/*
 * Copyright (C) 2013-2014 Dominik Schürmann <dominik@dominikschuermann.de>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.sufficientlysecure.keychain.util;

import android.content.res.AssetManager;

import org.sufficientlysecure.keychain.Constants;
import org.sufficientlysecure.keychain.util.Log;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.security.KeyManagementException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.util.HashMap;
import java.util.Map;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManagerFactory;

public class TlsHelper {

    public static class TlsHelperException extends Exception {
        public TlsHelperException(Exception e) {
            super(e);
        }
    }

    private static Map<String, byte[]> sStaticCA = new HashMap<String, byte[]>();

    public static void addStaticCA(String domain, byte[] certificate) {
        sStaticCA.put(domain, certificate);
    }

    public static void addStaticCA(String domain, AssetManager assetManager, String name) {
        try {
            InputStream is = assetManager.open(name);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            int reads = is.read();

            while(reads != -1){
                baos.write(reads);
                reads = is.read();
            }

            is.close();

            addStaticCA(domain, baos.toByteArray());
        } catch (IOException e) {
            Log.w(Constants.TAG, e);
        }
    }

    public static URLConnection openConnection(URL url) throws IOException, TlsHelperException {
        if (url.getProtocol().equals("https")) {
            for (String domain : sStaticCA.keySet()) {
                if (url.getHost().endsWith(domain)) {
                    return openCAConnection(sStaticCA.get(domain), url);
                }
            }
        }
        return url.openConnection();
    }

    /**
     * Opens a Connection that will only accept certificates signed with a specific CA and skips common name check.
     * This is required for some distributed Keyserver networks like sks-keyservers.net
     *
     * @param certificate The X.509 certificate used to sign the servers certificate
     * @param url         Connection target
     */
    public static HttpsURLConnection openCAConnection(byte[] certificate, URL url)
            throws TlsHelperException, IOException {
        try {
            // Load CA
            CertificateFactory cf = CertificateFactory.getInstance("X.509");
            Certificate ca = cf.generateCertificate(new ByteArrayInputStream(certificate));

            // Create a KeyStore containing our trusted CAs
            String keyStoreType = KeyStore.getDefaultType();
            KeyStore keyStore = KeyStore.getInstance(keyStoreType);
            keyStore.load(null, null);
            keyStore.setCertificateEntry("ca", ca);

            // Create a TrustManager that trusts the CAs in our KeyStore
            String tmfAlgorithm = TrustManagerFactory.getDefaultAlgorithm();
            TrustManagerFactory tmf = TrustManagerFactory.getInstance(tmfAlgorithm);
            tmf.init(keyStore);

            // Create an SSLContext that uses our TrustManager
            SSLContext context = SSLContext.getInstance("TLS");
            context.init(null, tmf.getTrustManagers(), null);

            // Tell the URLConnection to use a SocketFactory from our SSLContext
            HttpsURLConnection urlConnection = (HttpsURLConnection) url.openConnection();
            urlConnection.setSSLSocketFactory(context.getSocketFactory());

            return urlConnection;
        } catch (CertificateException e) {
            throw new TlsHelperException(e);
        } catch (NoSuchAlgorithmException e) {
            throw new TlsHelperException(e);
        } catch (KeyStoreException e) {
            throw new TlsHelperException(e);
        } catch (KeyManagementException e) {
            throw new TlsHelperException(e);
        }
    }
}
