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.
- Since:
- 1.7
-
Method Summary
Modifier and Type Method Description boolean
equals(Object other)
Compares the specified object with thisKeyTab
for equality.boolean
exists()
Checks if the keytab file exists.static KeyTab
getInstance()
Returns the defaultKeyTab
instance that is bound to an unknown service principal.static KeyTab
getInstance(File file)
Returns aKeyTab
instance from aFile
object that is bound to an unknown service principal.static KeyTab
getInstance(KerberosPrincipal princ)
Returns the defaultKeyTab
instance that is bound to the specified service principal.static KeyTab
getInstance(KerberosPrincipal princ, File file)
Returns aKeyTab
instance from aFile
object that is bound to the specified service principal.KerberosKey[]
getKeys(KerberosPrincipal principal)
Returns fresh keys for the given Kerberos principal.KerberosPrincipal
getPrincipal()
Returns the service principal thisKeyTab
object is bound to.static KeyTab
getUnboundInstance()
Returns the default unboundKeyTab
instance.static KeyTab
getUnboundInstance(File file)
Returns an unboundKeyTab
instance from aFile
object.int
hashCode()
Returns a hash code for thisKeyTab
.boolean
isBound()
Returns if the keytab is bound to a principalString
toString()
Returns an informative textual representation of thisKeyTab
.
-
Method Details
-
getInstance
Returns aKeyTab
instance from aFile
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.- Parameters:
file
- the keytabFile
object, must not be null- Returns:
- the keytab instance
- Throws:
NullPointerException
- if thefile
argument is null
-
getUnboundInstance
Returns an unboundKeyTab
instance from aFile
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.- Parameters:
file
- the keytabFile
object, must not be null- Returns:
- the keytab instance
- Throws:
NullPointerException
- if the file argument is null- Since:
- 1.8
-
getInstance
Returns aKeyTab
instance from aFile
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.- Parameters:
princ
- the bound service principal, must not be nullfile
- the keytabFile
object, must not be null- Returns:
- the keytab instance
- Throws:
NullPointerException
- if either of the arguments is null- Since:
- 1.8
-
getInstance
Returns the defaultKeyTab
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.
-
getUnboundInstance
Returns the default unboundKeyTab
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
-
getInstance
Returns the defaultKeyTab
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.- Parameters:
princ
- the bound service principal, must not be null- Returns:
- the default keytab instance
- Throws:
NullPointerException
- ifprinc
is null- Since:
- 1.8
-
getKeys
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.
- Parameters:
principal
- the Kerberos principal, must not be null.- Returns:
- the keys (never null, may be empty)
- Throws:
NullPointerException
- if theprincipal
argument is nullSecurityException
- if a security manager exists and the read access to the keytab file is not permitted
-
exists
public boolean exists()Checks if the keytab file exists. Implementation of this method should make sure that the result matches the latest status of the keytab file.- Returns:
- 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
-
toString
Returns an informative textual representation of thisKeyTab
. -
hashCode
public int hashCode()Returns a hash code for thisKeyTab
.- Overrides:
hashCode
in classObject
- Returns:
- a hash code for this
KeyTab
. - See Also:
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
-
equals
Compares the specified object with thisKeyTab
for equality. Returns true if the given object is also aKeyTab
and the twoKeyTab
instances are equivalent.- Overrides:
equals
in classObject
- Parameters:
other
- the object to compare to- Returns:
- true if the specified object is equal to this
KeyTab
- See Also:
Object.hashCode()
,HashMap
-
getPrincipal
Returns the service principal thisKeyTab
object is bound to. Returnsnull
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 callisBound()
to verify this case.- Returns:
- the service principal
- Since:
- 1.8
-
isBound
public boolean isBound()Returns if the keytab is bound to a principal- Returns:
- if the keytab is bound to a principal
- Since:
- 1.8
-