Building & Running Kerberos 5 on Windows
----------------------------------------
This file documents how to build MIT Kerberos for Windows.
The MIT Kerberos for Windows distribution contains additional components
not present in the Unix krb5 distribution, most notably the
MIT Kerberos Ticket Manager application.
To build Kerberos 5 on Windows, you will need the following:
* A version of Visual Studio (at least 2013) which includes the
Microsoft Foundation Classes libraries. These instructions will
work for Visual Studio 2017 Community or Professional, both of which
include the MFC libraries if the "Visual C++ MFC" checkbox is
selected after enabling the "Desktop development with C++" workload.
If you do not plan to build the graphical ticket manager
application, the MFC libraries are not required.
* A version of Perl.
* Some common Unix utilities such as sed/awk/cp/cat installed in the
command-line path.
* To build an MSI installer, the Windows Installer XML (WiX) toolkit,
and to ensure that the HTML Help Compiler (hhc.exe) and the WiX
tools are in your command-line path. WiX version 3.11.1 is verified
to work with this codebase.
A simple way to get the necessary Unix utilities is to install Git
BASH from https://gitforwindows.org and configure it to add the Unix
utilities to the command-line path. In some versions of Windows (not
the most current versions), the Unix utilities can alternatively be
obtained via the Utilities and SDK for UNIX-based Applications, which
may be enabled as a Windows feature and then the components installed.
Note that the Windows nmake will not find the SUA awk utility in the
path unless it is named awk.exe; the permissions on the utility may
need correcting if awk.exe is created as a copy of the original awk.
Git BASH contains a version of Perl, which will work to build krb5 if
the newlines in the source tree are not translated to native newlines.
Strawberry Perl will work regardless of whether newlines are
translated. If both Git BASH and Strawberry Perl are installed, you
may need to adjust the command line path to ensure that the preferred
Perl appears first.
The krb5 source tree may be obtained either directly on the Windows
machine with a native git client cloning the krb5 public mirror at
https://github.com/krb5/krb5.git or on a separate (Unix) machine and
copied over, such as from a VM host onto a Windows VM. If you are
checking out the sources with git and are using the Git BASH Perl,
make sure to set git's core.autocrlf variable to "input" or "false" to
avoid translating newlines.
After Visual Studio is installed, you should be able to invoke 32-bit
and 64-bit command prompts via the start menu (Visual Studio 2017 ->
x86 Native Tools Command Prompt and x64 Native Tools Command Prompt).
At the current time, Kerberos 5 can only be built for the x64 target
if the host platform is also 64-bit, because it compiles and runs
programs during the build.
IMPORTANT NOTE: By default, the sources are built with debug
information and linked against the debug version of the Microsoft C
Runtime library, which is not found on most Windows systems unless
they have development tools, and requires a separate license to
distribute. To build a release version, you need to define NODEBUG
either in the environment or the nmake command-line. Debug
information in the compiled binaries and libraries may be retained by
defining DEBUG_SYMBOL in the environment or on the nmake command line.
Building the code and installer:
-------------------------------
First, make sure you have sed, (g)awk, cat, and cp.
You must also define KRB_INSTALL_DIR either in the environment or
on the command line (for nmake install). If you are proceeding to build
the MSI installer, this directory should be a temporary staging area in or
near your build tree. The directory must exist before nmake install
is run. The 64-bit installer provides 32-bit libraries, so a 32-bit build
and install must be performed before the 64-bit build.
To skip building the graphical ticket manager, run "set NO_LEASH=1"
before building, and do not build the installers.
In a 32-bit command shell:
1) set KRB_INSTALL_DIR=\path\to\dir # Where bin/include/lib lives
2) cd xxx\src # Go to where source lives
3) nmake -f Makefile.in prep-windows # Create Makefile for Windows
4) nmake [NODEBUG=1] # Build the sources
5) nmake install [NODEBUG=1] # Copy headers, libs, executables
6) cd windows\installer\wix # Go to where the installer source is
7) nmake [NODEBUG=1] # Build the installer
8) rename kfw.msi kfw32.msi # Save the 32-bit installer
In a 64-bit command shell:
9) set PATH=%PATH%;"%WindowsSdkVerBinPath%"\x86 # To get uicc.exe
10) set KRB_INSTALL_DIR=\path\to\dir # Where bin/include/lib lives
11) cd xxx\src # Go to where source lives
12) nmake clean # Clean up the 32-bit objects
13) nmake [NODEBUG=1] # Build the sources for 64-bit
14) nmake install [NODEBUG=1] # Copy 64-bit lib/executables
15) cd windows\installer\wix # Back to the installer source
16) nmake clean # Remove 32-bit leavings
17) nmake [NODEBUG=1] # Build the 64-bit installer
18) rename kfw.msi kfw64.msi # And name it usefully
Step 9 may be skipped if uicc is already in the command-line path (try
running "uicc" to see if you get a usage message or a not-found
error), or if you are not building the graphical ticket manager.
Visual Studio 2013 and 2015 provide only a single command prompt.
Within this prompt, use "vcvarsall.bat x86" and "vcvarsall.bat amd64"
to switch to 32-bit and 64-bit mode.
Running Kerberos 5 Apps:
-----------------------
Make sure you have a valid krb5.ini file.
By default, an empty krb5.ini is installed in CSIDL_COMMON_APPDATA
(that is, %SystemDrive%\ProgramData\MIT\Kerberos5\ on newer-than-XP).
(ProgramData is a hidden folder.) You may need to customize it with
settings for your site, but since DNS lookups are enabled for locating
KDCs, many sites will not need further customization. The file format is
identical to that of a Unix krb5.conf file.
krb5.ini File:
-------------
WARNING: Despite its name, this is not a Windows .ini file.
Therefore, do not try to use any .ini tools, including the Windows API
or any installer tools to manipulate this file. Its format is subtly
different from Windows .ini files!
Controlling the Kerberos 5 Run-Time Environment:
-----------------------------------------------
The Kerberos 5 configuration file and credentials cache can be
controlled with environment variables and registry settings. The
environment variable for a particular setting always takes precedence.
Next in precedence comes the setting in the registry under
HKEY_CURRENT_USER\Software\MIT\Kerberos5. Then comes the registry
setting under HKEY_LOCAL_MACHINE\Software\MIT\Kerberos5. If none of
those are found, a default value is used.
Configuration File:
- Environment: KRB5_CONFIG
- Registry Value: config
- Default: looks in the user's AppData directory, the machine's ProgramData
directory, krb5_32.dll's dir and Windows directory
Default Credentials Cache:
- Environment: KRB5CCNAME
- Registry Value: ccname
- Default: API:
Credentials Cache:
-----------------
In addition to standard FILE: (disk file) and MEMORY: (in-process
non-shared memory) Windows supports the API: cache type, which is a
shared memory cache. Kerberos for Windows also has access to an
MSLSA: cache type, which directly accesses the Microsoft Kerberos
Logon Session credentials cache. The MSLSA: cache is available when the
user logon is performed using Kerberos either to an Active Directory Domain
or a non-Microsoft KDC; the ms2mit and mit2ms utilities can also be used
to interact with it, though there are some limitations.
A user is able to logon to Windows using the Kerberos LSA if the machine
is part of a Windows Active Directory domain or if the machine has been
configured to authenticate to a non-Microsoft KDC such as MIT.
The instructions for configuring a Windows 2000 XP workstation to
authenticate to a non-Microsoft KDC are documented in TechNet somewhere.
In brief:
1. Install the Windows support tools in order to obtain KSETUP.EXE
and KTPASS.EXE.
2. Install the Windows Resource Kit to obtain KERBTRAY.EXE and KLIST.EXE
3. Add Realms and associated KDCs with: *KSETUP /AddKdc <realm>
[<kdcname>]*. If you leave off the <kdcname> DNS SRV records will
be used.
4. Specify the password change service host for the realm with:
*KSETUP /AddKpasswd <realm> <Kpwdhost>*
5. Assign the realm of the local machine with: *KSETUP /SetRealm
<realm>* where realm must be all upper case.
6. Assign the local machine's password with: *KSETUP
/SetComputerPassword <Password>
*
7. Specify the capabilities of the Realm KDC with: *KSETUP
/SetRealmFlags <realm> <flag> [<flag> ...]* where flags may be
*None, SendAddress, TcpSupported, Delegate, *and *NcSupported*,
8. Map principal names to local accounts with: *KSETUP /MapUser
<principal> <account>*
On the MIT KDC, you must then create service principals using the "Password"
assigned to the machine. So far the minimum list of principals required appear
to be for a machine named "mymachine" in the realm "EXAMPLE.COM" with a
domain name of "example.com":
* host/mymachine@EXAMPLE.COM
* host/mymachine.example.com@EXAMPLE.COM
* cifs/mymachine@EXAMPLE.COM
* cifs/mymachine.example.com@EXAMPLE.COM
There may very well be other services for which principals must be created depending
on what services are being executed on the machine.
It is very important to note that while you can successfully log into a Windows
workstation by authenticating to the KDC without creating a host key; the logon
session you receive will not be a Kerberos Logon Session. There will be no Kerberos
principal and no LSA cache to access.
The result of a real KSETUP configuration looks like this:
[C:\4\4NT]ksetup
default realm = KRB5.COLUMBIA.EDU (external)
ATHENA.MIT.EDU:
kdc = kerberos.mit.edu
kdc = kerberos-1.mit.edu
kdc = kerberos-2.mit.edu
kdc = kerberos-3.mit.edu
Realm Flags = 0x0 none
CC.COLUMBIA.EDU:
kdc = kerberos.cc.columbia.edu
Realm Flags = 0x0 none
GRAND.CENTRAL.ORG:
kdc = penn.central.org
kdc = grand-opening.mit.edu
Realm Flags = 0x0 none
KRB5.COLUMBIA.EDU:
kdc = yclept.kermit.columbia.edu
Realm Flags = 0x0 none
OPENAFS.ORG:
kdc = virtue.openafs.org
Realm Flags = 0x0 none
Mapping jaltman@KRB5.COLUMBIA.EDU to jaltman.
Mapping jaltman@CC.COLUMBIA.EDU to jaltman.
Mapping jaltman@ATHENA.MIT.EDU to jaltman.
Mapping all users (*) to a local account by the same name (*).
The MSLSA: credential cache relies on the ability to extract the entire
Kerberos ticket including the session key from the Kerberos LSA. In an
attempt to increase security Microsoft has begun to implement a feature
by which they no longer export the session keys for Ticket Getting Tickets.
This has the side effect of making them useless to the MIT krb5 library
when attempting to request additional service tickets.
This new feature has been seen in Windows 2003 Server, Windows 2000 Server SP4,
and Windows XP SP2. We assume that it will be implemented in all future
Microsoft operating systems supporting the Kerberos SSPI. Microsoft does work
closely with MIT and has provided a registry key to disable this new feature.
On server platforms the key is specified as:
HKLM\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters
AllowTGTSessionKey = 0x01 (DWORD)
On workstation platforms the key is specified as:
HKLM\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos
AllowTGTSessionKey = 0x01 (DWORD)
The Kerberos for Windows installer automatically sets this key on installation
and unsets it on uninstall, allowing the MSLSA: cache type to be used.
It has been noted that the Microsoft Kerberos LSA does not provide enough
information within its KERB_EXTERNAL_TICKET structure to properly construct
the Client Principal simply by examining a single ticket. From the MSDN
Library:
ClientName
KERB_EXTERNAL_NAME structure that contains the client name in the ticket.
This name is relative to the current domain.
DomainName
UNICODE_STRING that contains the name of the domain that corresponds to
the ServiceName member. This is the domain that issued the ticket.
TargetDomainName
UNICODE_STRING that contains the name of the domain in which the ticket is
valid. For an interdomain ticket, this is the destination domain.
AltTargetDomainName
UNICODE_STRING that contains a synonym for the destination domain. Every
domain has two names: a DNS name and a NetBIOS name. If the name returned
in the ticket is different from the name used to request the ticket (the
Kerberos Key Distribution Center (KDC) may do name mapping), this string
contains the original name.
Unfortunately, there is no field here which contains the domain of the client.
In order for the krb5_ccache to properly report the client principal name, the
client principal name is constructed by utilizing the ClientName and DomainName
fields of the Initial TGT associated with the Kerberos LSA credential cache.
To disable the use of the TGT info and instead simply use the "DomainName" field
of the current ticket define one of the following registry keys depending on
whether the change should be system global or just for the current user.
HKLM\Software\MIT\Kerberos5\
PreserveInitialTicketIdentity = 0x0 (DWORD)
HKCU\Software\MIT\Kerberos5\
PreserveInitialTicketIdentity = 0x0 (DWORD)
GSSAPI Sample Client:
---------------------
The GSS API Sample Client provided in this distribution is compatible with the
gss-server application built on Unix/Linux systems. This client is not compatible
with the Platform SDK/Samples/Security/SSPI/GSS/ samples which Microsoft has been
shipping as of January 2004. Revised versions of these samples are available upon
request to krbdev@mit.edu.
More Information:
----------------
For more information, please read the Kerberos 5 documentation in
the doc directory of the distribution.