Kerberos presentation

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  • 1. Kerberos Introduction Kerberos in Greek mythology was the three-headed dog guarding the gates to the underworld Kerberos was developed as part of MITs Athena project and taken on board as the default authentication protocol by MS in Windows 2000. All flavours of Kerberos provide authentication however the MS implementation does provide extensions for authorization.
  • 2. So what does that mean? Provides a mechanism for authentication Based on Tickets THE default Based on a trusted and containing clientauthentication protocol third party model mutual authentication credentials encrypted for AD. between a client and a with Shared keys. server
  • 3. Authentication Interoperability ImpersonationIncreased authentication efficiencies (Its just faster) Mutual authentication(It can verify you and you can verify it) Protocol Transition (first NTLM then Kerberos) Constrained Delegation (Impersonation with Rules) Smartcards
  • 4. The KDC KDC trusted 3rd party, provides scalability KDC made up of 2 sub services (AS) Authentication Service, (TGS) Ticket Granting ServiceThe KDC holds a copy of each entities MasterKey (Symmetric Crypto)The KDC issues the Keys, encrypted with theMaster Key to each entity
  • 5. WWW.K2.COM SPNs Service DNS Entry FQDN Service Account SPNs Blackpearl K2K2serviceaccount K2server/ Server K2server/k2server:5252 K2HostServer/ K2HostServer/ k2server:5555 Blackpearl K2K2workspaceaccount HTTP/ Web HTTP/k2wks Components SSRS 2005 K2SSRSserviceaccount HTTP/ssrs HTTP/ Web App K2MOSSserviceaccount HTTP/SharePoint HTTP/ SQL Server K2SQLserviceaccount MSSQLSvc/k2sql:1433 MSSQLSvc/
  • 6. DelegationWindows 2000 the users TGT is passed to theservice to facilitate delegation Windows 2003 the service ticket can be used to request a new ticketWindows 2000 allowed only for non constraineddelegation model Windows 2003 introduced constrained delegation, this prevents user delegation to any systemConstrained delegation is only available whenrunning 2003 native!To check attribute on AD account holding thedelegate to SPNs msDS-AllowedToDelegateTo (see Adsiedit.msc)
  • 8. WWW.K2.COM Kerberos Integrated SQL Kerberos Kerberos K2 CONFIDENTIAL
  • 9. 1. Plan2. Understand all the services in play and how they will talk amongst each other3. Get service accounts for each service (best practice should be 1 per a service!)4. Get machine A NAME records and any Host Headers in IIS (Use A NAME records and avoid port numbers in HTTP requests)5. Generate required SPNs (Script?)6. Enable user accounts for delegation7. Determine the Delegation8. Is PT required?
  • 10. system.webServer/security/authentication/Windows-Authentication
  • 11. MSSQLSvc/FQDN:[port | instancename],MSSQLSvc/FQDN:port | MSSQLSvc/FQDN
  • 12. Troubleshooting NetworkAuditing Logging Debug Tracing
  • 13. AuditingHKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlLsaKerberosParameters -LogLevel DWORD value of 1-For Temporary use only
  • 14. Logging-LogToFile DWORD value 1, -log to file C:WindowsSystem32lsass.log
  • 15. Debug-KerbDebugLevel -DWORD value c0000043 (this value will print the most standard set of debug messages. Try it first. If you still want to see more output, set it to ffffffff).
  • 16. Some common Kerberos failure codes 0x6 KDC_ERR_C_PRINCIPAL_UNKNOWN STATUS_NO_SUCH_USER 0x7 KDC_ERR_S_PRINCIPAL_UNKNOWN Server not found in Kerberos database 0x8 - KDC_ERR_PRINCIPAL_NOT_UNIQUE Multiple principal entries in database 0x17 KDC_ERR_KEY_EXPIRED Password has expired change password to reset 0x25 KRB_AP_ERR_SKEW Clock skew too great 0x34 KRB_ERR_RESPONSE _TOO_BIG Response too big for UDP, retry with TCP
  • 17. Troubleshooting-Use the Windows security log, look for 540events showing you the protocol used and anytransited services-Check for duplicate SPNs-Check SPN Syntax-Check Delegation Settings-ADSI is your friend
  • 18. Multiforest-Kerberos since 2003 is supported acrossforests via the use of forest level trustintroduced in Windows 2003-Delegation across forests is not supported-FQDNs required to resolve across forests-Root hints used to find target KDC
  • 19.