public final class KeyTab extends Object
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(java.io.File), it is unbound and thus can be used by any service principal. Otherwise, if it's obtained from getInstance(KerberosPrincipal) or getInstance(KerberosPrincipal, java.io.File), it is bound to the specific service principal and can only be used by it.
Please note the constructors getInstance() and 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 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.
| Modifier and Type | Method | Description |
|---|---|---|
boolean |
equals |
Compares the specified object with this KeyTab for equality. |
boolean |
exists() |
Checks if the keytab file exists. |
static KeyTab |
getInstance() |
Returns the default KeyTab instance that is bound to an unknown service principal. |
static KeyTab |
getInstance |
Returns a KeyTab instance from a File object that is bound to an unknown service principal. |
static KeyTab |
getInstance |
Returns the default KeyTab instance that is bound to the specified service principal. |
static KeyTab |
getInstance |
Returns a KeyTab instance from a File object that is bound to the specified service principal. |
KerberosKey[] |
getKeys |
Returns fresh keys for the given Kerberos principal. |
KerberosPrincipal |
getPrincipal() |
Returns the service principal this KeyTab object is bound to. |
static KeyTab |
getUnboundInstance() |
Returns the default unbound KeyTab instance. |
static KeyTab |
getUnboundInstance |
Returns an unbound KeyTab instance from a File object. |
int |
hashCode() |
Returns a hash code for this KeyTab. |
boolean |
isBound() |
Returns if the keytab is bound to a principal |
String |
toString() |
Returns an informative textual representation of this KeyTab. |
public static KeyTab getInstance(File file)
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.
file - the keytab File object, must not be nullNullPointerException - if the file argument is nullpublic static KeyTab getUnboundInstance(File file)
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.
file - the keytab File object, must not be nullNullPointerException - if the file argument is nullpublic static KeyTab getInstance(KerberosPrincipal princ, File file)
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.
princ - the bound service principal, must not be nullfile - the keytab File object, must not be nullNullPointerException - if either of the arguments is nullpublic static KeyTab getInstance()
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.
public static KeyTab getUnboundInstance()
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.
public static KeyTab getInstance(KerberosPrincipal princ)
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.
princ - the bound service principal, must not be nullNullPointerException - if princ is nullpublic KerberosKey[] getKeys(KerberosPrincipal 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.
principal - the Kerberos principal, must not be null.NullPointerException - if the principal argument is nullSecurityException - if a security manager exists and the read access to the keytab file is not permittedpublic boolean exists()
SecurityException - if a security manager exists and the read access to the keytab file is not permittedpublic String toString()
KeyTab.public int hashCode()
KeyTab.public boolean equals(Object other)
KeyTab for equality. Returns true if the given object is also a KeyTab and the two KeyTab instances are equivalent.public KerberosPrincipal getPrincipal()
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.
public boolean isBound()
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https://docs.oracle.com/en/java/javase/21/docs/api/java.security.jgss/javax/security/auth/kerberos/KeyTab.html