Use Docker Buildx for multi-arch builds

The bitwarden_rs code is still cross-compiled exactly as before, but Docker
Buildx is used to rewrite the resulting Docker images with correct platform
metadata (reflecting the target platform instead of the build platform).
Buildx also now handles building and pushing the multi-arch manifest lists.

docker/Dockerfile.buildx

@@ -0,0 +1,33 @@
+# The cross-built images have the build arch (`amd64`) embedded in the image
+# manifest, rather than the target arch. For example:
+#
+#   $ docker inspect bitwardenrs/server:latest-armv7 | jq -r '.[]|.Architecture'
+#   amd64
+#
+# Recent versions of Docker have started printing a warning when the image's
+# claimed arch doesn't match the host arch. For example:
+#
+#   WARNING: The requested image's platform (linux/amd64) does not match the
+#   detected host platform (linux/arm/v7) and no specific platform was requested
+#
+# The image still works fine, but the spurious warning creates confusion.
+#
+# Docker doesn't seem to provide a way to directly set the arch of an image
+# at build time. To resolve the build vs. target arch discrepancy, we use
+# Docker Buildx to build a new set of images with the correct target arch.
+#
+# Docker Buildx uses this Dockerfile to build an image for each requested
+# platform. Since the Dockerfile basically consists of a single `FROM`
+# instruction, we're effectively telling Buildx to build a platform-specific
+# image by simply copying the existing cross-built image and setting the
+# correct target arch as a side effect.
+#
+# References:
+#
+# - https://docs.docker.com/buildx/working-with-buildx/#build-multi-platform-images
+# - https://docs.docker.com/engine/reference/builder/#automatic-platform-args-in-the-global-scope
+# - https://docs.docker.com/engine/reference/builder/#understand-how-arg-and-from-interact
+#
+ARG LOCAL_REPO
+ARG DOCKER_TAG
+FROM ${LOCAL_REPO}:${DOCKER_TAG}-${TARGETARCH}${TARGETVARIANT}

docker/Dockerfile.j2

@@ -7,24 +7,24 @@
 {%     set build_stage_base_image = "clux/muslrust:nightly-2020-11-22" %}
 {%     set runtime_stage_base_image = "alpine:3.12" %}
 {%     set package_arch_target = "x86_64-unknown-linux-musl" %}
-{%   elif "arm32v7" in target_file %}
+{%   elif "armv7" in target_file %}
 {%     set build_stage_base_image = "messense/rust-musl-cross:armv7-musleabihf" %}
 {%     set runtime_stage_base_image = "balenalib/armv7hf-alpine:3.12" %}
 {%     set package_arch_target = "armv7-unknown-linux-musleabihf" %}
 {%   endif %}
 {% elif "amd64" in target_file %}
 {%   set runtime_stage_base_image = "debian:buster-slim" %}
-{% elif "arm64v8" in target_file %}
+{% elif "arm64" in target_file %}
 {%   set runtime_stage_base_image = "balenalib/aarch64-debian:buster" %}
 {%   set package_arch_name = "arm64" %}
 {%   set package_arch_target = "aarch64-unknown-linux-gnu" %}
 {%   set package_cross_compiler = "aarch64-linux-gnu" %}
-{% elif "arm32v6" in target_file %}
+{% elif "armv6" in target_file %}
 {%   set runtime_stage_base_image = "balenalib/rpi-debian:buster" %}
 {%   set package_arch_name = "armel" %}
 {%   set package_arch_target = "arm-unknown-linux-gnueabi" %}
 {%   set package_cross_compiler = "arm-linux-gnueabi" %}
-{% elif "arm32v7" in target_file %}
+{% elif "armv7" in target_file %}
 {%   set runtime_stage_base_image = "balenalib/armv7hf-debian:buster" %}
 {%   set package_arch_name = "armhf" %}
 {%   set package_arch_target = "armv7-unknown-linux-gnueabihf" %}
@@ -178,7 +178,7 @@ RUN touch src/main.rs
 # your actual source files being built
 RUN cargo build --features ${DB} --release{{ package_arch_target_param }}
 {% if "alpine" in target_file %}
-{%   if "arm32v7" in target_file %}
+{%   if "armv7" in target_file %}
 RUN musl-strip target/{{ package_arch_target }}/release/bitwarden_rs
 {%   endif %}
 {% endif %}
@@ -225,7 +225,7 @@ RUN apt-get update && apt-get install -y \
     libpq5 \
     && rm -rf /var/lib/apt/lists/*
 {% endif %}
-{% if "alpine" in target_file and "arm32v7" in target_file %}
+{% if "alpine" in target_file and "armv7" in target_file %}
 RUN apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/community catatonit
 {% endif %}
 
@@ -256,7 +256,7 @@ HEALTHCHECK --interval=60s --timeout=10s CMD ["/healthcheck.sh"]
 
 # Configures the startup!
 WORKDIR /
-{% if "alpine" in target_file and "arm32v7" in target_file %}
+{% if "alpine" in target_file and "armv7" in target_file %}
 CMD ["catatonit", "/start.sh"]
 {% else %}
 CMD ["/start.sh"]

hooks/README.md

@@ -10,7 +10,7 @@ Docker Hub hooks provide these predefined [environment variables](https://docs.d
 * `DOCKER_TAG`: the Docker repository tag being built.
 * `IMAGE_NAME`: the name and tag of the Docker repository being built. (This variable is a combination of `DOCKER_REPO:DOCKER_TAG`.)
 
-The current multi-arch image build relies on the original bitwarden_rs Dockerfiles, which use cross-compilation for architectures other than `amd64`, and don't yet support all arch/database/OS combinations. However, cross-compilation is much faster than QEMU-based builds (e.g., using `docker buildx`). This situation may need to be revisited at some point.
+The current multi-arch image build relies on the original bitwarden_rs Dockerfiles, which use cross-compilation for architectures other than `amd64`, and don't yet support all arch/distro combinations. However, cross-compilation is much faster than QEMU-based builds (e.g., using `docker buildx`). This situation may need to be revisited at some point.
 
 ## References
 

hooks/arches.sh

@@ -1,19 +1,16 @@
-# The default Debian-based images support these arches for all database connections
-#
-# Other images (Alpine-based) currently
-# support only a subset of these.
+# The default Debian-based images support these arches for all database backends.
 arches=(
     amd64
-    arm32v6
-    arm32v7
-    arm64v8
+    armv6
+    armv7
+    arm64
 )
 
 if [[ "${DOCKER_TAG}" == *alpine ]]; then
-    # The Alpine build currently only works for amd64.
-    os_suffix=.alpine
+    # The Alpine image build currently only works for certain arches.
+    distro_suffix=.alpine
     arches=(
         amd64
-        arm32v7
+        armv7
     )
 fi

hooks/build

@@ -9,6 +9,6 @@ set -ex
 for arch in "${arches[@]}"; do
     docker build \
            -t "${DOCKER_REPO}:${DOCKER_TAG}-${arch}" \
-           -f docker/${arch}/Dockerfile${os_suffix} \
+           -f docker/${arch}/Dockerfile${distro_suffix} \
            .
 done

hooks/pre_build

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+set -ex
+
+# Print some environment info in case it's useful for troubleshooting.
+id
+pwd
+df -h
+env
+docker info
+docker version
+
+# Install build dependencies.
+deps=(
+    jq
+)
+apt-get update
+apt-get install -y "${deps[@]}"

hooks/push

@@ -1,117 +1,138 @@
 #!/bin/bash
 
-echo ">>> Pushing images..."
-
-export DOCKER_CLI_EXPERIMENTAL=enabled
-
-declare -A annotations=(
-    [amd64]="--os linux --arch amd64"
-    [arm32v6]="--os linux --arch arm --variant v6"
-    [arm32v7]="--os linux --arch arm --variant v7"
-    [arm64v8]="--os linux --arch arm64 --variant v8"
-)
-
 source ./hooks/arches.sh
 
+export DOCKER_CLI_EXPERIMENTAL=enabled
+
+# Join a list of args with a single char.
+# Ref: https://stackoverflow.com/a/17841619
+join() { local IFS="$1"; shift; echo "$*"; }
+
 set -ex
 
-declare -A images
+echo ">>> Starting local Docker registry..."
+
+# Docker Buildx's `docker-container` driver is needed for multi-platform
+# builds, but it can't access existing images on the Docker host (like the
+# cross-compiled ones we just built). Those images first need to be pushed to
+# a registry -- Docker Hub could be used, but since it's not trivial to clean
+# up those intermediate images on Docker Hub, it's easier to just run a local
+# Docker registry, which gets cleaned up automatically once the build job ends.
+#
+# https://docs.docker.com/registry/deploying/
+# https://hub.docker.com/_/registry
+#
+# Use host networking so the buildx container can access the registry via
+# localhost.
+#
+docker run -d --name registry --network host registry:2 # defaults to port 5000
+
+# Docker Hub sets a `DOCKER_REPO` env var with the format `index.docker.io/user/repo`.
+# Strip the registry portion to construct a local repo path for use in `Dockerfile.buildx`.
+LOCAL_REGISTRY="localhost:5000"
+REPO="${DOCKER_REPO#*/}"
+LOCAL_REPO="${LOCAL_REGISTRY}/${REPO}"
+
+echo ">>> Pushing images to local registry..."
+
 for arch in ${arches[@]}; do
-    images[$arch]="${DOCKER_REPO}:${DOCKER_TAG}-${arch}"
+    docker_image="${DOCKER_REPO}:${DOCKER_TAG}-${arch}"
+    local_image="${LOCAL_REPO}:${DOCKER_TAG}-${arch}"
+    docker tag "${docker_image}" "${local_image}"
+    docker push "${local_image}"
 done
 
-# Push the images that were just built; manifest list creation fails if the
-# images (manifests) referenced don't already exist in the Docker registry.
-for image in "${images[@]}"; do
-    docker push "${image}"
-done
+echo ">>> Setting up Docker Buildx..."
 
-manifest_lists=("${DOCKER_REPO}:${DOCKER_TAG}")
+# Same as earlier, use host networking so the buildx container can access the
+# registry via localhost.
+#
+# Ref: https://github.com/docker/buildx/issues/94#issuecomment-534367714
+#
+docker buildx create --name builder --use --driver-opt network=host
 
-# If the Docker tag starts with a version number, assume the latest release is
-# being pushed. Add an extra manifest (`latest` or `alpine`, as appropriate)
+echo ">>> Running Docker Buildx..."
+
+tags=("${DOCKER_REPO}:${DOCKER_TAG}")
+
+# If the Docker tag starts with a version number, assume the latest release
+# is being pushed. Add an extra tag (`latest` or `alpine`, as appropriate)
 # to make it easier for users to track the latest release.
 if [[ "${DOCKER_TAG}" =~ ^[0-9]+\.[0-9]+\.[0-9]+ ]]; then
     if [[ "${DOCKER_TAG}" == *alpine ]]; then
-        manifest_lists+=(${DOCKER_REPO}:alpine)
+        tags+=(${DOCKER_REPO}:alpine)
     else
-        manifest_lists+=(${DOCKER_REPO}:latest)
-
-        # Add an extra `latest-arm32v6` tag; Docker can't seem to properly
-        # auto-select that image on Armv6 platforms like Raspberry Pi 1 and Zero
-        # (https://github.com/moby/moby/issues/41017).
-        #
-        # Add this tag only for the SQLite image, as the MySQL and PostgreSQL
-        # builds don't currently work on non-amd64 arches.
-        #
-        # TODO: Also add an `alpine-arm32v6` tag if multi-arch support for
-        # Alpine-based bitwarden_rs images is implemented before this Docker
-        # issue is fixed.
-        if [[ ${DOCKER_REPO} == *server ]]; then
-            docker tag "${DOCKER_REPO}:${DOCKER_TAG}-arm32v6" "${DOCKER_REPO}:latest-arm32v6"
-            docker push "${DOCKER_REPO}:latest-arm32v6"
-        fi
+        tags+=(${DOCKER_REPO}:latest)
     fi
 fi
 
-for manifest_list in "${manifest_lists[@]}"; do
-    # Create the (multi-arch) manifest list of arch-specific images.
-    docker manifest create ${manifest_list} ${images[@]}
-
-    # Make sure each image manifest is annotated with the correct arch info.
-    # Docker does not auto-detect the arch of each cross-compiled image, so
-    # everything would appear as `linux/amd64` otherwise.
-    for arch in "${arches[@]}"; do
-        docker manifest annotate ${annotations[$arch]} ${manifest_list} ${images[$arch]}
+tag_args=()
+for tag in "${tags[@]}"; do
+    tag_args+=(--tag "${tag}")
 done
 
-    # Push the manifest list.
-    docker manifest push --purge ${manifest_list}
-done
-
-# Avoid logging credentials and tokens.
-set +ex
-
-# Delete the arch-specific tags, if credentials for doing so are available.
-# Note that `DOCKER_PASSWORD` must be the actual user password. Passing a JWT
-# obtained using a personal access token results in a 403 error with
-# {"detail": "access to the resource is forbidden with personal access token"}
-if [[ -z "${DOCKER_USERNAME}" || -z "${DOCKER_PASSWORD}" ]]; then
-    exit 0
-fi
-
-# Given a JSON input on stdin, extract the string value associated with the
-# specified key. This avoids an extra dependency on a tool like `jq`.
-extract() {
-    local key="$1"
-    # Extract "<key>":"<val>" (assumes key/val won't contain double quotes).
-    # The colon may have whitespace on either side.
-    grep -o "\"${key}\"[[:space:]]*:[[:space:]]*\"[^\"]\+\"" |
-    # Extract just <val> by deleting the last '"', and then greedily deleting
-    # everything up to '"'.
-    sed -e 's/"$//' -e 's/.*"//'
-}
-
-echo ">>> Getting API token..."
-jwt=$(curl -sS -X POST \
-           -H "Content-Type: application/json" \
-           -d "{\"username\":\"${DOCKER_USERNAME}\",\"password\": \"${DOCKER_PASSWORD}\"}" \
-           "https://hub.docker.com/v2/users/login" |
-      extract 'token')
-
-# Strip the registry portion from `index.docker.io/user/repo`.
-repo="${DOCKER_REPO#*/}"
-
+# Docker Buildx takes a list of target platforms (OS/arch/variant), so map
+# the arch list to a platform list (assuming the OS is always `linux`).
+declare -A arch_to_platform=(
+    [amd64]="linux/amd64"
+    [armv6]="linux/arm/v6"
+    [armv7]="linux/arm/v7"
+    [arm64]="linux/arm64"
+)
+platforms=()
 for arch in ${arches[@]}; do
-    # Don't delete the `arm32v6` tag; Docker can't seem to properly
-    # auto-select that image on Armv6 platforms like Raspberry Pi 1 and Zero
-    # (https://github.com/moby/moby/issues/41017).
-    if [[ ${arch} == 'arm32v6' ]]; then
-        continue
-    fi
-    tag="${DOCKER_TAG}-${arch}"
-    echo ">>> Deleting '${repo}:${tag}'..."
-    curl -sS -X DELETE \
-         -H "Authorization: Bearer ${jwt}" \
-         "https://hub.docker.com/v2/repositories/${repo}/tags/${tag}/"
+    platforms+=("${arch_to_platform[$arch]}")
 done
+platforms="$(join "," "${platforms[@]}")"
+
+# Run the build, pushing the resulting images and multi-arch manifest list to
+# Docker Hub. The Dockerfile is read from stdin to avoid sending any build
+# context, which isn't needed here since the actual cross-compiled images
+# have already been built.
+docker buildx build \
+       --network host \
+       --build-arg LOCAL_REPO="${LOCAL_REPO}" \
+       --build-arg DOCKER_TAG="${DOCKER_TAG}" \
+       --platform "${platforms}" \
+       "${tag_args[@]}" \
+       --push \
+       - < ./docker/Dockerfile.buildx
+
+# Add an extra arch-specific tag for `arm32v6`; Docker can't seem to properly
+# auto-select that image on ARMv6 platforms like Raspberry Pi 1 and Zero
+# (https://github.com/moby/moby/issues/41017).
+#
+# Note that we use `arm32v6` instead of `armv6` to be consistent with the
+# existing bitwarden_rs tags, which adhere to the naming conventions of the
+# Docker per-architecture repos (e.g., https://hub.docker.com/u/arm32v6).
+# Unfortunately, these per-arch repo names aren't always consistent with the
+# corresponding platform (OS/arch/variant) IDs, particularly in the case of
+# 32-bit ARM arches (e.g., `linux/arm/v6` is used, not `linux/arm32/v6`).
+#
+# TODO: It looks like this issue should be fixed starting in Docker 20.10.0,
+# so this step can be removed once fixed versions are in wider distribution.
+#
+# Tags:
+#
+#   testing        => testing-arm32v6
+#   testing-alpine => <ignored>
+#   x.y.z          => x.y.z-arm32v6, latest-arm32v6
+#   x.y.z-alpine   => <ignored>
+#
+if [[ "${DOCKER_TAG}" != *alpine ]]; then
+    image="${DOCKER_REPO}":"${DOCKER_TAG}"
+
+    # Fetch the multi-arch manifest list and find the digest of the armv6 image.
+    filter='.manifests|.[]|select(.platform.architecture=="arm" and .platform.variant=="v6")|.digest'
+    digest="$(docker manifest inspect "${image}" | jq -r "${filter}")"
+
+    # Pull the armv6 image by digest, retag it, and repush it.
+    docker pull "${DOCKER_REPO}"@"${digest}"
+    docker tag "${DOCKER_REPO}"@"${digest}" "${image}"-arm32v6
+    docker push "${image}"-arm32v6
+
+    if [[ "${DOCKER_TAG}" =~ ^[0-9]+\.[0-9]+\.[0-9]+ ]]; then
+        docker tag "${image}"-arm32v6 "${DOCKER_REPO}:latest"-arm32v6
+        docker push "${DOCKER_REPO}:latest"-arm32v6
+    fi
+fi