OAuth is Not Authentication

24 April 2018 OAuth

OAuth 2.0

OAuth is not authentication. It’s an authorization protocol, or, better yet, a delegation protocol. It’s for this reason that authentication protocols such as OpenID Connect exist and legacy protocols such as SAML use extension grants to link authentication and delegation.

There are articles on this subject already, but I still regularly see some confusion as to the reasons why on the internet and with new clients. So in this article, I’m going to discuss the key reasons why OAuth on its own does not provide client applications (relying parties) with user authentication.

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Why the Resource Owner Password Credentials Grant Type is not Authentication nor Suitable for Modern Applications

29 August 2017 OAuth

OAuth 2.0

When you ask a consultant if you should use the Resource Owner Password Credentials (ROPC) grant type, the standard response is: “It depends”. Whilst this is true, I’m going to take a stand and say no. Unfortunately, a lot of people see the username & password fields and say “ah! That’s the one for me!”, and I spend way too much of my time trying to convince them it’s a bad idea after they’ve already spent a lot of time implementing it.

So, let’s take a look at the ROPC grant type, why it’s so tempting, and what we can do to convince other developers and stake holders that it is a bad idea.

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The Wrong Ways to Protect an API

06 July 2017 OAuth

OAuth 2.0

Knowing why we don’t use past methodologies can be just as useful as knowing why we use current ones. In this article, we are going to look at past methods for delegating access to an API (the problem that OAuth is the current solution for) and why we shouldn’t use them anymore. Examples in this article are based on systems I’ve seen in the wild or discussed on StackOverflow.


For a user to delegate access (or authorize, give permission) to a mail service to send emails on the user’s behalf. Only send permission must be allowed.

We’re going to use the OAuth terminology of...

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Consuming External OAuth Services using IdentityModel

15 November 2016 OAuth


Recently as part of my audition process to become a Pluralsight author I created a 10 minute video on 'Consuming External OAuth Services using IdentityModel'. I’m pretty pleased with how it turned out, and luckily so were Pluralsight, so I thought I would share it for all to see.

In the video, I talk about why OAuth exists, what a basic OAuth request looks like and how we can use the IdentityModel library to help us simplify the process in .NET.

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