1@c $Id$ 2 3 4@node Windows compatibility, Programming with Kerberos, Kerberos 4 issues, Top 5@comment node-name, next, previous, up 6@chapter Windows compatibility 7 8Microsoft Windows, starting from version 2000 (formerly known as Windows NT 5), implements Kerberos 5. Their implementation, however, has some quirks, 9peculiarities, and bugs. This chapter is a short summary of the compatibility 10issues between Heimdal and various Windows versions. 11 12The big problem with the Kerberos implementation in Windows 13is that the available documentation is more focused on getting 14things to work rather than how they work, and not that useful in figuring 15out how things really work. It's of course subject to change all the time and 16mostly consists of our not so inspired guesses. Hopefully it's still 17somewhat useful. 18 19@menu 20* Configuring Windows to use a Heimdal KDC:: 21* Inter-Realm keys (trust) between Windows and a Heimdal KDC:: 22* Create account mappings:: 23* Encryption types:: 24* Authorisation data:: 25* Quirks of Windows 2000 KDC:: 26* Useful links when reading about the Windows:: 27@end menu 28 29@node Configuring Windows to use a Heimdal KDC, Inter-Realm keys (trust) between Windows and a Heimdal KDC, Windows compatibility, Windows compatibility 30@comment node-name, next, precious, up 31@section Configuring Windows to use a Heimdal KDC 32 33You 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. 34 35@command{Ksetup} store the domain information under the registry key: 36@code{HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\LSA\Kerberos\Domains}. 37 38Use the @command{kadmin} program in Heimdal to create a host principal in the 39Kerberos realm. 40 41@example 42unix% kadmin 43kadmin> ank --password=password host/datan.example.com 44@end example 45 46The name @samp{datan.example.com} should be replaced with DNS name of 47the workstation. 48 49You must configure the workstation as a member of a workgroup, as opposed 50to a member in an NT domain, and specify the KDC server of the realm 51as follows: 52@example 53C:> ksetup /setdomain EXAMPLE.COM 54C:> ksetup /addkdc EXAMPLE.COM kdc.example.com 55@end example 56 57Set the machine password, i.e.@: create the local keytab: 58@example 59C:> ksetup /SetComputerPassword password 60@end example 61 62The password used in @kbd{ksetup /setmachpassword} must be the same 63as the password used in the @kbd{kadmin ank} command. 64 65The workstation must now be rebooted. 66 67A mapping between local NT users and Kerberos principals must be specified. 68You have two choices. First: 69 70@example 71C:> ksetup /mapuser user@@MY.REALM nt_user 72@end example 73 74This will map a user to a specific principal; this allows you to have 75other usernames in the realm than in your NT user database. (Don't ask 76me why on earth you would want that@enddots{}) 77 78You can also say: 79@example 80C:> ksetup /mapuser * * 81@end example 82The Windows machine will now map any user to the corresponding principal, 83for example @samp{nisse} to the principal @samp{nisse@@MY.REALM}. 84(This is most likely what you want.) 85 86@node Inter-Realm keys (trust) between Windows and a Heimdal KDC, Create account mappings, Configuring Windows to use a Heimdal KDC, Windows compatibility 87@comment node-name, next, precious, up 88@section Inter-Realm keys (trust) between Windows and a Heimdal KDC 89 90See also the Step-by-Step guide from Microsoft, referenced below. 91 92Install Windows, and create a new controller (Active Directory 93Server) for the domain. 94 95By default the trust will be non-transitive. This means that only users 96directly from the trusted domain may authenticate. This can be changed 97to transitive by using the @command{netdom.exe} tool. @command{netdom.exe} 98can also be used to add the trust between two realms. 99 100You need to tell Windows on what hosts to find the KDCs for the 101non-Windows realm with @command{ksetup}, see @xref{Configuring Windows 102to use a Heimdal KDC}. 103 104This needs to be done on all computers that want enable cross-realm 105login with @code{Mapped Names}. @c XXX probably shouldn't be @code 106 107Then you need to add the inter-realm keys on the Windows KDC@. Start the 108Domain Tree Management tool (found in Programs, Administrative tools, 109Active Directory Domains and Trusts). 110 111Right click on Properties of your domain, select the Trust tab. Press 112Add on the appropriate trust windows and enter domain name and 113password. When prompted if this is a non-Windows Kerberos realm, press 114OK. 115 116Do not forget to add trusts in both directions (if that's what you want). 117 118If you want to use @command{netdom.exe} instead of the Domain Tree 119Management tool, you do it like this: 120 121@example 122netdom trust NT.REALM.EXAMPLE.COM /Domain:EXAMPLE.COM /add /realm /passwordt:TrustPassword 123@end example 124 125You also need to add the inter-realm keys to the Heimdal KDC. But take 126care to the encryption types and salting used for those keys. There should be 127no encryption type stronger than the one configured on Windows side for this 128relationship, itself limited to the ones supported by this specific version of 129Windows, nor any Kerberos 4 salted hashes, as Windows does not seem to 130understand them. Otherwise, the trust will not works. 131 132Here are the version-specific needed information: 133@enumerate 134@item Windows 2000: maximum encryption type is DES 135@item Windows 2003: maximum encryption type is DES 136@item Windows 2003RC2: maximum encryption type is RC4, relationship defaults to DES 137@item Windows 2008: maximum encryption type is AES, relationship defaults to RC4 138@end enumerate 139 140For Windows 2003RC2, to change the trust encryption type, you have to use the 141@command{ktpass}, from the Windows 2003 Resource kit *service pack2*, available 142from Microsoft web site. 143 144@example 145C:> ktpass /MITRealmName UNIX.EXAMPLE.COM /TrustEncryp RC4 146@end example 147 148For Windows 2008, the same operation can be done with the @command{ksetup}, installed by default. 149 150@example 151C:> ksetup /SetEncTypeAttre EXAMPLE.COM AES256-SHA1 152@end example 153 154Once the relationship is correctly configured, you can add the required 155inter-realm keys, using heimdal default encryption types: 156 157@example 158kadmin add krbtgt/NT.REALM.EXAMPLE.COM@@EXAMPLE.COM 159kadmin add krbtgt/REALM.EXAMPLE.COM@@NT.EXAMPLE.COM 160@end example 161 162Use the same passwords for both keys. 163 164And if needed, to remove unsupported encryptions, such as the following ones for a Windows 2003RC2 server. 165 166@example 167kadmin del_enctype krbtgt/REALM.EXAMPLE.COM@@NT.EXAMPLE.COM aes256-cts-hmac-sha1-96 168kadmin del_enctype krbtgt/REALM.EXAMPLE.COM@@NT.EXAMPLE.COM des3-cbc-sha1 169kadmin del_enctype krbtgt/NT.EXAMPLE.COM@@EXAMPLE.COM aes256-cts-hmac-sha1-96 170kadmin del_enctype krbtgt/NT.EXAMPLE.COM@@EXAMPLE.COM des3-cbc-sha1 171@end example 172 173Do not forget to reboot before trying the new realm-trust (after 174running @command{ksetup}). It looks like it might work, but packets are 175never sent to the non-Windows KDC. 176 177@node Create account mappings, Encryption types, Inter-Realm keys (trust) between Windows and a Heimdal KDC, Windows compatibility 178@comment node-name, next, precious, up 179@section Create account mappings 180 181Start the @code{Active Directory Users and Computers} tool. Select the 182View menu, that is in the left corner just below the real menu (or press 183Alt-V), and select Advanced Features. Right click on the user that you 184are going to do a name mapping for and choose Name mapping. 185 186Click on the Kerberos Names tab and add a new principal from the 187non-Windows domain. 188 189@c XXX check entry name then I have network again 190This adds @samp{authorizationNames} entry to the users LDAP entry to 191the Active Directory LDAP catalog. When you create users by script you 192can add this entry instead. 193 194@node Encryption types, Authorisation data, Create account mappings, Windows compatibility 195@comment node-name, next, previous, up 196@section Encryption types 197 198Windows 2000 supports both the standard DES encryptions (@samp{des-cbc-crc} and 199@samp{des-cbc-md5}) and its own proprietary encryption that is based on MD4 and 200RC4 that is documented in and is supposed to be described in 201@file{draft-brezak-win2k-krb-rc4-hmac-03.txt}. New users will get both 202MD4 and DES keys. Users that are converted from a NT4 database, will 203only have MD4 passwords and will need a password change to get a DES 204key. 205 206@node Authorisation data, Quirks of Windows 2000 KDC, Encryption types, Windows compatibility 207@comment node-name, next, previous, up 208@section Authorisation data 209 210The Windows 2000 KDC also adds extra authorisation data in tickets. 211It is at this point unclear what triggers it to do this. The format of 212this data is only available under a ``secret'' license from Microsoft, 213which prohibits you implementing it. 214 215A simple way of getting hold of the data to be able to understand it 216better is described here. 217 218@enumerate 219@item Find the client example on using the SSPI in the SDK documentation. 220@item Change ``AuthSamp'' in the source code to lowercase. 221@item Build the program. 222@item Add the ``authsamp'' principal with a known password to the 223database. Make sure it has a DES key. 224@item Run @kbd{ktutil add} to add the key for that principal to a 225keytab. 226@item Run @kbd{appl/test/nt_gss_server -p 2000 -s authsamp 227@kbd{--dump-auth}=@var{file}} where @var{file} is an appropriate file. 228@item It should authenticate and dump for you the authorisation data in 229the file. 230@item The tool @kbd{lib/asn1/asn1_print} is somewhat useful for 231analysing the data. 232@end enumerate 233 234@node Quirks of Windows 2000 KDC, Useful links when reading about the Windows, Authorisation data, Windows compatibility 235@comment node-name, next, previous, up 236@section Quirks of Windows 2000 KDC 237 238There 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 239as a Kerberos 4 compatible salt---does not work, as far as we can tell 240from out experiments and users' reports. Therefore, you have to make 241sure you keep around keys with all the different types of salts that are 242required. Microsoft have fixed this issue post Windows 2003. 243 244Microsoft seems also to have forgotten to implement the checksum 245algorithms @samp{rsa-md4-des} and @samp{rsa-md5-des}. This can make Name 246mapping (@pxref{Create account mappings}) fail if a @samp{des-cbc-md5} key 247is used. To make the KDC return only @samp{des-cbc-crc} you must delete 248the @samp{des-cbc-md5} key from the kdc using the @kbd{kadmin 249del_enctype} command. 250 251@example 252kadmin del_enctype lha des-cbc-md5 253@end example 254 255You should also add the following entries to the @file{krb5.conf} file: 256 257@example 258[libdefaults] 259 default_etypes = des-cbc-crc 260 default_etypes_des = des-cbc-crc 261@end example 262 263These configuration options will make sure that no checksums of the 264unsupported types are generated. 265 266@node Useful links when reading about the Windows, , Quirks of Windows 2000 KDC, Windows compatibility 267@comment node-name, next, previous, up 268@section Useful links when reading about the Windows 269 270See also our paper presented at the 2001 Usenix Annual Technical 271Conference, available in the proceedings or at 272@uref{http://www.usenix.org/publications/library/proceedings/usenix01/freenix01/westerlund.html}. 273 274There are lots of texts about Kerberos on Microsoft's web site, here is a 275short list of the interesting documents that we have managed to find. 276 277@itemize @bullet 278 279@item Step-by-Step Guide to Kerberos 5 (krb5 1.0) Interoperability: 280@uref{http://www.microsoft.com/technet/prodtechnol/windows2000serv/howto/kerbstep.mspx}. 281Kerberos GSS-API (in Windows-eze SSPI), Windows as a client in a 282non-Windows KDC realm, adding unix clients to a Windows 2000 KDC, and 283adding cross-realm trust (@pxref{Inter-Realm keys (trust) between Windows 284and a Heimdal KDC}). 285 286@item Windows 2000 Kerberos Authentication: 287@uref{www.microsoft.com/technet/prodtechnol/windows2000serv/deploy/confeat/kerberos.mspx}. 288White paper that describes how Kerberos is used in Windows 2000. 289 290@item Overview of Kerberos: 291@uref{http://support.microsoft.com/support/kb/articles/Q248/7/58.ASP}. 292Links to useful other links. 293 294@c @item Klist for Windows: 295@c @uref{http://msdn.microsoft.com/library/periodic/period00/security0500.htm}. 296@c Describes where to get a klist for Windows 2000. 297 298@item Event logging for Kerberos: 299@uref{http://support.microsoft.com/support/kb/articles/Q262/1/77.ASP}. 300Basically it say that you can add a registry key 301@code{HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters\LogLevel} 302with value DWORD equal to 1, and then you'll get logging in the Event 303Logger. 304 305@c @item Access to the Active Directory through LDAP: 306@c @uref{http://msdn.microsoft.com/library/techart/kerberossamp.htm} 307 308@end itemize 309 310Other useful programs include these: 311 312@itemize @bullet 313@item pwdump2 314@uref{http://www.bindview.com/Support/RAZOR/Utilities/Windows/pwdump2_readme.cfm}@end itemize 315