SSO (Single Sign-On)

Single Sign-On (SSO) is an authentication method that allows a user to log in once to access multiple interconnected applications or services. This technology eliminates the need to manage separate credentials for each system, improving user experience while strengthening security and access governance.

SSO Fundamentals

• Architecture based on a centralized Identity Provider (IdP) that authenticates the user
• Use of standardized protocols like SAML 2.0, OAuth 2.0, OpenID Connect (OIDC), or Kerberos
• Issuance of authentication tokens validated by consuming applications (Service Providers - SP)
• Centralized user session management with timeout and revocation mechanisms

Benefits of SSO

• Drastic reduction in password fatigue and reset requests (up to 70% fewer helpdesk tickets)
• Improved security through centralized access control and uniform enforcement of strong authentication policies (MFA)
• Seamless user experience promoting team adoption and productivity
• Simplified identity management with automated provisioning/deprovisioning during personnel changes
• Facilitated compliance with regulations (GDPR, SOC 2) through centralized access auditing

Practical Example with OpenID Connect

import { AuthOptions } from 'next-auth';
import GoogleProvider from 'next-auth/providers/google';
import AzureADProvider from 'next-auth/providers/azure-ad';

export const authOptions: AuthOptions = {
  providers: [
    GoogleProvider({
      clientId: process.env.GOOGLE_CLIENT_ID!,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET!,
    }),
    AzureADProvider({
      clientId: process.env.AZURE_AD_CLIENT_ID!,
      clientSecret: process.env.AZURE_AD_CLIENT_SECRET!,
      tenantId: process.env.AZURE_AD_TENANT_ID!,
    }),
  ],
  session: {
    strategy: 'jwt',
    maxAge: 8 * 60 * 60, // 8 hours
  },
  callbacks: {
    async jwt({ token, account, profile }) {
      // Enrich token with custom claims
      if (account) {
        token.accessToken = account.access_token;
        token.idToken = account.id_token;
        token.roles = profile?.roles || [];
      }
      return token;
    },
    async session({ session, token }) {
      // Transfer token information to session
      session.accessToken = token.accessToken;
      session.user.roles = token.roles;
      return session;
    },
  },
  pages: {
    signIn: '/auth/signin',
    error: '/auth/error',
  },
};

Implementing an SSO Solution

1. Audit the application ecosystem to identify applications to integrate and their authentication capabilities
2. Choose an appropriate Identity Provider (Okta, Auth0, Azure AD, Google Workspace, Keycloak for open-source)
3. Define authentication strategy: protocol(s) to use, MFA policies, role management (RBAC/ABAC)
4. Configure applications as Service Providers with metadata exchange (SAML) or OAuth registration
5. Implement directory synchronization (SCIM) for automatic account provisioning
6. Test authentication flows, session management, and logout scenarios (single logout)
7. Deploy progressively with pilot groups before full rollout
8. Monitor authentications and configure alerts for abnormal behaviors

SSO Tools and Solutions

• Cloud solutions: Okta, Auth0 (Okta), Azure AD/Entra ID, Google Workspace, OneLogin, Ping Identity
• Open-source solutions: Keycloak, Authelia, Authentik, Gluu Server
• Integration libraries: Passport.js, NextAuth.js, spring-security-saml, python-saml
• Protocols: SAML 2.0 (enterprise), OpenID Connect/OAuth 2.0 (modern), Kerberos (Windows network), LDAP/Active Directory

SSO adoption represents a strategic investment that reduces operational costs (support, password management), improves organizational security posture, and accelerates new employee onboarding. In a context of multiple SaaS applications and hybrid work, SSO becomes an essential pillar of modern identity infrastructure, facilitating the application of least privilege principle and regulatory compliance.