Allowing Java to use an untrusted certificate for SSL/HTTPS connection

Following code from here is a useful solution. No keystores etc. Just call method SSLUtilities.trustAllHttpsCertificates() before initializing the service and port (in SOAP).

import java.security.GeneralSecurityException;
import java.security.SecureRandom;
import java.security.cert.X509Certificate;
import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

/**
 * This class provide various static methods that relax X509 certificate and
 * hostname verification while using the SSL over the HTTP protocol.
 *  
 * @author Jiramot.info
 */
public final class SSLUtilities {

  /**
   * Hostname verifier for the Sun's deprecated API.
   *
   * @deprecated see {@link #_hostnameVerifier}.
   */
  private static com.sun.net.ssl.HostnameVerifier __hostnameVerifier;
  /**
   * Thrust managers for the Sun's deprecated API.
   *
   * @deprecated see {@link #_trustManagers}.
   */
  private static com.sun.net.ssl.TrustManager[] __trustManagers;
  /**
   * Hostname verifier.
   */
  private static HostnameVerifier _hostnameVerifier;
  /**
   * Thrust managers.
   */
  private static TrustManager[] _trustManagers;

  /**
   * Set the default Hostname Verifier to an instance of a fake class that
   * trust all hostnames. This method uses the old deprecated API from the
   * com.sun.ssl package.
   *  
   * @deprecated see {@link #_trustAllHostnames()}.
   */
  private static void __trustAllHostnames() {
    // Create a trust manager that does not validate certificate chains
    if (__hostnameVerifier == null) {
        __hostnameVerifier = new SSLUtilities._FakeHostnameVerifier();
    } // if
    // Install the all-trusting host name verifier
    com.sun.net.ssl.HttpsURLConnection
            .setDefaultHostnameVerifier(__hostnameVerifier);
  } // __trustAllHttpsCertificates

  /**
   * Set the default X509 Trust Manager to an instance of a fake class that
   * trust all certificates, even the self-signed ones. This method uses the
   * old deprecated API from the com.sun.ssl package.
   *
   * @deprecated see {@link #_trustAllHttpsCertificates()}.
   */
  private static void __trustAllHttpsCertificates() {
    com.sun.net.ssl.SSLContext context;

    // Create a trust manager that does not validate certificate chains
    if (__trustManagers == null) {
        __trustManagers = new com.sun.net.ssl.TrustManager[]{new SSLUtilities._FakeX509TrustManager()};
    } // if
    // Install the all-trusting trust manager
    try {
        context = com.sun.net.ssl.SSLContext.getInstance("SSL");
        context.init(null, __trustManagers, new SecureRandom());
    } catch (GeneralSecurityException gse) {
        throw new IllegalStateException(gse.getMessage());
    } // catch
    com.sun.net.ssl.HttpsURLConnection.setDefaultSSLSocketFactory(context
            .getSocketFactory());
  } // __trustAllHttpsCertificates

  /**
   * Return true if the protocol handler property java. protocol.handler.pkgs
   * is set to the Sun's com.sun.net.ssl. internal.www.protocol deprecated
   * one, false otherwise.
   *
   * @return true if the protocol handler property is set to the Sun's
   * deprecated one, false otherwise.
   */
  private static boolean isDeprecatedSSLProtocol() {
    return ("com.sun.net.ssl.internal.www.protocol".equals(System
            .getProperty("java.protocol.handler.pkgs")));
  } // isDeprecatedSSLProtocol

  /**
   * Set the default Hostname Verifier to an instance of a fake class that
   * trust all hostnames.
   */
  private static void _trustAllHostnames() {
      // Create a trust manager that does not validate certificate chains
      if (_hostnameVerifier == null) {
          _hostnameVerifier = new SSLUtilities.FakeHostnameVerifier();
      } // if
      // Install the all-trusting host name verifier:
      HttpsURLConnection.setDefaultHostnameVerifier(_hostnameVerifier);
  } // _trustAllHttpsCertificates

  /**
   * Set the default X509 Trust Manager to an instance of a fake class that
   * trust all certificates, even the self-signed ones.
   */
  private static void _trustAllHttpsCertificates() {
    SSLContext context;

      // Create a trust manager that does not validate certificate chains
      if (_trustManagers == null) {
          _trustManagers = new TrustManager[]{new SSLUtilities.FakeX509TrustManager()};
      } // if
      // Install the all-trusting trust manager:
      try {
          context = SSLContext.getInstance("SSL");
          context.init(null, _trustManagers, new SecureRandom());
      } catch (GeneralSecurityException gse) {
          throw new IllegalStateException(gse.getMessage());
      } // catch
      HttpsURLConnection.setDefaultSSLSocketFactory(context
            .getSocketFactory());
  } // _trustAllHttpsCertificates

  /**
   * Set the default Hostname Verifier to an instance of a fake class that
   * trust all hostnames.
   */
  public static void trustAllHostnames() {
      // Is the deprecated protocol setted?
      if (isDeprecatedSSLProtocol()) {
          __trustAllHostnames();
      } else {
          _trustAllHostnames();
      } // else
  } // trustAllHostnames

  /**
   * Set the default X509 Trust Manager to an instance of a fake class that
   * trust all certificates, even the self-signed ones.
   */
  public static void trustAllHttpsCertificates() {
    // Is the deprecated protocol setted?
    if (isDeprecatedSSLProtocol()) {
        __trustAllHttpsCertificates();
    } else {
        _trustAllHttpsCertificates();
    } // else
  } // trustAllHttpsCertificates

  /**
   * This class implements a fake hostname verificator, trusting any host
   * name. This class uses the old deprecated API from the com.sun. ssl
   * package.
   *
   * @author Jiramot.info
   *
   * @deprecated see {@link SSLUtilities.FakeHostnameVerifier}.
   */
  public static class _FakeHostnameVerifier implements
        com.sun.net.ssl.HostnameVerifier {

    /**
     * Always return true, indicating that the host name is an acceptable
     * match with the server's authentication scheme.
     *
     * @param hostname the host name.
     * @param session the SSL session used on the connection to host.
     * @return the true boolean value indicating the host name is trusted.
     */
    public boolean verify(String hostname, String session) {
        return (true);
    } // verify
  } // _FakeHostnameVerifier

  /**
   * This class allow any X509 certificates to be used to authenticate the
   * remote side of a secure socket, including self-signed certificates. This
   * class uses the old deprecated API from the com.sun.ssl package.
   *
   * @author Jiramot.info
   *
   * @deprecated see {@link SSLUtilities.FakeX509TrustManager}.
   */
  public static class _FakeX509TrustManager implements
        com.sun.net.ssl.X509TrustManager {

    /**
     * Empty array of certificate authority certificates.
     */
    private static final X509Certificate[] _AcceptedIssuers = new X509Certificate[]{};

    /**
     * Always return true, trusting for client SSL chain peer certificate
     * chain.
     *
     * @param chain the peer certificate chain.
     * @return the true boolean value indicating the chain is trusted.
     */
    public boolean isClientTrusted(X509Certificate[] chain) {
        return (true);
    } // checkClientTrusted

    /**
     * Always return true, trusting for server SSL chain peer certificate
     * chain.
     *
     * @param chain the peer certificate chain.
     * @return the true boolean value indicating the chain is trusted.
     */
    public boolean isServerTrusted(X509Certificate[] chain) {
        return (true);
    } // checkServerTrusted

    /**
     * Return an empty array of certificate authority certificates which are
     * trusted for authenticating peers.
     *
     * @return a empty array of issuer certificates.
     */
    public X509Certificate[] getAcceptedIssuers() {
        return (_AcceptedIssuers);
    } // getAcceptedIssuers
  } // _FakeX509TrustManager

  /**
   * This class implements a fake hostname verificator, trusting any host
   * name.
   *
   * @author Jiramot.info
   */
  public static class FakeHostnameVerifier implements HostnameVerifier {

    /**
     * Always return true, indicating that the host name is an acceptable
     * match with the server's authentication scheme.
     *
     * @param hostname the host name.
     * @param session the SSL session used on the connection to host.
     * @return the true boolean value indicating the host name is trusted.
     */
    public boolean verify(String hostname, javax.net.ssl.SSLSession session) {
        return (true);
    } // verify
  } // FakeHostnameVerifier

  /**
   * This class allow any X509 certificates to be used to authenticate the
   * remote side of a secure socket, including self-signed certificates.
   *
   * @author Jiramot.info
   */
  public static class FakeX509TrustManager implements X509TrustManager {

    /**
     * Empty array of certificate authority certificates.
     */
    private static final X509Certificate[] _AcceptedIssuers = new X509Certificate[]{};

    /**
     * Always trust for client SSL chain peer certificate chain with any
     * authType authentication types.
     *
     * @param chain the peer certificate chain.
     * @param authType the authentication type based on the client
     * certificate.
     */
    public void checkClientTrusted(X509Certificate[] chain, String authType) {
    } // checkClientTrusted

    /**
     * Always trust for server SSL chain peer certificate chain with any
     * authType exchange algorithm types.
     *
     * @param chain the peer certificate chain.
     * @param authType the key exchange algorithm used.
     */
    public void checkServerTrusted(X509Certificate[] chain, String authType) {
    } // checkServerTrusted

    /**
     * Return an empty array of certificate authority certificates which are
     * trusted for authenticating peers.
     *
     * @return a empty array of issuer certificates.
     */
    public X509Certificate[] getAcceptedIssuers() {
        return (_AcceptedIssuers);
    } // getAcceptedIssuers
  } // FakeX509TrustManager
} // SSLUtilities

Here is some relevant code:

// Create a trust manager that does not validate certificate chains
TrustManager[] trustAllCerts = new TrustManager[]{
    new X509TrustManager() {
        public java.security.cert.X509Certificate[] getAcceptedIssuers() {
            return null;
        }
        public void checkClientTrusted(
            java.security.cert.X509Certificate[] certs, String authType) {
        }
        public void checkServerTrusted(
            java.security.cert.X509Certificate[] certs, String authType) {
        }
    }
};

// Install the all-trusting trust manager
try {
    SSLContext sc = SSLContext.getInstance("SSL");
    sc.init(null, trustAllCerts, new java.security.SecureRandom());
    HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
} catch (Exception e) {
}

// Now you can access an https URL without having the certificate in the truststore
try {
    URL url = new URL("https://hostname/index.html");
} catch (MalformedURLException e) {
}

This will completely disable SSL checking—just don't learn exception handling from such code!

To do what you want, you would have to implement a check in your TrustManager that prompts the user.

Another option is to get a ".pem" (public key) file for that particular server, and install it locally into the heart of your JRE's "cacerts" file (use the keytool helper application), then it will be able to download from that server without complaint, without compromising the entire SSL structure of your running JVM and enabling download from other unknown cert servers...