Kerberos – Single Sign-On

Posted on 4th January 2018

Introduction – Kerberos SSO

Foldr can be configured to authenticate users using Kerberos authentication. This provides a convenient way to automatically sign users into Foldr if they are using a PC or Mac that is bound to Active Directory. With Kerberos SSO, a user can sign in automatically to either the Foldr web app and Windows drive mapping client (support is coming soon in the macOS client).  Kerberos SSO is not supported in the iOS or Android apps.

Appliance Time

To use Kerberos authentication, the Foldr appliance must have accurate system time – i.e. it must be in sync with the Active Directory domain.  You can check the appliance time from within Foldr Settings (show top right of the UI) or by running the date command from the console when signed in as fadmin.  Should you need to correct the appliance time, it is recommended that you enable NTP in Foldr Settings >> General >> Time Settings and obtain time from a local domain controller.

Once NTP is enabled, you can force the appliance’s clock to be synchronised with a time source using the console command:

time-sync IP-address-of-domain-controller

Enabling Kerberos authentication

1. Log onto the Foldr appliance console and issue the command:

krb5-enable <Active Directory FQDN> <Domain Controller FQDN> <Foldr Appliance FQDN> <Foldr Appliance Hostname> <AD Account to join Foldr to domain>


krb5-enable foldr-v4 administrator

2. Enter the Active Directory account password

The appliance will join the domain and a computer account object will be created in the default Computers container in Active Directory.

Specify the IP addresses / subnets to be used for SSO (Applies to web app only)

Within Foldr Settings >> Single Sign-on >> Kerberos you should now configure the subnets (or even individual IP addresses) that clients will be connecting that should use Kerberos SSO.  Configure one subnet / address per line.

Click Save.

 Windows Client Configuration (Applies to web app only)

The Foldr appliance URL must be added to the workstations INTRANET ZONE before they are able to use SSO in the web browser interface.

Control Panel >> Network and Internet >> Internet Options >> Security tab >> Local Intranet >> Sites >> Advanced

Once this change has been made Internet Explorer, Google Chrome and Firefox should sign into the Foldr web app automatically.

These settings can be controlled in a domain environment through Group Policy.

macOS Client Configuration

No client configuration is required on a domain bound macOS computer when using SSO in the Safari browser.

To use Google Chrome browser with Kerberos based SSO, you must run the following commands from the macOS terminal, replacing “your-appliance.fqdn” with the URL of the Foldr appliance.

defaults write AuthServerWhitelist "your-appliance.fqdn"

defaults write AuthNegotiateDelegateWhitelist "your-appliance.fqdn"

Authentication Fallback

Should you attempt to connect to web app from within a Kerberos SSO specified subnet, but the machine is not domain bound, you will be presented with a standard authentication prompt.  If valid credentials are entered into the prompt, the web app will sign in as usual.

SSL Certificate warnings and Domains

It is common to use different domain names inside an organisation (Active Directory) and externally (for the public website, email etc). Due to the way Kerberos works, accessing Foldr via the internal FQDN will work by default, however it will also present the user with unwanted SSL trust warnings in the browser that must be accepted before signing in. Assuming you have a signed SSL certificate installed on the Foldr appliance, it would be preferable for users to connect to the public URL while still be able to use Kerberos SSO.

In order to do this, assuming that one does not already exist, you must create a forward lookup zone on the internal DNS service (typically a Windows domain controller) for the EXTERNAL / PUBLIC domain and create a CNAME record pointing at the internal FQDN of the Foldr system. A CNAME in DNS is an alias and as such does not break Kerberos authentication in the same way that a simple A record would.

Creating the CNAME record in DNS

In the example below, the domains are as follows: = internal Active Directory domain with a Foldr appliance accessible at An A record already exists in this zone for ‘foldr’ pointing at the virtual appliance. = organisation’s public domain.

After creating a new lookup zone for, right click in the zone and select ‘New Alias (CNAME)

Enter the public FQDN of the appliance (i.e. that is covered by the SSL certificate installed on the appliance) and point this at the internal FQDN (

IMPORTANT – When creating the new lookup zone on the internal DNS service for the organisation’s public domain, you must also consider any other records that need to be created. Typical examples are the public website, webmail servers and so on. Create records for each as required, and point them at the relevant public IP address.

If you now browse to the Foldr at on a domain bound workstation, the SSL certificate will validate and it will sign in automatically with Kerberos authentication.

Foldr for Windows Configuration (Drive Mapping Client)

Kerberos SSO is supported in release v1.0.38.  By default Kerberos SSO is available to use, but not the default authentication type.  Should the user wish to sign in via Kerberos SSO on a domain bound machine, a Single Sign-On checkbox is available to use.

Kerberos SSO can set as the default authentication method through an MSI option when deploying the client (SSO_LOGIN_BY_DEFAULT=1) – More information on deploying the Windows application and the available MSI options can be found in the following KB article:

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