Class KerberosKey

All Implemented Interfaces:
Serializable, Key, SecretKey, Destroyable 
public class KerberosKey
extends Object
implements SecretKey

This class encapsulates a long term secret key for a Kerberos principal.

A KerberosKey object includes an EncryptionKey, a KerberosPrincipal as its owner, and the version number of the key.

An EncryptionKey is defined in Section 4.2.9 of the Kerberos Protocol Specification (RFC 4120) as: 

EncryptionKey   ::= SEQUENCE {
             keytype         [0] Int32 -- actually encryption type --,
             keyvalue        [1] OCTET STRING
     }
The key material of a KerberosKey is defined as the value of the keyValue above.

All Kerberos JAAS login modules that obtain a principal's password and generate the secret key from it should use this class. Sometimes, such as when authenticating a server in the absence of user-to-user authentication, 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.

A Kerberos service using a keytab to read secret keys should use the KeyTab class, where latest keys can be read when needed.

It might be necessary for the application to be granted a PrivateCredentialPermission if it needs to access the KerberosKey instance from a Subject. This permission is not needed when the application depends on the default JGSS Kerberos mechanism to access the KerberosKey. In that case, however, the application will need an appropriate ServicePermission.

When creating a KerberosKey using the KerberosKey(KerberosPrincipal, char[], String) constructor, an implementation may accept non-IANA algorithm names (For example, "ArcFourMac" for "rc4-hmac"), but the getAlgorithm() method must always return the IANA algorithm name.

Implementation Note:
Old algorithm names used before JDK 9 are supported in the KerberosKey(KerberosPrincipal, char[], String) constructor in this implementation for compatibility reasons, which are "DES" (and null) for "des-cbc-md5", "DESede" for "des3-cbc-sha1-kd", "ArcFourHmac" for "rc4-hmac", "AES128" for "aes128-cts-hmac-sha1-96", and "AES256" for "aes256-cts-hmac-sha1-96".
Since:
1.4
See Also:
Serialized Form

Constructor Summary

Constructors
Constructor Description
KerberosKey​(KerberosPrincipal principal, byte[] keyBytes, int keyType, int versionNum)

Constructs a KerberosKey from the given bytes when the key type and key version number are known.
KerberosKey​(KerberosPrincipal principal, char[] password, String algorithm)

Constructs a KerberosKey from a principal's password using the specified algorithm name.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type Method Description
void destroy()

Destroys this key by clearing out the key material of this secret key.
boolean equals​(Object other)

Compares the specified object with this KerberosKey for equality.
String getAlgorithm()

Returns the standard algorithm name for this key.
byte[] getEncoded()

Returns the key material of this secret key.
String getFormat()

Returns the name of the encoding format for this secret key.
int getKeyType()

Returns the key type for this long-term key.
KerberosPrincipal getPrincipal()

Returns the principal that this key belongs to.
int getVersionNumber()

Returns the key version number.
int hashCode()

Returns a hash code for this KerberosKey.
boolean isDestroyed()

Determines if this key has been destroyed.
String toString()

Returns an informative textual representation of this KerberosKey.

Methods declared in class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

KerberosKey

public KerberosKey​(KerberosPrincipal principal,
                   byte[] keyBytes,
                   int keyType,
                   int versionNum)

Constructs a KerberosKey from the given bytes when the key type and key version number are known. This can be used when reading the secret key information from a Kerberos "keytab".

Parameters:
principal - the principal that this secret key belongs to
keyBytes - the key material for the secret key
keyType - the key type for the secret key as defined by the Kerberos protocol specification.
versionNum - the version number of this secret key

KerberosKey

public KerberosKey​(KerberosPrincipal principal,
                   char[] password,
                   String algorithm)

Constructs a KerberosKey from a principal's password using the specified algorithm name. The algorithm name (case insensitive) should be provided as the encryption type string defined on the IANA Kerberos Encryption Type Numbers page. The version number of the key generated will be 0.

Parameters:
principal - the principal that this password belongs to
password - the password that should be used to compute the key
algorithm - the name for the algorithm that this key will be used for
Throws:
IllegalArgumentException - if the name of the algorithm passed is unsupported.

Method Detail

getPrincipal

public final KerberosPrincipal getPrincipal()

Returns the principal that this key belongs to.

Returns:
the principal this key belongs to.
Throws:
IllegalStateException - if the key is destroyed

getVersionNumber

public final int getVersionNumber()

Returns the key version number.

Returns:
the key version number.
Throws:
IllegalStateException - if the key is destroyed

getKeyType

public final int getKeyType()

Returns the key type for this long-term key.

Returns:
the key type.
Throws:
IllegalStateException - if the key is destroyed

getAlgorithm

public final String getAlgorithm()

Returns the standard algorithm name for this key. The algorithm names are the encryption type string defined on the IANA Kerberos Encryption Type Numbers page.

This method can return the following value not defined on the IANA page:

  1. none: for etype equal to 0
  2. unknown: for etype greater than 0 but unsupported by the implementation
  3. private: for etype smaller than 0
Specified by:
getAlgorithm in interface Key
Returns:
the name of the algorithm associated with this key.
Throws:
IllegalStateException - if the key is destroyed

getFormat

public final String getFormat()

Returns the name of the encoding format for this secret key.

Specified by:
getFormat in interface Key
Returns:
the String "RAW"
Throws:
IllegalStateException - if the key is destroyed

getEncoded

public final byte[] getEncoded()

Returns the key material of this secret key.

Specified by:
getEncoded in interface Key
Returns:
the key material
Throws:
IllegalStateException - if the key is destroyed

destroy

public void destroy()
             throws DestroyFailedException

Destroys this key by clearing out the key material of this secret key.

Specified by:
destroy in interface Destroyable
Throws:
DestroyFailedException - if some error occurs while destorying this key.

isDestroyed

public boolean isDestroyed()

Determines if this key has been destroyed.

Specified by:
isDestroyed in interface Destroyable
Returns:
true if this Object has been destroyed, false otherwise.

toString

public String toString()

Returns an informative textual representation of this KerberosKey.

Overrides:
toString in class Object
Returns:
an informative textual representation of this KerberosKey.

hashCode

public int hashCode()

Returns a hash code for this KerberosKey.

Overrides:
hashCode in class Object
Returns:
a hash code for this KerberosKey.
Since:
1.6
See Also:
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

equals

public boolean equals​(Object other)

Compares the specified object with this KerberosKey for equality. Returns true if the given object is also a KerberosKey and the two KerberosKey instances are equivalent. A destroyed KerberosKey object is only equal to itself.

Overrides:
equals in class Object
Parameters:
other - the object to compare to
Returns:
true if the specified object is equal to this KerberosKey, false otherwise.
Since:
1.6
See Also:
Object.hashCode(), HashMap