Question

How can one programmatically obtain a KeyStore from a PEM file containing both a certificate and a private key? I am attempting to provide a client certificate to a server in an HTTPS connection. I have confirmed that the client certificate works if I use openssl and keytool to obtain a jks file, which I load dynamically. I can even get it to work by dynamically reading in a p12 (PKCS12) file.

I’m looking into using the PEMReader class from BouncyCastle, but I can’t get past some errors. I’m running the Java client with the -Djavax.net.debug=all option and Apache web server with the debug LogLevel. I’m not sure what to look for though. The Apache error log indicates:

...
OpenSSL: Write: SSLv3 read client certificate B
OpenSSL: Exit: error in SSLv3 read client certificate B
Re-negotiation handshake failed: Not accepted by client!?

The Java client program indicates:

...
main, WRITE: TLSv1 Handshake, length = 48
main, waiting for close_notify or alert: state 3
main, Exception while waiting for close java.net.SocketException: Software caused connection abort: recv failed
main, handling exception: java.net.SocketException: Software caused connection abort: recv failed
%% Invalidated:  [Session-3, TLS_RSA_WITH_AES_128_CBC_SHA]
main, SEND TLSv1 ALERT:  fatal, description = unexpected_message
...

The client code :

public void testClientCertPEM() throws Exception {
    String requestURL = "https://mydomain/authtest";
    String pemPath = "C:/Users/myusername/Desktop/client.pem";

    HttpsURLConnection con;

    URL url = new URL(requestURL);
    con = (HttpsURLConnection) url.openConnection();
    con.setSSLSocketFactory(getSocketFactoryFromPEM(pemPath));
    con.setRequestMethod("GET");
    con.setDoInput(true);
    con.setDoOutput(false);  
    con.connect();

    String line;

    BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream()));

    while((line = reader.readLine()) != null) {
        System.out.println(line);
    }       

    reader.close();
    con.disconnect();
}

public SSLSocketFactory getSocketFactoryFromPEM(String pemPath) throws Exception {
    Security.addProvider(new BouncyCastleProvider());        
    SSLContext context = SSLContext.getInstance("TLS");

    PEMReader reader = new PEMReader(new FileReader(pemPath));
    X509Certificate cert = (X509Certificate) reader.readObject();        

    KeyStore keystore = KeyStore.getInstance("JKS");
    keystore.load(null);
    keystore.setCertificateEntry("alias", cert);

    KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
    kmf.init(keystore, null);

    KeyManager[] km = kmf.getKeyManagers(); 

    context.init(km, null, null);

    return context.getSocketFactory();
} 

I noticed the server is outputing SSLv3 in the log while the client is TLSv1. If I add the system property -Dhttps.protocols=SSLv3 then the client will use SSLv3 as well, but I get the same error message. I’ve also tried adding -Dsun.security.ssl.allowUnsafeRenegotiation=true with no change in outcome.

I’ve googled around and the usual answer for this question is to just use openssl and keytool first. In my case I need to read the PEM directly on the fly. I’m actually porting a C++ program that already does this, and frankly, I’m very surprised how difficult it is to do this in Java. The C++ code:

  curlpp::Easy request;
  ...
  request.setOpt(new Options::Url(myurl));
  request.setOpt(new Options::SslVerifyPeer(false));
  request.setOpt(new Options::SslCertType("PEM"));
  request.setOpt(new Options::SslCert(cert));
  request.perform();

Answer 1

I figured it out. The problem is that the X509Certificate by itself isn’t sufficient. I needed to put the private key into the dynamically generated keystore as well. It doesn’t seem that BouncyCastle PEMReader can handle a PEM file with both cert and private key all in one go, but it can handle each piece separately. I can read the PEM into memory myself and break it into two separate streams and then feed each one to a separate PEMReader. Since I know that the PEM files I’m dealing with will have the cert first and the private key second I can simplify the code at the cost of robustness. I also know that the END CERTIFICATE delimiter will always be surrounded with five hyphens. The implementation that works for me is:

protected static SSLSocketFactory getSocketFactoryPEM(String pemPath) throws Exception {        
    Security.addProvider(new BouncyCastleProvider());

    SSLContext context = SSLContext.getInstance("TLS");

    byte[] certAndKey = fileToBytes(new File(pemPath));

    String delimiter = "-----END CERTIFICATE-----";
    String[] tokens = new String(certAndKey).split(delimiter);

    byte[] certBytes = tokens[0].concat(delimiter).getBytes();
    byte[] keyBytes = tokens[1].getBytes();

    PEMReader reader;

    reader = new PEMReader(new InputStreamReader(new ByteArrayInputStream(certBytes)));
    X509Certificate cert = (X509Certificate)reader.readObject();        

    reader = new PEMReader(new InputStreamReader(new ByteArrayInputStream(keyBytes)));
    PrivateKey key = (PrivateKey)reader.readObject();        

    KeyStore keystore = KeyStore.getInstance("JKS");
    keystore.load(null);
    keystore.setCertificateEntry("cert-alias", cert);
    keystore.setKeyEntry("key-alias", key, "changeit".toCharArray(), new Certificate[] {cert});

    KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
    kmf.init(keystore, "changeit".toCharArray());

    KeyManager[] km = kmf.getKeyManagers(); 

    context.init(km, null, null);

    return context.getSocketFactory();
}

Update: It seems this can be done without BouncyCastle:

    byte[] certAndKey = fileToBytes(new File(pemPath));
    byte[] certBytes = parseDERFromPEM(certAndKey, "-----BEGIN CERTIFICATE-----", "-----END CERTIFICATE-----");
    byte[] keyBytes = parseDERFromPEM(certAndKey, "-----BEGIN PRIVATE KEY-----", "-----END PRIVATE KEY-----");

    X509Certificate cert = generateCertificateFromDER(certBytes);              
    RSAPrivateKey key  = generatePrivateKeyFromDER(keyBytes);

…

protected static byte[] parseDERFromPEM(byte[] pem, String beginDelimiter, String endDelimiter) {
    String data = new String(pem);
    String[] tokens = data.split(beginDelimiter);
    tokens = tokens[1].split(endDelimiter);
    return DatatypeConverter.parseBase64Binary(tokens[0]);        
}

protected static RSAPrivateKey generatePrivateKeyFromDER(byte[] keyBytes) throws InvalidKeySpecException, NoSuchAlgorithmException {
    PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);

    KeyFactory factory = KeyFactory.getInstance("RSA");

    return (RSAPrivateKey)factory.generatePrivate(spec);        
}

protected static X509Certificate generateCertificateFromDER(byte[] certBytes) throws CertificateException {
    CertificateFactory factory = CertificateFactory.getInstance("X.509");

    return (X509Certificate)factory.generateCertificate(new ByteArrayInputStream(certBytes));      
}