mitigations.md

Mitigation Strategies Analysis for googleapis/google-api-php-client

Mitigation Strategy: Principle of Least Privilege (API Scope Configuration)

• Mitigation Strategy: Grant the application only the necessary API scopes using the setScopes() method.

• Description:

  1. Identify Required Operations: List all the specific actions your application needs to perform with Google Cloud APIs.
  2. Find Granular Scopes: For each operation, identify the most specific OAuth 2.0 scopes required. Consult the Google API documentation for each service. Avoid broad scopes.
  3. Configure Scopes in Code: Use the $client->setScopes() method to explicitly set the required scopes. Pass an array of scope strings or a single space-separated string.

     $client = new Google\Client();
     $client->setScopes([
         'https://www.googleapis.com/auth/cloud-storage.read_only',
         'https://www.googleapis.com/auth/bigquery.readonly'
     ]);
     // OR
     $client->setScopes('https://www.googleapis.com/auth/cloud-storage.read_only https://www.googleapis.com/auth/bigquery.readonly');

  4. Avoid Default Scopes: Be aware that some API services might have default scopes if you don't explicitly set them. Always explicitly set the scopes you need.
  5. Regularly Review: Periodically review the scopes and remove any that are no longer needed.

• Threats Mitigated:

  • Unauthorized Access (Severity: High): Limits the impact of a compromised credential.
  • Data Breach (Severity: High): Limits the amount of data accessible.
  • Privilege Escalation (Severity: High): Prevents broader access.
  • Accidental Misuse (Severity: Medium): Reduces unintended actions.

• Impact:

  • Unauthorized Access: Risk significantly reduced.
  • Data Breach: Potential data loss significantly reduced.
  • Privilege Escalation: Highly effective prevention.
  • Accidental Misuse: Reduces likelihood and impact.

• Currently Implemented:

  • Scopes are set for Cloud Storage and BigQuery access.

• Missing Implementation:

  • Missing for Gmail API; currently using a broad scope. Needs to be refined using $client->setScopes().

Mitigation Strategy: Secure Credential Handling (Library Configuration)

• Mitigation Strategy: Use setAuthConfig() with environment variables or useApplicationDefaultCredentials() for secure credential loading.

• Description:

  1. Avoid Hardcoding: Never hardcode credentials directly in your code.
  2. Environment Variables:
     • Set the GOOGLE_APPLICATION_CREDENTIALS environment variable to the path of your service account key file.
     • Use $client->setAuthConfig(getenv('GOOGLE_APPLICATION_CREDENTIALS'));
  3. Application Default Credentials (ADC):
     • Use $client->useApplicationDefaultCredentials(); The library will automatically find credentials based on the environment (GCE metadata, environment variables, etc.). This is the preferred method when possible.
  4. Workload Identity (GKE): If running on GKE, configure Workload Identity. The library will automatically use these credentials (via ADC).
  5. Do not commit credentials: Ensure that credential files are not committed to version control.

• Threats Mitigated:

  • Credential Exposure (Severity: High): Prevents credentials from being exposed.
  • Source Code Compromise (Severity: High): Protects credentials if the source code is compromised.
  • Accidental Disclosure (Severity: Medium): Reduces accidental sharing.

• Impact:

  • Credential Exposure: Risk dramatically reduced.
  • Source Code Compromise: Highly effective.
  • Accidental Disclosure: Significantly reduces the chance.

• Currently Implemented:

  • Using getenv('GOOGLE_APPLICATION_CREDENTIALS') in development.
  • Using $client->useApplicationDefaultCredentials() in production (with Google Cloud Secret Manager).

• Missing Implementation:

  • None

Mitigation Strategy: Token Refresh and Error Handling (with Library Methods)

• Mitigation Strategy: Implement robust error handling, including handling token expiration and using retry mechanisms provided by the library.

• Description:

  1. Wrap API Calls: Wrap API calls in try-catch blocks to handle potential exceptions.
  2. Handle Google\Service\Exception: Specifically catch Google\Service\Exception to handle errors related to the API, including authentication and authorization failures.
  3. Implement Retry Logic: Use the library's built-in retry mechanisms:
     • setBackoff(): Configure exponential backoff on the request object.

     $request = $service->objects->get($bucket, $object);
     $request->setBackoff(new Google\Http\BackoffStrategy()); // Use default backoff
     // OR customize:
     $backoff = new Google\Http\BackoffStrategy(
         null, // Use default delay function
         Google\Http\BackoffStrategy::MAX_RETRIES, // Max retries
         [503, 429] // HTTP status codes to retry on
     );
     $request->setBackoff($backoff);
     
     try {
         $response = $request->execute();
     } catch (Google\Service\Exception $e) {
         // Handle the exception (log, report, etc.)
     }

     • Global Retry Configuration: Configure retry settings globally for the client using setClientConfig().

     $client = new Google\Client();
     $client->setClientConfig([
         'retry' => [
             'retries' => 3, // Number of retries
             'http_codes' => [503, 429], // Status codes to retry
             // ... other retry options
         ]
     ]);

  4. Handle Token Expiration: The library automatically handles token refresh. However, be prepared to handle cases where the refresh token itself is invalid or revoked.
  5. Log Errors: Log any errors encountered, but never log the access token or refresh token.

• Threats Mitigated:

  • Token Expiration/Revocation (Severity: Medium): Ensures the application can gracefully handle token issues.
  • Transient API Errors (Severity: Low): Improves application resilience by retrying temporary errors.
  • Denial of Service (DoS) (Severity: Medium): Backoff helps prevent overwhelming the API.

• Impact:

  • Token Expiration/Revocation: Improves application stability.
  • Transient API Errors: Reduces application errors.
  • Denial of Service: Helps prevent DoS.

• Currently Implemented:

  • try-catch blocks are used around API calls.

• Missing Implementation:

  • setBackoff() or global retry configuration is not currently implemented. Need to add retry logic with exponential backoff.

Mitigation Strategy: Data Minimization (Using fields Parameter)

• Mitigation Strategy: Request only the necessary data fields using the fields parameter in API requests.

• Description:

  1. Identify Required Fields: Determine the minimum set of data fields your application needs from the API response.
  2. Use the fields Parameter: Many Google APIs support a fields parameter that allows you to specify which fields to return. Use this parameter in your API requests.

     $optParams = [
         'fields' => 'items(id,name,email)' // Only retrieve id, name, and email
     ];
     $results = $service->users->listUsers($optParams);

  3. Consult API Documentation: Refer to the specific API documentation to understand the syntax and supported fields for the fields parameter.
  4. Avoid *: Avoid using fields=* (which retrieves all fields) unless absolutely necessary.

• Threats Mitigated:

  • Data Exposure (Severity: Medium): Reduces the amount of data retrieved, minimizing the potential impact of a data breach.
  • Performance Issues (Severity: Low): Retrieving only necessary data can improve API response times and reduce bandwidth usage.

• Impact:

  • Data Exposure: Reduces the risk of exposing unnecessary data.
  • Performance Issues: Can improve performance.

• Currently Implemented:

  • Not consistently implemented. Some API calls retrieve all fields.

• Missing Implementation:

  • Need to review all API calls and add the fields parameter where appropriate to limit the data retrieved.