Container Scanning (ULTIMATE)

Introduced in GitLab Ultimate 10.4.

Overview

If you are using GitLab CI/CD, you can check your Docker images (or more precisely the containers) for known vulnerabilities by using Clair and klar, two open source tools for Vulnerability Static Analysis for containers.

You can take advantage of Container Scanning by either including the CI job in your existing .gitlab-ci.yml file or by implicitly using Auto Container Scanning that is provided by Auto DevOps.

GitLab checks the Container Scanning report, compares the found vulnerabilities between the source and target branches, and shows the information right on the merge request.

Container Scanning Widget

Use cases

If you distribute your application with Docker, then there's a great chance that your image is based on other Docker images that may in turn contain some known vulnerabilities that could be exploited.

Having an extra job in your pipeline that checks for those vulnerabilities, and the fact that they are displayed inside a merge request, makes it very easy to perform audits for your Docker-based apps.

Requirements

To enable Container Scanning in your pipeline, you need:

  • A GitLab Runner with the docker or kubernetes executor.

  • Docker 18.09.03 or higher installed on the machine where the Runners are running. If you're using the shared Runners on GitLab.com, this is already the case.

  • To build and push your Docker image to your project's Container Registry. The name of the Docker image should match the following scheme:

    $CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG:$CI_COMMIT_SHA

    The variables above can be found in the predefined environment variables document.

Configuration

For GitLab 11.9 and later, to enable Container Scanning, you must include the Container-Scanning.gitlab-ci.yml template that's provided as a part of your GitLab installation. For GitLab versions earlier than 11.9, you can copy and use the job as defined in that template.

Add the following to your .gitlab-ci.yml file:

include:
  template: Container-Scanning.gitlab-ci.yml

The included template will:

  1. Create a container_scanning job in your CI/CD pipeline.
  2. Pull the already built Docker image from your project's Container Registry (see requirements) and scan it for possible vulnerabilities.

The results will be saved as a Container Scanning report artifact that you can later download and analyze. Due to implementation limitations, we always take the latest Container Scanning artifact available. Behind the scenes, the GitLab Klar analyzer is used and runs the scans.

Example

The following is a sample .gitlab-ci.yml that will build your Docker Image, push it to the container registry and run Container Scanning.

variables:
  DOCKER_DRIVER: overlay2

services:
  - docker:stable-dind

stages:
  - build
  - test

include:
  - template: Container-Scanning.gitlab-ci.yml

build:
  image: docker:stable
  stage: build
  variables:
    IMAGE: $CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG:$CI_COMMIT_SHA
  script:
    - docker info
    - docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
    - docker build -t $IMAGE .
    - docker push $IMAGE

Vulnerability Whitelisting

If you want to whitelist specific vulnerabilities, you'll need to:

  1. Set GIT_STRATEGY: fetch in your .gitlab-ci.yml file by following the instructions described in the overriding the Container Scanning template section of this document.
  2. Define the whitelisted vulnerabilities in a YAML file named clair-whitelist.yml which must use the format described in the following whitelist example file.
  3. Add the clair-whitelist.yml file to the git repository of your project

Overriding the Container Scanning template

If you want to override the job definition (for example, change properties like variables), you need to declare a container_scanning job after the template inclusion and specify any additional keys under it. For example:

include:
  - template: Container-Scanning.gitlab-ci.yml

container_scanning:
  variables:
    GIT_STRATEGY: fetch

Available variables

Container Scanning can be configured using environment variables.

Environment Variable Description Default
KLAR_TRACE Set to true to enable more verbose output from klar. "false"
DOCKER_USER Username for accessing a Docker registry requiring authentication. $CI_REGISTRY_USER
DOCKER_PASSWORD Password for accessing a Docker registry requiring authentication. $CI_REGISTRY_PASSWORD
CLAIR_OUTPUT Severity level threshold. Vulnerabilities with severity level higher than or equal to this threshold will be outputted. Supported levels are Unknown, Negligible, Low, Medium, High, Critical and Defcon1. Unknown
REGISTRY_INSECURE Allow Klar to access insecure registries (HTTP only). Should only be set to true when testing the image locally. "false"
CLAIR_VULNERABILITIES_DB_URL This variable is explicitly set in the services section of the Container-Scanning.gitlab-ci.yml file and defaults to clair-vulnerabilities-db. This value represents the address that the postgres server hosting the vulnerabilities definitions is running on and shouldn't be changed unless you're running the image locally as described in the Running the scanning tool section of the GitLab klar analyzer readme. clair-vulnerabilities-db
CI_APPLICATION_REPOSITORY Docker repository URL for the image to be scanned. $CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG
CI_APPLICATION_TAG Docker respository tag for the image to be scanned. $CI_COMMIT_SHA
CLAIR_DB_IMAGE The Docker image name and tag for the postgres server hosting the vulnerabilities definitions. It can be useful to override this value with a specific version, for example, to provide a consistent set of vulnerabilities for integration testing purposes, or to refer to a locally hosted vulnerabilities database for an on-premise air-gapped installation. arminc/clair-db:latest
CLAIR_DB_IMAGE_TAG (DEPRECATED - use CLAIR_DB_IMAGE instead) The Docker image tag for the postgres server hosting the vulnerabilities definitions. It can be useful to override this value with a specific version, for example, to provide a consistent set of vulnerabilities for integration testing purposes. latest

Security Dashboard

The Security Dashboard is a good place to get an overview of all the security vulnerabilities in your groups, projects and pipelines. Read more about the Security Dashboard.

Interacting with the vulnerabilities

Once a vulnerability is found, you can interact with it. Read more on how to interact with the vulnerabilities.

Vulnerabilities database update

For more information about the vulnerabilities database update, check the maintenance table.

Running Container Scanning in an offline air-gapped installation

Container Scanning can be executed on an offline air-gapped GitLab Ultimate installation using the following process:

  1. Host the following Docker images on a local Docker container registry:

  2. Override the container scanning template in your .gitlab-ci.yml file to refer to the Docker images hosted on your local Docker container registry:

    include:
      - template: Container-Scanning.gitlab-ci.yml
    
    container_scanning:
      image: $CI_REGISTRY/namespace/gitlab-klar-analyzer
      variables:
        CLAIR_DB_IMAGE: $CI_REGISTRY/namespace/clair-vulnerabilities-db

It may be worthwhile to set up a scheduled pipeline to automatically build a new version of the vulnerabilities database on a preset schedule. You can use the following .gitlab-yml.ci as a template:

image: docker:stable

services:
  - docker:stable-dind

stages:
  - build

build_latest_vulnerabilities:
  stage: build
  script:
    - docker pull arminc/clair-db:latest
    - docker tag arminc/clair-db:latest $CI_REGISTRY/namespace/clair-vulnerabilities-db
    - docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
    - docker push $CI_REGISTRY/namespace/clair-vulnerabilities-db

The above template will work for a GitLab Docker registry running on a local installation, however, if you're using a non-GitLab Docker registry, you'll need to change the $CI_REGISTRY value and the docker login credentials to match the details of your local registry.

Troubleshooting

docker: Error response from daemon: failed to copy xattrs

When the GitLab Runner uses the Docker executor and NFS is used (e.g., /var/lib/docker is on an NFS mount), Container Scanning might fail with an error like the following:

docker: Error response from daemon: failed to copy xattrs: failed to set xattr "security.selinux" on /path/to/file: operation not supported.

This is a result of a bug in Docker which is now fixed. To prevent the error, ensure the Docker version that the Runner is using is 18.09.03 or higher. For more information, see issue #10241.