How-to · Kerberos SSO

Zero-click sign-in.
For every domain-joined desktop.

On a domain-joined workstation, the user already authenticated when they unlocked the machine. Kerberos sign-in turns that into silent web SSO: the browser presents a ticket, Monosign validates it, and the sign-in form never appears. Configured per AD source, scoped by client network, with silent fallback everywhere else.

  • SPNEGO / Negotiate
  • Multiple AD forests
  • Keytab or SPN + password
Walkthrough

From SPN to silent sign-in.

Four steps on the AD source. Failure is always silent: the form stays.

  1. 01

    Register the SPN and create the credential

    Map an HTTP/<sso-host> service principal name to a dedicated AD service account and export a keytab with ktpass, or skip the keytab and use SPN + service account name + password mode. When both are configured, the keytab wins.

    Tip — The realm goes in uppercase, and the keytab is stored encrypted in the secret store; it never leaves the API tier.
  2. 02

    Enable Kerberos on the AD source in Monosign

    On the Active Directory user source, switch Kerberos on and enter the realm plus the keytab (or the SPN/account/password trio). Each source carries its own configuration, so several forests can run Kerberos side by side: tickets resolve to the right source by realm, and users are looked up in that source only.

  3. 03

    Scope the silent attempt by client network

    List the IP ranges (exact IPs or CIDR) where domain-joined machines actually live. Clients outside these networks are never offered the Negotiate challenge, which is exactly what prevents the raw browser credential popup on home laptops and phones.

    Tip — Empty means all clients; unresolvable addresses fail closed. Scope per source, so each forest can declare its own networks.
  4. 04

    Configure browsers and test the fallback

    Add the SSO host to the browsers’ trusted-for-SPNEGO list via group policy (Chrome, Edge, and Firefox each have a policy for it), then test three cases: a domain machine signs in with zero clicks, an off-network machine sees the normal form with no popup, and a domain machine with no matching user silently falls back to the form.

    Tip — Kerberos is an optimization, never a gate: every failure path must end at the standard sign-in form, invisibly.
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The complete walkthrough — with every screenshot, every flag, and version-specific notes — lives in our help center.

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