Using Self-Signed Certificates with Java and Maven

JAVA applications using JSSE (Java Secure Socket Extension) can’t connect to servers with self-signed or untrusted certificates by default. Maven for example is not able to download required dependencies from a nexus server, if that uses a self-signed certificate or the certificate authority is not recognized. If you try to connect to a server of that kind a security ValidatorException will be thrown:

Error transferring file: sun.security.validator.ValidatorException:
PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:
unable to find valid certification path to requested target
To make maven or other application work with a server using an untrusted certificate you have to create your own truststore, which than contains the certificate of the server. Next you would have to make your application use this created truststore in order make connections to the server. This can be done in several ways, but before that you can either use the JAVA class provided below or the attached JAR file J2EECert.jar to create that truststore yourself.
Using the JAR:
java -cp J2EECert.jar j2eecert.InstallCert  host[:port] [passphrase]
Where host is the URL to your server and you can also supply a pass phrase if necessarily. After running this you will be ask, which of the at the server present certificates – if more than one – you wish to install. Finally a file named jssecacerts is created in the current folder. This your new KeyStor containing the selected certificate. To use it with your application you can either supply the KeyStor at runtime with -Djava.security.KeyStore=jssecacerts or you copy the file to $JAVA_HOME/jre/lib/security, where the default truststore – cacerts – already exists. If you want all JAVA applications to recognize the certificate as trusted and not just JSSE, you could also overwrite the cacerts file in that directory.
The Source:
/*
* 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.
*/
package j2eecert;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLException;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

/**
* run it like this: java InstallCert ecc.fedora.redhat.com
* @author hkropp
*/
public class InstallCert {

public static void main(String[] args) throws Exception {
  String host;
  int port;
  char[] passphrase;
  if ((args.length == 1) || (args.length == 2)) {
    String[] c = args[0].split(":");
    host = c[0];
    port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
    String p = (args.length == 1) ? "changeit" : args[1];
    passphrase = p.toCharArray();
  } else {
    System.out.println("Usage: java InstallCert [:port] [passphrase]");
    return;
  }

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

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

System.out.println("Opening connection to " + host + ":" + port + "...");
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 (SSLException e) {
System.out.println();
e.printStackTrace(System.out);
}

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

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

System.out.println();
System.out.println("Server sent " + chain.length + " certificate(s):");
System.out.println();
MessageDigest sha1 = MessageDigest.getInstance("SHA1");
MessageDigest md5 = MessageDigest.getInstance("MD5");
for (int i = 0; i < chain.length; i++) { X509Certificate cert = chain[i]; System.out.println (" " + (i + 1) + " Subject " + cert.getSubjectDN()); System.out.println(" Issuer " + cert.getIssuerDN()); 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]"); String line = reader.readLine().trim(); int k; try { k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1; } catch (NumberFormatException e) { System.out.println("KeyStore not changed"); return; } X509Certificate cert = chain[k]; String alias = host + "-" + (k + 1); ks.setCertificateEntry(alias, cert); 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(byte[] bytes) { 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(X509TrustManager tm) {
this.tm = tm;
}

@Override
public X509Certificate[] getAcceptedIssuers() {
throw new UnsupportedOperationException();
}

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

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

 

File(s):

Further Reading:

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