Use the setspn command to map the Kerberos service
principal name, HTTP/<host name>, to a Microsoft user account.
An example of setspn usage is as follows: C:\Program Files\Support Tools>
setspn -A HTTP/myappserver.austin.ibm.com myappserver
Note: There may already be some SPNs related to the Microsoft Windows hosts that have been added to the
domain. You can display those that exist by using the setspn
-L command, but you still have to add an HTTP SPN for WebSphere Application Server.
For example, setspn -L myappserver would list the
SPNs.
Important: Make sure that you do not have
the same SPNs mapping to more than one Microsoft user account. If you map the
same SPN to more than one user account, the web browser client can
send a NTLM instead of SPNEGO token to WebSphere Application Server.
More information about the setspn command can be found here, Windows 2003 Technical Reference (setspn command)
Create the Kerberos keytab file and make it available to WebSphere Application Server.
Use the ktpass command to create the Kerberos keytab file (krb5.keytab).
The following
code shows the functions that are available when you enter
ktpass -? command on the command line. This information
might be different depending on the version of the toolkit that you
are using.
C:\Program Files\Support Tools>ktpass -?
Command line options:
---------------------most useful args
[- /] out : Keytab to produce
[- /] princ : Principal name (user@REALM)
[- /] pass : password to use
use "*" to prompt for password.
[- +] rndPass : ... or use +rndPass to generate a random password
[- /] minPass : minimum length for random password (def:15)
[- /] maxPass : maximum length for random password (def:256)
---------------------less useful stuff
[- /] mapuser : map princ (above) to this user account (default:
don't)
[- /] mapOp : how to set the mapping attribute (default: add it)
[- /] mapOp : is one of:
[- /] mapOp : add : add value (default)
[- /] mapOp : set : set value
[- +] DesOnly : Set account for des-only encryption (default:don't)
[- /] in : Keytab to read/digest
---------------------options for key generation
[- /] crypto : Cryptosystem to use
[- /] crypto : is one of:
[- /] crypto : DES-CBC-CRC : for compatibility
[- /] crypto : DES-CBC-MD5 : for compatibliity
[- /] crypto : RC4-HMAC-NT : default 128-bit encryption
[- /] ptype : principal type in question
[- /] ptype : is one of:
[- /] ptype : KRB5_NT_PRINCIPAL : The general ptype-- recommended
[- /] ptype : KRB5_NT_SRV_INST : user service instance
[- /] ptype : KRB5_NT_SRV_HST : host service instance
[- /] kvno : Override Key Version Number
Default: query DC for kvno. Use /kvno 1 for Win2K
compat.
[- +] Answer : +Answer answers YES to prompts. -Answer answers
NO.
[- /] Target : Which DC to use. Default:detect
---------------------options for trust attributes (Windows Server 2003
Sp1 Only
[- /] MitRealmName : MIT Realm which we want to enable RC4 trust on.
[- /] TrustEncryp : Trust Encryption to use; DES is default
[- /] TrustEncryp : is one of:
[- /] TrustEncryp : RC4 : RC4 Realm Trusts (default)
[- /] TrustEncryp : DES : go back to DES
Important: Do not use the -pass switch on the ktpass command to reset a password for a Microsoft Windows server account.
See Windows 2003 Technical Reference (Kerberos keytab file and ktpass
command) for more information. You must use
the -mapUser option with ktpass command to enable
the KDC to create an encryption key. Otherwise, when the SPENGO token
is received, it fails the validation process and the application server
challenges the user for a user name and password.Depending
on the encryption type, you use the
ktpass tool in one of the
following ways to create the Kerberos keytab file. The following section
shows the different types of encryption that are used by the ktpass
tool. It is important that you run the ktpass -? command to determine
which -crypto parameter value is expected by the particular toolkit
in your Microsoft Windows environment.
- For a single DES encryption type
From a command prompt, run
the
ktpass command:
ktpass -out c:\temp\myappserver.keytab
-princ HTTP/myappserver.austin.ibm.com@WSSEC.AUSTIN.IBM.COM
-mapUser myappserv
-mapOp set
-pass was1edu
-crypto DES-CBC-MD5
-pType KRB5_NT_PRINCIPAL
+DesOnly
Table 1. Using ktpass for a single DES encryption
type
Option |
Explanation |
-out c:\temp\myappserver.keytab |
The key is written to this output file. |
-princ HTTP/myappserver.austin.ibm.com@WSSEC.AUSTIN.IBM.COM |
The concatenation of the user logon name, and
the realm must be in uppercase. |
-mapUser |
The key is mapped to the user, myappserver. |
-mapOp |
This option sets the mapping. |
-pass was1edu |
This option is the password for the user ID. |
-crypto DES-CBC-MD5 |
This option uses the single DES encryption type. |
-pType KRB5_NT_PRINCIPAL |
This option specifies the KRB5_NT_PRINCIPAL principal value. Specify this option to avoid toolkit warning messages. |
+DesOnly |
This option generates only DES encryptions. |
- For the RC4-HMAC encryption type
Important: RC4-HMAC
encryption is only supported when using a Windows 2003 Server as KDC. RC4-HMAC encryption
is not supported with a Windows 2000 Server as KDC.
From a command prompt, run the
ktpass command.
ktpass -out c:\temp\myappserver.keytab
-princ HTTP/myappserver.austin.ibm.com@WSSEC.AUSTIN.IBM.COM
-mapUser myappserver
-mapOp set
–pass was1edu
-crypto RC4-HMAC
-pType KRB5_NT_PRINCIPAL
Table 2. Using ktpass for
the RC4-HMAC encryption type
Option |
Explanation |
-out c:\temp\myappserver.keytab |
The key is written to this output file. |
-princ HTTP/myappserver.austin.ibm.com@WSSEC.AUSTIN.IBM.COM |
The concatenation of the user logon name, and
the realm must be in uppercase. |
-mapUser |
The key is mapped to the user, myappserver. |
-mapOp |
This option sets the mapping. |
-pass was1edu |
This option is the password for the user ID. |
-crypto RC4-HMAC |
This option chooses the RC4-HMAC encryption
type. |
-pType KRB5_NT_PRINCIPAL |
This option specifies the KRB5_NT_PRINCIPAL principal value. Specify this option to avoid toolkit warning messages. |
- For the RC4-HMAC-NT encryption type
From a command prompt, run
the
ktpass command.
ktpass -out c:\temp\myappserver.keytab
-princ HTTP/myappserver.austin.ibm.com@WSSEC.AUSTIN.IBM.COM
-mapUser myappserver
-mapOp set
-pass was1edu
-crypto RC4-HMAC-NT
-pType KRB5_NT_PRINCIPAL
Table 3. Using ktpass for
the RC4-HMAC encryption type
Option |
Explanation |
-out c:\temp\myappserver.keytab |
The key is written to this output file. |
-princ HTTP/myappserver.austin.ibm.com@WSSEC.AUSTIN.IBM.COM |
The concatenation of the user logon name, and
the realm must be in uppercase. |
-mapUser |
The key is mapped to the user, myappserver. |
-mapOp |
This option sets the mapping. |
-pass was1edu |
This option is the password for the user ID. |
-crypto RC4-HMAC-NT |
This option chooses the RC4-HMAC-NT encryption
type. |
-pType KRB5_NT_PRINCIPAL |
This option specifies the KRB5_NT_PRINCIPAL principal value. Specify this option to avoid toolkit warning messages. |
The Kerberos keytab file is created for use with the SPNEGO
TAI.The krb5.conf configuration
file supports trigraphs to represent the {, }, [, and ] characters.
These characters depend on the language set. The natively generated
keytabs cannot be read by the Kerberos client. If you have difficulty
configuring SPNEGO TAI with the native krb5.conf or krb5.keytab files,
complete one of the following scenarios to address the trigraphs issue:
- Replace the trigraphs in the krb5.conf file with the characters
that they represent.
- Use the krb5.conf file that is generated by WebSphere Application Server.
- Use a Microsoft Windows or a key distribution
center (KDC) generated keytab file.
Note: A Kerberos keytab configuration file contains a list
of keys that are analogous to user passwords. It is important for
hosts to protect their Kerberos keytab files by storing them on the
local disk, which makes them readable only be authorized users.
You make the keytab file available to WebSphere Application Server by copying
the
krb5.keytab file from the Domain Controller (LDAP
machine) to the WebSphere Application Server machine.
ftp> bin
ftp> put c:\temp\KRB5_NT_SEV_HST\krb5.keytab