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package javax.security.auth.kerberos;
import java.io.File;
import java.security.AccessControlException;
import java.util.Objects;
import sun.misc.SharedSecrets;
import sun.security.krb5.EncryptionKey;
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.
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>
* It might be necessary for the application to be granted a
* {@link javax.security.auth.PrivateCredentialPermission
* 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
* {@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;
// Set up JavaxSecurityAuthKerberosAccess in SharedSecrets
static {
SharedSecrets.setJavaxSecurityAuthKerberosAccess(
new JavaxSecurityAuthKerberosAccessImpl());
}
private KeyTab(File file) {
this.file = file;
}
Returns a 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: - NullPointerException – if the
file argument is null
Returns: the keytab instance
/**
* Returns a {@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 {@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(file);
}
Returns the default 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.
/**
* Returns the default {@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.
*/
public static KeyTab getInstance() {
return new KeyTab(null);
}
//Takes a snapshot of the keytab content
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.
Params: - principal – the Kerberos principal, must not be null.
Throws: - NullPointerException – if the
principal argument is null - SecurityException – if a security manager exists and the read
access to the keytab file is not permitted
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.
*
* @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 {
EncryptionKey[] keys = takeSnapshot().readServiceKeys(
new PrincipalName(principal.getName()));
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();
}
public String toString() {
return file == null ? "Default keytab" : file.toString();
}
Returns a hashcode for this KeyTab.
Returns: a hashCode() for the KeyTab
/**
* Returns a hashcode for this KeyTab.
*
* @return a hashCode() for the {@code KeyTab}
*/
public int hashCode() {
return Objects.hash(file);
}
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 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 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.file, file);
}
}