OAuth, OIDC & JWT
Software Engineer path · lesson 85 of 99Understand the complete authentication and authorization flow using OAuth 2.0, OpenID Connect (OIDC), and JSON Web Tokens (JWT) with interactive diagrams.
OAuth 2.0 Authorization Flow
OAuth 2.0 is an authorization framework that allows applications to obtain limited access to user accounts on an HTTP service.
Security Analysis
OAuth 2.0 Security Considerations:
- PKCE: Proof Key for Code Exchange prevents authorization code interception
- State Parameter: Prevents CSRF attacks during authorization flow
- HTTPS: Required for all communications to prevent token interception
- Scope Limitation: Request minimal necessary permissions
JWT Security Best Practices
- Short Expiration: Access tokens should expire within 15-60 minutes
- Secure Storage: Use httpOnly cookies or secure storage mechanisms
- Signature Validation: Always verify JWT signature and claims
- Algorithm Verification: Explicitly check the 'alg' header to prevent algorithm confusion
System Design Applications
Microservices Authentication:
- API Gateway: Centralized token validation and routing
- Service-to-Service: JWT tokens for inter-service communication
- Token Refresh: Refresh token rotation for enhanced security
- Distributed Sessions: Stateless authentication across multiple services
Performance Considerations
Token Validation:
Local validation: time complexity
Remote validation: Network latency + DB lookup
Token Size:
JWT: ~200-1000 bytes
Session ID: ~32-128 bytes
Authorization code flow
Order a "Sign in with…" login using the OAuth authorization code flow.
Tap a piece, then tap where it goes — or drag it. Tap the tray to take one back.
- 1Drop a step here
- 2Drop a step here
- 3Drop a step here
- 4Drop a step here
- 5Drop a step here
Test your knowledge
What is the main difference between OAuth 2.0 and OpenID Connect?
The short version
Think of OAuth like a hotel key card system: the front desk (Authorization Server) verifies your identity and gives you a card (token) that grants access to specific areas (resources) without revealing your ID to every door scanner.
In more depth
OAuth, OIDC & JWT Authentication Flow
OAuth 2.0 (Authorization)
OAuth 2.0 is an authorization framework that allows applications to obtain limited access to user accounts. It works by delegating user authentication to the service that hosts the user account.
Key Components:
Authorization Code Flow:
OpenID Connect (Authentication)
OIDC extends OAuth 2.0 to provide authentication on top of authorization. It adds an identity layer.
Key Additions:
JSON Web Tokens (JWT)
JWT is a compact, URL-safe means of representing claims between two parties.
Structure:
Header.Payload.SignatureHeader: Specifies algorithm and token type
Payload: Contains claims (user info, permissions, expiration)
Signature: Verifies token integrity
Types:
Security Considerations
Interview Questions
References & Further Reading
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