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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package javax.security.auth.kerberos;

import java.io.File;
import java.security.AccessControlException;
import java.util.Objects;
import sun.security.krb5.EncryptionKey;
import sun.security.krb5.KerberosSecrets;
import sun.security.krb5.PrincipalName;
import sun.security.krb5.RealmException;


This class encapsulates a keytab file.

 A Kerberos JAAS login module that obtains long term secret keys from a keytab file should use this class. The login module will store an instance of this class in the private credential set of a Subject during the commit phase of the authentication process. 
 If a KeyTab object is obtained from getUnboundInstance() or getUnboundInstance(File), it is unbound and thus can be used by any service principal. Otherwise, if it's obtained from getInstance(KerberosPrincipal) or getInstance(KerberosPrincipal, File), it is bound to the specific service principal and can only be used by it. 
 Please note the constructors getInstance() and getInstance(File) were created when there was no support for unbound keytabs. These methods should not be used anymore. An object created with either of these methods are considered to be bound to an unknown principal, which means, its isBound() returns true and getPrincipal() returns null. 
 It might be necessary for the application to be granted a 
PrivateCredentialPermission if it needs to access the KeyTab instance from a Subject. This permission is not needed when the application depends on the default JGSS Kerberos mechanism to access the KeyTab. In that case, however, the application will need an appropriate ServicePermission. 

The keytab file format is described at

http://www.ioplex.com/utilities/keytab.txt.

Since:1.7
/**
 * This class encapsulates a keytab file.
 * <p>
 * A Kerberos JAAS login module that obtains long term secret keys from a
 * keytab file should use this class. The login module will store
 * an instance of this class in the private credential set of a
 * {@link javax.security.auth.Subject Subject} during the commit phase of the
 * authentication process.
 * <p>
 * If a {@code KeyTab} object is obtained from {@link #getUnboundInstance()}
 * or {@link #getUnboundInstance(java.io.File)}, it is unbound and thus can be
 * used by any service principal. Otherwise, if it's obtained from
 * {@link #getInstance(KerberosPrincipal)} or
 * {@link #getInstance(KerberosPrincipal, java.io.File)}, it is bound to the
 * specific service principal and can only be used by it.
 * <p>
 * Please note the constructors {@link #getInstance()} and
 * {@link #getInstance(java.io.File)} were created when there was no support
 * for unbound keytabs. These methods should not be used anymore. An object
 * created with either of these methods are considered to be bound to an
 * unknown principal, which means, its {@link #isBound()} returns true and
 * {@link #getPrincipal()} returns null.
 * <p>
 * It might be necessary for the application to be granted a
 * {@link javax.security.auth.PrivateCredentialPermission
 * PrivateCredentialPermission} if it needs to access the {@code KeyTab}
 * instance from a {@code Subject}. This permission is not needed when the
 * application depends on the default JGSS Kerberos mechanism to access the
 * {@code KeyTab}. In that case, however, the application will need an appropriate
 * {@link javax.security.auth.kerberos.ServicePermission ServicePermission}.
 * <p>
 * The keytab file format is described at
 * <a href="http://www.ioplex.com/utilities/keytab.txt">
 * http://www.ioplex.com/utilities/keytab.txt</a>.
 *
 * @since 1.7
 */
public final class KeyTab {

    /*
     * Impl notes:
     *
     * This class is only a name, a permanent link to the keytab source
     * (can be missing). Itself has no content. In order to read content,
     * take a snapshot and read from it.
     *
     * The snapshot is of type sun.security.krb5.internal.ktab.KeyTab, which
     * contains the content of the keytab file when the snapshot is taken.
     * Itself has no refresh function and mostly an immutable class (except
     * for the create/add/save methods only used by the ktab command).
     */

    // Source, null if using the default one. Note that the default name
    // is maintained in snapshot, this field is never "resolved".
    private final File file;

    // Bound user: normally from the "principal" value in a JAAS krb5
    // login conf. Will be null if it's "*".
    private final KerberosPrincipal princ;

    private final boolean bound;

    // Set up JavaxSecurityAuthKerberosAccess in KerberosSecrets
    static {
        KerberosSecrets.setJavaxSecurityAuthKerberosAccess(
                new JavaxSecurityAuthKerberosAccessImpl());
    }

    private KeyTab(KerberosPrincipal princ, File file, boolean bound) {
        this.princ = princ;
        this.file = file;
        this.bound = bound;
    }

    
Returns a KeyTab instance from a File object that is bound to an unknown service principal. 
 The result of this method is never null. This method only associates the returned KeyTab object with the file and does not read it. 
 Developers should call getInstance(KerberosPrincipal, File) when the bound service principal is known. 
Params:
  • file – the keytab File object, must not be null
Throws:
Returns:the keytab instance
/**
     * Returns a {@code KeyTab} instance from a {@code File} object
     * that is bound to an unknown service principal.
     * <p>
     * The result of this method is never null. This method only associates
     * the returned {@code KeyTab} object with the file and does not read it.
     * <p>
     * Developers should call {@link #getInstance(KerberosPrincipal,File)}
     * when the bound service principal is known.
     * @param file the keytab {@code File} object, must not be null
     * @return the keytab instance
     * @throws NullPointerException if the {@code file} argument is null
     */
    public static KeyTab getInstance(File file) {
        if (file == null) {
            throw new NullPointerException("file must be non null");
        }
        return new KeyTab(null, file, true);
    }

    
Returns an unbound KeyTab instance from a File object. 
 The result of this method is never null. This method only associates the returned KeyTab object with the file and does not read it. 
Params:
  • file – the keytab File object, must not be null
Throws:
Returns:the keytab instance
Since:1.8
/**
     * Returns an unbound {@code KeyTab} instance from a {@code File}
     * object.
     * <p>
     * The result of this method is never null. This method only associates
     * the returned {@code KeyTab} object with the file and does not read it.
     * @param file the keytab {@code File} object, must not be null
     * @return the keytab instance
     * @throws NullPointerException if the file argument is null
     * @since 1.8
     */
    public static KeyTab getUnboundInstance(File file) {
        if (file == null) {
            throw new NullPointerException("file must be non null");
        }
        return new KeyTab(null, file, false);
    }

    
Returns a KeyTab instance from a File object that is bound to the specified service principal. 
 The result of this method is never null. This method only associates the returned KeyTab object with the file and does not read it. 
Params:
  • princ – the bound service principal, must not be null
  • file – the keytab File object, must not be null
Throws:
Returns:the keytab instance
Since:1.8
/**
     * Returns a {@code KeyTab} instance from a {@code File} object
     * that is bound to the specified service principal.
     * <p>
     * The result of this method is never null. This method only associates
     * the returned {@code KeyTab} object with the file and does not read it.
     * @param princ the bound service principal, must not be null
     * @param file the keytab {@code File} object, must not be null
     * @return the keytab instance
     * @throws NullPointerException if either of the arguments is null
     * @since 1.8
     */
    public static KeyTab getInstance(KerberosPrincipal princ, File file) {
        if (princ == null) {
            throw new NullPointerException("princ must be non null");
        }
        if (file == null) {
            throw new NullPointerException("file must be non null");
        }
        return new KeyTab(princ, file, true);
    }

    
Returns the default KeyTab instance that is bound to an unknown service principal. 
 The result of this method is never null. This method only associates the returned KeyTab object with the default keytab file and does not read it. 
 Developers should call getInstance(KerberosPrincipal) when the bound service principal is known. 
Returns:the default keytab instance.
/**
     * Returns the default {@code KeyTab} instance that is bound
     * to an unknown service principal.
     * <p>
     * The result of this method is never null. This method only associates
     * the returned {@code KeyTab} object with the default keytab file and
     * does not read it.
     * <p>
     * Developers should call {@link #getInstance(KerberosPrincipal)}
     * when the bound service principal is known.
     * @return the default keytab instance.
     */
    public static KeyTab getInstance() {
        return new KeyTab(null, null, true);
    }

    
Returns the default unbound KeyTab instance. 
 The result of this method is never null. This method only associates the returned KeyTab object with the default keytab file and does not read it. 
Returns:the default keytab instance
Since:1.8
/**
     * Returns the default unbound {@code KeyTab} instance.
     * <p>
     * The result of this method is never null. This method only associates
     * the returned {@code KeyTab} object with the default keytab file and
     * does not read it.
     * @return the default keytab instance
     * @since 1.8
     */
    public static KeyTab getUnboundInstance() {
        return new KeyTab(null, null, false);
    }

    
Returns the default KeyTab instance that is bound to the specified service principal. 
 The result of this method is never null. This method only associates the returned KeyTab object with the default keytab file and does not read it. 
Params:
  • princ – the bound service principal, must not be null
Throws:
Returns:the default keytab instance
Since:1.8
/**
     * Returns the default {@code KeyTab} instance that is bound
     * to the specified service principal.
     * <p>
     * The result of this method is never null. This method only associates
     * the returned {@code KeyTab} object with the default keytab file and
     * does not read it.
     * @param princ the bound service principal, must not be null
     * @return the default keytab instance
     * @throws NullPointerException if {@code princ} is null
     * @since 1.8
     */
    public static KeyTab getInstance(KerberosPrincipal princ) {
        if (princ == null) {
            throw new NullPointerException("princ must be non null");
        }
        return new KeyTab(princ, null, true);
    }

    // Takes a snapshot of the keytab content. This method is called by
    // JavaxSecurityAuthKerberosAccessImpl so no more private
    sun.security.krb5.internal.ktab.KeyTab takeSnapshot() {
        try {
            return sun.security.krb5.internal.ktab.KeyTab.getInstance(file);
        } catch (AccessControlException ace) {
            if (file != null) {
                // It's OK to show the name if caller specified it
                throw ace;
            } else {
                AccessControlException ace2 = new AccessControlException(
                        "Access to default keytab denied (modified exception)");
                ace2.setStackTrace(ace.getStackTrace());
                throw ace2;
            }
        }
    }

    
Returns fresh keys for the given Kerberos principal.

 Implementation of this method should make sure the returned keys match the latest content of the keytab file. The result is a newly created copy that can be modified by the caller without modifying the keytab object. The caller should destroy the result keys after they are used. 
 Please note that the keytab file can be created after the KeyTab object is instantiated and its content may change over time. Therefore, an application should call this method only when it needs to use the keys. Any previous result from an earlier invocation could potentially be expired. 

If there is any error (say, I/O error or format error)
during the reading process of the keytab file, a saved result should be
returned. If there is no saved result (say, this is the first time this
method is called, or, all previous read attempts failed), an empty array
should be returned. This can make sure the result is not drastically
changed during the (probably slow) update of the keytab file.

 Each time this method is called and the reading of the file succeeds with no exception (say, I/O error or file format error), the result should be saved for principal. The implementation can also save keys for other principals having keys in the same keytab object if convenient. 

Any unsupported key read from the keytab is ignored and not included
in the result.


If this keytab is bound to a specific principal, calling this method on
another principal will return an empty array.

Params:
  • principal – the Kerberos principal, must not be null.
Throws:
Returns:the keys (never null, may be empty)
/**
     * Returns fresh keys for the given Kerberos principal.
     * <p>
     * Implementation of this method should make sure the returned keys match
     * the latest content of the keytab file. The result is a newly created
     * copy that can be modified by the caller without modifying the keytab
     * object. The caller should {@link KerberosKey#destroy() destroy} the
     * result keys after they are used.
     * <p>
     * Please note that the keytab file can be created after the
     * {@code KeyTab} object is instantiated and its content may change over
     * time. Therefore, an application should call this method only when it
     * needs to use the keys. Any previous result from an earlier invocation
     * could potentially be expired.
     * <p>
     * If there is any error (say, I/O error or format error)
     * during the reading process of the keytab file, a saved result should be
     * returned. If there is no saved result (say, this is the first time this
     * method is called, or, all previous read attempts failed), an empty array
     * should be returned. This can make sure the result is not drastically
     * changed during the (probably slow) update of the keytab file.
     * <p>
     * Each time this method is called and the reading of the file succeeds
     * with no exception (say, I/O error or file format error),
     * the result should be saved for {@code principal}. The implementation can
     * also save keys for other principals having keys in the same keytab object
     * if convenient.
     * <p>
     * Any unsupported key read from the keytab is ignored and not included
     * in the result.
     * <p>
     * If this keytab is bound to a specific principal, calling this method on
     * another principal will return an empty array.
     *
     * @param principal the Kerberos principal, must not be null.
     * @return the keys (never null, may be empty)
     * @throws NullPointerException if the {@code principal}
     * argument is null
     * @throws SecurityException if a security manager exists and the read
     * access to the keytab file is not permitted
     */
    public KerberosKey[] getKeys(KerberosPrincipal principal) {
        try {
            if (princ != null && !principal.equals(princ)) {
                return new KerberosKey[0];
            }
            PrincipalName pn = new PrincipalName(principal.getName());
            EncryptionKey[] keys = takeSnapshot().readServiceKeys(pn);
            KerberosKey[] kks = new KerberosKey[keys.length];
            for (int i=0; i<kks.length; i++) {
                Integer tmp = keys[i].getKeyVersionNumber();
                kks[i] = new KerberosKey(
                        principal,
                        keys[i].getBytes(),
                        keys[i].getEType(),
                        tmp == null ? 0 : tmp.intValue());
                keys[i].destroy();
            }
            return kks;
        } catch (RealmException re) {
            return new KerberosKey[0];
        }
    }

    EncryptionKey[] getEncryptionKeys(PrincipalName principal) {
        return takeSnapshot().readServiceKeys(principal);
    }

    
Checks if the keytab file exists. Implementation of this method
should make sure that the result matches the latest status of the
keytab file.


The caller can use the result to determine if it should fallback to
another mechanism to read the keys.

Throws:
  • SecurityException – if a security manager exists and the read
access to the keytab file is not permitted
Returns:true if the keytab file exists; false otherwise.
/**
     * Checks if the keytab file exists. Implementation of this method
     * should make sure that the result matches the latest status of the
     * keytab file.
     * <p>
     * The caller can use the result to determine if it should fallback to
     * another mechanism to read the keys.
     * @return true if the keytab file exists; false otherwise.
     * @throws SecurityException if a security manager exists and the read
     * access to the keytab file is not permitted
     */
    public boolean exists() {
        return !takeSnapshot().isMissing();
    }

    
Returns an informative textual representation of this KeyTab. 
Returns:an informative textual representation of this KeyTab.
/**
     * Returns an informative textual representation of this {@code KeyTab}.
     *
     * @return an informative textual representation of this {@code KeyTab}.
     */
    public String toString() {
        String s = (file == null) ? "Default keytab" : file.toString();
        if (!bound) return s;
        else if (princ == null) return s + " for someone";
        else return s + " for " + princ;
    }

    
Returns a hash code for this KeyTab. 
Returns:a hash code for this KeyTab.
/**
     * Returns a hash code for this {@code KeyTab}.
     *
     * @return a hash code for this {@code KeyTab}.
     */
    public int hashCode() {
        return Objects.hash(file, princ, bound);
    }

    
Compares the specified object with this KeyTab for equality. Returns true if the given object is also a KeyTab and the two KeyTab instances are equivalent. 
Params:
  • other – the object to compare to
Returns:true if the specified object is equal to this KeyTab
/**
     * Compares the specified object with this {@code KeyTab} for equality.
     * Returns true if the given object is also a
     * {@code KeyTab} and the two
     * {@code KeyTab} instances are equivalent.
     *
     * @param other the object to compare to
     * @return true if the specified object is equal to this {@code KeyTab}
     */
    public boolean equals(Object other) {
        if (other == this)
            return true;

        if (! (other instanceof KeyTab)) {
            return false;
        }

        KeyTab otherKtab = (KeyTab) other;
        return Objects.equals(otherKtab.princ, princ) &&
                Objects.equals(otherKtab.file, file) &&
                bound == otherKtab.bound;
    }

    
Returns the service principal this KeyTab object is bound to. Returns null if it's not bound. 
 Please note the deprecated constructors create a KeyTab object bound for some unknown principal. In this case, this method also returns null. User can call isBound() to verify this case. 
Returns:the service principal
Since:1.8
/**
     * Returns the service principal this {@code KeyTab} object
     * is bound to. Returns {@code null} if it's not bound.
     * <p>
     * Please note the deprecated constructors create a {@code KeyTab} object
     * bound for some unknown principal. In this case, this method also returns
     * null. User can call {@link #isBound()} to verify this case.
     * @return the service principal
     * @since 1.8
     */
    public KerberosPrincipal getPrincipal() {
        return princ;
    }

    
Returns if the keytab is bound to a principal

Returns:if the keytab is bound to a principal
Since:1.8
/**
     * Returns if the keytab is bound to a principal
     * @return if the keytab is bound to a principal
     * @since 1.8
     */
    public boolean isBound() {
        return bound;
    }
}