How to remediate – Atlassian Bitbucket Pipelines Configuration Detected

1. Introduction

Atlassian Bitbucket Pipelines Configuration Detected refers to the presence of a `bitbucket-pipelines.yml` file exposed via the web server. This configuration file contains instructions for automated builds, tests and deployments. If accessible publicly, it can expose sensitive information like credentials or internal network details. Affected systems are typically those running Bitbucket Server or Cloud instances with Pipelines enabled. A successful exploit could lead to data breaches, unauthorized access, and compromised CI/CD pipelines.

2. Technical Explanation

The vulnerability occurs when the `bitbucket-pipelines.yml` file is deployed within a web server’s document root without proper access controls. This allows anyone with network access to view its contents. An attacker could then extract sensitive data stored directly in the configuration or use it to understand the internal build process and identify further attack vectors. The primary exploit mechanism involves direct retrieval of the file via HTTP/HTTPS.

• Root cause: Insufficiently restricted permissions on the directory containing `bitbucket-pipelines.yml`.
• Exploit mechanism: An attacker can request the file directly from a web server using a standard browser or tool like curl. For example, https://example.com/repo/.bitbucket-pipelines.yml.
• Scope: Bitbucket Server and Cloud instances with publicly accessible Pipelines configurations.

3. Detection and Assessment

Confirming vulnerability involves checking for the presence of `bitbucket-pipelines.yml` in web server directories. A quick check is to browse the repository directly via a web browser. Thorough assessment requires scanning all web server document roots.

• Quick checks: Attempt to access https://example.com/repo/.bitbucket-pipelines.yml in a web browser. If the file downloads or displays, it is accessible.
• Scanning: Use vulnerability scanners like OWASP ZAP or Burp Suite configured with directory brute-forcing and file pattern matching for `bitbucket-pipelines.yml`.
• Logs and evidence: Check web server access logs for requests to /.bitbucket-pipelines.yml or similar paths within repository directories.

curl https://example.com/repo/.bitbucket-pipelines.yml

4. Solution / Remediation Steps

The solution is to restrict access to the `bitbucket-pipelines.yml` file, preventing direct web access. This involves configuring appropriate permissions on the directory containing the file.

4.1 Preparation

• Ensure you have SSH or console access for roll back if needed. A roll back plan is to restore the original web server configuration.
• Change windows may be required depending on your environment and approval processes.

4.2 Implementation

1. Step 1: Identify the directory containing the `bitbucket-pipelines.yml` file within the web server’s document root.
2. Step 2: Configure the web server to deny direct access to this directory and its contents. For example, in Apache, add a <Directory> block with Require all denied.
3. Step 3: Restart the web server to apply the changes.

4.3 Config or Code Example

Before

<Directory /var/www/html/repo>
    Options Indexes FollowSymLinks
    AllowOverride All
    Require all granted
</Directory>

After

<Directory /var/www/html/repo>
    Options -Indexes FollowSymLinks
    AllowOverride None
    Require all denied
</Directory>

4.4 Security Practices Relevant to This Vulnerability

• Practice 1: Implement least privilege principles for all web server accounts and directories.
• Practice 2: Use secure configuration management tools to enforce consistent access controls.

4.5 Automation (Optional)

Infrastructure-as-code tools can automate the enforcement of directory permissions. The following example uses Ansible:

---
- name: Deny access to bitbucket-pipelines.yml directory
  hosts: webservers
  become: true
  tasks:
    - name: Configure Apache directory access
      lineinfile:
        path: /etc/apache2/sites-available/000-default.conf # Adjust path as needed
        regexp: '^<Directory /var/www/html/repo>'
        line: '<Directory /var/www/html/repo>'
              'n    Options -Indexes FollowSymLinks'
              'n    AllowOverride None'
              'n    Require all denied'
      notify: Restart Apache
  handlers:
    - name: Restart Apache
      service:
        name: apache2
        state: restarted

5. Verification / Validation

• Post-fix check: Attempt to access https://example.com/repo/.bitbucket-pipelines.yml in a web browser. Expected output is a 403 Forbidden error.
• Re-test: Re-run the quick check from Section 3. The file should no longer be accessible.
• Smoke test: Verify that other repository functionality, such as code browsing and cloning, remains operational.
• Monitoring: Monitor web server access logs for any attempts to access the restricted directory.

curl -I https://example.com/repo/.bitbucket-pipelines.yml

6. Preventive Measures and Monitoring

Regular security baselines help prevent misconfigurations like this one. CI/CD pipelines can include static analysis tools to identify exposed sensitive data in configuration files. A consistent patch management process ensures timely updates to address known vulnerabilities.

• Baselines: Update your web server security baseline to include restrictions on access to sensitive directories.
• Pipelines: Add SAST checks to CI pipelines to scan for credentials or other sensitive data in `bitbucket-pipelines.yml` files.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Incorrect configuration may cause other parts of the website to become inaccessible.
• Risk or side effect 2: Changes could interfere with existing CI/CD pipelines if not carefully planned.

8. References and Resources

• Vendor advisory or bulletin: https://support.atlassian.com/