public class Krb5LoginModule
extends Object
implements LoginModule

此LoginModule使用Kerberos协议对用户进行身份验证。

Krb5LoginModule的配置条目有几个选项可用于控制身份验证过程以及对Subject的专用凭据集的添加。 无论这些选项如何， Subject的主要集和私有凭证集仅在commit时更新。 当commit ， KerberosPrincipal被添加到Subject的主体集中（除非将principal指定为“*”）。 如果isInitiator为true，则将KerberosTicket添加到Subject的专用凭证中。

如果KerberosLoginModule的配置条目将选项storeKey设置为true，则KerberosKey或KeyTab添加到主题的专用凭证中。 KerberosKey ，主体的密钥将从用户的密码派生， KeyTab是useKeyTab设置为true时使用的密钥表。 除非主值为“*”，否则KeyTab对象仅限于由指定的主体使用。

LoginModule识别doNotPrompt选项。 如果设置为true，则不会提示用户输入密码。

用户可以使用配置条目中的选项ticketCache指定票证缓存的位置。

用户可以使用配置条目中的选项keyTab指定密钥表位置。

可以使用选项principal在配置条目中指定主体名称。 主体名称可以是简单的用户名，服务名称，如host/mission.eng.sun.com ，或“*”。 也可以使用系统属性sun.security.krb5.principal设置sun.security.krb5.principal 。 登录期间会检查此属性。 如果未设置此属性，则使用配置中的主体名称。 如果未设置principal属性且主条目也不存在，则会提示用户输入名称。 如果设置了此属性，并且useTicketCache设置为true，则仅使用属于此主体的TGT。

以下是Krb5LoginModule支持的配置选项列表：

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 Solaris and 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 using ticketCache. 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, if principal is "*", the KeyTab 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 the principal option to set the principal when there are credentials for multiple principals in the keyTab or when you want a specific ticket cache only. The principal can also be set using the system property sun.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 "*" when isInitiator 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. When isInitiator 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.

此LoginModule还识别以下附加的Configuration选项，使您可以跨不同的身份验证模块共享用户名和密码：

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.

如果已提供主体系属性或键，则忽略共享状态中“javax.security.auth.login.name”的值。

当提供多种检索票证或密钥的机制时，首选项顺序为：

1. 票证缓存
2. 密钥表
3. 共享国家
4. 用户提示

请注意，如果任何步骤失败，它将回退到下一步。 只有一个例外，如果共享状态步骤失败并且useFirstPass = true ，则不会发出用户提示。

JAAS配置文件中Krb5LoginModule的一些配置值示例，结果如下：

 doNotPrompt = true

This is an illegal combination since none of useTicketCache, useKeyTab, useFirstPass and tryFirstPass is set and the user can not be prompted for the password.

 ticketCache = <filename>

This is an illegal combination since useTicketCache is not set to true and the ticketCache is set. A configuration error will occur.

 renewTGT = true

This is an illegal combination since useTicketCache is not set to true and renewTGT is set. A configuration error will occur.

 storeKey = true  useTicketCache = true  doNotPrompt = true

This is an illegal combination since 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.

 keyTab = <filename>  doNotPrompt = true

This is an illegal combination since useKeyTab is not set to true and the keyTab is set. A configuration error will occur.

 debug = true

Prompt the user for the principal name and the password. Use the authentication exchange to get TGT from the KDC and populate the Subject with the principal and TGT. Output debug messages.

 useTicketCache = true  doNotPrompt = true

Check the default cache for TGT and populate the Subject with the principal and TGT. If the TGT is not available, do not prompt the user, instead fail the authentication.

 principal = <name>  useTicketCache = true  doNotPrompt = true

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.

 useTicketCache = true
 ticketCache = <file name>
 useKeyTab = true
 keyTab = <keytab filename>
 principal = <principal name>
 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 = <filename>

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.

 useKeyTab = true  keyTab=<keytab filename>  principal = <principal name>  storeKey = true

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 = <keytabname>  storeKey = true  doNotPrompt = false

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.

 isInitiator = false  useKeyTab = true  keyTab = <keytabname>  storeKey = true  principal = *

The acceptor will be an unbound acceptor and it can act as any principal as long that principal has keys in the keytab.

 useTicketCache = true
 ticketCache = <file name>
 useKeyTab = true
 keyTab = <file name>
 storeKey = true
 principal = <principal name>

The client's TGT will be retrieved from the ticket cache and added to the 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.

 isInitiator = false

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 = true

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.