Cloud Audit Logs Tutorial


This tutorial demonstrates writing, deploying, and triggering an event-driven Cloud Run function with a Cloud Audit Logs trigger.

Cloud Run functions enables your functions to be triggered by Cloud Audit Logs entries. Many Google Cloud products write to Cloud Audit Logs when important in-product actions occur. These log entries can trigger the execution of Cloud Run functions in real time, which allows users to automatically process and/or act on them.

These logs are generated by many different events in Google Cloud and cover most Google Cloud products. Thus, Cloud Audit Logs triggers enable you to create functions that react to most state changes in Google Cloud.

This tutorial will show you how use Cloud Audit Logs triggers to label newly created Compute Engine instances with the name of the entity (person or service account) that created them.

If you are new to Cloud Audit Logs and want to learn more, see the Cloud Audit Logs documentation.

Objectives

  • Write an event-driven Cloud Run function that receives a Cloud Audit Logs event when a Compute Engine VM instance is created.
  • Trigger the function by creating a Compute Engine VM instance, at which point the instance will be labeled with the name of the entity (person or service account) that created it.

Costs

In this document, you use the following billable components of Google Cloud:

  • Cloud Run functions
  • Cloud Build
  • Pub/Sub
  • Artifact Registry
  • Eventarc
  • Cloud Logging
  • Compute Engine

For details, see Cloud Run functions pricing.

To generate a cost estimate based on your projected usage, use the pricing calculator. New Google Cloud users might be eligible for a free trial.

Before you begin

  1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.
  2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  3. Make sure that billing is enabled for your Google Cloud project.

  4. Enable the Cloud Functions, Cloud Run, Cloud Build, Artifact Registry, Eventarc, Logging, Compute Engine, and Pub/Sub APIs.

    Enable the APIs

  5. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  6. Make sure that billing is enabled for your Google Cloud project.

  7. Enable the Cloud Functions, Cloud Run, Cloud Build, Artifact Registry, Eventarc, Logging, Compute Engine, and Pub/Sub APIs.

    Enable the APIs

  8. Install and initialize the Cloud SDK.
  9. Update gcloud components:
  10. gcloud components update

    Need a command prompt? You can use the Google Cloud Shell. The Google Cloud Shell is a command line environment that already includes the Google Cloud SDK, so you don't need to install it. The Google Cloud SDK also comes preinstalled on Compute Engine Virtual Machines.

  11. Prepare your development environment.

Prerequisites

  1. Open the IAM & Admin > Audit Logs page in the Google Cloud console:

    Go to the IAM & Admin > Audit Logs page

  2. Enable the Cloud Audit Logs Admin Read, Data Read, and Data Write Log Types for the Compute Engine API:

    Screenshot that shows enabling audit logs for Compute Engine

  3. Check whether the Compute Engine Service Account has the Editor role. This service account will be used as the service identity for Cloud Run functions.

    Go to the IAM & Admin > IAM page

    Find the entry PROJECT_NUMBER-compute@developer.gserviceaccount.com in the table and look at the Roles column. If the column contains Editor you can skip the following steps. Otherwise, go to the next steps and assign the necessary roles to the service account.

  4. Grant the eventarc.eventReceiver role to the project's Compute Engine service account:

    PROJECT_ID=$(gcloud config get-value project)
    PROJECT_NUMBER=$(gcloud projects list --filter="project_id:$PROJECT_ID" --format='value(project_number)')
    
    # Allow service account token creation
    gcloud projects add-iam-policy-binding $PROJECT_ID \
     --member serviceAccount:$PROJECT_NUMBER-compute@developer.gserviceaccount.com \
     --role roles/eventarc.eventReceiver
    
  5. Grant the run.invoker role to the project's Compute Engine service account so that the Pub/Sub trigger can execute the function:

    PROJECT_ID=$(gcloud config get-value project)
    PROJECT_NUMBER=$(gcloud projects list --filter="project_id:$PROJECT_ID" --format='value(project_number)')
    
    # Allow service account token creation
    gcloud projects add-iam-policy-binding $PROJECT_ID \
     --member serviceAccount:$PROJECT_NUMBER-compute@developer.gserviceaccount.com \
     --role roles/run.invoker
    
  6. Grant the compute.instanceAdmin role to the project's Compute Engine service account so that the function code has the necessary permissions to get VM instances and set labels on them:

    PROJECT_ID=$(gcloud config get-value project)
    PROJECT_NUMBER=$(gcloud projects list --filter="project_id:$PROJECT_ID" --format='value(project_number)')
    
    # Allow service account token creation
    gcloud projects add-iam-policy-binding $PROJECT_ID \
     --member serviceAccount:$PROJECT_NUMBER-compute@developer.gserviceaccount.com \
     --role roles/compute.instanceAdmin
    

Preparing the application

  1. Clone the sample app repository to your local machine:

    Node.js

    git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Python

    git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Go

    git clone https://github.com/GoogleCloudPlatform/golang-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Java

    git clone https://github.com/GoogleCloudPlatform/java-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

  2. Change to the directory that contains the Cloud Run functions sample code for accessing Cloud Audit Logs:

    Node.js

    cd nodejs-docs-samples/functions/v2/autoLabelInstance/

    Python

    cd python-docs-samples/functions/v2/label_gce_instance/

    Go

    cd golang-samples/functions/functionsv2/label_gce_instance/

    Java

    cd java-docs-samples/functions/v2/label-compute-instance/

  3. Take a look at the sample code:

    Node.js

    const functions = require('@google-cloud/functions-framework');
    
    const compute = require('@google-cloud/compute');
    const instancesClient = new compute.InstancesClient();
    
    // Register a CloudEvent callback with the Functions Framework that labels
    // newly-created GCE instances with the entity (person or service account)
    // that created them.
    functions.cloudEvent('autoLabelInstance', async cloudEvent => {
      // Extract parameters from the CloudEvent + Cloud Audit Log data
      const payload = cloudEvent.data && cloudEvent.data.protoPayload;
      const authInfo = payload && payload.authenticationInfo;
      let creator = authInfo && authInfo.principalEmail;
    
      // Get relevant VM instance details from the CloudEvent's `subject` property
      // Example value:
      //   compute.googleapis.com/projects/<PROJECT>/zones/<ZONE>/instances/<INSTANCE>
      const params = cloudEvent.subject && cloudEvent.subject.split('/');
    
      // Validate data
      if (!creator || !params || params.length !== 7) {
        throw new Error('Invalid event structure');
      }
    
      // Format the 'creator' parameter to match GCE label validation requirements
      creator = creator.toLowerCase().replace(/\W/g, '_');
    
      // Get the newly-created VM instance's label fingerprint
      // This is required by the Compute Engine API to prevent duplicate labels
      const getInstanceRequest = {
        project: params[2],
        zone: params[4],
        instance: params[6],
      };
      const [instance] = await instancesClient.get(getInstanceRequest);
    
      // Label the instance with its creator
      const setLabelsRequest = Object.assign(
        {
          instancesSetLabelsRequestResource: {
            labels: {creator},
            labelFingerprint: instance.labelFingerprint,
          },
        },
        getInstanceRequest
      );
    
      return instancesClient.setLabels(setLabelsRequest);
    });

    Python

    import re
    
    from google.api_core.exceptions import GoogleAPIError
    from google.cloud import compute_v1
    from google.cloud.compute_v1.types import compute
    
    instances_client = compute_v1.InstancesClient()
    
    
    # CloudEvent function that labels newly-created GCE instances
    # with the entity (user or service account) that created them.
    #
    # @param {object} cloudevent A CloudEvent containing the Cloud Audit Log entry.
    # @param {object} cloudevent.data.protoPayload The Cloud Audit Log entry.
    def label_gce_instance(cloudevent):
        # Extract parameters from the CloudEvent + Cloud Audit Log data
        payload = cloudevent.data.get("protoPayload", dict())
        auth_info = payload.get("authenticationInfo", dict())
        creator = auth_info.get("principalEmail")
    
        # Get relevant VM instance details from the cloudevent's `subject` property
        # Example value:
        #   compute.googleapis.com/projects/<PROJECT_ID>/zones/<ZONE_ID>/instances/<INSTANCE_NAME>
        instance_params = cloudevent["subject"].split("/")
    
        # Validate data
        if not creator or not instance_params or len(instance_params) != 7:
            # This is not something retries will fix, so don't throw an Exception
            # (Thrown exceptions trigger retries *if* you enable retries in GCF.)
            print("ERROR: Invalid `principalEmail` and/or CloudEvent `subject`.")
            return
    
        instance_project = instance_params[2]
        instance_zone = instance_params[4]
        instance_name = instance_params[6]
    
        # Format the 'creator' parameter to match GCE label validation requirements
        creator = re.sub("\\W", "_", creator.lower())
    
        # Get the newly-created VM instance's label fingerprint
        # This is required by the Compute Engine API to prevent duplicate labels
        instance = instances_client.get(
            project=instance_project, zone=instance_zone, instance=instance_name
        )
    
        # Construct API call to label the VM instance with its creator
        request_init = {
            "project": instance_project,
            "zone": instance_zone,
            "instance": instance_name,
        }
        request_init[
            "instances_set_labels_request_resource"
        ] = compute.InstancesSetLabelsRequest(
            label_fingerprint=instance.label_fingerprint, labels={"creator": creator}
        )
        request = compute.SetLabelsInstanceRequest(request_init)
    
        # Perform instance-labeling API call
        try:
            instances_client.set_labels_unary(request)
            print(f"Labelled VM instance {instance_name} with creator: {creator}")
        except GoogleAPIError as e:
            # Swallowing the exception means failed invocations WON'T be retried
            print("Label operation failed", e)
    
            # Uncomment the line below to retry failed invocations.
            # (You'll also have to enable retries in Cloud Functions itself.)
            # raise e
    
        return
    
    

    Go

    
    // Package helloworld provides a set of Cloud Functions samples.
    package helloworld
    
    import (
    	"context"
    	"fmt"
    	"log"
    	"regexp"
    	"strings"
    
    	compute "cloud.google.com/go/compute/apiv1"
    	"cloud.google.com/go/compute/apiv1/computepb"
    	"github.com/GoogleCloudPlatform/functions-framework-go/functions"
    	"github.com/cloudevents/sdk-go/v2/event"
    	"google.golang.org/protobuf/proto"
    )
    
    // AuditLogEntry represents a LogEntry as described at
    // https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry
    type AuditLogEntry struct {
    	ProtoPayload *AuditLogProtoPayload `json:"protoPayload"`
    }
    
    // AuditLogProtoPayload represents AuditLog within the LogEntry.protoPayload
    // See https://cloud.google.com/logging/docs/reference/audit/auditlog/rest/Shared.Types/AuditLog
    type AuditLogProtoPayload struct {
    	MethodName         string                 `json:"methodName"`
    	ResourceName       string                 `json:"resourceName"`
    	AuthenticationInfo map[string]interface{} `json:"authenticationInfo"`
    }
    
    var client *compute.InstancesClient
    
    func init() {
    	// Create an Instances Client
    	var err error
    	client, err = compute.NewInstancesRESTClient(context.Background())
    	if err != nil {
    		log.Fatalf("Failed to create instances client: %s", err)
    	}
    
    	functions.CloudEvent("label-gce-instance", labelGceInstance)
    }
    
    // Cloud Function that receives GCE instance creation Audit Logs, and adds a
    // `creator` label to the instance.
    func labelGceInstance(ctx context.Context, ev event.Event) error {
    	// Extract parameters from the Cloud Event and Cloud Audit Log data
    	logentry := &AuditLogEntry{}
    	if err := ev.DataAs(logentry); err != nil {
    		err = fmt.Errorf("event.DataAs() : %w", err)
    		log.Printf("Error parsing proto payload: %s", err)
    		return err
    	}
    	payload := logentry.ProtoPayload
    	creator, ok := payload.AuthenticationInfo["principalEmail"]
    	if !ok {
    		err := fmt.Errorf("principalEmail not found in cloud event payload: %v", payload)
    		log.Printf("creator email not found: %s", err)
    		return err
    	}
    
    	// Get relevant VM instance details from the event's `subject` property
    	// Subject format:
    	// compute.googleapis.com/projects/<PROJECT>/zones/<ZONE>/instances/<INSTANCE>
    	paths := strings.Split(ev.Subject(), "/")
    	if len(paths) < 6 {
    		return fmt.Errorf("invalid event subject: %s", ev.Subject())
    	}
    	project := paths[2]
    	zone := paths[4]
    	instance := paths[6]
    
    	// Sanitize the `creator` label value to match GCE label requirements
    	// See https://cloud.google.com/compute/docs/labeling-resources#requirements
    	labelSanitizer := regexp.MustCompile("[^a-z0-9_-]+")
    	creatorstring := labelSanitizer.ReplaceAllString(strings.ToLower(creator.(string)), "_")
    
    	// Get the newly-created VM instance's label fingerprint
    	// This is a requirement of the Compute Engine API and avoids duplicate labels
    	inst, err := client.Get(ctx, &computepb.GetInstanceRequest{
    		Project:  project,
    		Zone:     zone,
    		Instance: instance,
    	})
    	if err != nil {
    		err = fmt.Errorf("could not retrieve GCE instance: %s", err)
    		log.Print(err)
    		return err
    	}
    	if v, ok := inst.Labels["creator"]; ok {
    		// Instance already has a creator label.
    		log.Printf("instance %s already labeled with creator: %s", instance, v)
    		return nil
    	}
    
    	// Add the creator label to the instance
    	op, err := client.SetLabels(ctx, &computepb.SetLabelsInstanceRequest{
    		Project:  project,
    		Zone:     zone,
    		Instance: instance,
    		InstancesSetLabelsRequestResource: &computepb.InstancesSetLabelsRequest{
    			LabelFingerprint: proto.String(inst.GetLabelFingerprint()),
    			Labels: map[string]string{
    				"creator": creatorstring,
    			},
    		},
    	})
    	if err != nil {
    		log.Fatalf("Could not label GCE instance: %s", err)
    	}
    	log.Printf("Creator label added to %s in operation %v", instance, op)
    	return nil
    }
    

    Java

    import com.google.cloud.compute.v1.GetInstanceRequest;
    import com.google.cloud.compute.v1.Instance;
    import com.google.cloud.compute.v1.InstancesClient;
    import com.google.cloud.compute.v1.InstancesSetLabelsRequest;
    import com.google.cloud.compute.v1.SetLabelsInstanceRequest;
    import com.google.cloud.functions.CloudEventsFunction;
    import com.google.gson.Gson;
    import com.google.gson.JsonObject;
    import com.google.gson.JsonSyntaxException;
    import io.cloudevents.CloudEvent;
    import java.nio.charset.StandardCharsets;
    import java.util.logging.Logger;
    
    public class AutoLabelInstance implements CloudEventsFunction {
      private static final Logger logger = Logger.getLogger(AutoLabelInstance.class.getName());
    
      @Override
      public void accept(CloudEvent event) throws Exception {
        // Extract CloudEvent data
        if (event.getData() != null) {
          String cloudEventData = new String(event.getData().toBytes(), StandardCharsets.UTF_8);
    
          // Convert data to JSON
          JsonObject eventData;
          try {
            Gson gson = new Gson();
            eventData = gson.fromJson(cloudEventData, JsonObject.class);
          } catch (JsonSyntaxException error) {
            throw new RuntimeException("CloudEvent data is not valid JSON: " + error.getMessage());
          }
    
          // Extract the Cloud Audit Logging entry from the data's protoPayload
          JsonObject payload = eventData.getAsJsonObject("protoPayload");
          JsonObject auth = payload.getAsJsonObject("authenticationInfo");
    
          // Extract the email address of the authenticated user
          // (or service account on behalf of third party principal) making the request
          String creator = auth.get("principalEmail").getAsString();
          if (creator == null) {
            throw new RuntimeException("`principalEmail` not found in protoPayload.");
          }
          // Format the 'creator' parameter to match GCE label validation requirements
          creator = creator.toLowerCase().replaceAll("\\W", "-");
    
          // Get relevant VM instance details from the CloudEvent `subject` property
          // Example: compute.googleapis.com/projects/<PROJECT>/zones/<ZONE>/instances/<INSTANCE>
          String subject = event.getSubject();
          if (subject == null || subject == "") {
            throw new RuntimeException("Missing CloudEvent `subject`.");
          }
          String[] params = subject.split("/");
    
          // Validate data
          if (params.length < 7) {
            throw new RuntimeException("Can not parse resource from CloudEvent `subject`: " + subject);
          }
          String project = params[2];
          String zone = params[4];
          String instanceName = params[6];
    
          // Instantiate the Compute Instances client
          try (InstancesClient instancesClient = InstancesClient.create()) {
            // Get the newly-created VM instance's label fingerprint
            // This is required by the Compute Engine API to prevent duplicate labels
            GetInstanceRequest getInstanceRequest =
                GetInstanceRequest.newBuilder()
                    .setInstance(instanceName)
                    .setProject(project)
                    .setZone(zone)
                    .build();
            Instance instance = instancesClient.get(getInstanceRequest);
            String fingerPrint = instance.getLabelFingerprint();
    
            // Label the instance with its creator
            SetLabelsInstanceRequest setLabelRequest =
                SetLabelsInstanceRequest.newBuilder()
                    .setInstance(instanceName)
                    .setProject(project)
                    .setZone(zone)
                    .setInstancesSetLabelsRequestResource(
                        InstancesSetLabelsRequest.newBuilder()
                            .putLabels("creator", creator)
                            .setLabelFingerprint(fingerPrint)
                            .build())
                    .build();
    
            instancesClient.setLabelsAsync(setLabelRequest);
            logger.info(
                String.format(
                    "Adding label, \"{'creator': '%s'}\", to instance, \"%s\".",
                    creator, instanceName));
          } catch (Exception error) {
            throw new RuntimeException(
                String.format(
                    "Error trying to label VM instance, %s: %s", instanceName, error.toString()));
          }
        }
      }
    }

Deploying the function

To deploy the function with a Cloud Audit Logs trigger, run the following command in the directory that contains the sample code (or in the case of Java, the pom.xml file):

Node.js

gcloud functions deploy nodejs-cal-function \
--gen2 \
--runtime=nodejs20 \
--region=REGION \
--source=. \
--entry-point=autoLabelInstance \
--trigger-location=REGION \
--trigger-event-filters="type=google.cloud.audit.log.v1.written" \
--trigger-event-filters="serviceName=compute.googleapis.com" \
--trigger-event-filters="methodName=v1.compute.instances.insert"

Use the --runtime flag to specify the runtime ID of a supported Node.js version to run your function.

Python

gcloud functions deploy python-cal-function \
--gen2 \
--runtime=python312 \
--region=REGION \
--source=. \
--entry-point=label_gce_instance \
--trigger-location=REGION \
--trigger-event-filters="type=google.cloud.audit.log.v1.written" \
--trigger-event-filters="serviceName=compute.googleapis.com" \
--trigger-event-filters="methodName=v1.compute.instances.insert"

Use the --runtime flag to specify the runtime ID of a supported Python version to run your function.

Go

gcloud functions deploy go-cal-function \
--gen2 \
--runtime=go121 \
--region=REGION \
--source=. \
--entry-point=label-gce-instance \
--trigger-location=REGION \
--trigger-event-filters="type=google.cloud.audit.log.v1.written" \
--trigger-event-filters="serviceName=compute.googleapis.com" \
--trigger-event-filters="methodName=v1.compute.instances.insert"

Use the --runtime flag to specify the runtime ID of a supported Go version to run your function.

Java

gcloud functions deploy java-cal-function \
--gen2 \
--runtime=java17 \
--region=REGION \
--source=. \
--entry-point=functions.AutoLabelInstance \
--memory=512MB \
--trigger-location=REGION \
--trigger-event-filters="type=google.cloud.audit.log.v1.written" \
--trigger-event-filters="serviceName=compute.googleapis.com" \
--trigger-event-filters="methodName=v1.compute.instances.insert"

Use the --runtime flag to specify the runtime ID of a supported Java version to run your function.

The deployment command above specifies the following event filter parameters that correspond to VM creation:

  • type: The Cloud Audit Logs event type (google.cloud.audit.log.v1.written).
  • serviceName: The name of the Google Cloud service that generated the log entry, in this case compute.googleapis.com.
  • methodName: The name of the API method that generated the log entry, in this case v1.compute.instances.insert.

Triggering the function

Once the function is deployed, you can confirm that it works:

  1. Create a Compute Engine VM instance:

    gcloud compute instances create YOUR_INSTANCE_NAME --zone YOUR_ZONE
    

    Alternatively, go to the Google Cloud console and click Create a VM.

  2. Run the following command to verify that the instance has been labeled appropriately:

    gcloud compute instances describe YOUR_INSTANCE_NAME \
        --zone YOUR_ZONE \
        --format 'value(labels)'
    

    You should see a label with the format creator=YOURNAMEYOUR_DOMAIN.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used in this tutorial, either delete the project that contains the resources, or keep the project and delete the individual resources.

Deleting the project

The easiest way to eliminate billing is to delete the project that you created for the tutorial.

To delete the project:

  1. In the Google Cloud console, go to the Manage resources page.

    Go to Manage resources

  2. In the project list, select the project that you want to delete, and then click Delete.
  3. In the dialog, type the project ID, and then click Shut down to delete the project.

Deleting the function

Deleting Cloud Run functions does not remove any resources stored in Cloud Storage.

To delete the Cloud Run function you created in this tutorial, run the following command:

Node.js

gcloud functions delete nodejs-cal-function --gen2 --region REGION 

Python

gcloud functions delete python-cal-function --gen2 --region REGION 

Go

gcloud functions delete go-cal-function --gen2 --region REGION 

Java

gcloud functions delete java-cal-function --gen2 --region REGION 

You can also delete Cloud Run functions from the Google Cloud console.

Deleting the Compute Engine VM instance

To delete the Compute Engine VM instance you created in this tutorial, run the following command:

gcloud compute instances delete YOUR_INSTANCE_NAME --zone YOUR_ZONE