@c $Id$ @node Windows compatibility, Programming with Kerberos, Kerberos 4 issues, Top @comment node-name, next, previous, up @chapter Windows compatibility Microsoft Windows, starting from version 2000 (formerly known as Windows NT 5), implements Kerberos 5. Their implementation, however, has some quirks, peculiarities, and bugs. This chapter is a short summary of the compatibility issues between Heimdal and various Windows versions. The big problem with the Kerberos implementation in Windows is that the available documentation is more focused on getting things to work rather than how they work, and not that useful in figuring out how things really work. It's of course subject to change all the time and mostly consists of our not so inspired guesses. Hopefully it's still somewhat useful. @menu * Configuring Windows to use a Heimdal KDC:: * Inter-Realm keys (trust) between Windows and a Heimdal KDC:: * Create account mappings:: * Encryption types:: * Authorisation data:: * Quirks of Windows 2000 KDC:: * Useful links when reading about the Windows:: @end menu @node Configuring Windows to use a Heimdal KDC, Inter-Realm keys (trust) between Windows and a Heimdal KDC, Windows compatibility, Windows compatibility @comment node-name, next, precious, up @section Configuring Windows to use a Heimdal KDC You need the command line program called @command{ksetup.exe}. This program comes with the Windows Support Tools, available from either the installation CD-ROM (@file{SUPPORT/TOOLS/SUPPORT.CAB}), or from Microsoft web site. Starting from Windows 2008, it is already installed. This program is used to configure the Kerberos settings on a Workstation. @command{Ksetup} store the domain information under the registry key: @code{HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\LSA\Kerberos\Domains}. Use the @command{kadmin} program in Heimdal to create a host principal in the Kerberos realm. @example unix% kadmin kadmin> ank --password=password host/datan.example.com @end example The name @samp{datan.example.com} should be replaced with DNS name of the workstation. You must configure the workstation as a member of a workgroup, as opposed to a member in an NT domain, and specify the KDC server of the realm as follows: @example C:> ksetup /setdomain EXAMPLE.COM C:> ksetup /addkdc EXAMPLE.COM kdc.example.com @end example Set the machine password, i.e.@: create the local keytab: @example C:> ksetup /SetComputerPassword password @end example The password used in @kbd{ksetup /setmachpassword} must be the same as the password used in the @kbd{kadmin ank} command. The workstation must now be rebooted. A mapping between local NT users and Kerberos principals must be specified. You have two choices. First: @example C:> ksetup /mapuser user@@MY.REALM nt_user @end example This will map a user to a specific principal; this allows you to have other usernames in the realm than in your NT user database. (Don't ask me why on earth you would want that@enddots{}) You can also say: @example C:> ksetup /mapuser * * @end example The Windows machine will now map any user to the corresponding principal, for example @samp{nisse} to the principal @samp{nisse@@MY.REALM}. (This is most likely what you want.) @node Inter-Realm keys (trust) between Windows and a Heimdal KDC, Create account mappings, Configuring Windows to use a Heimdal KDC, Windows compatibility @comment node-name, next, precious, up @section Inter-Realm keys (trust) between Windows and a Heimdal KDC See also the Step-by-Step guide from Microsoft, referenced below. Install Windows, and create a new controller (Active Directory Server) for the domain. By default the trust will be non-transitive. This means that only users directly from the trusted domain may authenticate. This can be changed to transitive by using the @command{netdom.exe} tool. @command{netdom.exe} can also be used to add the trust between two realms. You need to tell Windows on what hosts to find the KDCs for the non-Windows realm with @command{ksetup}, see @xref{Configuring Windows to use a Heimdal KDC}. This needs to be done on all computers that want enable cross-realm login with @code{Mapped Names}. @c XXX probably shouldn't be @code Then you need to add the inter-realm keys on the Windows KDC@. Start the Domain Tree Management tool (found in Programs, Administrative tools, Active Directory Domains and Trusts). Right click on Properties of your domain, select the Trust tab. Press Add on the appropriate trust windows and enter domain name and password. When prompted if this is a non-Windows Kerberos realm, press OK. Do not forget to add trusts in both directions (if that's what you want). If you want to use @command{netdom.exe} instead of the Domain Tree Management tool, you do it like this: @example netdom trust NT.REALM.EXAMPLE.COM /Domain:EXAMPLE.COM /add /realm /passwordt:TrustPassword @end example You also need to add the inter-realm keys to the Heimdal KDC. But take care to the encryption types and salting used for those keys. There should be no encryption type stronger than the one configured on Windows side for this relationship, itself limited to the ones supported by this specific version of Windows, nor any Kerberos 4 salted hashes, as Windows does not seem to understand them. Otherwise, the trust will not works. Here are the version-specific needed information: @enumerate @item Windows 2000: maximum encryption type is DES @item Windows 2003: maximum encryption type is DES @item Windows 2003RC2: maximum encryption type is RC4, relationship defaults to DES @item Windows 2008: maximum encryption type is AES, relationship defaults to RC4 @end enumerate For Windows 2003RC2, to change the trust encryption type, you have to use the @command{ktpass}, from the Windows 2003 Resource kit *service pack2*, available from Microsoft web site. @example C:> ktpass /MITRealmName UNIX.EXAMPLE.COM /TrustEncryp RC4 @end example For Windows 2008, the same operation can be done with the @command{ksetup}, installed by default. @example C:> ksetup /SetEncTypeAttre EXAMPLE.COM AES256-SHA1 @end example Once the relationship is correctly configured, you can add the required inter-realm keys, using heimdal default encryption types: @example kadmin add krbtgt/NT.REALM.EXAMPLE.COM@@EXAMPLE.COM kadmin add krbtgt/REALM.EXAMPLE.COM@@NT.EXAMPLE.COM @end example Use the same passwords for both keys. And if needed, to remove unsupported encryptions, such as the following ones for a Windows 2003RC2 server. @example kadmin del_enctype krbtgt/REALM.EXAMPLE.COM@@NT.EXAMPLE.COM aes256-cts-hmac-sha1-96 kadmin del_enctype krbtgt/REALM.EXAMPLE.COM@@NT.EXAMPLE.COM des3-cbc-sha1 kadmin del_enctype krbtgt/NT.EXAMPLE.COM@@EXAMPLE.COM aes256-cts-hmac-sha1-96 kadmin del_enctype krbtgt/NT.EXAMPLE.COM@@EXAMPLE.COM des3-cbc-sha1 @end example Do not forget to reboot before trying the new realm-trust (after running @command{ksetup}). It looks like it might work, but packets are never sent to the non-Windows KDC. @node Create account mappings, Encryption types, Inter-Realm keys (trust) between Windows and a Heimdal KDC, Windows compatibility @comment node-name, next, precious, up @section Create account mappings Start the @code{Active Directory Users and Computers} tool. Select the View menu, that is in the left corner just below the real menu (or press Alt-V), and select Advanced Features. Right click on the user that you are going to do a name mapping for and choose Name mapping. Click on the Kerberos Names tab and add a new principal from the non-Windows domain. @c XXX check entry name then I have network again This adds @samp{authorizationNames} entry to the users LDAP entry to the Active Directory LDAP catalog. When you create users by script you can add this entry instead. @node Encryption types, Authorisation data, Create account mappings, Windows compatibility @comment node-name, next, previous, up @section Encryption types Windows 2000 supports both the standard DES encryptions (@samp{des-cbc-crc} and @samp{des-cbc-md5}) and its own proprietary encryption that is based on MD4 and RC4 that is documented in and is supposed to be described in @file{draft-brezak-win2k-krb-rc4-hmac-03.txt}. New users will get both MD4 and DES keys. Users that are converted from a NT4 database, will only have MD4 passwords and will need a password change to get a DES key. @node Authorisation data, Quirks of Windows 2000 KDC, Encryption types, Windows compatibility @comment node-name, next, previous, up @section Authorisation data The Windows 2000 KDC also adds extra authorisation data in tickets. It is at this point unclear what triggers it to do this. The format of this data is only available under a ``secret'' license from Microsoft, which prohibits you implementing it. A simple way of getting hold of the data to be able to understand it better is described here. @enumerate @item Find the client example on using the SSPI in the SDK documentation. @item Change ``AuthSamp'' in the source code to lowercase. @item Build the program. @item Add the ``authsamp'' principal with a known password to the database. Make sure it has a DES key. @item Run @kbd{ktutil add} to add the key for that principal to a keytab. @item Run @kbd{appl/test/nt_gss_server -p 2000 -s authsamp @kbd{--dump-auth}=@var{file}} where @var{file} is an appropriate file. @item It should authenticate and dump for you the authorisation data in the file. @item The tool @kbd{lib/asn1/asn1_print} is somewhat useful for analysing the data. @end enumerate @node Quirks of Windows 2000 KDC, Useful links when reading about the Windows, Authorisation data, Windows compatibility @comment node-name, next, previous, up @section Quirks of Windows 2000 KDC There are some issues with salts and Windows 2000. Using an empty salt---which is the only one that Kerberos 4 supported, and is therefore known as a Kerberos 4 compatible salt---does not work, as far as we can tell from out experiments and users' reports. Therefore, you have to make sure you keep around keys with all the different types of salts that are required. Microsoft have fixed this issue post Windows 2003. Microsoft seems also to have forgotten to implement the checksum algorithms @samp{rsa-md4-des} and @samp{rsa-md5-des}. This can make Name mapping (@pxref{Create account mappings}) fail if a @samp{des-cbc-md5} key is used. To make the KDC return only @samp{des-cbc-crc} you must delete the @samp{des-cbc-md5} key from the kdc using the @kbd{kadmin del_enctype} command. @example kadmin del_enctype lha des-cbc-md5 @end example You should also add the following entries to the @file{krb5.conf} file: @example [libdefaults] default_etypes = des-cbc-crc default_etypes_des = des-cbc-crc @end example These configuration options will make sure that no checksums of the unsupported types are generated. @node Useful links when reading about the Windows, , Quirks of Windows 2000 KDC, Windows compatibility @comment node-name, next, previous, up @section Useful links when reading about the Windows See also our paper presented at the 2001 Usenix Annual Technical Conference, available in the proceedings or at @uref{http://www.usenix.org/publications/library/proceedings/usenix01/freenix01/westerlund.html}. There are lots of texts about Kerberos on Microsoft's web site, here is a short list of the interesting documents that we have managed to find. @itemize @bullet @item Step-by-Step Guide to Kerberos 5 (krb5 1.0) Interoperability: @uref{http://www.microsoft.com/technet/prodtechnol/windows2000serv/howto/kerbstep.mspx}. Kerberos GSS-API (in Windows-eze SSPI), Windows as a client in a non-Windows KDC realm, adding unix clients to a Windows 2000 KDC, and adding cross-realm trust (@pxref{Inter-Realm keys (trust) between Windows and a Heimdal KDC}). @item Windows 2000 Kerberos Authentication: @uref{www.microsoft.com/technet/prodtechnol/windows2000serv/deploy/confeat/kerberos.mspx}. White paper that describes how Kerberos is used in Windows 2000. @item Overview of Kerberos: @uref{http://support.microsoft.com/support/kb/articles/Q248/7/58.ASP}. Links to useful other links. @c @item Klist for Windows: @c @uref{http://msdn.microsoft.com/library/periodic/period00/security0500.htm}. @c Describes where to get a klist for Windows 2000. @item Event logging for Kerberos: @uref{http://support.microsoft.com/support/kb/articles/Q262/1/77.ASP}. Basically it say that you can add a registry key @code{HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters\LogLevel} with value DWORD equal to 1, and then you'll get logging in the Event Logger. @c @item Access to the Active Directory through LDAP: @c @uref{http://msdn.microsoft.com/library/techart/kerberossamp.htm} @end itemize Other useful programs include these: @itemize @bullet @item pwdump2 @uref{http://www.bindview.com/Support/RAZOR/Utilities/Windows/pwdump2_readme.cfm}@end itemize