Java SSL No Subject Alternative Matched

When you trying to connect to a server with untrusted SSL certificate, you might encounter below mentioned exceptions:

java.security.cert.CertificateException: No subject alternative names matching IP address xxx.xxx.xxx found

or

java.security.cert.CertificateException: No subject alternative DNS name matching hostname.com found.

The reason is because the certificate did not set the correct subject alternative value correctly. Two possible solution for above scenario:

• Change certificate’s subject alternative value
• Create customize HostnameVerifier

Change Certificate’s Subject Alternative Value

If you’re connecting to your host by using IP address, then you must change the subject alternative value to your IP address value. Likewise if you’re connecting using DNS name, the subject alternative value must match with the DNS name.

Create Customize HostnameVerifier

Basically you just need to create your customized HostnameVerifier class like example below:

private static class CustomizedHostnameVerifier implements HostnameVerifier {
public boolean verify(String hostname, SSLSession session) {
return true;
}
}

and then apply this class to your single SSL connection

HttpsURLConnection connection = (HttpsURLConnection) new URL("https://url").openConnection();
connection.setHostnameVerifier(new CustomizedHostNameVerifier());

or apply to all SLL connection

HttpsURLConnection.setDefaultHostnameVerifier(new CustomizedHostnameVerifier());

However this method might pose a security risk because basically we don’t verify the hostname anymore. The server may use other website’s certificate and the program will still accept it.