Deploying a Password-Protected Docker Registry Mirror

You can deploy a password-protected Docker registry mirror and authenticate clients using basic authentication or, preferably, token-based authentication. Here's how to do it, focusing on the more secure token-based approach:

1. Deploying the Registry with Password Authentication (Token-Based):

We'll use the official Docker Registry image and configure it with a .htpasswd file for user authentication. However, this will only protect the registry itself; pushing and pulling images will leverage token-based authentication managed by the registry.

# Create a htpasswd file (replace 'username' and 'password' with your credentials)
htpasswd -B /auth/htpasswd username

# Start the registry with the authentication configuration
docker run -d \
  -p 5000:5000 \
  -v /auth:/auth \
  --name registry \
  registry:2

# Check logs to ensure it started correctly
docker logs registry

Explanation:

• -v /auth:/auth: Mounts a volume containing the .htpasswd file into the container at /auth. The directory /auth on your host should contain the htpasswd file you created.
• registry:2: Specifies the Docker Registry version 2.

2. Authenticating Clients:

Clients interact with a password-protected registry by obtaining a time-limited authentication token. This is done automatically by the Docker client when you try to push or pull. However, you need to login first:

docker login localhost:5000
# Enter username and password when prompted.

Behind the Scenes:

• Login Process: When you docker login, the Docker client contacts the registry's authentication endpoint (configured automatically during registry startup). It sends the username and password (from the docker login command) for verification against the .htpasswd file.
• Token Issuance: If authentication is successful, the registry issues a JSON Web Token (JWT) to the client.
• Subsequent Requests: The Docker client includes this JWT in the Authorization header of all subsequent push and pull requests. The registry validates the token to authorize the operation.

3. Important Considerations for Production:

• HTTPS: In a production environment, always use HTTPS. This encrypts communication between clients and the registry, protecting sensitive data like passwords and image layers. You'll need to configure SSL certificates for your registry. Let's Encrypt is a popular choice for free certificates.
• Persistence: Use a volume to store registry data persistently, so you don't lose your images if the container restarts. Example: -v /var/lib/registry:/var/lib/registry
• Authentication Backends: For more robust authentication and authorization, consider integrating the registry with an external authentication provider like LDAP, Active Directory, or a cloud-based identity service. The registry's configuration supports various auth backends.
• Authorization: Authentication verifies who you are. Authorization determines what you can do. You might want to explore registry authorization solutions to fine-tune access control to specific images or repositories.

Example Docker Compose (with HTTPS and Persistence - replace placeholders):

version: "3.8"
services:
  registry:
    image: registry:2
    ports:
      - "5000:5000"  # Adjust port mappings as needed
    volumes:
      - /path/to/registry-data:/var/lib/registry
      - /path/to/certs:/certs
    environment:
      REGISTRY_HTTP_TLS_CERTIFICATE: /certs/your_certificate.crt
      REGISTRY_HTTP_TLS_KEY: /certs/your_certificate.key
      REGISTRY_AUTH_HTPASSWD_REALM: "Registry Realm"
      REGISTRY_AUTH_HTPASSWD_PATH: /auth/htpasswd
    volumes:
      - /path/to/auth/dir:/auth # Directory with htpasswd file

Remember to generate your certificates and replace the placeholder paths and filenames. This enhanced example provides a more secure and robust setup for a production-like environment. Always prioritize security best practices when deploying a Docker registry.