How to programmatically add certificates to a truststore and use that also for verifying server authentication

Question

I my app I want to use a https connection to a user-specified server which uses a self-signed certificate. What I gathered by now is, that

• self signed certificates

Answer 1

Solution was found a while ago but no one has created the Answer yet to help guide others, so I'll be the Point Pimp(ette) this morning and post the URL added as the solution, plus copy in the code from the public source. Hope this helps guide others to the solution. :)

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Here's the URL for the code below.

package com.fsck.k9.mail.store;

import android.app.Application;
import android.content.Context;
import android.util.Log;
import com.fsck.k9.K9;
import com.fsck.k9.helper.DomainNameChecker;
import org.apache.commons.io.IOUtils;

import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.HashMap;
import java.util.Map;

public final class TrustManagerFactory {
    private static final String LOG_TAG = "TrustManagerFactory";

    private static X509TrustManager defaultTrustManager;
    private static X509TrustManager unsecureTrustManager;
    private static X509TrustManager localTrustManager;

    private static X509Certificate[] lastCertChain = null;

    private static File keyStoreFile;
    private static KeyStore keyStore;


    private static class SimpleX509TrustManager implements X509TrustManager {
        public void checkClientTrusted(X509Certificate[] chain, String authType)
        throws CertificateException {
        }

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

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

    private static class SecureX509TrustManager implements X509TrustManager {
        private static final Map<String, SecureX509TrustManager> mTrustManager =
            new HashMap<String, SecureX509TrustManager>();

        private final String mHost;

        private SecureX509TrustManager(String host) {
            mHost = host;
        }

        public synchronized static X509TrustManager getInstance(String host) {
            SecureX509TrustManager trustManager;
            if (mTrustManager.containsKey(host)) {
                trustManager = mTrustManager.get(host);
            } else {
                trustManager = new SecureX509TrustManager(host);
                mTrustManager.put(host, trustManager);
            }

            return trustManager;
        }

        public void checkClientTrusted(X509Certificate[] chain, String authType)
        throws CertificateException {
            defaultTrustManager.checkClientTrusted(chain, authType);
        }

        public void checkServerTrusted(X509Certificate[] chain, String authType)
        throws CertificateException {
            // FIXME: Using a static field to store the certificate chain is a bad idea. Instead
            // create a CertificateException subclass and store the chain there.
            TrustManagerFactory.setLastCertChain(chain);
            try {
                defaultTrustManager.checkServerTrusted(chain, authType);
            } catch (CertificateException e) {
                localTrustManager.checkServerTrusted(new X509Certificate[] {chain[0]}, authType);
            }
            if (!DomainNameChecker.match(chain[0], mHost)) {
                try {
                    String dn = chain[0].getSubjectDN().toString();
                    if ((dn != null) && (dn.equalsIgnoreCase(keyStore.getCertificateAlias(chain[0])))) {
                        return;
                    }
                } catch (KeyStoreException e) {
                    throw new CertificateException("Certificate cannot be verified; KeyStore Exception: " + e);
                }
                throw new CertificateException("Certificate domain name does not match "
                                               + mHost);
            }
        }

        public X509Certificate[] getAcceptedIssuers() {
            return defaultTrustManager.getAcceptedIssuers();
        }

    }

    static {
        java.io.InputStream fis = null;
        try {
            javax.net.ssl.TrustManagerFactory tmf = javax.net.ssl.TrustManagerFactory.getInstance("X509");
            Application app = K9.app;
            keyStoreFile = new File(app.getDir("KeyStore", Context.MODE_PRIVATE) + File.separator + "KeyStore.bks");
            keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
            try {
                fis = new java.io.FileInputStream(keyStoreFile);
            } catch (FileNotFoundException e1) {
                fis = null;
            }
            try {
                keyStore.load(fis, "".toCharArray());
            } catch (IOException e) {
                Log.e(LOG_TAG, "KeyStore IOException while initializing TrustManagerFactory ", e);
                keyStore = null;
            } catch (CertificateException e) {
                Log.e(LOG_TAG, "KeyStore CertificateException while initializing TrustManagerFactory ", e);
                keyStore = null;
            }
            tmf.init(keyStore);
            TrustManager[] tms = tmf.getTrustManagers();
            if (tms != null) {
                for (TrustManager tm : tms) {
                    if (tm instanceof X509TrustManager) {
                        localTrustManager = (X509TrustManager)tm;
                        break;
                    }
                }
            }
            tmf = javax.net.ssl.TrustManagerFactory.getInstance("X509");
            tmf.init((KeyStore)null);
            tms = tmf.getTrustManagers();
            if (tms != null) {
                for (TrustManager tm : tms) {
                    if (tm instanceof X509TrustManager) {
                        defaultTrustManager = (X509TrustManager) tm;
                        break;
                    }
                }
            }

        } catch (NoSuchAlgorithmException e) {
            Log.e(LOG_TAG, "Unable to get X509 Trust Manager ", e);
        } catch (KeyStoreException e) {
            Log.e(LOG_TAG, "Key Store exception while initializing TrustManagerFactory ", e);
        } finally {
            IOUtils.closeQuietly(fis);
        }
        unsecureTrustManager = new SimpleX509TrustManager();
    }

    private TrustManagerFactory() {
    }

    public static X509TrustManager get(String host, boolean secure) {
        return secure ? SecureX509TrustManager.getInstance(host) :
               unsecureTrustManager;
    }

    public static KeyStore getKeyStore() {
        return keyStore;
    }

    public static void setLastCertChain(X509Certificate[] chain) {
        lastCertChain = chain;
    }
    public static X509Certificate[] getLastCertChain() {
        return lastCertChain;
    }

    public static void addCertificateChain(String alias, X509Certificate[] chain) throws CertificateException {
        try {
            javax.net.ssl.TrustManagerFactory tmf = javax.net.ssl.TrustManagerFactory.getInstance("X509");
            for (X509Certificate element : chain) {
                keyStore.setCertificateEntry
                (element.getSubjectDN().toString(), element);
            }

            tmf.init(keyStore);
            TrustManager[] tms = tmf.getTrustManagers();
            if (tms != null) {
                for (TrustManager tm : tms) {
                    if (tm instanceof X509TrustManager) {
                        localTrustManager = (X509TrustManager) tm;
                        break;
                    }
                }
            }
            java.io.OutputStream keyStoreStream = null;
            try {
                keyStoreStream = new java.io.FileOutputStream(keyStoreFile);
                keyStore.store(keyStoreStream, "".toCharArray());
            } catch (FileNotFoundException e) {
                throw new CertificateException("Unable to write KeyStore: " + e.getMessage());
            } catch (CertificateException e) {
                throw new CertificateException("Unable to write KeyStore: " + e.getMessage());
            } catch (IOException e) {
                throw new CertificateException("Unable to write KeyStore: " + e.getMessage());
            } finally {
                IOUtils.closeQuietly(keyStoreStream);
            }

        } catch (NoSuchAlgorithmException e) {
            Log.e(LOG_TAG, "Unable to get X509 Trust Manager ", e);
        } catch (KeyStoreException e) {
            Log.e(LOG_TAG, "Key Store exception while initializing TrustManagerFactory ", e);
        }
    }
}

Answer 2

You can use self-signed certificates. To use a self-signed certificate, you can convert it into bouncy castle format keystore which is supported by Android and then store it as a raw resource in your Android app project. How to convert and use it, all details can be found on Bob's blog. Here is the link for the same - http://blog.crazybob.org/2010/02/android-trusting-ssl-certificates.html. This worked quite well. Hope this helps