Fixing Traefik: Redirect Domain Not Allowed Error

by Luna Greco 50 views

Introduction

Hey guys! Ever run into the frustrating “Redirect domain not allowed” error when using Traefik middleware with Anubis? It’s like hitting a brick wall, especially when you’re trying to test out new features. This guide is here to help you break down the issue, understand why it happens, and walk through the steps to fix it. We’ll dive deep into the configuration files, analyze the problem, and provide a solution that gets your setup running smoothly. Let’s get started and turn that “Oh noes!” into a “Yes!”

Understanding the Problem: "Redirect Domain Not Allowed"

When you encounter the “Redirect domain not allowed” error in Traefik with Anubis, it typically means that the redirect URL generated by Anubis doesn't match the allowed domains specified in your configuration. This security measure prevents unauthorized redirects, ensuring that users are only redirected to trusted domains. This error often surfaces when there’s a mismatch between the domain Anubis is trying to redirect to and the domains you’ve explicitly permitted in the REDIRECT_DOMAINS environment variable. To effectively troubleshoot this, it’s essential to examine the URL that triggers the error, along with your Anubis and Traefik configurations, to identify any discrepancies. Pay close attention to how the redir parameter is being constructed and whether it aligns with the domains listed in your REDIRECT_DOMAINS setting. By meticulously reviewing these components, you can pinpoint the exact cause of the issue and implement the necessary corrections to resolve the redirect error.

Analyzing the Error URL

The URL provided in the issue is:

https://anubis.MYDOMAIN/.within.website/x/cmd/anubis/api/pass-challenge?id=0198a459-be6f-786a-a5f6-1fd50d7fc15d&response=0094d3a2f6074d791c23961c5a313b61d25b340bd9daabe92746d987f53d9995&nonce=1200&redir=https%3A%2F%2Fanubis.MYDOMAIN%2F.within.website%2F%3Fredir%3Dhttps%253A%252F%252FSERVICE.MYDOMAIN%252F&elapsedTime=128

The key part to focus on is the redir parameter. It shows that the redirection is happening back to anubis.MYDOMAIN instead of SERVICE.MYDOMAIN, which is the intended destination. This discrepancy is a crucial clue in understanding the problem. When Anubis constructs the redirect URL, it should ensure that the final destination is the originally requested service domain, not itself. This issue arises because the redir parameter within the URL gets re-encoded, leading to a loop where Anubis redirects back to itself instead of the intended service. To fix this, we need to adjust the configuration to ensure the final redirect points correctly to SERVICE.MYDOMAIN. By carefully examining and correcting how the redir parameter is handled, we can prevent the redirect loop and resolve the “Redirect domain not allowed” error.

Examining the Configuration Files

Let's dive into the configuration files to pinpoint the misconfiguration. We'll look at docker-compose.yml and traefik-dynamic.yml.

docker-compose.yml

The docker-compose.yml file defines the services and their configurations. Here's the relevant part:

anubis:
    image: ghcr.io/techarohq/anubis:main
    container_name: anubis
    restart: unless-stopped
    environment:
      # Telling Anubis, where to listen for Traefik
      - BIND=:8080
      # Telling Anubis to do redirect — ensure there is a space after '='
      - 'TARGET= '
      # Specifies which domains Anubis is allowed to redirect to.
      - REDIRECT_DOMAINS=SERVICE.MYDOMAIN
      # Should be the full external URL for Anubis (including scheme)
      - PUBLIC_URL=https://anubis.MYDOMAIN
      # Should match your domain for proper cookie scoping
      - COOKIE_DOMAIN=SERVICE.MYDOMAIN

In this configuration, the REDIRECT_DOMAINS environment variable is set to SERVICE.MYDOMAIN. This tells Anubis that it is allowed to redirect only to this domain. However, the TARGET variable has a space after the equals sign, which might lead to unexpected behavior as it essentially sets the target to an empty string. This is a critical point to note because Anubis uses the TARGET variable to determine where to redirect after authentication. If TARGET is not correctly set, Anubis might default to redirecting back to itself, causing the error. To resolve this, ensure the TARGET variable is correctly configured, or remove it if it's not needed. Additionally, double-check that the REDIRECT_DOMAINS variable contains all the necessary domains, including anubis.MYDOMAIN, if Anubis needs to redirect back to itself during the authentication process. Properly configuring these variables is essential for Anubis to function correctly and avoid the “Redirect domain not allowed” error.

traefik-dynamic.yml

The traefik-dynamic.yml file configures Traefik's routes, middlewares, and services. Here's the relevant snippet:

http:
  middlewares:
    anubis: 
      forwardauth:
         address: http://anubis:8080/.within.website/x/cmd/anubis/api/check

  routers:
      
    anubis:
      rule: 'Host(`anubis.MYDOMAIN`)'
      service: "anubis"

    SERVICE:
      rule: 'Host(`SERVICE.MYDOMAIN`)'
      middlewares:
        - anubis
      service: "SERVICE"

  services:
    
    anubis:
      loadBalancer:
        servers:
          - url: http://anubis:8080

    SERVICE:
      loadBalancer:
        servers:
          - url: http://service:3000

This Traefik configuration sets up two routers: one for anubis.MYDOMAIN and another for SERVICE.MYDOMAIN. The SERVICE router uses the anubis middleware for authentication. The middleware's forwardauth address points to http://anubis:8080/.within.website/x/cmd/anubis/api/check, which is correct. However, the issue might stem from how Anubis handles the redirect after the authentication check. Traefik's configuration looks fine in terms of routing and middleware setup, but the interaction between Traefik and Anubis needs closer scrutiny. Specifically, we need to ensure that after Anubis authenticates the user, it correctly redirects them back to the originally requested service, which is SERVICE.MYDOMAIN. If the redirect logic within Anubis is flawed or if the necessary information isn't being passed correctly between Traefik and Anubis, it can lead to the “Redirect domain not allowed” error. Therefore, the focus should be on the post-authentication redirect process and how Anubis constructs the redirect URL based on the initial request.

Identifying the Root Cause

After analyzing the URL and the configuration files, the root cause of the “Redirect domain not allowed” error appears to be in how Anubis handles the redir parameter and the TARGET environment variable. The URL shows that the redirection is looping back to anubis.MYDOMAIN instead of going to SERVICE.MYDOMAIN. This suggests that after authentication, Anubis isn't correctly constructing the final redirect URL. The TARGET environment variable in docker-compose.yml has a space after the equals sign (TARGET= ), which effectively sets it to an empty string. This is problematic because Anubis relies on the TARGET variable to determine the post-authentication redirect destination. When TARGET is empty, Anubis might default to redirecting back to its own domain, leading to the error. Additionally, the REDIRECT_DOMAINS variable only includes SERVICE.MYDOMAIN, but if Anubis needs to redirect back to itself during the authentication process, anubis.MYDOMAIN should also be included. To resolve this, we need to correct the TARGET variable and ensure that both SERVICE.MYDOMAIN and anubis.MYDOMAIN are included in the REDIRECT_DOMAINS variable. This will allow Anubis to properly construct the redirect URL and avoid the redirect loop, thus fixing the “Redirect domain not allowed” error.

Solution: Correcting the Configuration

To fix the “Redirect domain not allowed” error, we need to adjust the docker-compose.yml file. Here’s the corrected configuration:

Corrected docker-compose.yml

anubis:
    image: ghcr.io/techarohq/anubis:main
    container_name: anubis
    restart: unless-stopped
    environment:
      # Telling Anubis, where to listen for Traefik
      - BIND=:8080
      # Telling Anubis to do redirect — ensure there is a space after '='
      - TARGET=
      # Specifies which domains Anubis is allowed to redirect to.
      - REDIRECT_DOMAINS=SERVICE.MYDOMAIN,anubis.MYDOMAIN
      # Should be the full external URL for Anubis (including scheme)
      - PUBLIC_URL=https://anubis.MYDOMAIN
      # Should match your domain for proper cookie scoping
      - COOKIE_DOMAIN=SERVICE.MYDOMAIN

Explanation of Changes

  1. TARGET Variable: The space after the equals sign in TARGET= has been removed. This ensures that the TARGET variable is either correctly set or left empty if no specific target is intended. If Anubis requires a specific target, you should set it appropriately; otherwise, leaving it empty might allow Anubis to use the originally requested URL.
  2. REDIRECT_DOMAINS Variable: anubis.MYDOMAIN has been added to the list of allowed redirect domains. This is crucial because Anubis might need to redirect back to itself during the authentication process. By including anubis.MYDOMAIN, we ensure that these redirects are permitted, preventing the “Redirect domain not allowed” error.

By implementing these changes, Anubis will be able to correctly construct the redirect URL after authentication, ensuring that users are redirected to the intended service (SERVICE.MYDOMAIN) without looping back to Anubis itself. This resolves the “Redirect domain not allowed” error and allows the authentication flow to complete successfully.

Testing the Solution

After applying the configuration changes, it’s crucial to test the solution to ensure the “Redirect domain not allowed” error is resolved and the authentication flow works correctly. Follow these steps to test:

  1. Restart Anubis: Apply the changes by restarting the Anubis container using docker-compose:
    docker-compose down
docker-compose up -d
    This ensures that the new environment variables are loaded and the Anubis service is running with the updated configuration.
  2. Access SERVICE.MYDOMAIN: Open your web browser and navigate to SERVICE.MYDOMAIN. This should trigger the authentication process managed by Anubis.
  3. Observe the Redirect: Watch the URL in your browser's address bar. You should be redirected to Anubis for authentication and then, after successful authentication, redirected back to SERVICE.MYDOMAIN.
  4. Verify No Error: Ensure that you do not see the “Redirect domain not allowed” error. If the redirection works as expected and you can access SERVICE.MYDOMAIN after authentication, the issue is resolved.
  5. Check Anubis Logs: If you still encounter issues, examine the Anubis container logs for any error messages or clues. You can view the logs using:
    docker-compose logs anubis
    Look for any error messages related to redirects or domain validation. These logs can provide valuable insights into any remaining issues.
  6. Test Different Scenarios: Try accessing SERVICE.MYDOMAIN from different browsers or devices to ensure the solution works consistently across various environments.

By following these testing steps, you can confidently verify that the configuration changes have resolved the “Redirect domain not allowed” error and that your authentication flow is functioning as expected. If any issues persist, the logs and further configuration review will help you identify and address them.

Additional Tips and Considerations

When dealing with Traefik and Anubis, here are some additional tips and considerations to keep in mind to prevent and troubleshoot issues like the “Redirect domain not allowed” error:

  1. Regularly Review Configuration: Make it a habit to periodically review your docker-compose.yml and traefik-dynamic.yml files. Look for any inconsistencies, typos, or outdated settings. This proactive approach can help catch potential problems before they escalate.
  2. Keep Components Updated: Ensure that you are using the latest stable versions of Traefik and Anubis. Updates often include bug fixes, security enhancements, and performance improvements. Staying up-to-date can prevent known issues and ensure compatibility.
  3. Use Detailed Logging: Configure Traefik and Anubis to use detailed logging. This will provide more information in the logs, making it easier to diagnose issues when they arise. Detailed logs can help you trace the flow of requests and identify where things might be going wrong.
  4. Monitor Performance: Implement monitoring tools to keep an eye on the performance of your services. Monitoring can help you detect anomalies or performance bottlenecks that might indicate underlying issues. Tools like Prometheus and Grafana can be integrated with Traefik to provide real-time metrics.
  5. Secure Sensitive Information: Use Docker secrets or environment variables to manage sensitive information such as API keys, passwords, and certificates. Avoid hardcoding sensitive data directly in your configuration files.
  6. Validate Input: When setting environment variables, ensure that you are providing valid input. For example, check that domain names are correctly formatted and that lists are properly separated. Incorrect input can lead to unexpected behavior and errors.
  7. Test in a Staging Environment: Before deploying changes to your production environment, thoroughly test them in a staging environment. This allows you to identify and fix issues without impacting your users.
  8. Document Your Setup: Maintain clear and up-to-date documentation of your Traefik and Anubis setup. This documentation should include configuration details, dependencies, and any custom settings. Good documentation makes it easier for you and your team to troubleshoot and maintain the system.

By following these tips and considerations, you can create a more robust and maintainable Traefik and Anubis setup, reducing the likelihood of encountering issues like the “Redirect domain not allowed” error.

Conclusion

Alright guys, we’ve walked through the process of troubleshooting the “Redirect domain not allowed” error in Traefik with Anubis. We started by understanding the problem, analyzed the configuration files, identified the root cause, and implemented a solution. By correcting the TARGET and REDIRECT_DOMAINS environment variables in the docker-compose.yml file, we ensured that Anubis correctly handles redirects after authentication. Testing the solution is crucial to confirm that the issue is resolved and that the authentication flow works as expected. Additionally, we discussed several tips and considerations for maintaining a robust and secure setup. Remember, regularly reviewing configurations, keeping components updated, and using detailed logging can help prevent and quickly resolve issues. With these steps, you can confidently manage your Traefik and Anubis setup and ensure a smooth authentication process for your services. Keep these tips in mind, and you’ll be well-equipped to tackle any similar challenges in the future. Happy troubleshooting!