Editing OAuth 2.0

= OAuth 2.0 =
'''OAuth 2.0''' is an open-standard authorization framework that enables secure delegated access to protected resources without sharing user credentials, widely used across modern web and mobile applications.

== Remembering (Knowledge / Recall) 🧠 ==
=== Core terminology & definitions ===
* '''[https://wikipedia.org/wiki/OAuth OAuth]''' – A family of authorization standards allowing a resource owner to grant limited access to client applications.
* '''[https://wikipedia.org/wiki/OAuth Authorization Grant]''' – A credential representing the resource owner's permission.
* '''[https://wikipedia.org/wiki/JSON_Web_Token JSON Web Token (JWT)]''' – A compact token format often used for access tokens.
* '''RFC 6749''' – The IETF specification defining OAuth 2.0.
* '''Client ID / Client Secret''' – Identifiers used by applications requesting authorization.

=== Key components / actors / elements ===
* '''Authorization Server''' – Issues tokens after authenticating and authorizing the user.
* '''Resource Server''' – Hosts protected API endpoints.
* '''Client Application''' – Requests access on behalf of the user.
* '''Resource Owner''' – The user controlling access to resources.

=== Canonical models, tools, or artifacts ===
* '''[https://wikipedia.org/wiki/OpenID_Connect OpenID Connect]''' – Identity layer built on top of OAuth 2.0.
* '''Bearer Tokens''' – Standard token type transmitted in HTTP headers.
* '''PKCE (Proof Key for Code Exchange)''' – Extension improving authorization code security.

=== Typical recall-level facts ===
* Introduced in 2012 (RFC 6749).
* Used by major platforms such as Google, Facebook, GitHub, and Microsoft.
* Focuses on authorization, not authentication.

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== Understanding (Comprehension) 📖 ==
=== Conceptual relationships & contrasts ===
* Differs from '''[https://wikipedia.org/wiki/Basic_access_authentication Basic Authentication]''' by avoiding password sharing.
* Complements rather than replaces authentication systems; identity is addressed by OpenID Connect.
* Succeeds OAuth 1.0 by simplifying cryptographic requirements and expanding grant types.

=== Core principles & paradigms ===
* Separation of roles between authorization and resource servers.
* Delegation: users grant scoped access rather than full control.
* Token-based: access is mediated by time-limited, revocable tokens.

=== How it works (high-level) ===
* Client registers with authorization server → receives Client ID.
* User attempts protected action → client sends authorization request.
* Authorization server authenticates user and prompts for consent.
* Server issues an authorization grant → client exchanges it for a token.
* Client uses access token to call resource server APIs.

=== Roles & perspectives ===
* '''End users''' – Want privacy and minimal risk when granting access.
* '''Developers''' – Aim for secure flows with minimal friction.
* '''Service providers''' – Enforce policies, scopes, and token lifetimes.

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== Applying (Use / Application) 🛠️ ==
=== "Hello, World" example (minimal) ===
* A client app requests authorization to read a user's profile.
* The user approves via the authorization server's consent screen.
* The client obtains an access token and uses it in the `Authorization: Bearer` header to call the API.

=== Core task loops / workflows ===
* Register client → configure redirect URIs.
* Implement Authorization Code flow (with PKCE for public clients).
* Request and store tokens securely.
* Refresh tokens before expiry, if supported.

=== Frequently used actions / methods / techniques ===
* Constructing authorization URLs.
* Exchanging authorization codes for tokens.
* Validating token signatures and scopes on the resource server.
* Performing token introspection or revocation requests.

=== Real-world use cases ===
* Mobile apps accessing cloud APIs.
* Third-party integrations with social login providers.
* Enterprise applications delegating access to microservices.
* IoT devices using Device Authorization Grant.

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== Analyzing (Break Down / Analysis) 🔬 ==
=== Comparative analysis ===
* Versus API keys: OAuth provides scoped, revocable, user-consented access.
* Versus SAML: OAuth is lightweight and optimized for APIs rather than enterprise identity federation.
* Historically replaced OAuth 1.0’s complex signature system with simpler bearer tokens.

=== Structural insights ===
* Authorization Code, Client Credentials, Device Code, Refresh Token flows form the core architecture.
* Tokens carry scopes representing permitted operations.
* Separation of authorization vs resource servers allows distributed security design.

=== Failure modes & root causes ===
* Misconfigured redirect URIs → open redirect vulnerabilities.
* Storing tokens insecurely → token theft.
* Failing to use PKCE in public clients → authorization code interception.

=== Troubleshooting & observability ===
* Inspect access token expiry, issuer, and scope.
* Log authorization errors such as `invalid_grant` or `invalid_scope`.
* Monitor token issuance rates and misuse patterns.

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== Creating (Synthesis / Create) 🏗️ ==
=== Design patterns & best practices ===
* Prefer Authorization Code + PKCE for web, mobile, and native apps.
* Use short-lived access tokens with refresh tokens.
* Restrict scopes to the minimum required.
* Store sensitive credentials only on secure, confidential clients.

=== Integration & extension strategies ===
* Add OpenID Connect for authentication and identity claims.
* Integrate with API gateways for centralized token validation.
* Extend with JWT-based custom claims for domain-specific authorization.

=== Security, governance, or ethical considerations ===
* Protect user consent processes to prevent dark-pattern abuses.
* Ensure TLS is mandatory for all token exchanges.
* Provide revocation endpoints for user control and compliance.

=== Lifecycle management strategies ===
* Rotate keys used for signing tokens (JWKS).
* Version API scopes as services evolve.
* Migrate legacy flows to PKCE-enabled flows.

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== Evaluating (Judgment / Evaluation) ⚖️ ==
=== Evaluation frameworks & tools ===
* Assess token security (entropy, expiry, signature validation).
* Evaluate implementation via OAuth 2.0 Security Best Current Practice (BCP).
* Use test suites such as OpenID Foundation's conformance tests.

=== Maturity & adoption models ===
* Widely adopted across SaaS, consumer apps, and enterprise APIs.
* Active ecosystem with libraries for major languages and platforms.
* Barriers include complexity of correct implementation and security hardening.

=== Key benefits & limitations ===
* Benefits: delegated access, strong security properties, ecosystem support.
* Limitations: complexity, risk of insecure deployments, need for additional identity layer.

=== Strategic decision criteria ===
* Use when third-party or cross-service access delegation is required.
* Avoid for simple internal APIs where mutual TLS or API keys suffice.
* Consider long-term maintainability and compliance requirements.

=== Holistic impact analysis ===
* Enables interoperable, user-centric authorization across the web.
* Strong influence on microservices, identity, and API-driven architectures.
* Ongoing evolution includes OAuth 2.1 consolidation and hardened best practices.

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[[Category:Authentication]]
[[Category:Security Protocols]]
[[Category:Web Standards]]