Trusting all certificates using HttpClient over HTTPS

You basically have four potential solutions to fix a "Not Trusted" exception on Android using httpclient:

1. Trust all certificates. Don't do this, unless you really know what you're doing.
2. Create a custom SSLSocketFactory that trusts only your certificate. This works as long as you know exactly which servers you're going to connect to, but as soon as you need to connect to a new server with a different SSL certificate, you'll need to update your app.
3. Create a keystore file that contains Android's "master list" of certificates, then add your own. If any of those certs expire down the road, you are responsible for updating them in your app. I can't think of a reason to do this.
4. Create a custom SSLSocketFactory that uses the built-in certificate KeyStore, but falls back on an alternate KeyStore for anything that fails to verify with the default.

This answer uses solution #4, which seems to me to be the most robust.

The solution is to use an SSLSocketFactory that can accept multiple KeyStores, allowing you to supply your own KeyStore with your own certificates. This allows you to load additional top-level certificates such as Thawte that might be missing on some Android devices. It also allows you to load your own self-signed certificates as well. It will use the built-in default device certificates first, and fall back on your additional certificates only as necessary.

First, you'll want to determine which cert you are missing in your KeyStore. Run the following command:

openssl s_client -connect www.yourserver.com:443

And you'll see output like the following:

Certificate chain
 0 s:/O=www.yourserver.com/OU=Go to 
   https://www.thawte.com/repository/index.html/OU=Thawte SSL123 
   certificate/OU=Domain Validated/CN=www.yourserver.com
   i:/C=US/O=Thawte, Inc./OU=Domain Validated SSL/CN=Thawte DV SSL CA
 1 s:/C=US/O=Thawte, Inc./OU=Domain Validated SSL/CN=Thawte DV SSL CA
   i:/C=US/O=thawte, Inc./OU=Certification Services Division/OU=(c) 
   2006 thawte, Inc. - For authorized use only/CN=thawte Primary Root CA

As you can see, our root certificate is from Thawte. Go to your provider's website and find the corresponding certificate. For us, it was here, and you can see that the one we needed was the one Copyright 2006.

If you're using a self-signed certificate, you didn't need to do the previous step since you already have your signing certificate.

Then, create a keystore file containing the missing signing certificate. Crazybob has details how to do this on Android, but the idea is to do the following:

If you don't have it already, download the bouncy castle provider library from: http://www.bouncycastle.org/latest_releases.html. This will go on your classpath below.

Run a command to extract the certificate from the server and create a pem file. In this case, mycert.pem.

echo | openssl s_client -connect ${MY_SERVER}:443 2>&1 | \
 sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > mycert.pem

Then run the following commands to create the keystore.

export CLASSPATH=/path/to/bouncycastle/bcprov-jdk15on-155.jar
CERTSTORE=res/raw/mystore.bks
if [ -a $CERTSTORE ]; then
    rm $CERTSTORE || exit 1
fi
keytool \
      -import \
      -v \
      -trustcacerts \
      -alias 0 \
      -file <(openssl x509 -in mycert.pem) \
      -keystore $CERTSTORE \
      -storetype BKS \
      -provider org.bouncycastle.jce.provider.BouncyCastleProvider \
      -providerpath /path/to/bouncycastle/bcprov-jdk15on-155.jar \
      -storepass some-password

You'll notice that the above script places the result in res/raw/mystore.bks. Now you have a file that you'll load into your Android app that provides the missing certificate(s).

To do this, register your SSLSocketFactory for the SSL scheme:

final SchemeRegistry schemeRegistry = new SchemeRegistry();
schemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
schemeRegistry.register(new Scheme("https", createAdditionalCertsSSLSocketFactory(), 443));

// and then however you create your connection manager, I use ThreadSafeClientConnManager
final HttpParams params = new BasicHttpParams();
...
final ThreadSafeClientConnManager cm = new ThreadSafeClientConnManager(params,schemeRegistry);

To create your SSLSocketFactory:

protected org.apache.http.conn.ssl.SSLSocketFactory createAdditionalCertsSSLSocketFactory() {
    try {
        final KeyStore ks = KeyStore.getInstance("BKS");

        // the bks file we generated above
        final InputStream in = context.getResources().openRawResource( R.raw.mystore);  
        try {
            // don't forget to put the password used above in strings.xml/mystore_password
            ks.load(in, context.getString( R.string.mystore_password ).toCharArray());
        } finally {
            in.close();
        }

        return new AdditionalKeyStoresSSLSocketFactory(ks);

    } catch( Exception e ) {
        throw new RuntimeException(e);
    }
}

And finally, the AdditionalKeyStoresSSLSocketFactory code, which accepts your new KeyStore and checks if the built-in KeyStore fails to validate an SSL certificate:

/**
 * Allows you to trust certificates from additional KeyStores in addition to
 * the default KeyStore
 */
public class AdditionalKeyStoresSSLSocketFactory extends SSLSocketFactory {
    protected SSLContext sslContext = SSLContext.getInstance("TLS");

    public AdditionalKeyStoresSSLSocketFactory(KeyStore keyStore) throws NoSuchAlgorithmException, KeyManagementException, KeyStoreException, UnrecoverableKeyException {
        super(null, null, null, null, null, null);
        sslContext.init(null, new TrustManager[]{new AdditionalKeyStoresTrustManager(keyStore)}, null);
    }

    @Override
    public Socket createSocket(Socket socket, String host, int port, boolean autoClose) throws IOException {
        return sslContext.getSocketFactory().createSocket(socket, host, port, autoClose);
    }

    @Override
    public Socket createSocket() throws IOException {
        return sslContext.getSocketFactory().createSocket();
    }



    /**
     * Based on http://download.oracle.com/javase/1.5.0/docs/guide/security/jsse/JSSERefGuide.html#X509TrustManager
     */
    public static class AdditionalKeyStoresTrustManager implements X509TrustManager {

        protected ArrayList<X509TrustManager> x509TrustManagers = new ArrayList<X509TrustManager>();


        protected AdditionalKeyStoresTrustManager(KeyStore... additionalkeyStores) {
            final ArrayList<TrustManagerFactory> factories = new ArrayList<TrustManagerFactory>();

            try {
                // The default Trustmanager with default keystore
                final TrustManagerFactory original = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
                original.init((KeyStore) null);
                factories.add(original);

                for( KeyStore keyStore : additionalkeyStores ) {
                    final TrustManagerFactory additionalCerts = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
                    additionalCerts.init(keyStore);
                    factories.add(additionalCerts);
                }

            } catch (Exception e) {
                throw new RuntimeException(e);
            }



            /*
             * Iterate over the returned trustmanagers, and hold on
             * to any that are X509TrustManagers
             */
            for (TrustManagerFactory tmf : factories)
                for( TrustManager tm : tmf.getTrustManagers() )
                    if (tm instanceof X509TrustManager)
                        x509TrustManagers.add( (X509TrustManager)tm );


            if( x509TrustManagers.size()==0 )
                throw new RuntimeException("Couldn't find any X509TrustManagers");

        }

        /*
         * Delegate to the default trust manager.
         */
        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            final X509TrustManager defaultX509TrustManager = x509TrustManagers.get(0);
            defaultX509TrustManager.checkClientTrusted(chain, authType);
        }

        /*
         * Loop over the trustmanagers until we find one that accepts our server
         */
        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            for( X509TrustManager tm : x509TrustManagers ) {
                try {
                    tm.checkServerTrusted(chain,authType);
                    return;
                } catch( CertificateException e ) {
                    // ignore
                }
            }
            throw new CertificateException();
        }

        public X509Certificate[] getAcceptedIssuers() {
            final ArrayList<X509Certificate> list = new ArrayList<X509Certificate>();
            for( X509TrustManager tm : x509TrustManagers )
                list.addAll(Arrays.asList(tm.getAcceptedIssuers()));
            return list.toArray(new X509Certificate[list.size()]);
        }
    }

}

Note: Do not implement this in production code you are ever going to use on a network you do not entirely trust. Especially anything going over the public internet.

Your question is just what I want to know. After I did some searches, the conclusion is as follows.

In HttpClient way, you should create a custom class from org.apache.http.conn.ssl.SSLSocketFactory, not the one org.apache.http.conn.ssl.SSLSocketFactory itself. Some clues can be found in this post Custom SSL handling stopped working on Android 2.2 FroYo.

An example is like ...

import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
import java.security.KeyManagementException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import org.apache.http.conn.ssl.SSLSocketFactory;
public class MySSLSocketFactory extends SSLSocketFactory {
    SSLContext sslContext = SSLContext.getInstance("TLS");

    public MySSLSocketFactory(KeyStore truststore) throws NoSuchAlgorithmException, KeyManagementException, KeyStoreException, UnrecoverableKeyException {
        super(truststore);

        TrustManager tm = new X509TrustManager() {
            public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            }

            public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            }

            public X509Certificate[] getAcceptedIssuers() {
                return null;
            }
        };

        sslContext.init(null, new TrustManager[] { tm }, null);
    }

    @Override
    public Socket createSocket(Socket socket, String host, int port, boolean autoClose) throws IOException, UnknownHostException {
        return sslContext.getSocketFactory().createSocket(socket, host, port, autoClose);
    }

    @Override
    public Socket createSocket() throws IOException {
        return sslContext.getSocketFactory().createSocket();
    }
}

and use this class while creating instance of HttpClient.

public HttpClient getNewHttpClient() {
    try {
        KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
        trustStore.load(null, null);

        MySSLSocketFactory sf = new MySSLSocketFactory(trustStore);
        sf.setHostnameVerifier(SSLSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);

        HttpParams params = new BasicHttpParams();
        HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);
        HttpProtocolParams.setContentCharset(params, HTTP.UTF_8);

        SchemeRegistry registry = new SchemeRegistry();
        registry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
        registry.register(new Scheme("https", sf, 443));

        ClientConnectionManager ccm = new ThreadSafeClientConnManager(params, registry);

        return new DefaultHttpClient(ccm, params);
    } catch (Exception e) {
        return new DefaultHttpClient();
    }
}

BTW, the link below is for someone who is looking for HttpURLConnection solution. Https Connection Android

I have tested the above two kinds of solutions on froyo, and they all work like a charm in my cases. Finally, using HttpURLConnection may face the redirect problems, but this is beyond the topic.

Note: Before you decide to trust all certificates, you probably should know the site full well and won't be harmful of it to end-user.

Indeed, the risk you take should be considered carefully, including the effect of hacker's mock site mentioned in the following comments that I deeply appreciated. In some situation, although it might be hard to take care of all certificates, you'd better know the implicit drawbacks to trust all of them.