javakerberosgssapikeytab

Check whether a Kerberos KeyTab file is valid in Java

I'm working on a Java code base that checks whether a Kerberos KeyTab file is valid, but it uses the internal class sun.security.krb5.internal.ktab.KeyTab for its isValid() method. Currently, it is doing the following:

File keytabFile = new File("/path/to/keytab");
KeyTab keytab = KeyTab.getInstance(keytabFile);
boolean keytabIsValid = keytab.isValid();
if (!keytabIsValid) {
   throw new ApplicationSpecificException("Keytab is not valid");
}

Accessing this method is more of an annoyance in Java 9, so I'm looking for a way to avoid using this internal class, but browsing through the JDK source, I haven't seen anything that exposes the isValid() method or an equivalent in a non-internal class.

Are there options which don't rely on hacks like reflecting on private methods or accessing internal APIs?

Solution

  • 1)

    You can try using the native executable to validate the keytab file and proceed as per the output to determine validity, through java ProcessBuilder. e.g. for linux/*nix, you can run

    klist -k –t your.keytab

    2)

    Since, you already mention desire to exclude accessing internal API's, I assume you are aware of the options. But just including here for information for this particular case:

    javac --add-exports java.security.jgss/sun.security.krb5.internal.ktab=ALL-UNNAMED your-class.java
java --add-exports java.security.jgss/sun.security.krb5.internal.ktab=ALL-UNNAMED your-class

    3)

    You can also roll out your own validator. I think the source is not that complex.