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GCP API Token

A Google Cloud Platform (GCP) API Token is a credential used to authenticate and authorize access to various GCP services and resources. These tokens are typically used by applications and services to interact with GCP APIs programmatically. Exposure of a GCP API Token can lead to unauthorized access to cloud resources, potentially resulting in data breaches, financial loss, and service disruptions.

How Does It Look​

GCP API Tokens can appear in various contexts, such as:

  • Environment variables:

    export GCP_API_TOKEN="ya29.a0AfH6SMC..."

  • Configuration files (JSON, YAML, .env):

    {
      "api_key": "ya29.a0AfH6SMC..."
    }

  • Code snippets:

    import google.auth
    credentials, project = google.auth.default()
    credentials.token = "ya29.a0AfH6SMC..."

  • Connection strings:

    gcp://project-id?token=ya29.a0AfH6SMC...

Severity​

  • 🔴 Critical

The severity of a GCP API Token exposure is critical because it can provide access to a wide range of cloud services and resources. Depending on the permissions associated with the token, an attacker could potentially access sensitive data, modify configurations, or incur significant costs by provisioning resources.

What Can an Attacker Do?​

With immediate access to a GCP API Token, an attacker can interact with GCP services as if they were the legitimate user.

Key actions an attacker can perform:

  • Delete or modify data (if the token has write permissions)
  • Access billing information (if the account has billing scope enabled)
  • Spin up resources for cryptomining (if compute permissions are granted)
  • Access sensitive configurations (if the token has admin privileges)

An attacker could also use the token to escalate privileges or move laterally within the cloud environment, potentially compromising additional resources or services.

Real-World Impact​

The exposure of a GCP API Token poses significant business risks, including:

Potential consequences include:

  • Data Exposure: Access to customer data, intellectual property, or other sensitive information (if the token has read access to sensitive data)
  • Financial Loss: Unauthorized resource creation leading to increased billing (if billing/resource creation is permitted)
  • Operational Disruption: Service outages or degraded performance (if the attacker has delete/modify permissions)
  • Reputational Damage: Loss of customer trust and brand reputation

In the worst-case scenario, an attacker could gain control over critical infrastructure, leading to cascading failures across dependent systems and services.

Prerequisites for Exploitation​

To exploit a GCP API Token, an attacker needs:

  • Network access: Ability to send requests to GCP APIs
  • Additional context: Knowledge of specific project IDs or endpoints
  • No rate limits: Unrestricted API access without throttling

How to Verify If It's Active​

To verify if a GCP API Token is active, use the following command:

curl -H "Authorization: Bearer [TOKEN]" https://www.googleapis.com/auth/cloud-platform

Valid credential response: A successful response will return a JSON object with details about the authenticated user or service account.

Invalid/expired credential response: An error message indicating unauthorized access or token expiration.

Detection Patterns​

Common Variable Names:

  • GCP_API_TOKEN
  • GOOGLE_CLOUD_API_KEY
  • GCP_TOKEN
  • GOOGLE_API_TOKEN
  • CLOUD_API_KEY
  • GCP_KEY

File Locations:

  • .env
  • config.json
  • settings.yaml
  • credentials.json
  • application.properties

Regex Pattern:

ya29\.[0-9A-Za-z\-_]+

Remediation Steps​

  1. Revoke immediately - Go to Google Cloud Console > IAM & Admin > Service Accounts and delete the compromised token.
  2. Audit access logs - Review GCP audit logs for unauthorized API calls or resource changes during the exposure window.
  3. Assess blast radius - Identify all systems, applications, and environments that used the exposed credential.
  4. Rotate credential - Create a new API token in Google Cloud Console with least-privilege permissions.
  5. Update dependent systems - Deploy the new credential to all applications and update CI/CD pipelines securely.
  6. Harden access controls - Enable IP allowlisting and require multi-factor authentication for sensitive operations in GCP.
  7. Implement secrets management - Migrate credentials to a secrets manager (HashiCorp Vault, AWS Secrets Manager) to prevent hardcoding.
  8. Add detection controls - Set up pre-commit hooks and repository scanning to catch credential leaks before they reach production.

Credential exposures often go undetected for extended periods, increasing the window for exploitation. As a long-term strategy, plan to establish an internal process or engage an external vendor for continuous external exposure monitoring. This helps identify leaked secrets across public repositories, paste sites, dark web forums, and other external sources before attackers can leverage them. Proactive detection and rapid response are essential to minimizing the impact of credential leaks.

References​