how to check SSL certificate expiration date programmatically in Java

Question

I need to extract expiration date from SSL certificate on web site in Java,should support both trusted and self-signed certificate,such as: 1.trusted https://github.com 2.self-signed https://mms.nw.ru/

I already copy some code as:

import java.net.URL;
import java.security.SecureRandom;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.KeyManager;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

public class SSLTest {

    public static void main(String [] args) throws Exception {
        // configure the SSLContext with a TrustManager
        SSLContext ctx = SSLContext.getInstance("TLS");
        ctx.init(new KeyManager[0], new TrustManager[] {new DefaultTrustManager()}, new SecureRandom());
        SSLContext.setDefault(ctx);

        URL url = new URL("https://github.com");//https://mms.nw.ru
        HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
        conn.setHostnameVerifier(new HostnameVerifier() {
            @Override
            public boolean verify(String arg0, SSLSession arg1) {
                return true;
            }
        });
        System.out.println(conn.getResponseCode());
        Certificate[] certs = conn.getServerCertificates();
        for (Certificate cert :certs){
            System.out.println(cert.getType());
            System.out.println(cert);
        }

        conn.disconnect();
    }

    private static class DefaultTrustManager implements X509TrustManager {

        @Override
        public void checkClientTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {}

        @Override
        public void checkServerTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {}

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

The questions are:

1. How to parse the expiration date from the certificate, in my code the toString() did output the date,but it is hard to parse.

2. How to determine the certificate chain, eg, the github certificate with chains 3, how did i know which certificate to get the expiration date from?

Answer 1

How to parse the expiration date from the certificate

Cast it to an X509Certificate and call getNotAfter().

How to determine the certificate chain, eg, the github certificate with chains

You've got it. That's what the Certificate[] array is, as it says in the Javadoc.

How did i know which certificate to get the expiration date from?

Read the Javadoc. "The peer's own certificate first followed by any certificate authorities".

However I don't know why you're doing any of this. Java should already do it all for you.

And please throw away that insecure and incorrect TrustManager implementation. The correct way to handle self-signed certificates is to import them into the client truststore. Please also throw away your insecure HostnameVerifier, and use the default one, or a secure one. Why use HTTPS at all if you don't want it to be secure?