Tool to add an untrusted (self-signed) SSL certificate to JVM.

InstallCert.java

/*
 * Copyright 2006 Sun Microsystems, Inc.  All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/**
 * http://blogs.sun.com/andreas/resource/InstallCert.java
 * Use:
 * java InstallCert hostname
 * Example:
 *% java InstallCert ecc.fedora.redhat.com
 */

import javax.net.ssl.*;
import java.io.*;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

/**
 * Class used to add the server's certificate to the KeyStore with your trusted certificates.
 */
public class InstallCert
{
  public static void main(final String[] args) throws Exception
  {
    String host;
    int port;
    char[] passphrase;
    if ((args.length == 1) || (args.length == 2))
    {
      final String[] c = args[0].split(":");
      host = c[0];
      port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
      final String p = (args.length == 1) ? "changeit" : args[1];
      passphrase = p.toCharArray();
    }
    else
    {
      System.out.println("Usage: java InstallCert <host>[:port] [passphrase]");
      return;
    }

    File file = new File("jssecacerts");
    if (!file.isFile())
    {
      final char SEP = File.separatorChar;
      final File dir = new File(System.getProperty("java.home") + SEP + "lib" + SEP + "security");
      file = new File(dir, "jssecacerts");
      if (!file.isFile())
      {
        file = new File(dir, "cacerts");
      }
    }
    System.out.println("Loading KeyStore " + file + "...");
    final InputStream in = new FileInputStream(file);
    final KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
    ks.load(in, passphrase);
    in.close();

    final SSLContext context = SSLContext.getInstance("TLS");
    final TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
    tmf.init(ks);
    final X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];
    final SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
    context.init(null, new TrustManager[] { tm }, null);
    final SSLSocketFactory factory = context.getSocketFactory();

    System.out.println("Opening connection to " + host + ":" + port + "...");
    final SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
    socket.setSoTimeout(10000);
    try
    {
      System.out.println("Starting SSL handshake...");
      socket.startHandshake();
      socket.close();
      System.out.println();
      System.out.println("No errors, certificate is already trusted");
    }
    catch (final SSLException e)
    {
      System.out.println();
      e.printStackTrace(System.out);
    }

    final X509Certificate[] chain = tm.chain;
    if (chain == null)
    {
      System.out.println("Could not obtain server certificate chain");
      return;
    }

    final BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

    System.out.println();
    System.out.println("Server sent " + chain.length + " certificate(s):");
    System.out.println();
    final MessageDigest sha256 = MessageDigest.getInstance("SHA-256");
    final MessageDigest sha1 = MessageDigest.getInstance("SHA-1");
    final MessageDigest md5 = MessageDigest.getInstance("MD5");
    for (int i = 0; i < chain.length; i++)
    {
      final X509Certificate cert = chain[i];
      System.out.println(" " + (i + 1) + " Subject " + cert.getSubjectDN());
      System.out.println("   Issuer  " + cert.getIssuerDN());
      sha256.update(cert.getEncoded());
      System.out.println("   sha256  " + toHexString(sha256.digest()));
      sha1.update(cert.getEncoded());
      System.out.println("   sha1    " + toHexString(sha1.digest()));
      md5.update(cert.getEncoded());
      System.out.println("   md5     " + toHexString(md5.digest()));
      System.out.println();
    }

    System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");
    final String line = reader.readLine()
                              .trim();
    int k;
    try
    {
      k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;
    }
    catch (final NumberFormatException e)
    {
      System.out.println("KeyStore not changed");
      return;
    }

    final X509Certificate cert = chain[k];
    final String alias = host + "-" + (k + 1);
    ks.setCertificateEntry(alias, cert);

    final OutputStream out = new FileOutputStream("jssecacerts");
    ks.store(out, passphrase);
    out.close();

    System.out.println();
    System.out.println(cert);
    System.out.println();
    System.out.println("Added certificate to keystore 'jssecacerts' using alias '" + alias + "'");
  }

  private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();

  private static String toHexString(final byte[] bytes)
  {
    final StringBuilder sb = new StringBuilder(bytes.length * 3);
    for (int b : bytes)
    {
      b &= 0xff;
      sb.append(HEXDIGITS[b >> 4]);
      sb.append(HEXDIGITS[b & 15]);
      sb.append(' ');
    }
    return sb.toString();
  }

  private static class SavingTrustManager implements X509TrustManager
  {
    private final X509TrustManager tm;
    private X509Certificate[] chain;

    SavingTrustManager(final X509TrustManager tm)
    {
      this.tm = tm;
    }

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

    @Override
    public void checkClientTrusted(final X509Certificate[] chain, final String authType) throws CertificateException
    {
      throw new UnsupportedOperationException();
    }

    @Override
    public void checkServerTrusted(final X509Certificate[] chain, final String authType) throws CertificateException
    {
      this.chain = chain;
      tm.checkServerTrusted(chain, authType);
    }
  }

}

How to use

// The "port" is optional.

$ java InstallCert host:port 

e.g.)

$ java InstallCert somesite.com 
or
$ java InstallCert somesite.com:443 

When an Exception (probably SSLHandshakeException) is thrown, type 1 and press the enter key then it will create a keystore file named 'jssecacerts' which contains the certificate from the given host.

Run it again to check if the certificate is added correctly.

$ java InstallCert host:port 

Now it should say "No errors, certificate is already trusted".

Copy the jssecacerts file to the $JAVA_HOME/jre/lib/security/ folder.
e.g.)

$ cp jssecacerts /usr/lib/jvm/java-openjdk/jre/lib/security/