PAM configuration for Windows Active Directory

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If you want to configure OS4X to authentificate users with the configured username via a centralized Windows Active Directory service, you have to configure the PAM security system of the underlying Unix environment.


This documentation is based on the OS4Xvirtual VMware image, which is based on the latest Debian Linux distribution. If you have any other distribution, you may re-use these information in order to configure your environment accordingly.


Configuring the connectivity consists of several steps, which are described here:

Declarations

In this documentation, several values will be used for hostnames, domain name, usernames and password. These are only examples and must be changed according to your environment.

AD server: 

Hostname and aliases: 192.168.1.65
     name alias: w2k8
     local hostname seen from Windows side: dc.w2k8.c-works.net
Domain name: w2k8.c-works.net
Kerberos realm: W2K8.C-WORKS.NET

(The kerberos realm is the domain name in upper case characters!)

User for connecting to domain (with administrative rights, but without permission to login interactively on AD server): 

Username: pamauth
Password: Test1234

User to be authentificated (as an example) and configured in OS4X: 

Username: os4xuser
Password: Test1234

All commands on the Linux side are executed in the context of the user "root".

Network availability

The AD server must be reachable via network on the Linux side: 

os4xvirtual:~# ping -c 3  win2k8
PING win2k8.sbs.c-works.net (192.168.1.65) 56(84) bytes of data.
64 bytes from 192.168.1.65: icmp_req=1 ttl=128 time=0.762 ms
64 bytes from 192.168.1.65: icmp_req=2 ttl=128 time=0.737 ms
64 bytes from 192.168.1.65: icmp_req=3 ttl=128 time=0.659 ms

--- win2k8.sbs.c-works.net ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2013ms
rtt min/avg/max/mdev = 0.659/0.719/0.762/0.049 ms

Synchronize time

The underlying security model relies on synchronized time between (Active Directory) server and (Linux OS4X) client). Windows Active Directory servers offer a NTP server which can be used for time synchronization. 

ntpdate win2k8

If the domain controller server doesn't run as time server, be sure to use the same time source for local and remote time synchronization.

Install required software

The PAM user authentification relies on two packages:

  • Winbind
  • Samba
  • Kerberos

If not installed already, install these packages through the local Linux packaging system: 

apt-get install winbind samba krb5-kdc krb5-admin-server

During installation of Kerberos, you will be asked for a default realm: leave this entry empty, we will configure it afterwards.

Configure Samba

You have to configure the Samba component. Edit the file "/etc/samba/smb.conf" with your favorite text editor and make the following changes in the configuration section 'global': 

[global]
       security = ads
       realm = W2K8.C-WORKS.NET
       password server = 192.168.1.65
       workgroup = W2K8
       client ntlmv2 auth = yes
       encrypt passwords = yes
       winbind use default domain = yes
       restrict anonymous = 2

Restart services

In order to activate the changes, restart the needed services: 

os4xvirtual:/etc/samba# /etc/init.d/winbind stop
Stopping the Winbind daemon: winbind.
os4xvirtual:/etc/samba# /etc/init.d/samba restart
Stopping Samba daemons: nmbd smbd.
Starting Samba daemons: nmbd smbd.
os4xvirtual:/etc/samba# /etc/init.d/winbind start
Starting the Winbind daemon: winbind.

Configure Kerberos

Run the following command in order to configure Kerberos interactively: 

 dpkg-reconfigure krb5-config

Answer the following question according to our default values as described above: 

Default Kerberos version 5 realm: W2K8.C-WORKS.NET
Add locations of default Kerberos servers to /etc/krb5.conf? - Yes
Kerberos servers for your realm: win2k8.sbs.c-works.net (the IP address 192.168.1.65 would be valid, too)
Administrative server for your Kerberos realm: win2k8.sbs.c-works.net (the IP address 192.168.1.65 would be valid, too)

Initialize Kerberos

Setting up Kerberos with the Active Directory server will be finished via authentificating as administrative user of the domain: 

kinit pamauth@W2K8.C-WORKS.NET

Be sure to give the Kerberos realm name in uppercase characters completely!

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