OAuth 2.0 Simplified Book Cover

OAuth 2.0 Simplified

Fourth Edition, updated November 2021


OAuth 2.0 Simplified is a guide to building an OAuth 2.0 server. Through high-level overviews, step-by-step instructions, and real-world examples, you will learn how to take advantage of the OAuth 2.0 framework while building a secure API.

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The Nuts and Bolts of OAuth 2.0

This course includes the latest recommendations from the OAuth working group including covering everything from using PKCE for all types of applications to explaining the motivations behind dropping the Implicit and Password grants from the spec. These security recommendations and more will be rolled up into the new OAuth 2.1 update, so this course will give you an excellent head start on learning the best way to use OAuth going forward!

Topics include: OAuth 2.0, OpenID, PKCE, deprecated flows, JWTs, API Gateways, and scopes. No programming knowledge needed!

This course covers each of the OAuth flows and applies them to use cases such as implementing OAuth for web apps, native apps, and SPAs. In addition to learning how applications can use OAuth to access APIs, you’ll learn how to use OpenID Connect to get the user’s identity.

If you're building an API, you'll learn the differences and tradeoffs between different access token formats, how to choose an appropriate access token lifetime, and how to design scopes to protect various parts of your APIs.

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Advanced OAuth Security

Certain applications need a higher level of security compared to what is part of the core OAuth 2.0 specifications. This course will guide you through the details of FAPI, a set of extensions of OAuth 2.0 that provide additional layers of security throughout the OAuth flows.

Topics include: Pushed Authorization Requests (PAR), JWT Secured Authorization Request (JAR), JWT Authorization Response Mode (JARM), Mutual TLS (MTLS), DPoP, Authorization Server Issuer Identifier (iss), and HTTP Signatures.

The content is divided into five parts, beginning with and overview of the OAuth authorization code flow, an overview of the security goals set out by FAPI and related extensions, as well as a description of the types of attacks we are concerned about protecting against. Part two focuses on securing the front channel, where we'll discuss authorization code injection attacks, PKCE, authorization server mixup attacks, and using Pushed Authorization Requests. Part three focuses on the back channel, and discusses the differences between Mutual TLS and Private Key JWT for client authentication. Part four is all about proof-of-possession (sender-constraining) access tokens using Mutual TLS and DPoP. Part five discusses how to achieve non-repudiation throughout each leg of the OAuth flow.

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The Little Book of OAuth 2.0 RFCs

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This reference guide will help you understand the context of each RFC that is part of OAuth.

This book is a reproduction of all the RFCs relating to OAuth, everything from OAuth core RFC6749 to the latest Security Best Current Practice. Each RFC is prefaced by a short introduction to set the context for why it's important to the space.

Why OAuth?

The OAuth 2.0 authorization framework has become the industry standard in providing secure access to web APIs. OAuth allows users to grant external applications access to their data, such as profile data, photos, and email, without compromising security.

Whether you’re a software architect, application developer, project manager, or a casual programmer, this book will introduce you to the concepts of OAuth 2.0 and demonstrate what is required when building a server.

About the Author

Aaron Parecki is a Senior Security Architect at Okta with over two decades of experience in the industry. He is the author of OAuth 2.0 Simplified, and maintains oauth.net. He has been invited to speak at events around the world about OAuth, online security, privacy and data ownership. He is a regular contributor to several specs at the IETF including OAuth 2.1 and GNAP.

Aaron is the co-founder of IndieWebCamp, a yearly worldwide conference on data ownership and online identity. His work has been featured in Wired, Fast Company, and made Inc. Magazine’s 30 Under 30 while building a startup that was later acquired. Aaron holds a B.S. in Computer Science from University of Oregon and lives in Portland, Oregon.

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