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Single Sign-On (SSO)

A comprehensive guide to SSO and authentication protocols

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🎯 Overview

Single Sign-On (SSO) enables users to access multiple systems with a single authentication process.

💡 What is SSO?

SSO is an authentication scheme that allows users to access multiple applications with one set of credentials. It:

  • Improves user experience
  • Reduces authentication complexity
  • Enhances security
  • Centralizes access management

✨ Key Benefits

1. Enhanced User Experience
   - Single login for multiple services
   - Reduced password management

2. Improved Security
   - Centralized authentication
   - Stronger password policies

3. Efficient Resource Management
   - Centralized user management
   - Simplified administration


🔐 Authentication Protocols

OAuth (Open Authorization)

Purpose:
- Delegation of access rights
- Third-party application authentication
- API authorization

Operation:
- Token-based authentication
- Resource owner authorization
- Defined access scopes
sequenceDiagram participant User as 🙋 User participant ClientApp as 💻 Client Application participant AuthServer as 🔐 Authorization Server participant ResourceServer as 📦 Resource Server User->>ClientApp: 🔑 Request access to resource ClientApp->>AuthServer: 🔁 Redirect user for authentication AuthServer->>User: ✅ Authenticate and grant permission AuthServer-->>ClientApp: 🔓 Return authorization code ClientApp->>AuthServer: 🔄 Exchange auth code for access token AuthServer-->>ClientApp: 🔑 Access token ClientApp->>ResourceServer: 📥 Request resource with access token ResourceServer-->>ClientApp: 📤 Return resource


SAML (Security Assertion Markup Language)

Purpose:
- Enterprise SSO
- XML-based framework
- Identity provider communication

Operation:
- IdP authentication
- SAML assertions
- Service provider validation
sequenceDiagram participant User as 🙋 User participant ServiceProvider as 🏢 Service Provider participant IdentityProvider as 🔐 Identity Provider User->>ServiceProvider: 📥 Access request ServiceProvider->>User: 🔀 Redirect to IdP for SSO User->>IdentityProvider: 🔐 Authenticate (if not already) IdentityProvider-->>ServiceProvider: 📄 SAML Assertion (authentication response) ServiceProvider->>IdentityProvider: 📄 SAML Assertion ServiceProvider-->>ServiceProvider: ✅ Validate Assertion and create session ServiceProvider-->>User: 🎉 Access granted


OIDC (OpenID Connect)

Purpose:
- Identity layer over OAuth 2.0
- User authentication
- Profile information access

Operation:
- JWT-based ID tokens
- OAuth 2.0 extension
- RESTful implementation
sequenceDiagram participant User as 🙋 User participant ClientApp as 💻 Client Application participant OpenIDProvider as 🔐 OpenID Provider User->>ClientApp: 📝 Request login ClientApp->>OpenIDProvider: 🔀 Redirect user to OP OpenIDProvider->>OpenIDProvider: 🔐 Authenticate OpenIDProvider->>User: ✅ Consent (if required) OpenIDProvider-->>ClientApp: 🪪 ID Token + 🔑 Access Token ClientApp->>ClientApp: 🔍 Validate ID Token ClientApp-->>User: 🎉 User logged in


📊 OAuth vs SAML vs OIDC Comparison

🔑 Feature 🔐 OAuth 🏢 SAML 🔎 OIDC
Primary Use 🔑 Authorization 🏢 Enterprise SSO 🛂 Authentication
Format 📄 JSON/JWT 📄 XML 📄 JSON/JWT
Complexity ⚖️ Medium ⚙️ High 🟢 Low
Modern Apps ✅ Yes ⚠️ Limited ✅ Yes
Mobile Support 📱 Good 📵 Limited 📱 Excellent


📚 Reference