OAuth 2.0 and OpenID Connect (OIDC) are the foundation of modern authentication. This guide covers implementing these protocols securely in web applications.
Understanding the Protocols
OAuth 2.0
OAuth 2.0 is an authorization framework that enables applications to obtain limited access to user accounts.
┌──────────┐ ┌──────────────┐
│ │──(1) Authorization Request──>│ │
│ │ │ Resource │
│ │<─(2) Authorization Grant────│ Owner │
│ │ │ │
│ Client │ └──────────────┘
│ │ ┌──────────────┐
│ │──(3) Authorization Grant──> │ │
│ │ │ Authorization│
│ │<─(4) Access Token───────── │ Server │
│ │ │ │
│ │ └──────────────┘
│ │ ┌──────────────┐
│ │──(5) Access Token──────────>│ │
│ │ │ Resource │
│ │<─(6) Protected Resource────│ Server │
│ │ │ │
└──────────┘ └──────────────┘
OpenID Connect
OIDC adds an identity layer on top of OAuth 2.0:
- ID Token: JWT containing user identity claims
- UserInfo Endpoint: Returns user profile information
- Standard Scopes: openid, profile, email, address, phone
Authorization Code Flow with PKCE
The recommended flow for web applications:
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Token Handling
Validating ID Tokens
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Refresh Token Flow
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Backend for Frontend (BFF) Pattern
Keep tokens secure on the server:
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Social Login Integration
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Security Best Practices
State and Nonce
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Token Storage
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Logout
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Conclusion
OAuth 2.0 and OIDC provide secure, standardized authentication. Always use PKCE for public clients, validate tokens properly, store tokens securely in HTTP-only cookies, and implement proper logout. Consider using the BFF pattern for SPAs to keep tokens server-side.