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Kerberos is a method that let you identify to other services with your windows logon. Having configured LDAP and Kerberos you can achieve Single Sign On which means, that custo diagnostic will automatically use the user that is logged on to Windows for authentication and the user does not need to enter any passwords.

Kerberos lets you automatically login to the custo manager with you windows user if your user has a valid LDAP mapping. To do this you need to configure LDAP first.

It involves configuring Tomcat (the application server that hosts the custo diagnostic server), so we use Tomcat as a synonym for custo diagnostic server at this place. Most of this manual is copied from https://tomcat.apache.org/tomcat-8.0-doc/windows-auth-howto.html

Steps to configure the Kerberos System:

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E.g. In our Example we used the following names:

General Information

Kerberos (the basis for integrated Windows authentication) requires careful configuration. If the steps in this guide are followed exactly, then a working configuration will result. It is important that the steps below are followed exactly. There is very little scope for flexibility in the configuration. From the testing to date it is known that:

• The host name used to access the Tomcat server must match the host name in the SPN exactly else authentication will fail. A checksum error may be reported in the debug logs in this case.
• The SPN must be HTTP/<hostname> and it must be exactly the same in all the places it is used.
• The port number must not be included in the SPN.
• No more than one SPN may be mapped to a domain user.

Create Domain User for Apache Tomcat

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This step has to be done by the domain administrator.

Watch out:  Some entries are CASE SENSITIVE! 

Please use the following command to create the keytab-file.

ktpass -princ HTTP/win-tc01.yourdomain@YOURDOMAIN.DE
       -mapuser custoKerberos@yourdomain.de tst2srv01-2016.xy-hospital.xy@XY-HOSPITAL.XY 
-mapuser custoKerberos@xy-hospital.xy 
-crypto rc4-hmac-nt
       -ptype KRB5_NT_PRINCIPAL 
-pass secretPW!
       -out "C:\Program Files\custo diagnostic server\conf\tomcat.keytab"

This command:

• links the service principal name "HTTP/tst2srv01-2016.xy-hospital.xy@XY-HOSPITAL.XY"   to your custoKerberos-User (and defines the authentication/crypto way)
• stores the private key in tomcat.keytab file

This file contains the Tomcat private key for the service provider. To generate the file, run the following command as a domain administrator (all on a single line). You can do this step on the server where tomcat runs on.

Configure Apache Tomcat

Watch out:  Some entries are CASE SENSITIVE!  Some Path-Names need forward-slashes!

We attached the file to download it for you. Please do not use copy/paste from the code below - use the files attached to this website.

Replace / Edit krb5.ini and jaas.conf file, located in your ...\custo diagnostic server\conf Directory:

krb5.ini (Downlaod krb5.ini)

#krb5.ini
[libdefaults]
  debug = true
  default_realm = YOURDOMAINXY-HOSPITAL.DEXY
  dns_lookup_kdc = false
  default_keytab_name = FILE:C:\Program Files\custo diagnostic server\conf\tomcat.keytab
  krb4_config = /etc/krb.conf
  krb4_realms = /etc/krb.realms
  kdc_timesync = 1
  ccache_type = 4
  forwardable = true
  proxiable = true
 

[realms]
  YOURDOMAINXY-HOSPITAL.DEXY = {
    kdc = tstdc01tst2dc01.yourdomainxy-hospital.dexy
    admin_server = tstdc01tst2dc01.yourdomainxy-hospital.dexy
    default_domain = yourdomainxy-hospital.dexy
} 



[domain_realm]

.yourdomainxy-hospital.dexy = YOURDOMAIN.DEXY-HOSPITAL.XY

 

[login]
krb4_convert = true
krb4_get_tickets = false

jaas.conf (doanload jaas.conf)

We attached the file to download it for you. Please do not use copy/paste from the code below - use the files attached to this website.

Attention !

principal Name must be IDENTICAL (case sensitive) to the principal Name used with ktpass

Be aware of forward slahes in file Name

com.sun.security.jgss.krb5.initiate {
    com.sun.security.auth.module.Krb5LoginModule required
    doNotPrompt=true
    principal="HTTP/tstsrv01tst2srv01-2016.yourdomain.de@YOURDOMAIN.DExy-hospital.xy@XY-HOSPITAL.XY"
    useKeyTab=true
    keyTab="C:/Program Files/custo diagnostic server/conf/tomcat.keytab"
    storeKey=true;
};

 

com.sun.security.jgss.krb5.accept {
    com.sun.security.auth.module.Krb5LoginModule required
    doNotPrompt=true
    principal="HTTP/tstsrv01tst2srv01-2016.yourdomain.de@YOURDOMAIN.DExy-hospital.xy@XY-HOSPITAL.XY"
    useKeyTab=true
    keyTab="C:/Program Files/custo diagnostic server/conf/tomcat.keytab"
    storeKey=true;
};

Kerberos

Kerberos lets you automatically login to the custo manager with you windows user if your user has a valid LDAP mapping. To do this you need to configure LDAP first.

Configuring Kerberos is somewhat complicated and for at least one step you need to be the Windows Domain Administrator. It involves configuring Tomcat (the application server that hosts the custo diagnostic server), so we use Tomcat as a synonym for custo diagnostic server at this place. Most of this manual is copied from https://tomcat.apache.org/tomcat-8.0-doc/windows-auth-howto.html

Kerberos (the basis for integrated Windows authentication) requires careful configuration. If the steps in this guide are followed exactly, then a working configuration will result. It is important that the steps below are followed exactly. There is very little scope for flexibility in the configuration. From the testing to date it is known that:

• The host name used to access the Tomcat server must match the host name in the SPN exactly else authentication will fail. A checksum error may be reported in the debug logs in this case.
• The SPN must be HTTP/<hostname> and it must be exactly the same in all the places it is used.
• The port number must not be included in the SPN.
• No more than one SPN may be mapped to a domain user.
• Tomcat must run as the domain account with which the SPN has been associated or as domain admin. It is NOT recommended to run Tomcat under a domain admin user.
• The domain name (DEV.LOCAL) is not case sensitive when used in the ktpass command, nor when used in jaas.conf
• The domain must be specified when using the ktpass command

There are three components to the configuration of the built-in Tomcat support for Windows authentication. The domain controller, the server hosting Tomcat, the web application wishing to use Windows authentication. The following sections describe the configuration required for each component.

The names of the three machines used in the configuration examples below are win-dc01.dev.local (the domain controller), win-tc01.dev.local (the Tomcat instance) and win-pc01.dev.local (client). All are members of the DEV.LOCAL domain.

Note: In order to use the passwords in the steps below, the domain password policy had to be relaxed. This is not recommended for production environments.

Domain Controller

These steps assume that the server has already been configured to act as a domain controller. Configuration of a Windows server as a domain controller is outside the scope of this how-to. The steps to configure the domain controller to enable Tomcat to support Windows authentication are as follows:

• Create a domain user that will be mapped to the service name used by the Tomcat server. In this how-to, this user is called tc01 and has a password of tc01pass.
• Map the service principal name (SPN) to the user account. SPNs take the form <service class>/<host>:<port>/<service name>. The SPN used in this how-to is HTTP/win-tc01.dev.local. To map the user to the SPN, run the following:

  setspn -A HTTP/win-tc01.dev.local tc01

• Generate the keytab file that the Tomcat server will use to authenticate itself to the domain controller. This file contains the Tomcat private key for the service provider account and should be protected accordingly. To generate the file, run the following command (all on a single line):

  ktpass /out c:\tomcat.keytab /mapuser tc01@DEV.LOCAL
            /princ HTTP/win-tc01.dev.local@DEV.LOCAL
            /pass tc01pass /kvno 0 /crypto ALL

• Create a domain user to be used on the client. In this how-to the domain user is test with a password of testpass.

The above steps have been tested on a domain controller running Windows Server 2008 R2 64-bit Standard using the Windows Server 2003 functional level for both the forest and the domain.

Configure Tomcat (the custo diagnostic server)

Copy the tomcat.keytab file created on the domain controller to <custo diagnostic server installation directory>/conf/tomcat.keytab.

Edit the file <custo diagnostic server installation directory>/conf/krb5.ini so it looks like this:

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[libdefaults]
default_realm = DEV.LOCAL
default_keytab_name = FILE:<custo diagnostic server installation directory>\conf\tomcat.keytab
default_tkt_enctypes = rc4-hmac,aes256-cts-hmac-sha1-96,aes128-cts-hmac-sha1-96
default_tgs_enctypes = rc4-hmac,aes256-cts-hmac-sha1-96,aes128-cts-hmac-sha1-96
forwardable=true
 
[realms]
DEV.LOCAL = {
    kdc = win-dc01.dev.local:88
}
 
[domain_realm]
dev.local= DEV.LOCAL
.dev.local= DEV.LOCAL

Edit the file <custo diagnostic server installation directory>/conf/jaas.conf so it looks like this:

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com.sun.security.jgss.krb5.initiate {
    com.sun.security.auth.module.Krb5LoginModule required
    doNotPrompt=true
    principal="HTTP/win-tc01.dev.local@DEV.LOCAL"
    useKeyTab=true
    keyTab="<custo diagnostic server installation directory>/conf/tomcat.keytab"
    storeKey=true;
};
 
com.sun.security.jgss.krb5.accept {
    com.sun.security.auth.module.Krb5LoginModule required
    doNotPrompt=true
    principal="HTTP/win-tc01.dev.local@DEV.LOCAL"
    useKeyTab=true
    keyTab="<custo diagnostic server installation directory>/conf/tomcat.keytab"
    storeKey=true;
};

Please copy the editied files and the keytab file to a save location. 

Now you can change Login Method to Remote User:

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As the last step, please restart the custo diagnostic server now.

Please do do your test on a normal pc - NOT using an administrator/special account. Use a normal domain account.

If everything works and the logged in windows user is allowed to use custo diagnostic then this command should return "true".

Debugging & Testing

First check whether the LDAP works. Switch back to "LDAP" login-method, and check whether the test-user can login with windows password.
Switch back to Kerberos/Remote-Login-Method to go ahead.

For testing Kerberos authentication without using the custo manager, you can use the curl utility that is installed in the same folder as the custo diagnostic client:

You can add the following switches to the Java command line (via Configure custo diagnostic server in Startmenu):

After restarting Tomcat, you will find logging information in stdout and stderr files in the <custo diagnostic server installation directory>/logs directory 


and   <custo diagnostic data directory>/logs

Typical Error Messages and possible cause:

• Cannot Obtain Password: Apache Tomcat looks for the password somewhere.
  Meaning, that it either cannot find the tomcat.keytab file (file location?) or the service principal name used in jaas.conf, tomcat.keytab file.
• Cannot Sign In (Without Cannot Obtain Password): Tomcat gets the credentials from tomcat.keytab file, but it cannot sign in to the domain/domaincontroller. May be the Service Principal Name  used in the configuration files differ from the one used with ktpass?
• Cannot locate Domain Controller.  The krb5.ini leads from the domain name to the domain controller

Note the correct usage of forward and backward slashes when editing the files.

Please copy the editied files and the keytab file to a save location. 

Now you can change Login Method to Remote User:

Image Removed

As the last step, please restart the custo diagnostic server now.

For testing Kerberos authentication without using the custo manager, you can use the curl utility that is installed in the same folder as the custo diagnostic client:

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