catch (NoSuchAlgorithmException | KeyManagementException e) {
                    Toast.makeText(MainActivity.this, "Error: " + e.getMessage(), Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

Benefits of SSL Pinning

• Enhanced Security: Prevents man-in-the-middle attacks.
• Trust Verification: Ensures communication is only with the intended server.
• Data Protection: Safeguards sensitive information transmitted over HTTPS.

Considerations

• Certificate Updates: Regularly update pinned certificates as they expire.
• Complexity: SSL pinning adds complexity to development and maintenance.
• Compatibility: Not all platforms or libraries support SSL pinning natively.

Comparison Table

Conclusion

SSL pinning is a valuable security measure for mobile applications. It significantly strengthens security by limiting the certificates trusted for communication. By implementing SSL pinning using Google Volley, you can enhance the security of your Android applications and protect sensitive data.