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How To: Setup Active Directory Integration for ESMC (Linux Component Install)

Staj

By Staj
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Staj

Staj 5

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I had some issues configuring Active Directory integration (Kerberos etc.) with ESMC so I decided to do a write-up on what I did to get it working. This is for Ubuntu Server 18.04 but it should be applicable to other Debian based distros, adjust where required.

Let's assume we have the following environment:

ESMC Linux Distribution: Ubuntu Server 18.04
ESMC Hostname: esmc
ESMC FQDN: esmc.test.local
ESMC IP Address: 10.123.1.2

Active Directory Domain: test.local
NetBIOS Domain: TEST
Domain Controller: dc.test.local (10.123.1.1)
ESET ESMC AD User Account: eset.esmc@test.local (eset.esmc)

  1. Ensure the required Server prerequisites (v7.2) are installed. 
    sudo apt-get install krb5-user ldap-utils libsasl2-modules-gssapi-mit samba

     

  2. Configure Samba at /etc/samba/smb.conf
    Ensure you change workgroup to the NetBIOS Domain, netbios name to the ESMC Hostname and realm to the Active Directory Domain.
    The following configuration is based on one found in ESMC VA v7.2 

    [global]
        workgroup = TEST
        netbios name = esmc
        server string = Samba Server Version %v
        security = ads
        realm = test.local
        domain master = no
        local master = no
        preferred master = no
        socket options = TCP_NODELAY IPTOS_LOWDELAY SO_RCVBUF=131072 SO_SNDBUF=131072
        use sendfile = true

        idmap config * : backend = tdb
        idmap config * : range = 100000-299999
        idmap config TEST : backend = rid
        idmap config TEST : range = 10000-99999

        winbind separator = +
        winbind enum users = yes
        winbind enum groups = yes
        winbind use default domain = yes
        winbind nested groups = yes
        winbind refresh tickets = yes
        template homedir = /home/%D/%U
        template shell = /bin/bash

        client max protocol = SMB3
        client use spnego = yes
        client ntlmv2 auth = yes
        encrypt passwords = yes
        restrict anonymous = 2

        log file = /var/log/samba/log.%m
        max log size = 50

        load printers = no
        printing = bsd
        printcap name = /dev/null
        disable spoolss = yes

        client ipc signing = auto
  3. Configure Kerberos at /etc/krb5.conf
    Ensure you change default_realm to Active Directory Domain (Must be capitalised) and the realm definition Active Directory Domain (Must be capitalised). Ensure you specify your Domain Controller as a kdc under the realm definition for your Active Directory Domain, if you have multiple Domain Controllers, specify multiple kdc's. Ensure you map Active Directory Domain (prefixed with ".") to the realm name (Your Active Directory Domain but capitalised) under domain_realm.
    The following configuration is based on one found in ESMC VA v7.2 
    [libdefaults]
        default_realm = TEST.LOCAL
        ticket_lifetime = 24h
        forwardable = true

[realms]
TEST.LOCAL = {
   kdc = dc.test.local
}

[domain_realm]
        .test.local = TEST.LOCAL

     

  4. Configure DNS Resolution.
    systemd-resolved can cause issues with Kerberos, it can probably be worked around but disabling it as follows also works. 
    1. sudo systemctl disable systemd-resolved.service
sudo systemctl stop systemd-resolved
    2. Configure /etc/resolv.conf
      Specify your Domain Controller as a nameserver, create additional nameserver definitions for each Domain Controller. Specify Active Directory Domain for search 
      nameserver 10.123.1.1
search test.local
    3. Ensure Hostname is set correctly
      If you need to change your hostname, you can use: 
      sudo hostnamectl set-hostname esmc.test.local

       

    4. Configure /etc/hosts
      Add your ESMC and your Domain Controllers to the hosts file. Take note of the ordering of FQDN and aliases after the IP Address as net join will use the first defined alias for your host as SPNs etc. when joining the system to the domain. All values are tab separated. 
      127.0.0.1	localhost
10.123.1.2	esmc.test.local	esmc
10.123.1.1	dc.test.local	dc
  5. Configure Time Synchronisation
    By default, the maximum tolerance for computer clock synchronization for Active Directory Kerberos participants is 5 minutes from a Kerberos Key Distribution Center (KDC; in our case, the Domain Controller) to operate correctly. If ESMC is in a VM, you may already be using a Hypervisor with some VM Agent that handles this but, if not, then systemd-timesyncd should suffice or you can use ntpd. Let's assume you use systemd-timesyncd:
    1. Configure /etc/systemd/timesyncd.conf
      NTP Server addresses are separated by spaces. specify each of  your Domain Controllers 
      [Time]
NTP=10.123.1.1
    2. Ensure systemd-timesyncd is set to sync and force it to resync. You should see a log entry that it "Sychronized to time server 10.123.1.123" as per your configuration. 
      sudo timedatectl set-ntp on
sudo timedatectl status
sudo systemctl restart systemd-timesyncd.service
systemctl status systemd-timesyncd.service

       

  6. Join System to Domain
    1. If you have Webmin you can use Rejoin Domain (VA v7.2) but it more or less just runs the following command (Replace Administrator with an authorised AD User that can join systems to the domain): 
      sudo net join ads join -U Administrator

      This relies on a correctly configured /etc/smb.conf
      You will probably want to move the resulting Computer object this creates in your domain from the default Computers OU to a more relevant OU given your OU hierarchy design in your domain.

  7. Setup Mapped Domain Security Groups under Access Rights in ESMC
    1. Configure Active Directory under Advanced Settings in Server Settings (v7.2)
    2. Map Domain Security Groups and assign Permission Setting
      Map Domain Security Group users (v7.2)
  8. Setup a Static Group Synchronization Server Task in ESMC
    Synchronization mode - Active Directory / Open Directory / LDAP (v7.2)
  9. Setup a User Synchronization Server Task in ESMC
    User Synchronization (v7.2)

Troubleshooting
The following can be used to test Kerberos login and LDAP GSSAPI whilst showing debug information, useful for troubleshooting. It destroys and existing Kerberos tickets for your user, obtains a Kerberos ticket for the specified AD user, lists obtained Kerberos tickets then performs LDAP Search by authenticating with GSSAPI.
When troubleshooting Kerberos, you should always check the system time with the relevant Domain Controller (KDC) to ensure they are within 5 minutes of each other (by default).

  • Replace eset.esmc with the AD User Account that ESET ESMC will connect under.
  • Replace dc.test.local with your Domain Controller.
  • Replace DC=test,DC=local with the Distinguished Name (DN) of the Base OU in your Domain where you want to list all child Computer objects of. 
kdestroy
KRB5_TRACE=/dev/stdout kinit eset.esmc
klist -f
KRB5_TRACE=/dev/stdout ldapsearch -LLL -Y GSSAPI -h dc.test.local -b 'DC=test,DC=local' '(&(objectCategory=computer))' 'distinguishedName' 'dNSHostName'

@tomasS @Peter Randziak

Edited by Staj
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