In Java, what is the simplest way to create an SSLContext with just a PEM file?

Question

I used LetsEncrypt's CertBot to generate PEM files for free. In other languages it is easy to start an HTTPS server using just a couple lines of code and the PEM/key files. The solutions I have found so far in java are overly complex and I'm looking for something simpler.

1. I do not want to use java's command-line "keytool". I just want to drag and drop my PEM/key files into my eclipse, and programatically start up an HTTPS server using an SSLContext.
2. I do not want to include massive external libraries like BouncyCastle. See the following link for a supposed solution using BouncyCastle: How to build a SSLSocketFactory from PEM certificate and key without converting to keystore?

Is there a better/easier way to do this?

Answer 1

The following code shows in general how create a SSLContext for an HTTPS server by parsing a PEM file that has multiple entries, e.g. several certificates and one RSA PRIVATE KEY. However it is incomplete because plain Java 8 is unable to parse the PKCS#1 RSA private key data. Therefore it seems that your wish to do it without any library is not possible. At least BouncyCastle for parsing the PKCS#1 data is required (and then the PEM parser of BouncyCastle could be used, too).

private SSLContext createSslContext() throws Exception {
    URL url = getClass().getResource("/a.pem");
    InputStream in = url.openStream();
    String pem = new String(in.readAllBytes(), StandardCharsets.UTF_8);
    Pattern parse = Pattern.compile("(?m)(?s)^---*BEGIN ([^-]+)---*$([^-]+)^---*END[^-]+-+$");
    Matcher m = parse.matcher(pem);
    CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
    Decoder decoder = Base64.getMimeDecoder();
    List<Certificate> certList = new ArrayList<>(); // java.security.cert.Certificate

    PrivateKey privateKey = null;

    int start = 0;
    while (m.find(start)) {
        String type = m.group(1);
        String base64Data = m.group(2);
        byte[] data = decoder.decode(base64Data);
        start += m.group(0).length();
        type = type.toUpperCase();
        if (type.contains("CERTIFICATE")) {
            Certificate cert = certFactory.generateCertificate(new ByteArrayInputStream(data));
            certList.add(cert);
        } else if (type.contains("RSA PRIVATE KEY")) {
            // TODO: load and parse PKCS1 data structure to get the RSA private key  
            privateKey = ...
        } else {
            System.err.println("Unsupported type: " + type);
        }

    }
    if (privateKey == null)
        throw new RuntimeException("RSA private key not found in PEM file");

    char[] keyStorePassword = new char[0];

    KeyStore keyStore = KeyStore.getInstance("JKS");
    keyStore.load(null, null);

    int count = 0;
    for (Certificate cert : certList) {
        keyStore.setCertificateEntry("cert" + count, cert);
        count++;
    }
    Certificate[] chain = certList.toArray(new Certificate[certList.size()]);
    keyStore.setKeyEntry("key", privateKey, keyStorePassword, chain);

    TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
    tmf.init(keyStore);
    KeyManagerFactory kmf = KeyManagerFactory.getInstance("RSA");
    kmf.init(keyStore, keyStorePassword);
    SSLContext sslContext = SSLContext.getInstance("TLS");
    sslContext.init(kmf.getKeyManagers(), tmf.getTrustManagers(), new SecureRandom());
    return sslContext;
}

Answer 2

Although an answer has been provided, I would like to provide an alternative which requires less code. See below for an example setup:

X509ExtendedKeyManager keyManager = PemUtils.loadIdentityMaterial("certificate-chain.pem", "private-key.pem", "private-key-password".toCharArray());
X509ExtendedTrustManager trustManager = PemUtils.loadTrustMaterial("some-trusted-certificate.pem");

SSLFactory sslFactory = SSLFactory.builder()
          .withIdentityMaterial(keyManager)
          .withTrustMaterial(trustManager)
          .build();

SSLContext sslContext = sslFactory.getSslContext();

To use the above setup you can use this library:

<dependency>
    <groupId>io.github.hakky54</groupId>
    <artifactId>sslcontext-kickstart-for-pem</artifactId>
    <version>7.0.0</version>
</dependency>

The setup above requires less custom code while it is still achieving what you are trying to accomplish. You can view the library and documentation here: https://github.com/Hakky54/sslcontext-kickstart

Answer 3

My full solution that I currently use:

1. Use certbot on your server to generate the certificate. I use the command "certbot certonly -d myawesomedomain.com"
2. I use the following code to convert that certbot certificate into a java SSLContext: https://github.com/mirraj2/bowser/blob/master/src/bowser/SSLUtils.java

package bowser;

import static com.google.common.base.Preconditions.checkState;
import static ox.util.Utils.propagate;

import java.io.File;
import java.security.KeyStore;

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

import com.google.common.base.Splitter;

import ox.IO;
import ox.Log;

public class SSLUtils {

  public static SSLContext createContext(String domain) {
    String pass = "spamspam";

    File dir = new File("/etc/letsencrypt/live/" + domain);
    if (!dir.exists()) {
      Log.warn("Could not find letsencrypt dir: " + dir);
      return null;
    }

    File keystoreFile = new File(dir, "keystore.jks");
    File pemFile = new File(dir, "fullchain.pem");

    boolean generateKeystore = false;

    if (keystoreFile.exists()) {
      if (keystoreFile.lastModified() < pemFile.lastModified()) {
        Log.info("SSUtils: It looks like a new PEM file was created. Regenerating the keystore.");
        keystoreFile.delete();
        generateKeystore = true;
      }
    } else {
      generateKeystore = true;
    }

    if (generateKeystore) {
      Splitter splitter = Splitter.on(' ');
      try {
        String command = "openssl pkcs12 -export -out keystore.pkcs12 -in fullchain.pem -inkey privkey.pem -passout pass:"
            + pass;
        Log.debug(command);
        Process process = new ProcessBuilder(splitter.splitToList(command))
            .directory(dir).inheritIO().start();
        checkState(process.waitFor() == 0);

        command = "keytool -importkeystore -srckeystore keystore.pkcs12 -srcstoretype PKCS12 -destkeystore keystore.jks -srcstorepass "
            + pass + " -deststorepass " + pass;
        Log.debug(command);
        process = new ProcessBuilder(splitter.splitToList(command))
            .directory(dir).inheritIO().start();
        checkState(process.waitFor() == 0);

        new File(dir, "keystore.pkcs12").delete();// cleanup
      } catch (Exception e) {
        throw propagate(e);
      }
    }

    try {
      KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
      keystore.load(IO.from(keystoreFile).asStream(), pass.toCharArray());

      KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
      keyManagerFactory.init(keystore, pass.toCharArray());

      SSLContext ret = SSLContext.getInstance("TLSv1.2");
      TrustManagerFactory factory = TrustManagerFactory.getInstance(
          TrustManagerFactory.getDefaultAlgorithm());
      factory.init(keystore);
      ret.init(keyManagerFactory.getKeyManagers(), factory.getTrustManagers(), null);

      return ret;
    } catch (Exception e) {
      throw propagate(e);
    }
  }

}