LoginModule
public class Krb5LoginModule extends Object implements LoginModule
LoginModule
authenticates users using Kerberos protocols. The configuration entry for Krb5LoginModule
has several options that control the authentication process and additions to the Subject
's private credential set. Irrespective of these options, the Subject
's principal set and private credentials set are updated only when commit
is called. When commit
is called, the KerberosPrincipal
is added to the Subject
's principal set (unless the principal
is specified as "*"). If isInitiator
is true, the KerberosTicket
is added to the Subject
's private credentials.
If the configuration entry for KerberosLoginModule
has the option storeKey
set to true, then KerberosKey
or KeyTab
will also be added to the subject's private credentials. KerberosKey
, the principal's key(s) will be derived from user's password, and KeyTab
is the keytab used when useKeyTab
is set to true. The KeyTab
object is restricted to be used by the specified principal unless the principal value is "*".
This LoginModule
recognizes the doNotPrompt
option. If set to true the user will not be prompted for the password.
The user can specify the location of the ticket cache by using the option ticketCache
in the configuration entry.
The user can specify the keytab location by using the option keyTab
in the configuration entry.
The principal name can be specified in the configuration entry by using the option principal
. The principal name can either be a simple user name, a service name such as host/mission.eng.sun.com
, or "*". The principal can also be set using the system property sun.security.krb5.principal
. This property is checked during login. If this property is not set, then the principal name from the configuration is used. In the case where the principal property is not set and the principal entry also does not exist, the user is prompted for the name. When this property of entry is set, and useTicketCache
is set to true, only TGT belonging to this principal is used.
The following is a list of configuration options supported for Krb5LoginModule
:
refreshKrb5Config
:- Set this to true, if you want the configuration to be refreshed before the
login
method is called.useTicketCache
:- Set this to true, if you want the TGT to be obtained from the ticket cache. Set this option to false if you do not want this module to use the ticket cache. (Default is False). This module will search for the ticket cache in the following locations: On Linux it will look for the ticket cache in /tmp/krb5cc_
uid
where the uid is numeric user identifier. If the ticket cache is not available in the above location, or if we are on a Windows platform, it will look for the cache as {user.home}{file.separator}krb5cc_{user.name}. You can override the ticket cache location by usingticketCache
. For Windows, if a ticket cannot be retrieved from the file ticket cache, it will use Local Security Authority (LSA) API to get the TGT.ticketCache
:- Set this to the name of the ticket cache that contains user's TGT. If this is set,
useTicketCache
must also be set to true; Otherwise a configuration error will be returned.renewTGT
:- Set this to true, if you want to renew the TGT when it's more than half-way expired (the time until expiration is less than the time since start time). If this is set,
useTicketCache
must also be set to true; otherwise a configuration error will be returned.doNotPrompt
:- Set this to true if you do not want to be prompted for the password if credentials can not be obtained from the cache, the keytab, or through shared state.(Default is false) If set to true, credential must be obtained through cache, keytab, or shared state. Otherwise, authentication will fail.
useKeyTab
:- Set this to true if you want the module to get the principal's key from the the keytab.(default value is False) If
keytab
is not set then the module will locate the keytab from the Kerberos configuration file. If it is not specified in the Kerberos configuration file then it will look for the file{user.home}{file.separator}
krb5.keytab.keyTab
:- Set this to the file name of the keytab to get principal's secret key.
storeKey
:- Set this to true to if you want the keytab or the principal's key to be stored in the Subject's private credentials. For
isInitiator
being false, ifprincipal
is "*", theKeyTab
stored can be used by anyone, otherwise, it's restricted to be used by the specified principal only.principal
:- The name of the principal that should be used. The principal can be a simple username such as "
testuser
" or a service name such as "host/testhost.eng.sun.com
". You can use theprincipal
option to set the principal when there are credentials for multiple principals in thekeyTab
or when you want a specific ticket cache only. The principal can also be set using the system propertysun.security.krb5.principal
. In addition, if this system property is defined, then it will be used. If this property is not set, then the principal name from the configuration will be used. The principal name can be set to "*" whenisInitiator
is false. In this case, the acceptor is not bound to a single principal. It can act as any principal an initiator requests if keys for that principal can be found. WhenisInitiator
is true, the principal name cannot be set to "*".isInitiator
:- Set this to true, if initiator. Set this to false, if acceptor only. (Default is true). Note: Do not set this value to false for initiators.
This LoginModule
also recognizes the following additional Configuration
options that enable you to share username and passwords across different authentication modules:
useFirstPass
:- if, true, this LoginModule retrieves the username and password from the module's shared state, using "javax.security.auth.login.name" and "javax.security.auth.login.password" as the respective keys. The retrieved values are used for authentication. If authentication fails, no attempt for a retry is made, and the failure is reported back to the calling application.
tryFirstPass
:- if, true, this LoginModule retrieves the the username and password from the module's shared state using "javax.security.auth.login.name" and "javax.security.auth.login.password" as the respective keys. The retrieved values are used for authentication. If authentication fails, the module uses the CallbackHandler to retrieve a new username and password, and another attempt to authenticate is made. If the authentication fails, the failure is reported back to the calling application
storePass
:- if, true, this LoginModule stores the username and password obtained from the CallbackHandler in the modules shared state, using "javax.security.auth.login.name" and "javax.security.auth.login.password" as the respective keys. This is not performed if existing values already exist for the username and password in the shared state, or if authentication fails.
clearPass
:- if, true, this LoginModule clears the username and password stored in the module's shared state after both phases of authentication (login and commit) have completed.
If the principal system property or key is already provided, the value of "javax.security.auth.login.name" in the shared state is ignored.
When multiple mechanisms to retrieve a ticket or key is provided, the preference order is:
Note that if any step fails, it will fallback to the next step. There's only one exception, if the shared state step fails and useFirstPass = true
, no user prompt is made.
Examples of some configuration values for Krb5LoginModule in JAAS config file and the results are:
This is an illegal combination since none ofdoNotPrompt = true
useTicketCache, useKeyTab, useFirstPass
andtryFirstPass
is set and the user can not be prompted for the password.This is an illegal combination sinceticketCache = <filename>
useTicketCache
is not set to true and the ticketCache is set. A configuration error will occur.This is an illegal combination sincerenewTGT = true
useTicketCache
is not set to true and renewTGT is set. A configuration error will occur.This is an illegal combination sincestoreKey = true useTicketCache = true doNotPrompt = true
storeKey
is set to true but the key can not be obtained either by prompting the user or from the keytab, or from the shared state. A configuration error will occur.This is an illegal combination since useKeyTab is not set to true and the keyTab is set. A configuration error will occur.keyTab = <filename> doNotPrompt = true
Prompt the user for the principal name and the password. Use the authentication exchange to get TGT from the KDC and populate thedebug = true
Subject
with the principal and TGT. Output debug messages.Check the default cache for TGT and populate theuseTicketCache = true doNotPrompt = true
Subject
with the principal and TGT. If the TGT is not available, do not prompt the user, instead fail the authentication.Get the TGT from the default cache for the principal and populate the Subject's principal and private creds set. If ticket cache is not available or does not contain the principal's TGT authentication will fail.principal = <name> useTicketCache = true doNotPrompt = true
Search the cache for the principal's TGT. If it is not available use the key in the keytab to perform authentication exchange with the KDC and acquire the TGT. The Subject will be populated with the principal and the TGT. If the key is not available or valid then authentication will fail.useTicketCache = true ticketCache = <file name> useKeyTab = true keyTab = <keytab filename> principal = <principal name> doNotPrompt = true
The TGT will be obtained from the cache specified. The Kerberos principal name used will be the principal name in the Ticket cache. If the TGT is not available in the ticket cache the user will be prompted for the principal name and the password. The TGT will be obtained using the authentication exchange with the KDC. The Subject will be populated with the TGT.useTicketCache = true ticketCache = <filename>
The key for the principal will be retrieved from the keytab. If the key is not available in the keytab the user will be prompted for the principal's password. The Subject will be populated with the principal's key either from the keytab or derived from the password entered.useKeyTab = true keyTab=<keytab filename> principal = <principal name> storeKey = true
The user will be prompted for the service principal name. If the principal's longterm key is available in the keytab , it will be added to the Subject's private credentials. An authentication exchange will be attempted with the principal name and the key from the Keytab. If successful the TGT will be added to the Subject's private credentials set. Otherwise the authentication will fail.useKeyTab = true keyTab = <keytabname> storeKey = true doNotPrompt = false
The acceptor will be an unbound acceptor and it can act as any principal as long that principal has keys in the keytab.isInitiator = false useKeyTab = true keyTab = <keytabname> storeKey = true principal = *
The client's TGT will be retrieved from the ticket cache and added to theuseTicketCache = true ticketCache = <file name> useKeyTab = true keyTab = <file name> storeKey = true principal = <principal name>
Subject
's private credentials. If the TGT is not available in the ticket cache, or the TGT's client name does not match the principal name, Java will use a secret key to obtain the TGT using the authentication exchange and added to the Subject's private credentials. This secret key will be first retrieved from the keytab. If the key is not available, the user will be prompted for the password. In either case, the key derived from the password will be added to the Subject's private credentials set.Configured to act as acceptor only, credentials are not acquired via AS exchange. For acceptors only, set this value to false. For initiators, do not set this value to false.isInitiator = false
Configured to act as initiator, credentials are acquired via AS exchange. For initiators, set this value to true, or leave this option unset, in which case default value (true) will be used.isInitiator = true
Constructor | Description |
---|---|
Krb5LoginModule() |
Creates a Krb5LoginModule . |
Modifier and Type | Method | Description |
---|---|---|
boolean |
abort() |
This method is called if the LoginContext's overall authentication failed. |
boolean |
commit() |
This method is called if the LoginContext's overall authentication succeeded (the relevant REQUIRED, REQUISITE, SUFFICIENT and OPTIONAL LoginModules succeeded). |
void |
initialize |
Initialize this LoginModule . |
boolean |
login() |
Authenticate the user |
boolean |
logout() |
Logout the user. |
public Krb5LoginModule()
Krb5LoginModule
.public void initialize(Subject subject, CallbackHandler callbackHandler, Map<String,?> sharedState, Map<String,?> options)
LoginModule
.initialize
in interface LoginModule
subject
- the Subject
to be authenticated.callbackHandler
- a CallbackHandler
for communication with the end user (prompting for usernames and passwords, for example).sharedState
- shared LoginModule
state.options
- options specified in the login Configuration
for this particular LoginModule
.public boolean login() throws LoginException
login
in interface LoginModule
LoginModule
should not be ignored.FailedLoginException
- if the authentication fails.LoginException
- if this LoginModule
is unable to perform the authentication.public boolean commit() throws LoginException
If this LoginModule's own authentication attempt succeeded (checked by retrieving the private state saved by the login
method), then this method associates a Krb5Principal
with the Subject
located in the LoginModule
. It adds Kerberos Credentials to the the Subject's private credentials set. If this LoginModule's own authentication attempted failed, then this method removes any state that was originally saved.
commit
in interface LoginModule
LoginException
- if the commit fails.public boolean abort() throws LoginException
If this LoginModule's own authentication attempt succeeded (checked by retrieving the private state saved by the login
and commit
methods), then this method cleans up any state that was originally saved.
abort
in interface LoginModule
LoginException
- if the abort fails.public boolean logout() throws LoginException
This method removes the Krb5Principal
that was added by the commit
method.
logout
in interface LoginModule
LoginModule
should not be ignored.LoginException
- if the logout fails.
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.security.auth/com/sun/security/auth/module/Krb5LoginModule.html