Introduction

This article describes the single sign-on (SSO) setup between Joget Workflow and Microsoft Active Directory using Kerberos and SPNEGO.

Kerberos is a network authentication protocol designed by the Massachusetts Institute of Technology (MIT) for SSO in client-server environments, while SPNEGO (Simple and Protected GSS-API Negotiation Mechanism) extends Kerberos SSO to web applications. 

Test Environment

• Joget Server: Joget Workflow v5 Enterprise on Apache Tomcat 8 and Java 8

• Windows Server: Windows Server 2012 R2 Datacenter (running on VirtualBox within a NAT Network, downloaded from https://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-2012-r2)

• Windows Client PC: IE11 on Windows 10 (running on VirtualBox within a NAT Network, downloaded from https://developer.microsoft.com/en-us/microsoft-edge/tools/vms/) 

Test Settings

• Windows Server COMPUTER NAME is WIN-TKDH9LCHUUO 

• WINDOWS DOMAIN is windows.local

• DOMAIN USER is joget

• JOGET DOMAIN is joget.windows.local

   

Kerberos SSO Setup Configuration

1. Setup Windows Server Kerberos Key Distribution Center (KDC):

1.1 Install DNS Server

1. Go to Server Manager > Add roles and features to install the DNS Server. 

   

2. In the Network and Sharing Center, configure the network adapter so that the Preferred DNS server is 127.0.0.1. 

   

3. In the DNS Manager, right click on the server name and Configure a DNS Server to create a forward lookup zone for windows.local. 

1.2 Add Joget Domain Name into the Windows Server DNS

1. In the windows.local DNS zone, add an A record for joget to point to the Joget server IP. 

    

2. Test ping to ensure that joget.windows.local resolves to the correct IP. 

    

1.3 Create a Windows Domain User for the Service

1. In Active Directory Users and Computers, create a domain user joget. This is the user account to be mapped to the service name used by the Joget server. 

1.4 Register Service Principal Name (SPN)

1. In PowerShell, execute: setspn -s HTTP/{JOGET DOMAIN} {DOMAIN USER} e.g. 

   setspn -s HTTP/JOGET.WINDOWS.LOCAL joget

In PowerShell, check that the SPN has been registered 

setspn -L joget

should display 

Registered ServicePrincipalNames for CN=Joget,CN=Users,DC=windows,DC=local:
         HTTP/JOGET.WINDOWS.LOCAL

2. Setup Joget Server for Kerberos

2.1 Add Windows Domain to Hosts File

1. Edit /etc/hosts (Linux or macOS) or C:\Windows\System32\drivers\etc\hosts (Windows) and add the server IP e.g. 

   192.168.56.102        windows.local win-tkdh9lchuuo win-tkdh9lchuuo.windows.local

   NOTE: This step is not required if the Joget Server is using the Windows Server as the DNS server.

 2.2 Create Kerberos Identification (Keytab) File

Using Windows

1. In PowerShell on the Windows Server, generate a keytab file using the Ktpass tool: 

   ktpass -out joget.keytab -mapuser joget@WINDOWS.LOCAL  -pass Pass@word1  -crypto all -ptype KRB5_NT_PRINCIPAL  -princ HTTP/joget.windows.local@WINDOWS.LOCAL

   
   

2. Copy the generated joget.keytab file into the Joget server e.g. at C:\Joget-v5-Enterprise\wflow\joget.keytab

3. Java 8 may be required for the Kerberos authentication to work with the ktpass generated keytab. Download and install JDK 8, and edit the tomcat-run.bat startup script to update the JAVA_HOME path accordingly.

Using Linux

1. Install the krb5-user package 

   sudo apt-get install krb5-user
   

    and configure the realm as WINDOWS.LOCAL and the KDC as WIN-TKDH9LCHUUO.WINDOWS.LOCAL:88

2. In a terminal, run

   kinit joget@WINDOWS.LOCAL

   
   

   IMPORTANT NOTE: The domain must be UPPER CASE

   
   The command should run without error

   
   

3. Confirm the configuration in /etc/krb5.conf 

   [libdefaults]
   default = WINDOWS.LOCAL
   default_realm = WINDOWS.LOCAL
   dns_lookup_realm = true
   dns_lookup_kdc = true
   
   [realms]
      WINDOWS.LOCAL = {
          kdc = WIN-TKDH9LCHUUO.WINDOWS.LOCAL:88
          default_domain = WINDOWS.LOCAL
      }
   
   [domain_realm]
      .windows.local = WINDOWS.LOCAL
      windows.local = WINDOWS.LOCAL

   IMPORTANT NOTE: The domain must be UPPER CASE

4. In a terminal, generate a keytab file using: 

   ktutil
    ktutil: add_entry -password -p HTTP/JOGET.WINDOWS.LOCAL@WINDOWS.LOCAL -k 1 -e arcfour-hmac-md5
    Password for HTTP/JOGET.WINDOWS.LOCAL@WINDOWS.LOCAL:
    ktutil: wkt /etc/joget.keytab

5. List the SPNs in the keytab using: 

   ktutil
    ktutil: rkt /etc/joget.keytab
    ktutil: list

Using macOS

1. In a terminal, run 

   kinit joget@WINDOWS.LOCAL

   IMPORTANT NOTE: The domain must be UPPER CASE

   
   The command should run without error, or just a warning “Encryption type arcfour-hmac-md5(23) used for authentication is weak and will be deprecated”

2. Edit /etc/krb5.conf 

   [libdefaults]
   default = WINDOWS.LOCAL
   default_realm = WINDOWS.LOCAL
   dns_lookup_realm = true
   dns_lookup_kdc = true
   
   [realms]
      WINDOWS.LOCAL = {
          kdc = WIN-TKDH9LCHUUO.WINDOWS.LOCAL:88
          default_domain = WINDOWS.LOCAL
      }
   
   [domain_realm]
       .windows.local = WINDOWS.LOCAL
       windows.local = WINDOWS.LOCAL

   IMPORTANT NOTE: The domain must be UPPER CASE

3. In a terminal, generate a keytab file using: 

    ktutil -k joget.keytab add -p HTTP/JOGET.WINDOWS.LOCAL@WINDOWS.LOCAL -e arcfour-hmac-md5 -V 1

4. List the SPNs in the keytab using: 

    ktutil -k joget.keytab list

5. Keep a copy of the generated joget.keytab file e.g. in /etc/joget.keytab

3. Configure Kerberos Directory Manager Plugin

3.1 Upload Kerberos Directory Manager Plugin

1. Download the Kerberos Directory Manager plugin and upload it in Settings > Manage Plugins. 

   

3.2 Configure Kerberos Directory Manager Plugin

1. In Settings > Directory Manager, select the Kerberos Directory Manager plugin, and key in the appropriate values in the configuration: 

   • Service Principal: HTTP/JOGET.WINDOWS.LOCAL

   • Path to Keytab File: /etc/joget.keytab (Linux) or C:/Joget-v5-Enterprise/wflow/joget.keytab (Windows)

   • Debug Enabled: View debugging messages in the logs 

   

3.3 Configure API Domain Whitelist

1. In Settings > General Settings, set the API Domain Whitelist to * to allow SSO requests to the Kerberos Directory Manager. 

   

4. Setup Client PC for SSO

4.1 Add Client PC to Windows Domain

1. Ensure that the Windows Server is reachable on the network from the Client PC.

2. Set the DNS server to the IP address of the Windows Server. 

   

3. Ping the windows domain name to test. 

   

4. Click on File Explorer, right click on the This PC and choose Properties. Click on Change Settings next to the computer name. Click on Change and set the Domain e.g. windows.local, keying in the domain administrator login when prompted. Restart after joining the domain is successful, and login as a domain user. 

   

4.2 Setup Browser for Windows Authentication

1. In IE, click on Internet Options > Security > Local intranet site > Advanced and add the Joget domain e.g. http://joget.windows.local  

4.3 Test the SSO

1. If using the Kerberos Directory Manager plugin approach, access http://joget.windows.local/jw/web/json/plugin/org.joget.plugin.kerberos.KerberosDirectoryManager/service to SSO.

2. If using the Spring Security Kerberos Extension approach, access http://joget.windows.local/jw/web/sso to SSO. 

   • NOTE: Please note that for the SSO to work properly:

   • the client PC and Joget server must reside on different machines,

   • the Windows server and client PC must reside on the same Windows domain.

Resources

Introduction to Kerberos and SPNEGO

• http://thekspace.com/home/component/content/article/54-kerberos-and-spnego.html

• https://developer.ibm.com/answers/questions/246107/what-is-the-difference-between-kerberos-and-spnego.html?lnk=hm

• http://web.mit.edu/kerberos/www/index.html

Configuring Kerberos on Windows Server

• https://technet.microsoft.com/en-us/library/hh831553(v=ws.11).aspx

• https://msftplayground.com/2009/08/configure-kerberos-authentication/

• https://technet.microsoft.com/en-us/library/cc731241(v=ws.11).aspx

• https://technet.microsoft.com/en-us/library/hh831553(v=ws.11).aspx

• https://msftplayground.com/2009/08/configure-kerberos-authentication/

Kerberos with Java and Spring

• https://venkatsadasivam.com/2009/08/29/single-sign-on-in-java-platform/

• http://docs.spring.io/spring-security-kerberos/docs/1.0.1.RELEASE/reference/htmlsingle/

• http://projects.spring.io/spring-security-kerberos/

• https://tomcat.apache.org/tomcat-8.0-doc/windows-auth-howto.html

• http://docs.oracle.com/javase/jndi/tutorial/ldap/security/gssapi.html

• http://docs.oracle.com/javase/8/docs/technotes/guides/security/jgss/lab/part1.html#PART1

• https://docs.oracle.com/cd/E23943_01/web.1111/e13707/sso.htm#SECMG481

• https://stackoverflow.com/questions/25289231/using-gssmanager-to-validate-a-kerberos-ticket