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Thursday, November 25, 2010

Kerberos Debugging Tips

I worked on adding Kerberos support for Apache Rampart and WSS4J during last few weeks and interop testing with WCF.

Following lists some useful debugging tips I came across..

1. How to list all the Kerberos tickets issued to the logged in client principal in Windows
c:\Program Files (x86)\Resource Kit>klist

Current LogonId is 0:0x29a6f

Cached Tickets: (2)

#0>     Client: administrator @ WSO2.COM
        Server: krbtgt/WSO2.COM @ WSO2.COM
        KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
        Ticket Flags 0x40e00000 -> forwardable renewable initial pre_authent
        Start Time: 11/25/2010 13:19:58 (local)
        End Time:   11/25/2010 23:19:58 (local)
        Renew Time: 12/2/2010 13:19:58 (local)
        Session Key Type: AES-256-CTS-HMAC-SHA1-96


#1>     Client: administrator @ WSO2.COM
        Server: service/myserver @ WSO2.COM
        KerbTicket Encryption Type: RSADSI RC4-HMAC(NT)
        Ticket Flags 0x40a40000 -> forwardable renewable pre_authent ok_as_delegate
        Start Time: 11/25/2010 13:19:58 (local)
        End Time:   11/25/2010 23:19:58 (local)
        Renew Time: 12/2/2010 13:19:58 (local)
        Session Key Type: RSADSI RC4-HMAC(NT)

2. How to remove cached Kerberos tickets in Windows
c:\Program Files (x86)\Resource Kit>klist purge

Current LogonId is 0:0x29a6f
        Deleting all tickets:
        Ticket(s) purged!

3. How to publish Kerberos error logs in to the Event Viewer in Windows

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters
The Parameters subkey stores configuration options for the Kerberos V5 authentication protocol in Windows Server 2003/2008.

LogValue
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry does not exist in the registry by default. The default value is false - to publish to to Event Viewer set it to 1

Following are some more registry entries related to Kerberos...

AllowTgtSessionKey
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry controls whether session keys are exported with initial or cross-realm TGTs. This entry does not exist in the registry by default. The default value is false due to security concerns.

CacheS4UTickets
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry enables and disables Service-for-User (S4U) caching. This entry does not exist in the registry by default. The default value is true.

ClientIpAddresses
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry controls adding IP addresses in KRB_AS_REQ, thus forcing the Caddr field to contain IP addresses in all tickets. This entry does not exist in the registry by default. The default value is false, due to potential DHCP client and network address translation (NAT) issues.

DefaultEncryptionType
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry controls the default encryption type for PreAuth. This entry does not exist in the registry by default. The default value is KERB_ETYPE_RC4_HMAC_NT.

FarKdcTimeout
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry controls the time-out interval, in minutes, that is used to invalidate a domain controller from a different site in the domain controller cache. This entry does not exist in the registry by default. The default value is 10 minutes.

KdcBackoffTime
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry specifies a time value, in seconds, between successive calls to the Key Distribution Center (KDC) if the previous call failed. This entry does not exist in the registry by default. The default value is 5 seconds.

KdcSendRetries
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry controls the number of retry attempts that a client makes in order to contact a KDC. This entry does not exist in the registry by default. The default value is 3.

KdcWaitTime
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

This entry specifies a time value, in seconds, that is used to time out the Winsock calls. This entry does not exist in the registry by default. The default value is 5 seconds.

KerbDebugLevel
Registry path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

4. How to set a Service Principal Name [SPN] for a user in AD - in Windows
c:\Program Files (x86)\Resource Kit>setspn -A test/wso2 prabath
Registering ServicePrincipalNames for CN=prabath,CN=Users,DC=wso2,DC=com
        test/wso2
Updated object

5. How to list all the SPNs of a given user in AD - Windows
c:\Program Files (x86)\Resource Kit>setspn -L prabath
Registered ServicePrincipalNames for CN=prabath,CN=Users,DC=wso2,DC=com:
        test/wso2
        service/myserver

6. How to make java clients work with IWA

By default, Windows does not allow the session key of a TGT to be accessed. Add the following registry key on the client side, so that the session key for TGT is accessible and Java can use it to acquire additional service tickets.

For Windows XP and Windows 2000, the registry key and value should be:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa\Kerberos
Value Name: allowtgtsessionkey
Value Type: REG_DWORD
Value: 0x01

For Windows 2003 and Windows Vista, the registry key and value should be:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa\Kerberos\Parameters

Value Name: allowtgtsessionkey
Value Type: REG_DWORD
Value: 0x01

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