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Active Directory and NT Kerberos. Introduction to NT Kerberos v5. What is NT Kerberos? How is it different from NTLM NT Kerberos vs MIT Kerberos Delegation and Client Authentication What does NT Kerberos look like on the wire? KTNet - A native NT Kerberos telnet server.
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Introduction to NT Kerberos v5 • What is NT Kerberos? • How is it different from NTLM • NT Kerberos vs MIT Kerberos • Delegation and Client Authentication • What does NT Kerberos look like on the wire? • KTNet - A native NT Kerberos telnet server
What is NT Kerberos • NT’s new authentication system • MIT Kerberos v5 - an Open Standard • Kerberos is the default authenticator in W2K domains • NTLM still used for compatibility • usually the weakest version
How is it different from NTLM • Doesn’t use a password hash system • Requires fewer authentication calls • More sophisticated - Yes • More secure? - Possibly in pure mode • Backwards compatibility hinders it • NTLM v2 is strong in pure mode as well
NT Kerberos • Integrated with platform • Locates KDC via DNS - DNS server required for install • No support for DCE style cross-realm trust • No “raw” krb5 API • Postdated tickets (not implemented) • Uses authdata field in ticket
Windows 2000 Kerberos standards • RFC-1510 • Kerberos change password protocol Kerberos set password protocolRC4-HMAC Kerberos Encryption type • PKINIT
Kerberos Interoperability Scenarios • Kerberos clients in a Win2000 domain • Kerberos servers in a Win2000 domain • Standalone Win2000 systems in a Kerberos realm • Using a Kerberos realm as a resource domain • Using a Kerberos realm as an account domain
MIT Kerberos Differences Win2000 • Clients • Just logon • Just logoff • Domain membership • Example app: everything • Servers • Use computer account via SCM MIT • Clients • User logon with ‘kinit’ • User logoff with ‘kdestroy’ • Configured with /etc/krb5.conf • Example app: telnet • Servers • Do not logon – use saved keys from keytab
Using Kerberos clients Customer wants to have its non-windows Kerberos users use their Win2000 accounts nt.company.com • Setup the /etc/krb5.conf • Users kinit with their Win2000 account Unix workstation Windows 2000 Server
Using Kerberos servers Customer wants to user their Kerberos enabled database server in an n-tier application front-ended by IIS nt.company.com • /etc/krb5.conf on database server • Create service account in domain • Use ktpass to export a keytab • Copy keytab to database server • IIS server is trusted for delegation Windows 2000 Wks Windows 2000 IIS Server Unix Database Server
Kerberos realm as an account domain • User logon with Kerberos principal • User has shadow account in an account domain (for applying authz) • Mapping is used at logon for domain identity Domain trusts realm users user@win2k.domain.com (user@MIT.REALM.COM) comp$@win2k.domain.com User@MIT.REALM.COM win2k.domain.com MIT.REALM.COM
Standalone Win2000 computers An employee has a Win2000 computer that they want to use in a Kerberos realm MIT.REALM.COM • Configure system as standalone (no domain) • Use Ksetup to configure the realm • Use Ksetup to establish the local account mapping • Logon to Kerberos realm Linux/Unix Win2000
Trusting a Kerberos realm • Win2000 users accessing services in Kerberos realms • Kerberos users accessing services in domains
Shortcut trust Kerberos trust Windows 2000 Domain Trusts Explicit Kerberos trust microsoft.com Kerberos realm Domain fareast. microsoft. com europe. microsoft. com Explicit Windows NT 4.0-style trust Domain Domain Domain Domain
2 TGT 3 TGT 1 TGT 4 TICKET Cross-domain Authentication company.com west.company.com east.company.com KDC KDC srv1.east.company.com Windows 2000 Professional Windows 2000 Server
2 TGT 1 3 TICKET TGT 4 TICKET With NT Auth Data Using Unix KDCs with Windows 2000 Authorization COMPANY.REALM nt.company.com MITKDC Windows 2000KDC Name Mapping to NT account Windows 2000 Server Win2000 Professional
NT Kerberos vs MIT Kerberos • NT caches the password for ticket renewal • It’s not certain whether NT uses ticket caching tracking stolen ‘replay’ tickets