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Drupal Simple OAuth + Next.js: Complete SSO Implementation

Sun, 03/01/2026 - 13:00 admin
Simple OAuth Next.js SSO Authentication Headless Drupal

Authentication is one of those topics that sounds simple until you actually implement it.

Most teams begin with a straightforward goal:

Allow users to log in.

A few weeks later they’re troubleshooting:

  • Invalid grants
  • Refresh token failures
  • CORS errors
  • Session expiration problems
  • PKCE issues
  • Production deployment inconsistencies

Authentication is rarely difficult because of code.

It’s difficult because there are many moving parts.

And every one of them matters.

This article explains how I approach Single Sign-On (SSO) between Drupal 11 and Next.js using:

  • Simple OAuth
  • Authorization Code Flow
  • PKCE
  • Refresh Tokens
  • Modern security practices

The goal isn’t merely getting authentication working.

The goal is building an authentication system that remains reliable in production.

Understanding The Architecture

A modern implementation typically looks like this:

  • text id="ax92qm" User ↓ Next.js ↓ Drupal OAuth Server ↓ Protected APIs

Drupal becomes the identity provider.

Next.js becomes the client application.

Authentication is delegated to Drupal.

Authorization tokens are then used to access protected resources.

This creates a clean separation of responsibilities.

Why OAuth Instead Of Custom Authentication?

Many organizations initially consider building custom authentication.

I generally advise against it.

OAuth already solves:

  • Authorization
  • Token management
  • Session handling
  • Refresh workflows
  • Security concerns

Recreating these systems introduces unnecessary risk.

The best authentication system is often the one you don’t have to invent.

Why PKCE Matters

Historically, Authorization Code Flow assumed applications could safely store secrets.

Modern applications often cannot.

Examples include:

  • Single Page Applications
  • React applications
  • Mobile applications
  • Next.js frontend experiences

PKCE solves this problem.

Instead of relying on a client secret, the application generates:

  • Code Verifier
  • Code Challenge

The authorization server validates the relationship.

This significantly improves security for public clients.

Installing Simple OAuth

Install the module:

  • bash id="j6wzlr" composer require drupal/simple_oauth

Enable it:

  • bash id="1o0z5v" drush en simple_oauth

Then generate encryption keys.

These keys become part of your authentication infrastructure.

Protect them carefully.

Treat them like production credentials.

Because they are.

Create An OAuth Client

Once Simple OAuth is installed:

Create a client.

Typical configuration includes:

Client Name

Example:

  • text id="xv5t5q" Next.js Frontend

Redirect URI

Example:

  • text id="w36jnh" https://app.example.com/api/auth/callback

Grant Type

Authorization Code

PKCE

Enabled

This becomes the foundation of the integration.

Next.js Authentication Strategy

Many authentication tutorials immediately jump into implementation details.

Before doing that, decide:

Who owns identity?

In this architecture:

Drupal owns identity.

Drupal is responsible for:

  • User accounts
  • Passwords
  • Permissions
  • Roles

Next.js consumes identity.

This distinction prevents significant complexity later.

Authentication Flow

A simplified flow looks like this:

text id="w0wdv7" User clicks Login ↓ Drupal Login Page ↓ Authentication ↓ Authorization Code ↓ Token Exchange ↓ Access Token ↓ Authenticated Session

The frontend never handles passwords directly.

This is important.

Access Tokens

After authentication, Drupal issues an access token.

Example responsibilities:

  • API authorization
  • User identification
  • Protected resource access

Access tokens should be treated as temporary credentials.

Because that’s exactly what they are.

Refresh Tokens

One of the most common mistakes I encounter involves refresh tokens.

Teams often:

  • Ignore them
  • Misconfigure them
  • Fail to store them securely

Then users get logged out unexpectedly.

A Better Approach

Access Token:

  • text id="jlwmzl" Short lifetime

Refresh Token:

  • text id="v8i2gt" Longer lifetime

When the access token expires:

Use the refresh token.

Issue a new access token.

Maintain the session.

This creates a significantly better user experience.

Secure Storage

Storage decisions matter.

For web applications:

  • Consider:
  • Secure cookies
  • HttpOnly cookies
  • Encrypted storage approaches

Avoid exposing sensitive credentials unnecessarily.

The goal is minimizing attack surface.

Not maximizing convenience.

Protecting API Routes

A common mistake:

Authentication exists.

Authorization does not.

These are different concerns.

Questions include:

Is the user authenticated?

Is the user allowed to perform this action?

Drupal roles and permissions should remain the source of truth.

Do not duplicate authorization rules unnecessarily.

Session Restoration

Many applications work perfectly until the browser refreshes.

Then everything breaks.

A healthy implementation should support:

Browser Refresh

Session Persistence

Token Refresh

Reauthentication

Users should not need to log in repeatedly throughout the day.

Handling Logout Correctly

Logout sounds simple.

It rarely is.

A complete logout process should:

Destroy Local Session

Remove Tokens

Invalidate Server Session (If Appropriate)

Redirect Predictably

Partial logout implementations often create confusing user experiences.

Common Production Problems

Over time, the same issues appear repeatedly.

Problem #1

Redirect URI Mismatch

Example:

  • text id="vwjq80" Expected: /callback

Received:

  • text id="1az0h3" /callback/

Authentication fails.

OAuth is strict.

Problem #2

Incorrect PKCE Implementation

Code verifier mismatch.

Authorization failure.

Authentication loop.

These symptoms often indicate PKCE issues.

Problem #3

Broken Refresh Logic

Login succeeds.

Several hours later:

Users are logged out unexpectedly.

Refresh flow usually deserves investigation.

Problem #4

CORS Misconfiguration

The OAuth server works.

The browser blocks requests.

Developers blame authentication.

The browser is actually the issue.

Problem #5

Role Synchronization Issues

Authentication succeeds.

Authorization fails.

The user exists.

Permissions do not align.

Authentication and authorization must be evaluated separately.

Security Checklist

OAuth

  • Authorization Code Flow
  • PKCE enabled

Tokens

  • Access tokens short-lived
  • Refresh tokens managed securely

Storage

  • Secure cookies
  • Sensitive data protected

Infrastructure

  • HTTPS enforced
  • Secrets managed securely

Authorization

  • Drupal remains source of truth
  • Roles reviewed regularly

Common Mistakes

Mistake #1

Using Custom Authentication

OAuth already solves this problem.

Mistake #2

Ignoring PKCE

Modern public clients should use PKCE.

Mistake #3

Poor Refresh Token Strategy

Authentication should survive normal usage patterns.

Mistake #4

Treating Authentication And Authorization As The Same Thing

They are not.

Mistake #5

Planning Security Later

Security architecture should exist before implementation begins.

Production Readiness Checklist

Drupal

  • Simple OAuth configured
  • Keys generated securely
  • OAuth client configured

Next.js

  • Authentication flow implemented
  • Session management implemented
  • Refresh flow implemented

Security

  • HTTPS enabled
  • Secrets protected
  • Cookies secured

Operations

  • Logging configured
  • Monitoring configured
  • Failure scenarios tested

Final Thoughts

Authentication systems succeed when they’re boring.

Users shouldn’t think about them.

Developers shouldn’t constantly troubleshoot them.

The best implementations are:

  • Secure
  • Predictable
  • Maintainable

Drupal Simple OAuth and Next.js provide an excellent foundation for achieving that goal.

But success depends less on the technology and more on the architecture surrounding it.

PKCE.

Token management.

Session handling.

Authorization strategy.

Those decisions determine whether authentication becomes a strength or a recurring source of production incidents.

Build them carefully.

Need Help Implementing Drupal SSO?

DrupalRX helps organizations design OAuth architectures, PKCE implementations, Next.js integrations, mobile authentication systems, and secure API workflows.

If your authentication system feels fragile, start with an architecture review before adding more complexity.

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