All You Need to Know About Open Source OAuth: How to Secure Your Next App

Hi there! With data breaches so common, users no longer feel safe entering credentials into apps. This is where OAuth comes in – it allows your app to connect to services like Facebook without ever handling user passwords!

In this guide, I‘ll explain OAuth flows, show integration examples using top open source libraries, and give recommendations based on real-world use. My goal is to save you weeks of research so you can quickly secure user access. Let‘s get started!

A Brief History of OAuth

OAuth was created in 2006 to solve a pressing problem – users were handing out their credentials left and right, and it became a security nightmare. Then came OAuth…

It enabled delegated authorization – access third party apps on behalf of users without ever seeing their passwords…

Over the years OAuth evolved with version 2.0 standardizing in 2012. It‘s now the most adopted protocol with over 50% of developers using it. Research forecasts continued growth as apps rely on accessing capabilities across platforms.

The Problem OAuth Solves

Imagine Sarah wants to access files on her Google Drive through a project management app. Traditionally, she would provide her Google username and password to the PM app so it can log in on her behalf. This is dangerous!

Instead with OAuth, Sarah authorizes the PM app to connect to a limited Google account under her identity. The PM app gets a token granting temporary access without ever handling Sarah‘s actual password. Much more secure!

OAuth introduces immediate security benefits:

✅ Users avoid sharing passwords

✅ Limited scopes reduce data exposure

✅ Short-lived tokens minimize attack windows

Now let‘s understand how OAuth accomplishes this by looking at the different flows available.

OAuth Authentication Flows

There are four OAuth 2.0 flows catering to different types of apps:

Authorization Code Flow

Best suited for web apps executing logic on a server. After the user signs in and authorizes access, the app uses the authorization code returned to get access tokens from the OAuth server:

Code samples:

https://oauth.service/?
  response_type=code&
  client_id=1234&
  redirect_uri=REDIRECT-URL  

Exchange code for tokens:

curl -X POST https://oauth.service/token 
  -d grant_type=authorization_code  
  -d client_id=1234
  -d code=AUTH-CODE
  -d redirect_uri=REDIRECT-URL

Implicit Flow

Ideal for pure client-side/mobile apps that have no secure place to store tokens. Tokens are directly provided in the redirect URI for the app to consume:

Request tokens from OAuth server:

https://oauth.service/authorize?
  response_type=token
  client_id=1234  
  redirect_uri=REDIRECT-URL
  scope=user-profile

Resource Owner Password Credentials Flow

Used when apps highly trusted by users can securely store passwords, such as wallets or email clients. App collects user credentials and posts them in exchange for access tokens:

Exchange user credentials for tokens:

curl -X POST https://oauth.service/token  
  -d grant_type=password
  -d client_id=CLIENT-ID  
  -d username=USER  
  -d password=PASS

Client Credentials Flow

Enables app APIs to access other services on behalf of themselves rather than any user. Does not use end user authorization. Relies on app‘s client ID + secret to get tokens:


Authenticate and retrieve access token:

curl -X POST https://oauth.service/token
  -d grant_type=client_credentials 
  -d client_id=CLIENT-ID
  -d client_secret=SECRET   

This covers the common OAuth flows you‘ll encounter. Now let‘s explore some leading open source implementations.

Open Source OAuth Libraries

While OAuth is a standard protocol, apps need concrete libraries with hooks to implement it. Here are top open source options:

1. SuperTokens

A secure, easily customizable authentication service supporting email login, social login, and passwordless flows with UI included out of the box…

2. Apereo CAS

A popular single sign-on server that lets users access multiple apps under one identity. Comes with password management, 2FA, customization via Java…

3. ORY Kratos

A feature packed identity and user management solution written in Go but with SDKs for every language. Supports registration, SSO, profile management, and more.

See the full comparison here:

Library	Languages	Authentication Support	Custom Claims	UI Included
SuperTokens	Javascript, React Native, Java, Go	Email, OAuth social, passwordless	Yes	Yes
Apereo CAS	Java, .NET	300+ protocols, LDAP, MFA, Saml	Limited	No
ORY Kratos	Go, Java, JS, Python	MFA, profile management, registration	Yes	No

To pick the right library:

• Align with your tech stack
• Evaluate ease of customization
• Check scalability for future growth

Now let‘s go through a sample integration!

Integrating SuperTokens

SuperTokens makes it easy to add authentication flows within frontend apps. Let‘s see it in action for React apps.

First install the libraries:

npm install supertokens-auth-react

Then initialize the SessionAuth component:

import { SessionAuth } from "supertokens-auth-react";

function App() {

  return (
    <SessionAuth>
      <RestOfApp />
    </SessionAuth>
  );
}

That hooks up the core auth! Now add EmailPasswordAuth for email login:

import EmailPasswordAuth from "supertokens-auth-react/recipe/emailpassword";

function App() {
  return (
    <SessionAuth>
      <EmailPasswordAuth> 
        <RestOfApp />  
      </EmailPasswordAuth>
    </SessionAuth>
  );
}

And you instantly get UI screens for login, signup, forgot password!

For full documentation see supertokens.com

Recommendations from Experts

I spoke to several developers with OAuth integration experience across fintech, ecommerce, and healthcare apps. Here are their top tips:

"Always check your identity provider follows security best practices around encryption,TOKEN storáge, session handling. Compromise there exposes all apps."

"Understand the various OAuth flows thoroughly and choose the right one. I‘ve seen teams use the wrong flow and struggle with auth logic."

"Integrate a secondary provider even if using a commercial platform. This prevents vendor lock-in and gives backup options."

Conclusion

OAuth enables secure, fast access delegation so apps can provide value using external capabilities, without the risks of traditional auth.

Evaluating both open source libraries like SuperTokens as well as managed services is key – align to your tech stack and custom use cases.

Follow security best practices, understand protocol flows, and leverage community insights from this guide to implement smooth, safe authentication!

Questions or comments? Let me know below.