Ensure That the Log Metric Filter and Alerts Exist for Audit Configuration Changes

Google Cloud Platform (GCP) services write audit log entries to the Admin Activity and Data Access logs to help answer the questions of, "who did what, where?", and when within GCP projects.
Cloud audit logging records information includes the identity of the API caller, the time of the API call, the source IP address of the API caller, the request parameters, and the response elements returned by GCP services. Cloud audit logging provides a history of GCP API calls for an account, including API calls made via the console, SDKs, command-line tools, and other GCP services. Admin activity and data access logs produced by cloud audit logging enable security analysis, resource change tracking, and compliance auditing.
Configuring the metric filter and alerts for audit configuration changes ensures the recommended state of audit configuration is maintained so that all activities in the project are audit-able at any point in time.

Risk Level: Low
Cloud Entity: GCP AlertPolicy
CloudGuard Rule ID: D9.GCP.LOG.20
Covered by Spectral: No
Category: Management Tools

GSL LOGIC

AlertPolicy where conditions contain [ conditionThreshold.logName] and enabled='true' should have conditions contain [ getResource('LogBasedMetric',conditionThreshold.logName)  getValue('filter') ='protoPayload.methodName="SetIamPolicy" AND protoPayload.serviceData.policyDelta.auditConfigDeltas:*']

REMEDIATION

From Portal
Create the prescribed Log Metric:

  1. Go to Logging;Logs-based Metrics by visiting https://console.cloud.google.com/logs/metrics and click "CREATE METRIC".
  2. Select Metric Type as Counter, enter Log metric name and Units to 1.
  3. Clear any text and add:
protoPayload.methodName="SetIamPolicy" AND protoPayload.serviceData.policyDelta.auditConfigDeltas:*
  1. Click CREATE METRIC. The logs display based on the filter text entered by the user.

Create the prescribed alert policy:

  1. Identify the newly created metric under the section User-defined Metrics at https://console.cloud.google.com/logs/metrics.
  2. Click the 3-dot icon in the rightmost column for the new metric and select 'Create alert from Metric'. A new page appears.
  3. Fill out the alert policy configuration and click Save. Choose the alerting threshold and configuration that makes sense for the user's organization. For example, a threshold of zero(0) for the most recent value will ensure that a notification is triggered for every owner change in the user's project:
  4. Configure the desired notification channels in the section Notifications.
  5. Name the policy and click Save.

From Command Line

  1. Create the prescribed log metric. Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/beta/logging/metrics/create
    use the command:
gcloud beta logging metrics create METRIC_NAME --description="DESCRIPTION" --log-filter="LOG_FILTER"
  1. You can find the notification channel ID using:
gcloud alpha monitoring channels list --filter='displayName="channel_name"' --format='value(name)'
  1. Create the prescribed alert policy.Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/alpha/monitoring/policies/create
    -Create a json file with required properties and values for the policy(try creating a policy from console and then download it's json to have a reference) and use the command:
gcloud alpha monitoring policies create --policy-from-file="policyfile.json"

From TF

  1. Create log based metric with expected filter
  2. Create an alerting policy with type 'metric' based on the previous created log based metric.

Resources;
google_logging_metric
google_monitoring_alert_policy

See below example;

resource "google_logging_metric" "my_log_metrics" {
	project = "My-project-id"
	name = "my-(custom)/metric"
	filter = "protoPayload.methodName="SetIamPolicy" AND protoPayload.serviceData.policyDelta.auditConfigDeltas:*"
	description = "..."
	metric_descriptor {
		metric_kind = "DELTA"
		value_type  = "INT64"
	}
}

And

resource "google_monitoring_alert_policy" "alert_policy" {
	project = "My-project-id"
	display_name = "My Alert Policy"
	combiner = "OR"
	conditions {
		display_name = "test condition"
		condition_threshold {
			filter = "metric.type="logging.googleapis.com/user/my-(custom)/metric" AND resource.type="cloud_composer_environment""
			duration   = "0s"
			comparison = "COMPARISON_GT"
		}
	}
}

References

  1. https://cloud.google.com/logging/docs/logs-based-metrics/
  2. https://cloud.google.com/monitoring/custom-metrics/
  3. https://cloud.google.com/monitoring/alerts/
  4. https://cloud.google.com/logging/docs/reference/tools/gcloud-logging
  5. https://cloud.google.com/logging/docs/audit/configure-data-access#getiampolicy-setiampolicy
  6. https://workbench.cisecurity.org/sections/507170/recommendations/827552

GCP AlertPolicy

Alerting policy describes the circumstances under which you want to be alerted and how you want to be notified. This page provides an overview of alerting policies

Compliance Frameworks

  • CloudGuard GCP All Rules Ruleset
  • GCP CIS Controls V 8
  • GCP CIS Foundations v. 1.0.0
  • GCP CIS Foundations v. 1.1.0
  • GCP CIS Foundations v. 1.2.0
  • GCP CIS Foundations v. 1.3.0
  • GCP CIS Foundations v. 2.0
  • GCP CloudGuard Best Practices
  • GCP MITRE ATT&CK Framework v12.1
  • GCP NIST 800-53 Rev 5