Mocking OAuth services in testing with Dex

Table of contents

Dex is an open-source OpenID Connect (OIDC) and OAuth 2.0 identity provider that can be configured to authenticate against various backend identity providers, such as LDAP, SAML, and OAuth. Running Dex in a Docker container allows developers to simulate an OAuth 2.0 server for testing and development purposes. This guide will walk you through setting up Dex as an OAuth mock server using Docker containers.

Nowadays OAuth is the preferred choice to authenticate in web services, the highest part of them give the possibility to access using popular OAuth services like GitHub, Google or Apple. Using OAuth guarantees a higher level of security and simplification since it is not necessary to create new profiles for each service. This means that, by allowing applications to access resources on behalf of users without sharing passwords, OAuth minimizes the risk of credential exposure.

In this guide, you'll learn how to:

  • Use Docker to launch up a Dex container.
  • Use mock OAuth in the GitHub Action (GHA) without relying on an external OAuth provider.

Using Dex with Docker

The official Docker image for Dex provides a convenient way to deploy and manage Dex instances. Dex is available for various CPU architectures, including amd64, armv7, and arm64, ensuring compatibility with different devices and platforms. You can learn more about Dex standalone on the Dex docs site.

Prerequisites

Docker Compose: Recommended for managing multi-container Docker applications.

Setting Up Dex with Docker

Begin by creating a directory for your Dex project:

mkdir dex-mock-server cd dex-mock-server

Organize your project with the following structure:

dex-mock-server/ ├── config.yaml └── compose.yaml

Create the Dex Configuration File: The config.yaml file defines Dex's settings, including connectors, clients, and storage. For a mock server setup, you can use the following minimal configuration:

# config.yaml issuer: http://localhost:5556/dex storage:  type: memory web:  http: 0.0.0.0:5556 staticClients:  - id: example-app  redirectURIs:  - 'http://localhost:5555/callback'  name: 'Example App'  secret: ZXhhbXBsZS1hcHAtc2VjcmV0 enablePasswordDB: true staticPasswords:  - email: "admin@example.com"  hash: "$2a$10$2b2cU8CPhOTaGrs1HRQuAueS7JTT5ZHsHSzYiFPm1leZck7Mc8T4W"  username: "admin"  userID: "1234"

Explanation:

  • issuer: The public URL of Dex.

  • storage: Using in-memory storage for simplicity.

  • web: Dex will listen on port 5556.

  • staticClients: Defines a client application (example-app) with its redirect URI and secret.

  • enablePasswordDB: Enables static password authentication.

  • staticPasswords: Defines a static user for authentication. The hash is a bcrypt hash of the password.

Note

Ensure the hash is a valid bcrypt hash of your desired password. You can generate this using tools like bcrypt-generator.com. or use CLI tools like htpasswd like in this following example:echo password | htpasswd -BinC 10 admin | cut -d: -f2

With Docker Compose configured, start Dex:

# docker-compose.yaml  services:  dex:  image: dexidp/dex:latest  container_name: dex  ports:  - "5556:5556"  volumes:  - ./config.yaml:/etc/dex/config.yaml  command: ["dex", "serve", "/etc/dex/config.yaml"]

Now it is possible to run the container using the docker compose command.

docker compose up -d

This command will download the Dex Docker image (if not already available) and start the container in detached mode.

To verify that Dex is running, check the logs to ensure Dex started successfully:

docker compose logs -f dex

You should see output indicating that Dex is listening on the specified port.

Using Dex OAuth testing in GHA

To test the OAuth flow, you'll need a client application configured to authenticate against Dex. One of the most typical use cases is to use it inside GitHub Actions. Since Dex supports mock authentication, you can predefine test users as suggested in the docs. The config.yaml file should looks like:

issuer: http://127.0.0.1:5556/dex  storage:  type: memory  web:  http: 0.0.0.0:5556  oauth2:  skipApprovalScreen: true  staticClients:  - name: TestClient  id: client_test_id  secret: client_test_secret  redirectURIs:  - http://{ip-your-app}/path/to/callback/ # example: http://localhost:5555/callback  connectors: # mockCallback connector always returns the user 'kilgore@kilgore.trout'. - type: mockCallback  id: mock  name: Mock

Now you can insert the Dex service inside your ~/.github/workflows/ci.yaml file:

[...] jobs:  test-oauth:  runs-on: ubuntu-latest  steps:  - name: Install Dex  run: |  curl -L https://github.com/dexidp/dex/releases/download/v2.37.0/dex_linux_amd64 -o dex  chmod +x dex   - name: Start Dex Server  run: |  nohup ./dex serve config.yaml > dex.log 2>&1 &  sleep 5 # Give Dex time to start [...]

Conclusion

By following this guide, you've set up Dex as an OAuth mock server using Docker. This setup is invaluable for testing and development, allowing you to simulate OAuth flows without relying on external identity providers. For more advanced configurations and integrations, refer to the Dex documentation.