The following examples runs in GitLab CI in a repository containing a Docker image's definition and contents. Triggered by a commit, the pipeline builds the image. If the commit was to the default branch, it uses Docker Scout to get a CVE report. If the commit was to a different branch, it uses Docker Scout to compare the new version to the current published version.

Steps#

First, set up the rest of the workflow. There's a lot that's not specific to Docker Scout but needed to create the images to compare.

Add the following to a .gitlab-ci.yml file at the root of your repository.

docker-build:
  image: docker:latest
  stage: build
  services:
    - docker:dind
  before_script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY

    # Install curl and the Docker Scout CLI
    - |
      apk add --update curl
      curl -sSfL https://raw.githubusercontent.com/docker/scout-cli/main/install.sh | sh -s --
      apk del curl
      rm -rf /var/cache/apk/*
    # Login to Docker Hub required for Docker Scout CLI
    - docker login -u "$DOCKER_HUB_USER" -p "$DOCKER_HUB_PAT"

This sets up the workflow to build Docker images with Docker-in-Docker mode, running Docker inside a container.

It then downloads curl and the Docker Scout CLI plugin, logs into the Docker registry using environment variables defined in your repository's settings.

Add the following to the YAML file:

script:
  - |
    if [[ "$CI_COMMIT_BRANCH" == "$CI_DEFAULT_BRANCH" ]]; then
      tag=""
      echo "Running on default branch '$CI_DEFAULT_BRANCH': tag = 'latest'"
    else
      tag=":$CI_COMMIT_REF_SLUG"
      echo "Running on branch '$CI_COMMIT_BRANCH': tag = $tag"
    fi
  - docker build --pull -t "$CI_REGISTRY_IMAGE${tag}" .
  - |
    if [[ "$CI_COMMIT_BRANCH" == "$CI_DEFAULT_BRANCH" ]]; then
      # Get a CVE report for the built image and fail the pipeline when critical or high CVEs are detected
      docker scout cves "$CI_REGISTRY_IMAGE${tag}" --exit-code --only-severity critical,high
    else
      # Compare image from branch with latest image from the default branch and fail if new critical or high CVEs are detected
      docker scout compare "$CI_REGISTRY_IMAGE${tag}" --to "$CI_REGISTRY_IMAGE:latest" --exit-code --only-severity critical,high --ignore-unchanged
    fi

  - docker push "$CI_REGISTRY_IMAGE${tag}"

This creates the flow mentioned previously. If the commit was to the default branch, Docker Scout generates a CVE report. If the commit was to a different branch, Docker Scout compares the new version to the current published version. It only shows critical or high-severity vulnerabilities and ignores vulnerabilities that haven't changed since the last analysis.

Add the following to the YAML file:

rules:
  - if: $CI_COMMIT_BRANCH
    exists:
      - Dockerfile

These final lines ensure that the pipeline only runs if the commit contains a Dockerfile and if the commit was to the CI branch.

Video walkthrough#

The following is a video walkthrough of the process of setting up the workflow with GitLab.