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Creating Secure Container Images with apko

Erika Heidi
September 29, 2022

Creating Secure Container Images with apko

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

Erika Heidi

September 29, 2022
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  1. Creating Secure Container
    Images with apko
    The declarative OCI image builder
    chainguard.dev

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  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

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  3. What is apko

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  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

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  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

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  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

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  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

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  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

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  9. Why distroless?

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  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

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  11. The distroless philosophy: less CVEs = win

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  12. Case Study: Dynacover
    Migrating a PHP image to apko / distroless

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  13. Dynacover Overview
    ● Dynamic header images
    for Twitter
    ● PHP application built
    with Minicli
    ● Main dependencies: PHP
    (cli), Curl and GD

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  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

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  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

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  16. Migration step 2: finding appropriate apks

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  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

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  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

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  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

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  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"]

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  21. 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

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  22. 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

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