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Single Sign-On Integration in Symfony

3 min readMay 30, 2025

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Introduction
Single Sign-On (SSO) streamlines user access across services via one authentication flow. In Symfony, you can integrate any SSO provider by implementing a custom “credentials provider” (Authenticator) that exchanges an authorization code for a token, fetches user info, and issues a Security token.

Why Use a Custom SSO Authenticator?

  • Uniform Authentication: Centralized login across apps.
  • External Identity Management: Leverage Keycloak, Auth0, Okta, etc.
  • Enhanced Security: Benefit from MFA, anomaly detection, key rotation, etc.

Symfony’s Security component (v5.4+) supports a custom Authenticator model — ideal for OAuth2/OpenID Connect flows.

High-Level Flow

  1. User hits /login → redirects to IdP’s /authorize with response_type=code.
  2. IdP returns ?code=… → your SsoAuthenticator exchanges it at /token.
  3. Receive access_token → query /userinfo.
  4. Create Passport & UserBadge → Symfony issues a session token.
flowchart LR
A[Login Form] --> B{Supports?}
B -- yes --> C[Exchange Code at /token]
C --> D[Get User Info]
D --> E[Build Passport → Token]
E -->…

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Petr Lzicar
Petr Lzicar

Written by Petr Lzicar

Web/Mobile React/PHP/Python fullstack developer with passion for AI and AWS services.

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