Password Auth to OIDC SSO Blueprint

What and Why

Per-app password authentication means every application stores its own credentials, with inconsistent password policies, no shared multi-factor authentication (MFA), duplicated user records, and a large attack surface. Offboarding a departing employee means hunting through many systems. OpenID Connect (OIDC) single sign-on (SSO) centralizes authentication in one identity provider (IdP): users log in once, applications delegate authentication, and policy (MFA, session length, conditional access) lives in one place. OIDC is an identity layer on top of OAuth 2.0.

The migration consolidates fragmented logins into one IdP and replaces passwords-everywhere with federated tokens and strong MFA, reducing both attack surface and operational toil.

Phases

Assessment. Inventory every application and its auth method (local passwords, LDAP, legacy SAML, social login). Identify user directories, MFA gaps, and apps that cannot speak OIDC. Map who owns each app and how users are provisioned and deprovisioned today, paying attention to orphaned accounts and shared logins.

Design. Choose an IdP (Keycloak, Auth0, or similar) and a user store strategy (federate existing directories or migrate users into the IdP). Define the OIDC flows per client type: authorization code with PKCE for web and mobile, client credentials for service-to-service. Plan automated provisioning with SCIM, MFA policy with WebAuthn/FIDO2, role-to-claim mapping, and token lifetimes with refresh-token rotation. Decide how legacy apps will integrate.

IdP setup. Stand up the IdP with high availability, configure realms/tenants, connect user directories, and enforce MFA and password policies centrally. Establish session and token lifetimes, refresh-token rotation, and conditional access rules based on device and risk. Store client secrets in a secrets manager rather than config.

Migration. Onboard applications in waves, starting with low-risk internal apps. For OIDC-native apps, register a client and switch login to the IdP. For legacy apps, bridge via SAML federation or front them with an authenticating reverse proxy. Migrate or federate user accounts and link existing identities to avoid duplicate accounts and forced re-registration.

Decommission. Once an app is fully on SSO, remove its local password store and disable local login. Roll out SCIM provisioning so joiners and leavers are handled automatically across apps, closing the deprovisioning gap that perimeter-era systems leave open.

Key Risks and Mitigations

• Lockout during cutover. A misconfigured client or policy can lock everyone out. Migrate app by app, keep a tested break-glass admin path that bypasses SSO, and validate flows in staging with real accounts.
• Token misconfiguration. Wrong scopes, audiences, redirect URIs, or lifetimes cause subtle security holes. Follow OAuth/OIDC best practices, use authorization code with PKCE, validate audiences, and review token settings in code review.
• Legacy app support. Some apps cannot do OIDC. Use SAML federation or an authenticating proxy, isolate them, or schedule those apps for modernization.

Recommended Tooling

An OIDC identity provider (Keycloak, Auth0, or Clerk), SCIM for automated provisioning, WebAuthn/FIDO2 for phishing-resistant MFA, an authenticating reverse proxy for legacy apps, and a secrets manager (Vault) for client secrets.

Success Metrics

Track MFA coverage, password-reset support volume (which should drop sharply), authentication incident rate, and time to deprovision a departing user.

Prerequisites

A consolidated user directory or federation plan, an HA platform for the IdP, application owners engaged for client setup, and a tested break-glass access plan for cutover.