/* MemorizingTrustManager - a TrustManager which asks the user about invalid
 *  certificates and memorizes their decision.
 *
 * Copyright (c) 2010 Georg Lukas <georg@op-co.de>
 *
 * MemorizingTrustManager.java contains the actual trust manager and interface
 * code to create a MemorizingActivity and obtain the results.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package eu.siacs.conversations.services;

import android.support.v7.app.AppCompatActivity ;
import android.app.Application;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.preference.PreferenceManager;
import android.util.Base64;
import android.util.Log;
import android.util.SparseArray;
import android.os.Handler;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.security.NoSuchAlgorithmException;
import java.security.cert.*;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.MessageDigest;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Enumeration;
import java.util.List;
import java.util.Locale;
import java.util.regex.Pattern;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

import eu.siacs.conversations.R;
import eu.siacs.conversations.crypto.DomainHostnameVerifier;
import eu.siacs.conversations.entities.MTMDecision;
import eu.siacs.conversations.ui.MemorizingActivity;

/**
 * A X509 trust manager implementation which asks the user about invalid
 * certificates and memorizes their decision.
 * <p>
 * The certificate validity is checked using the system default X509
 * TrustManager, creating a query Dialog if the check fails.
 * <p>
 * <b>WARNING:</b> This only works if a dedicated thread is used for
 * opening sockets!
 */
public class MemorizingTrustManager {


	private static final Pattern PATTERN_IPV4 = Pattern.compile("\\A(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
	private static final Pattern PATTERN_IPV6_HEX4DECCOMPRESSED = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?) ::((?:[0-9A-Fa-f]{1,4}:)*)(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
	private static final Pattern PATTERN_IPV6_6HEX4DEC = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}:){6,6})(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
	private static final Pattern PATTERN_IPV6_HEXCOMPRESSED = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)::((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)\\z");
	private static final Pattern PATTERN_IPV6 = Pattern.compile("\\A(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}\\z");

	final static String DECISION_INTENT = "de.duenndns.ssl.DECISION";
	public final static String DECISION_INTENT_ID     = DECISION_INTENT + ".decisionId";
	public final static String DECISION_INTENT_CERT   = DECISION_INTENT + ".cert";
	final static String DECISION_INTENT_CHOICE = DECISION_INTENT + ".decisionChoice";

	private final static Logger LOGGER = Logger.getLogger(MemorizingTrustManager.class.getName());
	public final static String DECISION_TITLE_ID      = DECISION_INTENT + ".titleId";
	private final static int NOTIFICATION_ID = 100509;

	final static String NO_TRUST_ANCHOR = "Trust anchor for certification path not found.";
	
	static String KEYSTORE_DIR = "KeyStore";
	static String KEYSTORE_FILE = "KeyStore.bks";

	Context master;
	AppCompatActivity foregroundAct;
	NotificationManager notificationManager;
	private static int decisionId = 0;
	private static SparseArray<MTMDecision> openDecisions = new SparseArray<MTMDecision>();

	Handler masterHandler;
	private File keyStoreFile;
	private KeyStore appKeyStore;
	private X509TrustManager defaultTrustManager;
	private X509TrustManager appTrustManager;
	private String poshCacheDir;

	/** Creates an instance of the MemorizingTrustManager class that falls back to a custom TrustManager.
	 *
	 * You need to supply the application context. This has to be one of:
	 *    - Application
	 *    - Activity
	 *    - Service
	 *
	 * The context is used for file management, to display the dialog /
	 * notification and for obtaining translated strings.
	 *
	 * @param m Context for the application.
	 * @param defaultTrustManager Delegate trust management to this TM. If null, the user must accept every certificate.
	 */
	public MemorizingTrustManager(Context m, X509TrustManager defaultTrustManager) {
		init(m);
		this.appTrustManager = getTrustManager(appKeyStore);
		this.defaultTrustManager = defaultTrustManager;
	}

	/** Creates an instance of the MemorizingTrustManager class using the system X509TrustManager.
	 *
	 * You need to supply the application context. This has to be one of:
	 *    - Application
	 *    - Activity
	 *    - Service
	 *
	 * The context is used for file management, to display the dialog /
	 * notification and for obtaining translated strings.
	 *
	 * @param m Context for the application.
	 */
	public MemorizingTrustManager(Context m) {
		init(m);
		this.appTrustManager = getTrustManager(appKeyStore);
		this.defaultTrustManager = getTrustManager(null);
	}

	void init(Context m) {
		master = m;
		masterHandler = new Handler(m.getMainLooper());
		notificationManager = (NotificationManager)master.getSystemService(Context.NOTIFICATION_SERVICE);

		Application app;
		if (m instanceof Application) {
			app = (Application)m;
		} else if (m instanceof Service) {
			app = ((Service)m).getApplication();
		} else if (m instanceof AppCompatActivity) {
			app = ((AppCompatActivity)m).getApplication();
		} else throw new ClassCastException("MemorizingTrustManager context must be either Activity or Service!");

		File dir = app.getDir(KEYSTORE_DIR, Context.MODE_PRIVATE);
		keyStoreFile = new File(dir + File.separator + KEYSTORE_FILE);

		poshCacheDir = app.getFilesDir().getAbsolutePath()+"/posh_cache/";

		appKeyStore = loadAppKeyStore();
	}


	/**
	 * Binds an Activity to the MTM for displaying the query dialog.
	 *
	 * This is useful if your connection is run from a service that is
	 * triggered by user interaction -- in such cases the activity is
	 * visible and the user tends to ignore the service notification.
	 *
	 * You should never have a hidden activity bound to MTM! Use this
	 * function in onResume() and @see unbindDisplayActivity in onPause().
	 *
	 * @param act Activity to be bound
	 */
	public void bindDisplayActivity(AppCompatActivity act) {
		foregroundAct = act;
	}

	/**
	 * Removes an Activity from the MTM display stack.
	 *
	 * Always call this function when the Activity added with
	 * {@link #bindDisplayActivity(AppCompatActivity)} is hidden.
	 *
	 * @param act Activity to be unbound
	 */
	public void unbindDisplayActivity(AppCompatActivity act) {
		// do not remove if it was overridden by a different activity
		if (foregroundAct == act)
			foregroundAct = null;
	}

	/**
	 * Changes the path for the KeyStore file.
	 *
	 * The actual filename relative to the app's directory will be
	 * <code>app_<i>dirname</i>/<i>filename</i></code>.
	 *
	 * @param dirname directory to store the KeyStore.
	 * @param filename file name for the KeyStore.
	 */
	public static void setKeyStoreFile(String dirname, String filename) {
		KEYSTORE_DIR = dirname;
		KEYSTORE_FILE = filename;
	}

	/**
	 * Get a list of all certificate aliases stored in MTM.
	 *
	 * @return an {@link Enumeration} of all certificates
	 */
	public Enumeration<String> getCertificates() {
		try {
			return appKeyStore.aliases();
		} catch (KeyStoreException e) {
			// this should never happen, however...
			throw new RuntimeException(e);
		}
	}

	/**
	 * Get a certificate for a given alias.
	 *
	 * @param alias the certificate's alias as returned by {@link #getCertificates()}.
	 *
	 * @return the certificate associated with the alias or <tt>null</tt> if none found.
	 */
	public Certificate getCertificate(String alias) {
		try {
			return appKeyStore.getCertificate(alias);
		} catch (KeyStoreException e) {
			// this should never happen, however...
			throw new RuntimeException(e);
		}
	}

	/**
	 * Removes the given certificate from MTMs key store.
	 *
	 * <p>
	 * <b>WARNING</b>: this does not immediately invalidate the certificate. It is
	 * well possible that (a) data is transmitted over still existing connections or
	 * (b) new connections are created using TLS renegotiation, without a new cert
	 * check.
	 * </p>
	 * @param alias the certificate's alias as returned by {@link #getCertificates()}.
	 *
	 * @throws KeyStoreException if the certificate could not be deleted.
	 */
	public void deleteCertificate(String alias) throws KeyStoreException {
		appKeyStore.deleteEntry(alias);
		keyStoreUpdated();
	}

	/**
	 * Creates a new hostname verifier supporting user interaction.
	 *
	 * <p>This method creates a new {@link HostnameVerifier} that is bound to
	 * the given instance of {@link MemorizingTrustManager}, and leverages an
	 * existing {@link HostnameVerifier}. The returned verifier performs the
	 * following steps, returning as soon as one of them succeeds:
	 *  </p>
	 *  <ol>
	 *  <li>Success, if the wrapped defaultVerifier accepts the certificate.</li>
	 *  <li>Success, if the server certificate is stored in the keystore under the given hostname.</li>
	 *  <li>Ask the user and return accordingly.</li>
	 *  <li>Failure on exception.</li>
	 *  </ol>
	 *
	 * @param defaultVerifier the {@link HostnameVerifier} that should perform the actual check
	 * @return a new hostname verifier using the MTM's key store
	 *
	 * @throws IllegalArgumentException if the defaultVerifier parameter is null
	 */
	public DomainHostnameVerifier wrapHostnameVerifier(final HostnameVerifier defaultVerifier, final boolean interactive) {
		if (defaultVerifier == null)
			throw new IllegalArgumentException("The default verifier may not be null");
		
		return new MemorizingHostnameVerifier(defaultVerifier, interactive);
	}
	
	X509TrustManager getTrustManager(KeyStore ks) {
		try {
			TrustManagerFactory tmf = TrustManagerFactory.getInstance("X509");
			tmf.init(ks);
			for (TrustManager t : tmf.getTrustManagers()) {
				if (t instanceof X509TrustManager) {
					return (X509TrustManager)t;
				}
			}
		} catch (Exception e) {
			// Here, we are covering up errors. It might be more useful
			// however to throw them out of the constructor so the
			// embedding app knows something went wrong.
			LOGGER.log(Level.SEVERE, "getTrustManager(" + ks + ")", e);
		}
		return null;
	}

	KeyStore loadAppKeyStore() {
		KeyStore ks;
		try {
			ks = KeyStore.getInstance(KeyStore.getDefaultType());
		} catch (KeyStoreException e) {
			LOGGER.log(Level.SEVERE, "getAppKeyStore()", e);
			return null;
		}
		try {
			ks.load(null, null);
			ks.load(new java.io.FileInputStream(keyStoreFile), "MTM".toCharArray());
		} catch (java.io.FileNotFoundException e) {
			LOGGER.log(Level.INFO, "getAppKeyStore(" + keyStoreFile + ") - file does not exist");
		} catch (Exception e) {
			LOGGER.log(Level.SEVERE, "getAppKeyStore(" + keyStoreFile + ")", e);
		}
		return ks;
	}

	void storeCert(String alias, Certificate cert) {
		try {
			appKeyStore.setCertificateEntry(alias, cert);
		} catch (KeyStoreException e) {
			LOGGER.log(Level.SEVERE, "storeCert(" + cert + ")", e);
			return;
		}		
		keyStoreUpdated();
	}
	
	void storeCert(X509Certificate cert) {
		storeCert(cert.getSubjectDN().toString(), cert);
	}

	void keyStoreUpdated() {
		// reload appTrustManager
		appTrustManager = getTrustManager(appKeyStore);

		// store KeyStore to file
		java.io.FileOutputStream fos = null;
		try {
			fos = new java.io.FileOutputStream(keyStoreFile);
			appKeyStore.store(fos, "MTM".toCharArray());
		} catch (Exception e) {
			LOGGER.log(Level.SEVERE, "storeCert(" + keyStoreFile + ")", e);
		} finally {
			if (fos != null) {
				try {
					fos.close();
				} catch (IOException e) {
					LOGGER.log(Level.SEVERE, "storeCert(" + keyStoreFile + ")", e);
				}
			}
		}
	}

	// if the certificate is stored in the app key store, it is considered "known"
	private boolean isCertKnown(X509Certificate cert) {
		try {
			return appKeyStore.getCertificateAlias(cert) != null;
		} catch (KeyStoreException e) {
			return false;
		}
	}

	private boolean isExpiredException(Throwable e) {
		do {
			if (e instanceof CertificateExpiredException)
				return true;
			e = e.getCause();
		} while (e != null);
		return false;
	}

	public void checkCertTrusted(X509Certificate[] chain, String authType, String domain, boolean isServer, boolean interactive)
		throws CertificateException
	{
		LOGGER.log(Level.FINE, "checkCertTrusted(" + chain + ", " + authType + ", " + isServer + ")");
		try {
			LOGGER.log(Level.FINE, "checkCertTrusted: trying appTrustManager");
			if (isServer)
				appTrustManager.checkServerTrusted(chain, authType);
			else
				appTrustManager.checkClientTrusted(chain, authType);
		} catch (CertificateException ae) {
			LOGGER.log(Level.FINER, "checkCertTrusted: appTrustManager failed", ae);
			// if the cert is stored in our appTrustManager, we ignore expiredness
			if (isExpiredException(ae)) {
				LOGGER.log(Level.INFO, "checkCertTrusted: accepting expired certificate from keystore");
				return;
			}
			if (isCertKnown(chain[0])) {
				LOGGER.log(Level.INFO, "checkCertTrusted: accepting cert already stored in keystore");
				return;
			}
			try {
				if (defaultTrustManager == null)
					throw ae;
				LOGGER.log(Level.FINE, "checkCertTrusted: trying defaultTrustManager");
				if (isServer)
					defaultTrustManager.checkServerTrusted(chain, authType);
				else
					defaultTrustManager.checkClientTrusted(chain, authType);
			} catch (CertificateException e) {
				boolean trustSystemCAs = !PreferenceManager.getDefaultSharedPreferences(master).getBoolean("dont_trust_system_cas", false);
				if (domain != null && isServer && trustSystemCAs && !isIp(domain)) {
					String hash = getBase64Hash(chain[0],"SHA-256");
					List<String> fingerprints = getPoshFingerprints(domain);
					if (hash != null && fingerprints.contains(hash)) {
						Log.d("mtm","trusted cert fingerprint of "+domain+" via posh");
						return;
					}
				}
				e.printStackTrace();
				if (interactive) {
					interactCert(chain, authType, e);
				} else {
					throw e;
				}
			}
		}
	}

	private List<String> getPoshFingerprints(String domain) {
		List<String> cached = getPoshFingerprintsFromCache(domain);
		if (cached == null) {
			return getPoshFingerprintsFromServer(domain);
		} else {
			return cached;
		}
	}

	private List<String> getPoshFingerprintsFromServer(String domain) {
		return getPoshFingerprintsFromServer(domain, "https://"+domain+"/.well-known/posh/xmpp-client.json",-1,true);
	}

	private List<String> getPoshFingerprintsFromServer(String domain, String url, int maxTtl, boolean followUrl) {
		Log.d("mtm","downloading json for "+domain+" from "+url);
		try {
			List<String> results = new ArrayList<>();
			HttpsURLConnection connection = (HttpsURLConnection) new URL(url).openConnection();
			connection.setConnectTimeout(5000);
			connection.setReadTimeout(5000);
			BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
			String inputLine;
			StringBuilder builder = new StringBuilder();
			while ((inputLine = in.readLine()) != null) {
				builder.append(inputLine);
			}
			JSONObject jsonObject = new JSONObject(builder.toString());
			in.close();
			int expires = jsonObject.getInt("expires");
			if (expires <= 0) {
				return new ArrayList<>();
			}
			if (maxTtl >= 0) {
				expires = Math.min(maxTtl,expires);
			}
			String redirect;
			try {
				redirect = jsonObject.getString("url");
			} catch (JSONException e) {
				redirect = null;
			}
			if (followUrl && redirect != null && redirect.toLowerCase().startsWith("https")) {
				return getPoshFingerprintsFromServer(domain, redirect, expires, false);
			}
			JSONArray fingerprints = jsonObject.getJSONArray("fingerprints");
			for(int i = 0; i < fingerprints.length(); i++) {
				JSONObject fingerprint = fingerprints.getJSONObject(i);
				String sha256 = fingerprint.getString("sha-256");
				if (sha256 != null) {
					results.add(sha256);
				}
			}
			writeFingerprintsToCache(domain, results,1000L * expires+System.currentTimeMillis());
			return results;
		} catch (Exception e) {
			Log.d("mtm","error fetching posh "+e.getMessage());
			return new ArrayList<>();
		}
	}

	private File getPoshCacheFile(String domain) {
		return new File(poshCacheDir+domain+".json");
	}

	private void writeFingerprintsToCache(String domain, List<String> results, long expires) {
		File file = getPoshCacheFile(domain);
		file.getParentFile().mkdirs();
		try {
			file.createNewFile();
			JSONObject jsonObject = new JSONObject();
			jsonObject.put("expires",expires);
			jsonObject.put("fingerprints",new JSONArray(results));
			FileOutputStream outputStream = new FileOutputStream(file);
			outputStream.write(jsonObject.toString().getBytes());
			outputStream.flush();
			outputStream.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private List<String> getPoshFingerprintsFromCache(String domain) {
		File file = getPoshCacheFile(domain);
		try {
			InputStream is = new FileInputStream(file);
			BufferedReader buf = new BufferedReader(new InputStreamReader(is));

			String line = buf.readLine();
			StringBuilder sb = new StringBuilder();

			while(line != null){
				sb.append(line).append("\n");
				line = buf.readLine();
			}
			JSONObject jsonObject = new JSONObject(sb.toString());
			is.close();
			long expires = jsonObject.getLong("expires");
			long expiresIn = expires - System.currentTimeMillis();
			if (expiresIn < 0) {
				file.delete();
				return null;
			} else {
				Log.d("mtm","posh fingerprints expire in "+(expiresIn/1000)+"s");
			}
			List<String> result = new ArrayList<>();
			JSONArray jsonArray = jsonObject.getJSONArray("fingerprints");
			for(int i = 0; i < jsonArray.length(); ++i) {
				result.add(jsonArray.getString(i));
			}
			return result;
		} catch (FileNotFoundException e) {
			return null;
		} catch (IOException e) {
			return null;
		} catch (JSONException e) {
			file.delete();
			return null;
		}
	}

	private static boolean isIp(final String server) {
		return server != null && (
				PATTERN_IPV4.matcher(server).matches()
						|| PATTERN_IPV6.matcher(server).matches()
						|| PATTERN_IPV6_6HEX4DEC.matcher(server).matches()
						|| PATTERN_IPV6_HEX4DECCOMPRESSED.matcher(server).matches()
						|| PATTERN_IPV6_HEXCOMPRESSED.matcher(server).matches());
	}

	private static String getBase64Hash(X509Certificate certificate, String digest) throws CertificateEncodingException {
		MessageDigest md;
		try {
			md = MessageDigest.getInstance(digest);
		} catch (NoSuchAlgorithmException e) {
			return null;
		}
		md.update(certificate.getEncoded());
		return Base64.encodeToString(md.digest(),Base64.NO_WRAP);
	}

	private X509Certificate[] getAcceptedIssuers() {
		LOGGER.log(Level.FINE, "getAcceptedIssuers()");
		return defaultTrustManager.getAcceptedIssuers();
	}

	private int createDecisionId(MTMDecision d) {
		int myId;
		synchronized(openDecisions) {
			myId = decisionId;
			openDecisions.put(myId, d);
			decisionId += 1;
		}
		return myId;
	}

	private static String hexString(byte[] data) {
		StringBuffer si = new StringBuffer();
		for (int i = 0; i < data.length; i++) {
			si.append(String.format("%02x", data[i]));
			if (i < data.length - 1)
				si.append(":");
		}
		return si.toString();
	}

	private static String certHash(final X509Certificate cert, String digest) {
		try {
			MessageDigest md = MessageDigest.getInstance(digest);
			md.update(cert.getEncoded());
			return hexString(md.digest());
		} catch (java.security.cert.CertificateEncodingException e) {
			return e.getMessage();
		} catch (java.security.NoSuchAlgorithmException e) {
			return e.getMessage();
		}
	}

	private void certDetails(StringBuffer si, X509Certificate c) {
		SimpleDateFormat validityDateFormater = new SimpleDateFormat("yyyy-MM-dd");
		si.append("\n");
		si.append(c.getSubjectDN().toString());
		si.append("\n");
		si.append(validityDateFormater.format(c.getNotBefore()));
		si.append(" - ");
		si.append(validityDateFormater.format(c.getNotAfter()));
		si.append("\nSHA-256: ");
		si.append(certHash(c, "SHA-256"));
		si.append("\nSHA-1: ");
		si.append(certHash(c, "SHA-1"));
		si.append("\nSigned by: ");
		si.append(c.getIssuerDN().toString());
		si.append("\n");
	}
	
	private String certChainMessage(final X509Certificate[] chain, CertificateException cause) {
		Throwable e = cause;
		LOGGER.log(Level.FINE, "certChainMessage for " + e);
		StringBuffer si = new StringBuffer();
		if (e.getCause() != null) {
			e = e.getCause();
			// HACK: there is no sane way to check if the error is a "trust anchor
			// not found", so we use string comparison.
			if (NO_TRUST_ANCHOR.equals(e.getMessage())) {
				si.append(master.getString(R.string.mtm_trust_anchor));
			} else
				si.append(e.getLocalizedMessage());
			si.append("\n");
		}
		si.append("\n");
		si.append(master.getString(R.string.mtm_connect_anyway));
		si.append("\n\n");
		si.append(master.getString(R.string.mtm_cert_details));
		for (X509Certificate c : chain) {
			certDetails(si, c);
		}
		return si.toString();
	}

	private String hostNameMessage(X509Certificate cert, String hostname) {
		StringBuffer si = new StringBuffer();

		si.append(master.getString(R.string.mtm_hostname_mismatch, hostname));
		si.append("\n\n");
		try {
			Collection<List<?>> sans = cert.getSubjectAlternativeNames();
			if (sans == null) {
				si.append(cert.getSubjectDN());
				si.append("\n");
			} else for (List<?> altName : sans) {
				Object name = altName.get(1);
				if (name instanceof String) {
					si.append("[");
					si.append((Integer)altName.get(0));
					si.append("] ");
					si.append(name);
					si.append("\n");
				}
			}
		} catch (CertificateParsingException e) {
			e.printStackTrace();
			si.append("<Parsing error: ");
			si.append(e.getLocalizedMessage());
			si.append(">\n");
		}
		si.append("\n");
		si.append(master.getString(R.string.mtm_connect_anyway));
		si.append("\n\n");
		si.append(master.getString(R.string.mtm_cert_details));
		certDetails(si, cert);
		return si.toString();
	}
	/**
	 * Returns the top-most entry of the activity stack.
	 *
	 * @return the Context of the currently bound UI or the master context if none is bound
	 */
	Context getUI() {
		return (foregroundAct != null) ? foregroundAct : master;
	}

	int interact(final String message, final int titleId) {
		/* prepare the MTMDecision blocker object */
		MTMDecision choice = new MTMDecision();
		final int myId = createDecisionId(choice);

		masterHandler.post(new Runnable() {
			public void run() {
				Intent ni = new Intent(master, MemorizingActivity.class);
				ni.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
				ni.setData(Uri.parse(MemorizingTrustManager.class.getName() + "/" + myId));
				ni.putExtra(DECISION_INTENT_ID, myId);
				ni.putExtra(DECISION_INTENT_CERT, message);
				ni.putExtra(DECISION_TITLE_ID, titleId);

				// we try to directly start the activity and fall back to
				// making a notification
				try {
					getUI().startActivity(ni);
				} catch (Exception e) {
					LOGGER.log(Level.FINE, "startActivity(MemorizingActivity)", e);
				}
			}
		});

		LOGGER.log(Level.FINE, "openDecisions: " + openDecisions + ", waiting on " + myId);
		try {
			synchronized(choice) { choice.wait(); }
		} catch (InterruptedException e) {
			LOGGER.log(Level.FINER, "InterruptedException", e);
		}
		LOGGER.log(Level.FINE, "finished wait on " + myId + ": " + choice.state);
		return choice.state;
	}
	
	void interactCert(final X509Certificate[] chain, String authType, CertificateException cause)
			throws CertificateException
	{
		switch (interact(certChainMessage(chain, cause), R.string.mtm_accept_cert)) {
		case MTMDecision.DECISION_ALWAYS:
			storeCert(chain[0]); // only store the server cert, not the whole chain
		case MTMDecision.DECISION_ONCE:
			break;
		default:
			throw (cause);
		}
	}

	boolean interactHostname(X509Certificate cert, String hostname)
	{
		switch (interact(hostNameMessage(cert, hostname), R.string.mtm_accept_servername)) {
		case MTMDecision.DECISION_ALWAYS:
			storeCert(hostname, cert);
		case MTMDecision.DECISION_ONCE:
			return true;
		default:
			return false;
		}
	}

	public static void interactResult(int decisionId, int choice) {
		MTMDecision d;
		synchronized(openDecisions) {
			 d = openDecisions.get(decisionId);
			 openDecisions.remove(decisionId);
		}
		if (d == null) {
			LOGGER.log(Level.SEVERE, "interactResult: aborting due to stale decision reference!");
			return;
		}
		synchronized(d) {
			d.state = choice;
			d.notify();
		}
	}
	
	class MemorizingHostnameVerifier implements DomainHostnameVerifier {
		private final HostnameVerifier defaultVerifier;
		private final boolean interactive;
		
		public MemorizingHostnameVerifier(HostnameVerifier wrapped, boolean interactive) {
			this.defaultVerifier = wrapped;
			this.interactive = interactive;
		}

		@Override
		public boolean verify(String domain, String hostname, SSLSession session) {
			LOGGER.log(Level.FINE, "hostname verifier for " + domain + ", trying default verifier first");
			// if the default verifier accepts the hostname, we are done
			if (defaultVerifier instanceof DomainHostnameVerifier) {
				if (((DomainHostnameVerifier) defaultVerifier).verify(domain,hostname, session)) {
					return true;
				}
			} else {
				if (defaultVerifier.verify(domain, session)) {
					return true;
				}
			}


			// otherwise, we check if the hostname is an alias for this cert in our keystore
			try {
				X509Certificate cert = (X509Certificate)session.getPeerCertificates()[0];
				//Log.d(TAG, "cert: " + cert);
				if (cert.equals(appKeyStore.getCertificate(domain.toLowerCase(Locale.US)))) {
					LOGGER.log(Level.FINE, "certificate for " + domain + " is in our keystore. accepting.");
					return true;
				} else {
					LOGGER.log(Level.FINE, "server " + domain + " provided wrong certificate, asking user.");
					if (interactive) {
						return interactHostname(cert, domain);
					} else {
						return false;
					}
				}
			} catch (Exception e) {
				e.printStackTrace();
				return false;
			}
		}

		@Override
		public boolean verify(String domain, SSLSession sslSession) {
			return verify(domain,null,sslSession);
		}
	}

	
	public X509TrustManager getNonInteractive(String domain) {
		return new NonInteractiveMemorizingTrustManager(domain);
	}

	public X509TrustManager getInteractive(String domain) {
		return new InteractiveMemorizingTrustManager(domain);
	}

	public X509TrustManager getNonInteractive() {
		return new NonInteractiveMemorizingTrustManager(null);
	}

	public X509TrustManager getInteractive() {
		return new InteractiveMemorizingTrustManager(null);
	}
	
	private class NonInteractiveMemorizingTrustManager implements X509TrustManager {

		private final String domain;

		public NonInteractiveMemorizingTrustManager(String domain) {
			this.domain = domain;
		}

		@Override
		public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
			MemorizingTrustManager.this.checkCertTrusted(chain, authType, domain, false, false);
		}

		@Override
		public void checkServerTrusted(X509Certificate[] chain, String authType)
				throws CertificateException {
			MemorizingTrustManager.this.checkCertTrusted(chain, authType, domain, true, false);
		}

		@Override
		public X509Certificate[] getAcceptedIssuers() {
			return MemorizingTrustManager.this.getAcceptedIssuers();
		}
		
	}

	private class InteractiveMemorizingTrustManager implements X509TrustManager {
		private final String domain;

		public InteractiveMemorizingTrustManager(String domain) {
			this.domain = domain;
		}

		@Override
		public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
			MemorizingTrustManager.this.checkCertTrusted(chain, authType, domain, false, true);
		}

		@Override
		public void checkServerTrusted(X509Certificate[] chain, String authType)
				throws CertificateException {
			MemorizingTrustManager.this.checkCertTrusted(chain, authType, domain, true, true);
		}

		@Override
		public X509Certificate[] getAcceptedIssuers() {
			return MemorizingTrustManager.this.getAcceptedIssuers();
		}
	}
}