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.