Creating Secure Container Images with apko

This talk was presented at the Full Stack NL meetup group on September 29, 2022.

Transcript

1. Creating Secure Container Images with apko The declarative OCI image builder chainguard.dev
2. What to Expect from this Talk • What is apko ◦ Tool overview ◦ Why apk • Why Distroless • Case Study / Demo ◦ Migrating dynacover to a distroless apko image • Q&A
3. What is apko
4. What is apko • Declarative OCI image builder tool based on apk • Part of the building toolkit behind Wolfi / Chainguard Images • Images are defined in YAML files • Builds are fully reproducible • Automatically generates SBOMs for every image • Platform-agnostic builds via Docker + apko image
5. Example apko.yaml file contents: repositories: - https://dl-cdn.alpinelinux.org/alpine/edge/main packages: - alpine-base cmd: /bin/sh -l environment: PATH: /usr/sbin:/sbin:/usr/bin:/bin
6. Building the image with apko via Docker $ docker run --rm -v ${PWD}:/work cgr.dev/chainguard/apko build alpine-base.yaml alpine-base:test alpine-test.tar Testing the image with Docker $ docker load < alpine-test.tar $ docker run -it alpine-base:test
7. Why apk • Introduced by Alpine, it uses a different methodology to handle package management • Package installation or removal is done as a side effect of modifying the system state • This creates the ideal conditions for reproducible and declarative pipelines
8. Where do packages come from • For Alpine-based images, use Alpine apks found at pkgs.alpinelinux.org/packages • For Wolfi-based images, use Wolfi apks that are listed in the wolfi-os repository, hosted at packages.wolfi.dev/os • Don't mix! • You can also create your own apks with melange
9. Why distroless?
10. The distroless philosophy • Minimalist container images with only what's absolutely necessary to build or execute your application • Popular base images are full of software that only makes sense on bare-metal • No need for package managers or interactive shells on production images • Less dependencies = smaller attack surface, less CVEs
11. The distroless philosophy: less CVEs = win
12. Case Study: Dynacover Migrating a PHP image to apko / distroless
13. Dynacover Overview • Dynamic header images for Twitter • PHP application built with Minicli • Main dependencies: PHP (cli), Curl and GD
14. Dynacover Overview • GitHub Action that runs on schedule • Using an image based on the official php:7.4-cli ◦ Size: 589MB ◦ CVEs (Trivy): 331
15. Migration step 1: collecting dependencies FROM php:7.4-cli ARG user=dynacover ARG uid=1000 RUN apt-get update && apt-get install -y git curl libonig-dev libxml2-dev libfreetype6-dev libjpeg62-turbo-dev libpng-dev zip unzip RUN apt-get clean && rm -rf /var/lib/apt/lists/* RUN docker-php-ext-configure gd --with-freetype --with-jpeg && \ docker-php-ext-install pdo_mysql mbstring exif pcntl bcmath gd COPY --from=composer:latest /usr/bin/composer /usr/bin/composer RUN useradd -G sudo,root -u $uid -d /home/$user $user RUN mkdir -p /home/$user/.composer && \ chown -R $user:$user /home/$user USER $user RUN mkdir -p /home/$user/dynacover COPY . /home/$user/dynacover/ WORKDIR /home/$user/dynacover RUN composer install • git • curl • zip • unzip • libonig-dev • libfreetype6-dev • libjpeg62-turbo-dev • libpng-dev • php-mbstring • php-exif • php-pcntl • php-bcmath • php-gd
16. Migration step 2: finding appropriate apks
17. Migration step 3: creating the apko.yaml file contents: repositories: - https://dl-cdn.alpinelinux.org/alpine/edge/main - https://dl-cdn.alpinelinux.org/alpine/edge/community … … packages: - alpine-baselayout-data - ca-certificates-bundle - curl - git - zip - unzip - libxml2-dev - freetype - freetype-dev - libjpeg-turbo - libjpeg-turbo-dev - libpng - php81 - php81-gd - php81-curl - php81-mbstring - php81-phar - php81-openssl - php81-pcntl
18. Migration step 3: creating the apko.yaml file entrypoint: command: /usr/bin/php81 environment: PATH: /usr/sbin:/sbin:/usr/bin:/bin … … accounts: groups: - groupname: minicli gid: 65532 users: - username: minicli uid: 65532 run-as: root - php81-pcntl
19. Migration step 4: building/pushing the image $ docker run --rm -v ${PWD}:/work cgr.dev/chainguard/apko build apko.yaml \ erikaheidi/minicli:php81 minicli-php81.tar $ docker load < minicli-php81.tar $ docker push erikaheidi/minicli:php81
20. Migration step 5: updating GH Action Dockerfile FROM erikaheidi/minicli:php81 COPY --from=composer:latest /usr/bin/composer /usr/bin/composer RUN git clone -b 1.0.1 --depth 1 https://github.com/erikaheidi/dynacover.git && \ cd dynacover && \ composer install --no-progress --no-dev --prefer-dist ENTRYPOINT [ "php81", "/dynacover/dynacover" ] CMD ["cover", "update"]
22. Dynacover base image: before / after • Based on php:7.4-cli • Base image total size: 589MB • Total CVEs: 331 • Distroless based on Alpine • Base image total size: 48MB • Total CVEs: 0
23. Resources to Learn More • minicli:php81 on GitHub • Getting Started with apko tutorial on Chainguard Academy • apko on GitHub • Troubleshooting apko builds • Chainguard Images documentation • Wolfi documentation
24. Questions?
25. Thank You!