Using On-Demand Scanning in your Cloud Build pipeline

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Using On-Demand Scanning as part of your Cloud Build pipeline allows you to block builds if the container image has vulnerabilities with a severity matching a predefined level.

This tutorial shows you how to use Cloud Build to build your container image from the source code, scan it for vulnerabilities, check the severity levels of the vulnerabilities, and push the image to Artifact Registry if there are no vulnerabilities of a specific severity level.

We recommend that you create a new Google Cloud project for this tutorial, and complete the steps in an isolated environment.

Objectives

  • Build an image with Cloud Build.
  • Scan the built image with On-Demand Scanning.
  • Assess acceptable vulnerability levels.
  • Store the image in Artifact Registry.

Costs

This tutorial uses the following billable components of Google Cloud:

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.

When you finish this tutorial, you can avoid continued billing by deleting the resources you created. For more information, see Clean up.

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 Cloud project. Learn how to check if billing is enabled on a project.

  4. Enable the On-Demand Scanning, Cloud Build, and Artifact Registry APIs.

    Enable the APIs

  5. Install the Google Cloud CLI.
  6. To initialize the gcloud CLI, run the following command:

    gcloud init
  7. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  8. Make sure that billing is enabled for your Cloud project. Learn how to check if billing is enabled on a project.

  9. Enable the On-Demand Scanning, Cloud Build, and Artifact Registry APIs.

    Enable the APIs

  10. Install the Google Cloud CLI.
  11. To initialize the gcloud CLI, run the following command:

    gcloud init

Required roles

The service account that you use with Cloud Build requires the following roles:

The default Cloud Build service account has the required permissions for Artifact Registry repositories in the same project. If your repositories are in the same project that you use for Cloud Build, you only need to grant the On-Demand Scanning Admin role.

If you are using a user-provided service account for Cloud Build, you need to grant both roles.

Prepare your source file

For this tutorial you are going to build an image from a Dockerfile. A Dockerfile is a source file that contains instructions for Docker to build an image.

  1. Open a terminal, create a new directory named ods-tutorial, and navigate to it:

    mkdir ods-tutorial && cd ods-tutorial
    
  2. Create a file named Dockerfile with the following contents:

    # Debian10 image
    FROM gcr.io/google-appengine/debian10:latest
    
    # Ensures that the built image is always unique
    RUN apt-get update && apt-get -y install uuid-runtime && uuidgen > /IAMUNIQUE
    

Create an Artifact Registry repository

  1. Set the project ID to the same project where you enabled the APIs:

    gcloud config set project PROJECT_ID
    
  2. Create a Docker repository named ods-build-repo in the location us-central1:

    gcloud artifacts repositories create ods-build-repo --repository-format=docker \
    --location=us-central1 --description="Repository for scan and build"
    
  3. Verify that your repository was successfully created:

    gcloud artifacts repositories list
    

Build and scan

In this section you will run your build pipeline using a build config file. A build config file instructs Cloud Build how to perform several tasks based on your specifications.

  1. In the ods-tutorial/ folder, create the file cloudbuild.yaml with the following contents:

    steps:
       - id: build
         name: gcr.io/cloud-builders/docker
         entrypoint: /bin/bash
         args:
         - -c
         - |
           docker build -t us-central1-docker.pkg.dev/$_PROJECT_ID/ods-build-repo/ods-test:latest -f ./Dockerfile . &&
           docker image inspect us-central1-docker.pkg.dev/$_PROJECT_ID/ods-build-repo/ods-test:latest --format \
           '{{index .RepoTags 0}}@{{.Id}}' > /workspace/image-digest.txt &&
           cat image-digest.txt
       - id: scan
         name: gcr.io/google.com/cloudsdktool/cloud-sdk
         entrypoint: /bin/bash
         args:
         - -c
         - |
           gcloud artifacts docker images scan us-central1-docker.pkg.dev/$_PROJECT_ID/ods-build-repo/ods-test:latest \
           --format='value(response.scan)' > /workspace/scan_id.txt
       - id: severity check
         name: gcr.io/google.com/cloudsdktool/cloud-sdk
         entrypoint: /bin/bash
         args:
         - -c
         - |
           gcloud artifacts docker images list-vulnerabilities $(cat /workspace/scan_id.txt) \
           --format='value(vulnerability.effectiveSeverity)' | if grep -Exq $_SEVERITY; \
           then echo 'Failed vulnerability check' && exit 1; else exit 0; fi
       - id: push
         name: gcr.io/cloud-builders/docker
         entrypoint: /bin/bash
         args:
         - -c
         - |
           docker push us-central1-docker.pkg.dev/$_PROJECT_ID/ods-build-repo/ods-test:latest
    images: ['us-central1-docker.pkg.dev/$_PROJECT_ID/ods-build-repo/ods-test:latest']
    
    

    This file includes the location and repository previously created in Artifact Registry. If you decide to use different values, modify the cloudbuild.yaml file accordingly. The values for PROJECT_ID and SEVERITY are passed to the script in the build command.

  2. Specify the vulnerability SEVERITY levels you want to block and start your build.

    You can use the following values for SEVERITY:

    • CRITICAL
    • HIGH
    • MEDIUM
    • LOW
    • MINIMAL

    You can specify multiple severities by using a regular expression.

    In the following example, you specify both the CRITICAL and HIGH severity values. This instructs Cloud Build to check for vulnerabilities that are classified at or above the HIGH severity level.

    gcloud builds submit --substitutions=_PROJECT_ID=PROJECT_ID,_SEVERITY='"CRITICAL|HIGH"' \
    --config cloudbuild.yaml
    

    Where

    • PROJECT_ID is your project ID.
    • SEVERITY allows you to set the severity levels that you want to block. If On-Demand Scanning finds vulnerabilities that match any of the specified severity levels, your build fails.

Understand your results

When you set your SEVERITY value to CRITICAL|HIGH, after On-Demand Scanning scans for vulnerabilities, it will see if there are any at the HIGH level and the more severe CRITICAL level. If no matching vulnerabilities are found in your image, your build succeeds and Cloud Build pushes your image to Artifact Registry.

The output is similar to the following:

DONE
--------------------------------------------------------------------------------------------------------------------------------------------

ID                                    CREATE_TIME                DURATION  SOURCE                                                                                         IMAGES                                                                        STATUS
abb3ce73-6ae8-41d1-9080-7d74a7ecd7bc  2021-03-15T06:50:32+00:00  1M48S     gs://ods-tests_cloudbuild/source/1615791031.906807-a648d10faf4a46d695c163186a6208d5.tgz  us-central1-docker.pkg.dev/ods-tests/ods-build-repo/ods-test (+1 more)  SUCCESS

If On-Demand Scanning finds HIGH or CRITICAL vulnerabilities in your image, then the scan build step fails, subsequent build steps do not start, and Cloud Build does not push an image to Artifact Registry.

The output is similar to the following:

Step #2 - "severity check": Failed vulnerability check
Finished Step #2 - "severity check"
ERROR
ERROR: build step 2 "gcr.io/cloud-builders/gcloud" failed: step exited with non-zero status: 1

In this tutorial, your results may vary, because the sample source code is a publicly available Linux distribution, debian10:latest. Linux distributions and related vulnerability data receive updates on an ongoing basis.

To learn about additional Google Cloud tools and best practices to help protect your software supply chain, see Software Delivery Shield overview.

For more information on Linux vulnerability management best practices, you can use free online training provided by the Linux Foundation. See Developing Secure Software.

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.

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.

Delete individual resources

Before you remove the repository, ensure that any images you want to keep are available in another location.

To delete the repository:

Console

  1. Open the Repositories page in the Google Cloud console.

    Open the Repositories page

  2. In the repository list, select the ods-build-repo repository.

  3. Click Delete.

gcloud

To delete ods-build-repo the repository, run the following command:

gcloud artifacts repositories delete ods-build-repo --location=us-central1

What's next