Container Scan

This action can be used to help you add some additional checks to help you secure your Docker Images in your CI. This would help you attain some confidence in your docker image before pushing them to your container registry or a deployment.

It internally uses Trivy and Dockle for running certain kinds of scans on these images.

• Trivy helps you find the common vulnerabilities within your docker images.
• Dockle is a container linter, which helps you identify if you haven't followed
  • Certain best practices while building the image
  • CIS Benchmarks to secure your docker image

Please checkout Trivy and Dockle licenses.

Action inputs

Action input	Description	Default Value
image-name	(Required) The Docker image to be scanned	''
severity-threshold	(Optional) Minimum severity threshold set to control flagging of the vulnerabilities found during the scan. The available levels are: (UNKNOWN, LOW, MEDIUM, HIGH, CRITICAL); if you set the severity-threshold to be `MEDIUM` every CVE found of a level higher than or equal to `MEDIUM` would be displayed	HIGH
run-quality-checks	(Optional) This is a boolean value. When set to `true` adds additional checks to ensure the image follows best practices and CIS standards.	true
username	(Optional) Username to authenticate to the Docker registry. This is only required when you're trying to pull an image from your private registry	''
password	(Optional) Password to authenticate to the Docker registry. This is only required when you're trying to pull an image from your private registry	''

Action output

The action generates an output file consisting of detailed description of all the detected vulnerabilities and best practice violations in JSON format. This file can be accessed by using the output variable scan-report-path.
Here is a sample scan report:

{
  "imageName": "myacr.azurecr.io/testapp:770aed6bd33d7240b4bdb55f16348ce37b86bb09",
  "vulnerabilities": [
    {
      "vulnerabilityId": "CVE-2018-12886",
      "packageName": "gcc-8-base",
      "severity": "HIGH",
      "description": "stack_protect_prologue in cfgexpand.c and stack_protect_epilogue in function.c in GNU Compiler Collection (GCC) 4.1 through 8 (under certain circumstances) generate instruction sequences when targeting ARM targets that spill the address of the stack protector guard, which allows an attacker to bypass the protection of -fstack-protector, -fstack-protector-all, -fstack-protector-strong, and -fstack-protector-explicit against stack overflow by controlling what the stack canary is compared against.",
      "target": "myacr.azurecr.io/ascdemo:770aed6bd33d7240b4bdb55f16348ce37b86bb09 (debian 10.4)"
    },
    {
      "vulnerabilityId": "CVE-2019-20367",
      "packageName": "libbsd0",
      "severity": "CRITICAL",
      "description": "nlist.c in libbsd before 0.10.0 has an out-of-bounds read during a comparison for a symbol name from the string table (strtab).",
      "target": "myacr.azurecr.io/ascdemo:770aed6bd33d7240b4bdb55f16348ce37b86bb09 (debian 10.4)"
    },
    {
      "vulnerabilityId": "CVE-2020-1751",
      "packageName": "libc-bin",
      "severity": "HIGH",
      "description": "An out-of-bounds write vulnerability was found in glibc before 2.31 when handling signal trampolines on PowerPC. Specifically, the backtrace function did not properly check the array bounds when storing the frame address, resulting in a denial of service or potential code execution. The highest threat from this vulnerability is to system availability.",
      "target": "myacr.azurecr.io/ascdemo:770aed6bd33d7240b4bdb55f16348ce37b86bb09 (debian 10.4)"
    }
  ],
  "bestPracticeViolations": [
    {
      "code": "CIS-DI-0001",
      "title": "Create a user for the container",
      "level": "WARN",
      "alerts": "Last user should not be root"
    },
    {
      "code": "CIS-DI-0005",
      "title": "Enable Content trust for Docker",
      "level": "INFO",
      "alerts": "export DOCKER_CONTENT_TRUST=1 before docker pull/build"
    }
  ],
  "vulnerabilityScanTimestamp": "2021-03-05T09:38:48.036Z"
}

Ignoring vulnerabilities

In case you would like the action to ignore any vulnerabilities and best practice checks, create an allowedlist file at the path .github/containerscan/allowedlist.yaml in your repo. Here's an example allowedlist.yaml file.

general:
  vulnerabilities:
    - CVE-2003-1307
    - CVE-2007-0086
    - CVE-2019-3462
    - CVE-2011-3374
  bestPracticeViolations:
    - CIS-DI-0005
    - DKL-LI-0003
    - CIS-DI-0006
    - DKL-DI-0006

Install Scanitizer (currently in Beta) on your repository for more convenient management of allowedlist file.

Example YAML snippets

Container scan of an image available locally or publically available on dockerhub

- uses: azure/container-scan@v0
  with:
    image-name: my-image:my-tag

Container scan of an image available on a private registry

- uses: azure/container-scan@v0
  with:
    image-name: loginServerUrl/my-image:${{ github.sha }} # loginServerlUrl/ would be empty if it's hosted on dockerhub; ${{ github.sha }} could also be replaced with any desired image tag
    username: ${{ secrets.DOCKER_USERNAME }}
    password: ${{ secrets.DOCKER_PASSWORD }}

Container scan of an image available locally, publically, or privately using workflow environment variables

- uses: azure/container-scan@v0
  with:
    image-name: ${{ env.loginServerUrl }}/my-image:${{ github.sha }} # ${{ env.loginServerUrl }}/ would be empty if it's hosted on dockerhub; ${{ github.sha }} could also be replaced with any desired image tag
    username: ${{ secrets.DOCKER_USERNAME }}
    password: ${{ secrets.DOCKER_PASSWORD }}

End to end workflow using Azure

The following is an example of not just this action, but how this action could be used along with other actions to setup a CI.

Where your CI would:

• Build a docker image
• Scan the docker image for any security vulnerabilities
• Publish it to your private container registry.

on: [push]

jobs:
  build-secure-and-push:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@master

    - run: docker build . -t contoso.azurecr.io/k8sdemo:${{ github.sha }}
      
    - uses: Azure/container-scan@v0
      with:
        image-name: contoso.azurecr.io/k8sdemo:${{ github.sha }}
    
    - uses: Azure/docker-login@v1
      with:
        login-server: contoso.azurecr.io
        username: ${{ secrets.REGISTRY_USERNAME }}
        password: ${{ secrets.REGISTRY_PASSWORD }}
    
    - run: docker push contoso.azurecr.io/k8sdemo:${{ github.sha }}

End to end workflow using any container repository and workflow environment variables

The following is an example of not just this action, but how this action could be used along with other actions to setup a CI.

Where your CI would:

• Build a docker image
• Scan the docker image for any security vulnerabilities
• Publish it to your preferred container registry.

This example assumes you have defined an evironment variable in your workflow for CONTAINER_REGISTRY.

on: [push]

jobs:
  build-secure-and-push:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@master

    - run: docker build . -t ${{ env.CONTAINER_REGISTRY }}/k8sdemo:${{ github.sha }}
      
    - uses: Azure/container-scan@v0
      with:
        image-name: ${{ env.CONTAINER_REGISTRY }}/k8sdemo:${{ github.sha }}
    
    - uses: Azure/docker-login@v1
      with:
        login-server: ${{ env.CONTAINER_REGISTRY }}
        username: ${{ secrets.REGISTRY_USERNAME }}
        password: ${{ secrets.REGISTRY_PASSWORD }}
    
    - run: docker push ${{ env.CONTAINER_REGISTRY }}/k8sdemo:${{ github.sha }}

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.opensource.microsoft.com.

When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.