How to remediate – Apache Airflow Web API Detection

1. Introduction

The Apache Airflow Web API Detection indicates that a web application or API for Apache Airflow is running on the remote host. This could allow unauthenticated access to sensitive data and functionality if not properly secured. Systems affected are those with Apache Airflow installed, typically used for programmatically authoring, scheduling and monitoring workflows. A successful exploit may lead to information disclosure, workflow manipulation, and potential code execution.

2. Technical Explanation

The vulnerability stems from the presence of an exposed web API. Prior to Apache Airflow 2.0.0, this API is considered experimental and might not consistently return version information. This can hinder accurate identification and patching efforts. An attacker could potentially enumerate workflows, tasks, and connections within the Airflow environment.

• Root cause: The web application or API for Apache Airflow is accessible without sufficient authentication or authorization controls.
• Exploit mechanism: An attacker can send HTTP requests to the Airflow web API endpoints to gather information about the system and potentially execute malicious code.
• Scope: Affected platforms are those running Apache Airflow versions prior to 2.0.0, as well as any systems with exposed APIs even on newer versions without proper security measures in place.

3. Detection and Assessment

Confirming the presence of the API is the first step. Then check for version information if possible.

• Quick checks: Access the Airflow web UI via a web browser to confirm its availability. Check network ports using netstat -tulnp or similar tools.
• Scanning: Nessus plugin ID 16823 can detect exposed Apache Airflow instances. OpenVAS also has relevant scan queries. These are examples only, as scanner coverage varies.
• Logs and evidence: Examine web server logs for requests to the Airflow API endpoints (e.g., /api/v1/). Look for unusual activity or attempts to access sensitive data.

# Example command placeholder:
netstat -tulnp | grep airflow

4. Solution / Remediation Steps

The primary solution is to secure the Airflow web API with appropriate authentication and authorization mechanisms.

4.1 Preparation

• Ensure you have access to the Airflow configuration file (airflow.cfg). A roll back plan involves restoring the backed-up database and restarting the stopped services.
• A change window may be required depending on service impact, with approval from system owners.

4.2 Implementation

1. Step 1: Configure authentication for the Airflow web UI by setting appropriate user credentials in the airflow.cfg file.
2. Step 2: Enable authorization using RBAC (Role-Based Access Control) to restrict access to sensitive data and functionality based on user roles.
3. Step 3: If running a version prior to 2.0.0, consider upgrading to the latest stable release of Apache Airflow.

4.3 Config or Code Example

Before

# airflow.cfg (example - no authentication)
[webserver]
authenticate = False

After

# airflow.cfg (example - basic authentication enabled)
[webserver]
authenticate = True
auth_backend = airflow.providers.fab.auth_manager.FabAuthManager

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help mitigate this vulnerability type.

• Practice 1: Least privilege – grant users only the minimum necessary permissions to perform their tasks, reducing the impact of a potential compromise.
• Practice 2: Input validation – validate all user inputs to prevent injection attacks and ensure data integrity.

4.5 Automation (Optional)

If using configuration management tools like Ansible, you can automate the changes to airflow.cfg.

# Example Ansible snippet:
- name: Configure Airflow authentication
  copy:
    src: airflow.cfg
    dest: /etc/airflow/airflow.cfg
    owner: airflow
    group: airflow
    mode: 0644
  notify: Restart Airflow services

5. Verification / Validation

Confirm that authentication is now required to access the web UI and API endpoints.

• Post-fix check: Attempt to access the Airflow web UI without credentials. You should be prompted for a username and password.
• Smoke test: Log in with a valid user account and confirm you can access basic workflow monitoring features.
• Monitoring: Monitor web server logs for failed login attempts or unauthorized access to API endpoints.

# Post-fix command and expected output (example - attempting access without credentials)
curl http://airflow_host/api/v1/dags
# Expected Output: 401 Unauthorized

6. Preventive Measures and Monitoring

Regularly review security baselines and incorporate checks into CI/CD pipelines to prevent similar issues.

• Baselines: Update your security baseline with the latest recommendations for Apache Airflow configuration, including authentication and authorization settings.
• Pipelines: Add static code analysis (SAST) tools to your CI pipeline to identify potential vulnerabilities in your Airflow workflows and configurations.
• Asset and patch process: Implement a regular patch review cycle for all software components, including Apache Airflow, to ensure timely application of security updates.

7. Risks, Side Effects, and Roll Back

Incorrect configuration may lock out users or disrupt service functionality.

• Risk or side effect 2: Enabling RBAC without proper planning may disrupt existing workflows. Mitigation: Carefully define user roles and permissions based on your organization’s needs.
• Roll back: Restore the backed-up airflow.cfg file and restart the Airflow scheduler and webserver services.

8. References and Resources

• Vendor advisory or bulletin: https://airflow.apache.org/