Authentication

OAuth

1. What is OAuth?

• an open-standard authorization protocol or framework

1. Give an example of what using OAuth would look like.

• when visiting a website and it asks you to link to other website and that website authenticates you

1. How does OAuth work? What are the steps that it takes to authenticate the user?

2. The first website connects to the second website on behalf of the user, using OAuth, providing the user’s verified identity.
3. The second site generates a one-time token and a one-time secret unique to the transaction and parties involved.
4. The first site gives this token and secret to the initiating user’s client software.
5. The client’s software presents the request token and secret to their authorization provider (which may or may not be the second site)
6. If not already authenticated to the authorization provider, the client may be asked to authenticate. After authentication, the client is asked to approve the authorization transaction to the second website.
7. The user approves (or their software silently approves) a particular transaction type at the first website.
8. The user is given an approved access token (notice it’s no longer a request token).
9. The user gives the approved access token to the first website.
10. The first website gives the access token to the second website as proof of authentication on behalf of the user.
11. The second website lets the first website access their site on behalf of the user.
12. The user sees a successfully completed transaction occurring.

13. OAuth is not the first authentication/authorization system to work this way on behalf of the end-user.

14. What is OpenID?

• OpenId is about authentication for humans logging into machines

Authorization and Authentication flows

1. What is the difference between authorization and authentication?

• authentication is the process of verifying who a user is
• authorization is the process of verifying what they have access to

1. What is Authorization Code Flow?

• it exchanges an Authorization Code for a token

1. What is Authorization Code Flow with Proof Key for Code Exchange (PKCE)?

• The PKCE-enhanced Authorization Code Flow introduces a Code Verifier created by the calling application that can be verified by the authorization server

1. What is Implicit Flow with Form Post?

• The web app requests and obtains tokens through the front channel, without the need for secrets or extra backend calls

1. What is Client Credentials Flow?

• in machine-to-machine apps they pass along their Client ID and Client Secret to authenticate themselves and get a token

1. What is Device Authorization Flow?

• the device asks the user to go to a link on their computer or smartphone and authorize the device

1. What is Resource Owner Password Flow?

• it requests that users provide credentials (username and password), typically using an interactive form

more on OAuth

more on Authentication flows

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