• Requirements
• Configuration
  • Customizing the container scanning settings
    • Available variables
  • Overriding the container scanning template
  • Using a custom SSL CA certificate authority
  • Vulnerability allowlisting
  • Running container scanning in an offline environment
    • Requirements for offline container Scanning
      • Support for Custom Certificate Authorities
    • Make GitLab container scanning analyzer images available inside your Docker registry
    • Set container scanning CI/CD variables to use local container scanner analyzers
    • Automating container scanning vulnerability database updates with a pipeline
• Running the standalone container scanning tool
• Reports JSON format
• Security Dashboard
• Vulnerabilities database update
• Interacting with the vulnerabilities
• Solutions for vulnerabilities (auto-remediation)
• Troubleshooting
  • docker: Error response from daemon: failed to copy xattrs
  • Getting warning message gl-container-scanning-report.json: no matching files

Container Scanning

Your application’s Docker image may itself be based on Docker images that contain known vulnerabilities. By including an extra job in your pipeline that scans for those vulnerabilities and displays them in a merge request, you can use GitLab to audit your Docker-based apps. By default, container scanning in GitLab is based on Clair and Klar, which are open-source tools for vulnerability static analysis in containers. The GitLab Klar analyzer scans the containers and serves as a wrapper for Clair.

To integrate security scanners other than Clair and Klar into GitLab, see Security scanner integration.

You can enable container scanning by doing one of the following:

• Include the CI job in your existing .gitlab-ci.yml file.
• Implicitly use Auto Container Scanning, provided by Auto DevOps.

GitLab compares the found vulnerabilities between the source and target branches, and shows the information directly in the merge request.

Requirements

To enable container scanning in your pipeline, you need the following:

• GitLab Runner with the docker or kubernetes executor.
• Docker 18.09.03 or higher installed on the same computer as the runner. If you’re using the shared runners on GitLab.com, then this is already the case.
• An image matching Clair’s list of supported distributions.

• Build and push your Docker image to your project’s container registry. The name of the Docker image should use the following predefined CI/CD variables:

  $CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG:$CI_COMMIT_SHA
  

  You can use these directly in your .gitlab-ci.yml file:

  build:
    image: docker:19.03.12
    stage: build
    services:
      - docker:19.03.12-dind
    variables:
      IMAGE_TAG: $CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG:$CI_COMMIT_SHA
    script:
      - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
      - docker build -t $IMAGE_TAG .
      - docker push $IMAGE_TAG
  

Configuration

How you enable container scanning depends on your GitLab version:

• GitLab 11.9 and later: Include the Container-Scanning.gitlab-ci.yml template that comes with your GitLab installation.
• GitLab versions earlier than 11.9: Copy and use the job from the Container-Scanning.gitlab-ci.yml template.
• GitLab 13.6 introduced better support for FIPS by upgrading the CS_MAJOR_VERSION from 2 to 3.

To include the Container-Scanning.gitlab-ci.yml template (GitLab 11.9 and later), add the following to your .gitlab-ci.yml file:

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

The included template:

• Creates a container_scanning job in your CI/CD pipeline.
• Pulls the built Docker image from your project’s container registry (see requirements) and scans it for possible vulnerabilities.

GitLab saves the results as a Container Scanning report artifact that you can download and analyze later. When downloading, you always receive the most-recent artifact.

The following is a sample .gitlab-ci.yml that builds your Docker image, pushes it to the container registry, and scans the containers:

variables:
  DOCKER_DRIVER: overlay2

stages:
  - build
  - test

build:
  image: docker:stable
  stage: build
  services:
    - docker:19.03.12-dind
  variables:
    IMAGE: $CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG:$CI_COMMIT_SHA
  script:
    - docker info
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
    - docker build -t $IMAGE .
    - docker push $IMAGE

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

Customizing the container scanning settings

There may be cases where you want to customize how GitLab scans your containers. For example, you may want to enable more verbose output from Clair or Klar, access a Docker registry that requires authentication, and more. To change such settings, use the variables parameter in your .gitlab-ci.yml to set CI/CD variables. The variables you set in your .gitlab-ci.yml overwrite those in Container-Scanning.gitlab-ci.yml.

This example includes the container scanning template and enables verbose output from Clair by setting the CLAIR_OUTPUT variable to High:

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

variables:
  CLAIR_OUTPUT: High

Version 3 of the container_scanning Docker image uses centos:centos8 as the new base. It also removes the use of the start.sh script and instead executes the analyzer by default. Any customizations made to the container_scanning job’s before_script and after_script blocks may not work with the new version. To roll back to the previous alpine:3.11.3-based Docker image, you can specify the major version through the CS_MAJOR_VERSION variable.

This example includes the container scanning template and enables version 2 of the analyzer:

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

variables:
  CS_MAJOR_VERSION: '2'

Available variables

You can configure container scanning by using the following CI/CD variables:

Overriding the container scanning template

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

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

container_scanning:
  variables:
    GIT_STRATEGY: fetch

Using a custom SSL CA certificate authority

You can use the ADDITIONAL_CA_CERT_BUNDLE CI/CD variable to configure a custom SSL CA certificate authority, which is used to verify the peer when fetching Docker images from a registry which uses HTTPS. The ADDITIONAL_CA_CERT_BUNDLE value should contain the text representation of the X.509 PEM public-key certificate. For example, to configure this value in the .gitlab-ci.yml file, use the following:

container_scanning:
  variables:
    ADDITIONAL_CA_CERT_BUNDLE: |
        -----BEGIN CERTIFICATE-----
        MIIGqTCCBJGgAwIBAgIQI7AVxxVwg2kch4d56XNdDjANBgkqhkiG9w0BAQsFADCB
        ...
        jWgmPqF3vUbZE0EyScetPJquRFRKIesyJuBFMAs=
        -----END CERTIFICATE-----

The ADDITIONAL_CA_CERT_BUNDLE value can also be configured as a custom variable in the UI, either as a file, which requires the path to the certificate, or as a variable, which requires the text representation of the certificate.

Vulnerability allowlisting

To allowlist specific vulnerabilities, follow these steps:

1. Set GIT_STRATEGY: fetch in your .gitlab-ci.yml file by following the instructions in overriding the container scanning template.
2. Define the allowlisted vulnerabilities in a YAML file named vulnerability-allowlist.yml. This must use the format described in the allowlist example file.
3. Add the vulnerability-allowlist.yml file to your project’s Git repository.

Running container scanning in an offline environment

For self-managed GitLab instances in an environment with limited, restricted, or intermittent access to external resources through the internet, some adjustments are required for the container scanning job to successfully run. For more information, see Offline environments.

Requirements for offline container Scanning

To use container scanning in an offline environment, you need:

• GitLab Runner with the docker or kubernetes executor.
• To configure a local Docker container registry with copies of the container scanning analyzer images, found in the container scanning container registry.

Note that GitLab Runner has a default pull policy of always, meaning the runner tries to pull Docker images from the GitLab container registry even if a local copy is available. The GitLab Runner pull_policy can be set to if-not-present in an offline environment if you prefer using only locally available Docker images. However, we recommend keeping the pull policy setting to always if not in an offline environment, as this enables the use of updated scanners in your CI/CD pipelines.

Support for Custom Certificate Authorities

Support for custom certificate authorities was introduced in the following versions:

Make GitLab container scanning analyzer images available inside your Docker registry

For container scanning, import the following default images from registry.gitlab.com into your local Docker container registry:

registry.gitlab.com/gitlab-org/security-products/analyzers/klar
https://hub.docker.com/r/arminc/clair-db

The process for importing Docker images into a local offline Docker registry depends on your network security policy. Please consult your IT staff to find an accepted and approved process by which you can import or temporarily access external resources. Note that these scanners are updated periodically with new definitions, so consider if you are able to make periodic updates yourself.

For more information, see the specific steps on how to update an image with a pipeline.

For details on saving and transporting Docker images as a file, see Docker’s documentation on docker save, docker load, docker export, and docker import.

Set container scanning CI/CD variables to use local container scanner analyzers

1. 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
   

2. If your local Docker container registry is running securely over HTTPS, but you’re using a self-signed certificate, then you must set DOCKER_INSECURE: "true" in the above container_scanning section of your .gitlab-ci.yml.

Automating container scanning vulnerability database updates with a pipeline

It can be worthwhile to set up a scheduled pipeline to build a new version of the vulnerabilities database on a preset schedule. Automating this with a pipeline means you do not have to do it manually each time. You can use the following .gitlab-yml.ci as a template:

image: docker:stable

stages:
  - build

build_latest_vulnerabilities:
  stage: build
  services:
    - docker:19.03.12-dind
  script:
    - docker pull arminc/clair-db:latest
    - docker tag arminc/clair-db:latest $CI_REGISTRY/namespace/clair-vulnerabilities-db
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
    - docker push $CI_REGISTRY/namespace/clair-vulnerabilities-db

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

Running the standalone container scanning tool

It’s possible to run the GitLab container scanning tool against a Docker container without needing to run it within the context of a CI job. To scan an image directly, follow these steps:

1. Run Docker Desktop or Docker Machine.

2. Run the latest prefilled vulnerabilities database Docker image:

   docker run -p 5432:5432 -d --name clair-db arminc/clair-db:latest
   

3. Configure a CI/CD variable to point to your local machine’s IP address (or insert your IP address instead of the LOCAL_MACHINE_IP_ADDRESS variable in the CLAIR_DB_CONNECTION_STRING in the next step):

   export LOCAL_MACHINE_IP_ADDRESS=your.local.ip.address
   

4. Run the analyzer’s Docker image, passing the image and tag you want to analyze in the CI_APPLICATION_REPOSITORY and CI_APPLICATION_TAG variables:

   docker run \
     --interactive --rm \
     --volume "$PWD":/tmp/app \
     -e CI_PROJECT_DIR=/tmp/app \
     -e CLAIR_DB_CONNECTION_STRING="postgresql://postgres:password@${LOCAL_MACHINE_IP_ADDRESS}:5432/postgres?sslmode=disable&statement_timeout=60000" \
     -e CI_APPLICATION_REPOSITORY=registry.gitlab.com/gitlab-org/security-products/dast/webgoat-8.0@sha256 \
     -e CI_APPLICATION_TAG=bc09fe2e0721dfaeee79364115aeedf2174cce0947b9ae5fe7c33312ee019a4e \
     registry.gitlab.com/gitlab-org/security-products/analyzers/klar
   

The results are stored in gl-container-scanning-report.json.

Reports JSON format

The container scanning tool emits a JSON report file. For more information, see the schema for this report.

Here’s an example container scanning report:

{
  "version": "2.3",
  "vulnerabilities": [
    {
      "id": "ac0997ad-1006-4c81-81fb-ee2bbe6e78e3",
      "category": "container_scanning",
      "message": "CVE-2019-3462 in apt",
      "description": "Incorrect sanitation of the 302 redirect field in HTTP transport method of apt versions 1.4.8 and earlier can lead to content injection by a MITM attacker, potentially leading to remote code execution on the target machine.",
      "severity": "High",
      "confidence": "Unknown",
      "solution": "Upgrade apt from 1.4.8 to 1.4.9",
      "scanner": {
        "id": "klar",
        "name": "klar"
      },
      "location": {
        "dependency": {
          "package": {
            "name": "apt"
          },
          "version": "1.4.8"
        },
        "operating_system": "debian:9",
        "image": "registry.gitlab.com/gitlab-org/security-products/dast/webgoat-8.0@sha256:bc09fe2e0721dfaeee79364115aeedf2174cce0947b9ae5fe7c33312ee019a4e"
      },
      "identifiers": [
        {
          "type": "cve",
          "name": "CVE-2019-3462",
          "value": "CVE-2019-3462",
          "url": "https://security-tracker.debian.org/tracker/CVE-2019-3462"
        }
      ],
      "links": [
        {
          "url": "https://security-tracker.debian.org/tracker/CVE-2019-3462"
        }
      ]
    }
  ],
  "remediations": [
    {
      "fixes": [
        {
          "id": "c0997ad-1006-4c81-81fb-ee2bbe6e78e3"
        }
      ],
      "summary": "Upgrade apt from 1.4.8 to 1.4.9",
      "diff": "YXB0LWdldCB1cGRhdGUgJiYgYXB0LWdldCB1cGdyYWRlIC15IGFwdA=="
    }
  ]
}

Security Dashboard

The Security Dashboard shows you an overview of all the security vulnerabilities in your groups, projects and pipelines.

Vulnerabilities database update

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

Interacting with the vulnerabilities

After a vulnerability is found, you can interact with it.

Solutions for vulnerabilities (auto-remediation)

Some vulnerabilities can be fixed by applying the solution that GitLab automatically generates.

To enable remediation support, the scanning tool must have access to the Dockerfile specified by the DOCKERFILE_PATH CI/CD variable. To ensure that the scanning tool has access to this file, it’s necessary to set GIT_STRATEGY: fetch in your .gitlab-ci.yml file by following the instructions described in this document’s overriding the container scanning template section.

Read more about the solutions for vulnerabilities.

Troubleshooting

docker: Error response from daemon: failed to copy xattrs

When the runner uses the docker executor and NFS is used (for example, /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.

Getting warning message gl-container-scanning-report.json: no matching files

For information on this, see the general Application Security troubleshooting section.