xref: /freebsd/crypto/heimdal/doc/win2k.texi (revision 4137ff4c)

@c $Id: win2k.texi,v 1.15 2001/07/19 16:44:41 assar Exp $

@node Windows 2000 compatability, Programming with Kerberos, Kerberos 4 issues, Top
@comment  node-name,  next,  previous,  up
@chapter Windows 2000 compatability

Windows 2000 (formerly known as Windows NT 5) from Microsoft implements
Kerberos 5.  Their implementation, however, has some quirks,
peculiarities, and bugs.  This chapter is a short summary of the things
that we have found out while trying to test Heimdal against Windows
2000.  Another big problem with the Kerberos implementation in Windows
2000 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.

This information should apply to Heimdal @value{VERSION} and Windows
2000 Professional.  It's of course subject all the time and mostly consists of
our not so inspired guesses.  Hopefully it's still somewhat useful.

@menu
* Configuring Windows 2000 to use a Heimdal KDC::
* Inter-Realm keys (trust) between Windows 2000 and a Heimdal KDC::
* Create account mappings::
* Encryption types::
* Authorization data::
* Quirks of Windows 2000 KDC::
* Useful links when reading about the Windows 2000::
@end menu

@node Configuring Windows 2000 to use a Heimdal KDC, Inter-Realm keys (trust) between Windows 2000 and a Heimdal KDC, Windows 2000 compatability, Windows 2000 compatability
@comment node-name, next, precious, up
@section Configuring Windows 2000 to use a Heimdal KDC

You need the command line program called @code{ksetup.exe} which is available
in the file @code{SUPPORT/TOOLS/SUPPORT.CAB} on the Windows 2000 Professional
CD-ROM. This program is used to configure the Kerberos settings on a
Workstation.

@code{Ksetup} store the domain information under the registry key:
@code{HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\LSA\Kerberos\Domains}.

Use the kadmin program in Heimdal to create a host principal in the
Kerberos realm.

@example
unix% kadmin
kadmin> ank -pw password host/datan.my.domain
@end example

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 MY.REALM
C:> ksetup /addkdc MY.REALM kdc.my.domain
@end example

Set the machine password, i.e. create the local keytab:
@example
C:> ksetup /setmachpassword password
@end example

The workstation must now be rebooted.

A mapping between local NT users and Kerberos principals must be specified,
you have two choices:

@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...)

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 2000 and a Heimdal KDC, Create account mappings, Configuring Windows 2000 to use a Heimdal KDC, Windows 2000 compatability
@comment node-name, next, precious, up
@section Inter-Realm keys (trust) between Windows 2000 and a Heimdal KDC

See also the Step-by-Step guide from Microsoft, referenced below.

Install Windows 2000, 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 @code{netdom.exe} tool.

You need to tell Windows 2000 on what hosts to find the KDCs for the
non-Windows realm with @code{ksetup}, see @xref{Configuring Windows 2000
to use a Heimdal KDC}.

This need to be done on all computers that want enable cross-realm
login with @code{Mapped Names}.

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.

You also need to add the inter-realm keys to the Heimdal KDC. There are
some tweaks that you need to do to @file{krb5.conf} beforehand.

@example
[libdefaults]
	default_etypes = des-cbc-crc
	default_etypes_des = des-cbc-crc
@end example

since otherwise checksum types that are not understood by Windows 2000
will be generated (@xref{Quirks of Windows 2000 KDC}.).

Another issue is salting.  Since Windows 2000 does not seem to
understand Kerberos 4 salted hashes you might need to turn off anything
similar to the following if you have it, at least while adding the
principals that are going to share keys with Windows 2000.

@example
	[kadmin]default_keys = v5 v4
@end example

You must also set:

Once that is also done, you can add the required inter-realm keys:

@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.

Do not forget to reboot before trying the new realm-trust (after running
@code{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 2000 and a Heimdal KDC, Windows 2000 compatability
@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.

@node Encryption types, Authorization data, Create account mappings, Windows 2000 compatability
@comment  node-name,  next,  previous,  up
@section Encryption types

Windows 2000 supports both the standard DES encryptions (des-cbc-crc and
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.

Heimdal implements both of these encryption types, but since DES is the
standard and the hmac-code is somewhat newer, it is likely to work better.

@node Authorization data, Quirks of Windows 2000 KDC, Encryption types, Windows 2000 compatability
@comment  node-name,  next,  previous,  up
@section Authorization data

The Windows 2000 KDC also adds extra authorization 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
--dump-auth=file} where file is an appropriate file.
@item It should authenticate and dump for you the authorization data in
the file.
@item The tool @kbd{lib/asn1/asn1_print} is somewhat useful for
analyzing the data.
@end enumerate

@node Quirks of Windows 2000 KDC, Useful links when reading about the Windows 2000, Authorization data, Windows 2000 compatability
@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 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 @code{des-cbc-md5} key
is used. To make the KDC return only @code{des-cbc-crc} you must delete
the @code{des-cbc-md5} key from the kdc using the @code{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 2000,  , Quirks of Windows 2000 KDC, Windows 2000 compatability
@comment  node-name,  next,  previous,  up
@section Useful links when reading about the Windows 2000

See also our paper presented at the 2001 usenix Annual Technical
Conference, available in the proceedings or at
@url{http://www.usenix.org/publications/library/proceedings/usenix01/freenix01/westerlund.html}.

There are lots of text 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 -
@url{http://www.microsoft.com/windows2000/library/planning/security/kerbsteps.asp}
Kerberos GSS-API (in Windows-ize SSPI), Windows as a client in a
non-Windows KDC realm, adding unix clients to a Windows 2000 KDC, and
adding cross-realm trust (@xref{Inter-Realm keys (trust) between Windows 2000
and a Heimdal KDC}.).

@item Windows 2000 Kerberos Authentication -
@url{http://www.microsoft.com/TechNet/win2000/win2ksrv/technote/kerberos.asp}
White paper that describes how Kerberos is used in Windows 2000.

@item Overview of kerberos -
@url{http://support.microsoft.com/support/kb/articles/Q248/7/58.ASP}
Links to useful other links.

@item Klist for windows -
@url{http://msdn.microsoft.com/library/periodic/period00/security0500.htm}
Describes where to get a klist for Windows 2000.

@item Event logging for kerberos -
@url{http://support.microsoft.com/support/kb/articles/Q262/1/77.ASP}.
Basicly 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.

@item Access to the active directory through LDAP
@url{http://msdn.microsoft.com/library/techart/kerberossamp.htm}

@end itemize

Other useful programs include these:

@itemize @bullet
@item pwdump2
@url{http://www.webspan.net/~tas/pwdump2/}
@end itemize