[Kerberos] Add missing javadocs (#32469)

This commit adds missing javadocs and fixes few where
the build failed when using JDK 11 for compilation.

Closes#32461

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/KerberosTestCase.java

@@ -133,7 +133,7 @@ public void tearDownMiniKdc() throws IOException, PrivilegedActionException {
      * @param dir Directory where the key tab would be created.
      * @param princNames principal names to be created
      * @return {@link Path} to key tab file.
-     * @throws Exception
+     * @throws Exception thrown if principal or keytab could not be created
      */
     protected Path createPrincipalKeyTab(final Path dir, final String... princNames) throws Exception {
         final Path path = dir.resolve(randomAlphaOfLength(10) + ".keytab");
@@ -146,7 +146,7 @@ protected Path createPrincipalKeyTab(final Path dir, final String... princNames)
      * 
      * @param principalName Principal name
      * @param password Password
-     * @throws Exception
+     * @throws Exception thrown if principal could not be created
      */
     protected void createPrincipal(final String principalName, final char[] password) throws Exception {
         simpleKdcLdapServer.createPrincipal(principalName, new String(password));
@@ -168,8 +168,8 @@ protected String principalName(final String user) {
      * @param subject {@link Subject}
      * @param action {@link PrivilegedExceptionAction} action for performing inside
      *            Subject.doAs
-     * @return <T> Type of value as returned by PrivilegedAction
-     * @throws PrivilegedActionException
+     * @return T Type of value as returned by PrivilegedAction
+     * @throws PrivilegedActionException when privileged action threw exception
      */
     static <T> T doAsWrapper(final Subject subject, final PrivilegedExceptionAction<T> action) throws PrivilegedActionException {
         return AccessController.doPrivileged((PrivilegedExceptionAction<T>) () -> Subject.doAs(subject, action));
@@ -181,7 +181,7 @@ static <T> T doAsWrapper(final Subject subject, final PrivilegedExceptionAction<
      * @param keytabPath {@link Path} to keytab file.
      * @param content Content for keytab
      * @return key tab path
-     * @throws IOException
+     * @throws IOException if I/O error occurs while writing keytab file
      */
     public static Path writeKeyTab(final Path keytabPath, final String content) throws IOException {
         try (BufferedWriter bufferedWriter = Files.newBufferedWriter(keytabPath, StandardCharsets.US_ASCII)) {

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/SimpleKdcLdapServer.java

@@ -66,7 +66,7 @@ public class SimpleKdcLdapServer {
      * @param orgName Org name for base dn
      * @param domainName domain name for base dn
      * @param ldiff for ldap directory.
-     * @throws Exception
+     * @throws Exception when KDC or Ldap server initialization fails
      */
     public SimpleKdcLdapServer(final Path workDir, final String orgName, final String domainName, final Path ldiff) throws Exception {
         this.workDir = workDir;
@@ -194,7 +194,7 @@ public synchronized void createPrincipal(final Path keytabFile, final String...
     /**
      * Stop Simple Kdc Server
      * 
-     * @throws PrivilegedActionException
+     * @throws PrivilegedActionException when privileged action threw exception
      */
     public synchronized void stop() throws PrivilegedActionException {
         AccessController.doPrivileged(new PrivilegedExceptionAction<Void>() {

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/SpnegoClient.java

@@ -11,7 +11,6 @@
 import org.elasticsearch.common.SuppressForbidden;
 import org.elasticsearch.common.logging.ESLoggerFactory;
 import org.elasticsearch.common.settings.SecureString;
-import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.xpack.security.authc.kerberos.KerberosTicketValidator;
 import org.ietf.jgss.GSSContext;
 import org.ietf.jgss.GSSCredential;
@@ -67,8 +66,8 @@ class SpnegoClient implements AutoCloseable {
      * @param password password for client
      * @param servicePrincipalName Service principal name with whom this client
      *            interacts with.
-     * @throws PrivilegedActionException
-     * @throws GSSException
+     * @throws PrivilegedActionException when privileged action threw exception
+     * @throws GSSException thrown when GSS API error occurs
      */
     SpnegoClient(final String userPrincipalName, final SecureString password, final String servicePrincipalName)
             throws PrivilegedActionException, GSSException {
@@ -99,7 +98,7 @@ class SpnegoClient implements AutoCloseable {
      * base64 encoded token to be sent to server.
      *
      * @return Base64 encoded token
-     * @throws PrivilegedActionException
+     * @throws PrivilegedActionException when privileged action threw exception
      */
     String getBase64EncodedTokenForSpnegoHeader() throws PrivilegedActionException {
         final byte[] outToken = KerberosTestCase.doAsWrapper(loginContext.getSubject(),
@@ -114,7 +113,7 @@ String getBase64EncodedTokenForSpnegoHeader() throws PrivilegedActionException {
      *            gss negotiation
      * @return Base64 encoded token to be sent to server. May return {@code null} if
      *         nothing to be sent.
-     * @throws PrivilegedActionException
+     * @throws PrivilegedActionException when privileged action threw exception
      */
     String handleResponse(final String base64Token) throws PrivilegedActionException {
         if (gssContext.isEstablished()) {
@@ -160,10 +159,9 @@ boolean isEstablished() {
      *
      * @param principal Principal name
      * @param password {@link SecureString}
-     * @param settings {@link Settings}
      * @return authenticated {@link LoginContext} instance. Note: This needs to be
      *         closed {@link LoginContext#logout()} after usage.
-     * @throws LoginException
+     * @throws LoginException thrown if problem with login configuration or when login fails
      */
     private static LoginContext loginUsingPassword(final String principal, final SecureString password) throws LoginException {
         final Set<Principal> principals = Collections.singleton(new KerberosPrincipal(principal));
@@ -182,8 +180,8 @@ private static LoginContext loginUsingPassword(final String principal, final Sec
      * Instead of an additional file setting as we do not want the options to be
      * customizable we are constructing it in memory.
      * <p>
-     * As we are uing this instead of jaas.conf, this requires refresh of
-     * {@link Configuration} and reqires appropriate security permissions to do so.
+     * As we are using this instead of jaas.conf, this requires refresh of
+     * {@link Configuration} and requires appropriate security permissions to do so.
      */
     static class PasswordJaasConf extends Configuration {
         private final String principal;