Ever wondered how the login to Google and Facebook buttons work on many web-applications? In a nutshell, these web-applications rely on Google/Facebook to handle the user identification piece and then Google/Facebook shares some information about the user with the web-application. This relieves the web-application from having to devise a login mechanism and store passwords, and also relieves the user from having to remember multiple usernames and passwords. So, WIN-WIN.
Suppose you are setting up a web-application that would like to use google's login. Your web-app runs at http://www.example.com/tracker (or http://localhost:3000/) . So, how do you integrate with Google's login?
Turns out, it can be done in 4 steps:
1. register your application with Google. After all, Google needs to know who is using it's login service. This step creates a client-id (which is used to identify your application) and a client-secret (something that is used by your application in communicating with Google).
2. The user gets a code from Google. This is done by clicking a button or link on your web application that makes a request to Google. This request has your client-id and an endpoint that should be called after successful login. The endpoint is something like http://localhost:3000/google_auth, and will be called after successful login.
3. The web-application exchanges the code for an authorization token. The authorization token is recognized by Google services. The web-application's client-secret is used to verify that it is your application which is involved in this transaction.
4. The authorization token is used to query the Google's Oauth2 webservice to get the user profile.
Suppose you are setting up a web-application that would like to use google's login. Your web-app runs at http://www.example.com/tracker (or http://localhost:3000/) . So, how do you integrate with Google's login?
Turns out, it can be done in 4 steps:
1. register your application with Google. After all, Google needs to know who is using it's login service. This step creates a client-id (which is used to identify your application) and a client-secret (something that is used by your application in communicating with Google).
2. The user gets a code from Google. This is done by clicking a button or link on your web application that makes a request to Google. This request has your client-id and an endpoint that should be called after successful login. The endpoint is something like http://localhost:3000/google_auth, and will be called after successful login.
3. The web-application exchanges the code for an authorization token. The authorization token is recognized by Google services. The web-application's client-secret is used to verify that it is your application which is involved in this transaction.
4. The authorization token is used to query the Google's Oauth2 webservice to get the user profile.
Registration
In order to use Google's services, you need to register your application. This involves creating a project in Google Developer Console and setting up credentials for the application(project). At the end of this step, you will have a client-id (a public id that is used to identify your application), a client-secret (which is known only to your application and is used to exchange code for tokens), and a set of well known endpoints in your application that google knows it's OK to redirect users back to after successful authentication.
Steps 2..4
A sequence of what needs to happen in steps 2..4 to get the user's identity is as follows.
The article gives a straightforward view of how “Login with Google” works behind the scenes, rather than treating it as a single authentication button. Breaking the process into application registration, receiving an authorization code, exchanging it for a token, and finally retrieving the user's profile makes the OAuth2 flow much easier to understand.
ReplyDeleteThe explanation of the client-id, client-secret, redirect endpoint, and authorization token is particularly useful because these pieces show how the web application and Google coordinate during authentication. This is an important concept for anyone learning Web Development Course, especially when moving beyond basic login forms to external identity providers.
The four-step sequence also highlights an important architectural benefit of OAuth2: the application does not need to create its own password storage and user-identification mechanism when Google handles that part of the process. Understanding this interaction between the application, authorization server, callback endpoint, and user profile provides useful context for a Full Stack Course, where authentication becomes part of the complete application architecture.
ReplyDeleteThe explanation of the client-id, client-secret, redirect endpoint, and authorization token is especially useful because these components are central to implementing secure authentication with an external identity provider. Understanding how these credentials and tokens work together provides useful context for Cyber Security Projects for Final Year Students, particularly for projects involving authentication and application security.
ReplyDeleteThe four-step sequence also shows why OAuth2 is more than just a login feature, since the application must correctly handle authorization codes, callback endpoints, tokens, and access to user information. These concepts are closely related to Information Security Projects, where secure identity management and controlled access are important considerations when designing web applications.
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