Cis GCP Foundations 2.5

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

Description

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.

Rationale

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.

Impact

Enabling of logging may result in your project being charged for the additional logs usage.

Audit Procedure

Using Google Cloud Console

Ensure the prescribed log metric is present:

1. Go to Logging/Logs-based Metrics by visiting https://console.cloud.google.com/logs/metrics.
2. In the User-defined Metrics section, ensure that at least one metric <Log_Metric_Name> is present with the filter text:

protoPayload.methodName="SetIamPolicy" AND
protoPayload.serviceData.policyDelta.auditConfigDeltas:*

Ensure that the prescribed alerting policy is present:

3. Go to Alerting by visiting https://console.cloud.google.com/monitoring/alerting.
4. Under the Policies section, ensure that at least one alert policy exists for the log metric above. Clicking on the policy should show that it is configured with a condition. For example, Violates when: Any logging.googleapis.com/user/<Log Metric Name> stream is above a threshold of 0 for greater than zero(0) seconds, means that the alert will trigger for any new owner change. Verify that the chosen alerting thresholds make sense for the user's organization.
5. Ensure that appropriate notification channels have been set up.

Using Google Cloud CLI

Ensure that the prescribed log metric is present:

1. List the log metrics:

gcloud beta logging metrics list --format json

2. Ensure that the output contains at least one metric with the filter set to:

protoPayload.methodName="SetIamPolicy" AND
protoPayload.serviceData.policyDelta.auditConfigDeltas:*

3. Note the value of the property metricDescriptor.type for the identified metric, in the format logging.googleapis.com/user/<Log Metric Name>.

Ensure that the prescribed alerting policy is present:

4. List the alerting policies:

gcloud alpha monitoring policies list --format json

5. Ensure that the output contains at least one alert policy where:

• conditions.conditionThreshold.filter is set to metric.type=\"logging.googleapis.com/user/<Log Metric Name>\"
• AND enabled is set to true

Expected Result

A log metric filter exists matching the audit configuration changes filter, and at least one alert policy is configured and enabled for it.

Remediation

Using Google Cloud Console

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. Click the down arrow symbol on the Filter Bar at the rightmost corner and select Convert to Advanced Filter.
3. Clear any text and add:

protoPayload.methodName="SetIamPolicy" AND
protoPayload.serviceData.policyDelta.auditConfigDeltas:*

4. Click Submit Filter. Display logs appear based on the filter text entered by the user.
5. In the Metric Editor menu on the right, fill out the name field. Set Units to 1 (default) and Type to Counter. This ensures that the log metric counts the number of log entries matching the user's advanced logs query.
6. Click Create Metric.

Create a prescribed Alert Policy:

1. Identify the new metric the user just created, 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 opens.
3. Fill out the alert policy configuration and click Save. Choose the alerting threshold and configuration that makes sense for the 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 project:

Set `Aggregator` to `Count`
Set `Configuration`:
- Condition: above
- Threshold: 0
- For: most recent value

4. Configure the desired notifications channels in the section Notifications.
5. Name the policy and click Save.

Using Google Cloud CLI

Create a prescribed Log Metric:

• Use the command: gcloud beta logging metrics create
• Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/beta/logging/metrics/create

Create prescribed Alert Policy:

• Use the command: gcloud alpha monitoring policies create
• Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/alpha/monitoring/policies/create

Default Value

By default, no log metrics and alert policies are configured.

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

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