Technical Analysis of "$7.5k Google Cloud Platform Organization Policy Bypass"

Overview

This write-up by Ezequiel Soria provides a detailed account of discovering and exploiting a vulnerability in Google Cloud Platform (GCP). The vulnerability allowed bypassing organization policies, which can lead to significant security risks, such as unauthorized resource creation and potential malicious activities within the compromised GCP organization.

Key Technical Details

Vulnerability Description

The core of the vulnerability lies in the ability to bypass organization-level policies in GCP. Organization Policies in GCP create governance constraints across projects in an organization to ensure compliance, limit exposure, and streamline permissions. By exploiting this vulnerability, an attacker could effectively nullify these safeguards.

Exploitation Steps

1. Understanding GCP Organization Policies:
2. Organization Policies: These are used to centrally manage restrictions on projects, folders, and other resources. Examples include restricting allowed domains for Identity and Access Management (IAM) and limiting the locations where resources can be created.

3. Policies are hierarchical and applied from the organization level down to individual projects and folders.

4. Initial Access:

5. Ezequiel gained access to a GCP environment with limited permissions. The target policy in this write-up restricted the creation of VM instances to specific regions.

6. Policy Constraints Bypass:

7. Through thorough exploration, Ezequiel found a misconfigured organization policy that allowed the modification of resource constraints. This misconfiguration enabled the bypass of geographical restrictions.

8. The exploitation involved leveraging the compute.instances.insert permission with a modification to the request payload, specifically:

   • Intercepting the original request to create a VM instance.
   • Adjusting the zone parameter to a different (restricted) region.

9. Proof of Concept (PoC):

10. Using gcloud CLI: sh gcloud compute instances create example-instance --zone=<restricted-zone>
11. The above command would typically be restricted, but due to the misconfigured policies, modifying the request payload facilitated the successful creation of resources in the restricted zone.

Impact and Implications

• Security Risks:
• Unauthorized creation and deployment of resources in restricted regions.
• Potential for data exfiltration and non-compliant resource allocation.

• Increased risk of malicious activities, including cryptocurrency mining, distributed denial-of-service (DDoS) attacks, etc.

• Financial Risks:

• Unintended and excess usage charges in regions with higher operational costs.
• The possibility of attackers setting up expensive resource configurations, leading to substantial unexpected bills.

Mitigation and Recommendations

1. Secure Organization Policy Configuration:
2. Ensure that organization policies are correctly configured and applied across all projects.

3. Regular audits should be conducted to detect and rectify any misconfigurations.

4. Least Privilege Principle:

5. Limit permissions to the minimum required for users and services.

6. Monitor and update roles and permissions regularly to prevent overexposure.

7. Monitoring and Alerts:

8. Implement continuous monitoring to detect unauthorized changes to organization policies and resource creation.

9. Set up alerts for anomalous activities, especially in restricted zones.

10. Regular Access Reviews:

11. Periodically review and validate IAM roles and policies to ensure they are aligned with security best practices.

12. Patch Management and Incident Response:

13. Apply patches and security updates promptly as issued by GCP.
14. Develop an incident response plan to handle breaches and policy violations efficiently.

Discovery and Reporting

Ezequiel responsibly disclosed the vulnerability to Google, which subsequently patched the issue. For his significant contribution to improving the security of GCP, he was rewarded $7,500 under Google's Vulnerability Reward Program.

Conclusion

This write-up underscores the importance of diligent cloud security practices, effective policy management, and the necessity for regular security reviews. Organization policies are critical in safeguarding cloud environments, and misconfigurations can lead to severe vulnerabilities. Organizations must employ comprehensive security strategies to mitigate risks and ensure compliance.

For a detailed account, you can read the full write-up here.