Dockerfile-builder.template

{{ if env.variant == "musl" then ( -}}
FROM alpine:3.20

RUN set -eux; \
	apk add --no-cache \
		bzip2 \
		coreutils \
		curl \
		gcc \
		gnupg \
		linux-headers \
		make \
		musl-dev \
		patch \
		tzdata \
# busybox's tar ironically does not maintain mtime of directories correctly (which we need for SOURCE_DATE_EPOCH / reproducibility)
		tar \
	;
{{ ) else ( -}}
FROM debian:bookworm-slim

RUN set -eux; \
	apt-get update; \
	apt-get install -y \
		bzip2 \
		curl \
		gcc \
		gnupg \
		make \
		patch \
	; \
	rm -rf /var/lib/apt/lists/*
{{ ) end -}}
{{ if env.variant == "uclibc" then ( -}}

# grab/use buildroot for its uClibc toolchain

RUN set -eux; \
	apt-get update; \
	apt-get install -y \
		bc \
		cpio \
		dpkg-dev \
		file \
		g++ \
		perl \
		python3 \
		rsync \
		unzip \
		wget \
	; \
	rm -rf /var/lib/apt/lists/*

# pub   1024D/59C36319 2009-01-15
#       Key fingerprint = AB07 D806 D2CE 741F B886  EE50 B025 BA8B 59C3 6319
# uid                  Peter Korsgaard <jacmet@uclibc.org>
# sub   2048g/45428075 2009-01-15
RUN mkdir -p ~/.gnupg && gpg --batch --keyserver keyserver.ubuntu.com --recv-keys AB07D806D2CE741FB886EE50B025BA8B59C36319

# https://buildroot.org/download.html
# https://buildroot.org/downloads/?C=M;O=D
ENV BUILDROOT_VERSION {{ .buildroot.version }}

RUN set -eux; \
	tarball="buildroot-${BUILDROOT_VERSION}.tar.xz"; \
	curl -fL -o buildroot.tar.xz "https://buildroot.org/downloads/$tarball"; \
	curl -fL -o buildroot.tar.xz.sign "https://buildroot.org/downloads/$tarball.sign"; \
	gpg --batch --decrypt --output buildroot.tar.xz.txt buildroot.tar.xz.sign; \
	awk '$1 == "SHA1:" && $2 ~ /^[0-9a-f]+$/ && $3 == "'"$tarball"'" { print $2, "*buildroot.tar.xz" }' buildroot.tar.xz.txt > buildroot.tar.xz.sha1; \
	test -s buildroot.tar.xz.sha1; \
	sha1sum -c buildroot.tar.xz.sha1; \
	mkdir -p /usr/src/buildroot; \
	tar -xf buildroot.tar.xz -C /usr/src/buildroot --strip-components 1; \
	rm buildroot.tar.xz*

RUN set -eux; \
	\
	cd /usr/src/buildroot; \
	\
	setConfs=' \
		BR2_STATIC_LIBS=y \
		BR2_TOOLCHAIN_BUILDROOT_UCLIBC=y \
		BR2_TOOLCHAIN_BUILDROOT_WCHAR=y \
	'; \
	\
	unsetConfs=' \
		BR2_SHARED_LIBS \
		BR2_TOOLCHAIN_BUILDROOT_GLIBC \
	'; \
	\
# buildroot arches: https://gitlab.com/buildroot.org/buildroot/-/tree/HEAD/arch
# buildroot+uclibc arches: https://gitlab.com/buildroot.org/buildroot/-/blob/HEAD/package/uclibc/Config.in ("config BR2_PACKAGE_UCLIBC_ARCH_SUPPORTS")
	dpkgArch="$(dpkg --print-architecture)"; \
	case "$dpkgArch" in \
# explicitly target amd64 v1
		amd64) \
			setConfs="$setConfs \
				BR2_x86_64=y \
				BR2_x86_x86_64=y \
			"; \
			;; \
			\
		arm64) \
			setConfs="$setConfs \
				BR2_aarch64=y \
			"; \
# https://github.com/docker-library/busybox/issues/149
			setConfs="$setConfs BR2_ARM64_PAGE_SIZE_64K=y"; \
			unsetConfs="$unsetConfs BR2_ARM64_PAGE_SIZE_4K"; \
# (it's reasonable to use a larger page size than the host, but not the reverse, and some distros default to 64k instead of 4k)
			;; \
			\
# https://wiki.debian.org/ArmEabiPort#Choice_of_minimum_CPU
# https://github.com/free-electrons/toolchains-builder/blob/db259641eaf5bbcf13f4a3c5003e5436e806770c/configs/arch/armv5-eabi.config
# https://gitlab.com/buildroot.org/buildroot/-/blob/HEAD/arch/Config.in.arm
# (Debian minimums at ARMv4, we minimum at ARMv5 instead)
		armel) \
			setConfs="$setConfs \
				BR2_arm=y \
				BR2_arm926t=y \
				BR2_ARM_EABI=y \
				BR2_ARM_INSTRUCTIONS_THUMB=y \
				BR2_ARM_SOFT_FLOAT=y \
			"; \
			;; \
			\
# "Currently the Debian armhf port requires at least an ARMv7 CPU with Thumb-2 and VFP3D16."
# https://wiki.debian.org/ArmHardFloatPort#Supported_devices
# https://github.com/free-electrons/toolchains-builder/blob/db259641eaf5bbcf13f4a3c5003e5436e806770c/configs/arch/armv7-eabihf.config
# https://gitlab.com/buildroot.org/buildroot/-/blob/HEAD/arch/Config.in.arm
		armhf) \
			setConfs="$setConfs \
				BR2_arm=y \
				BR2_cortex_a9=y \
				BR2_ARM_EABIHF=y \
				BR2_ARM_ENABLE_VFP=y \
				BR2_ARM_FPU_VFPV3D16=y \
				BR2_ARM_INSTRUCTIONS_THUMB2=y \
			"; \
			unsetConfs="$unsetConfs BR2_ARM_SOFT_FLOAT"; \
			;; \
			\
		i386) \
			setConfs="$setConfs \
				BR2_i386=y \
			"; \
			;; \
			\
		mips64el) \
			setConfs="$setConfs \
				BR2_mips64el=y \
				BR2_mips_64r2=y \
				BR2_MIPS_NABI64=y \
			"; \
			unsetConfs="$unsetConfs \
				BR2_MIPS_SOFT_FLOAT \
			"; \
			;; \
			\
# TODO ppc64el ? (needs BR2_TOOLCHAIN_BUILDROOT_UCLIBC support)
			\
		riscv64) \
			setConfs="$setConfs \
				BR2_riscv=y \
				BR2_RISCV_64=y \
			"; \
			;; \
			\
# TODO s390x ? (needs BR2_TOOLCHAIN_BUILDROOT_UCLIBC support)
			\
		*) \
			echo >&2 "error: unsupported architecture '$dpkgArch'!"; \
			exit 1; \
			;; \
	esac; \
	if [ "$dpkgArch" != 'i386' ]; then \
		unsetConfs="$unsetConfs BR2_i386"; \
	fi; \
	\
	make defconfig; \
	\
	for conf in $unsetConfs; do \
		sed -i \
			-e "s!^$conf=.*\$!# $conf is not set!" \
			.config; \
	done; \
	\
	for confV in $setConfs; do \
		conf="${confV%=*}"; \
		sed -i \
			-e "s!^$conf=.*\$!$confV!" \
			-e "s!^# $conf is not set\$!$confV!" \
			.config; \
		if ! grep -q "^$confV\$" .config; then \
			echo "$confV" >> .config; \
		fi; \
	done; \
	\
	make oldconfig; \
	\
# trust, but verify
	for conf in $unsetConfs; do \
		! grep -q "^$conf=" .config; \
	done; \
	for confV in $setConfs; do \
		grep -q "^$confV\$" .config; \
	done;

# https://www.finnie.org/2014/02/13/compiling-busybox-with-uclibc/
RUN set -eux; \
# force a particular GNU arch for "host-gmp" (otherwise it fails on some arches)
	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
	make -C /usr/src/buildroot \
		HOST_GMP_CONF_OPTS="--build='"$gnuArch"'" \
# building host-tar:
#   configure: error: you should not run configure as root (set FORCE_UNSAFE_CONFIGURE=1 in environment to bypass this check)
		FORCE_UNSAFE_CONFIGURE=1 \
		-j "$(nproc)" \
		toolchain
ENV PATH /usr/src/buildroot/output/host/usr/bin:$PATH
{{ ) else "" end -}}

# pub   1024D/ACC9965B 2006-12-12
#       Key fingerprint = C9E9 416F 76E6 10DB D09D  040F 47B7 0C55 ACC9 965B
# uid                  Denis Vlasenko <vda.linux@googlemail.com>
# sub   1024g/2C766641 2006-12-12
RUN mkdir -p ~/.gnupg && gpg --batch --keyserver keyserver.ubuntu.com --recv-keys C9E9416F76E610DBD09D040F47B70C55ACC9965B

# https://busybox.net: {{ .date }}
ENV BUSYBOX_VERSION {{ .version }}
ENV BUSYBOX_SHA256 {{ .sha256 }}

RUN set -eux; \
	tarball="busybox-${BUSYBOX_VERSION}.tar.bz2"; \
	curl -fL -o busybox.tar.bz2.sig "https://busybox.net/downloads/$tarball.sig"; \
	curl -fL -o busybox.tar.bz2 "https://busybox.net/downloads/$tarball"; \
	echo "$BUSYBOX_SHA256 *busybox.tar.bz2" | sha256sum -c -; \
	gpg --batch --verify busybox.tar.bz2.sig busybox.tar.bz2; \
# Alpine... 😅
	mkdir -p /usr/src; \
	tar -xf busybox.tar.bz2 -C /usr/src "busybox-$BUSYBOX_VERSION"; \
	mv "/usr/src/busybox-$BUSYBOX_VERSION" /usr/src/busybox; \
	rm busybox.tar.bz2*; \
	\
# save the tarball's filesystem timestamp persistently (in case building busybox modifies it) so we can use it for reproducible rootfs later
	SOURCE_DATE_EPOCH="$(stat -c '%Y' /usr/src/busybox | tee /usr/src/busybox.SOURCE_DATE_EPOCH)"; \
	date="$(date -d "@$SOURCE_DATE_EPOCH" '+%Y%m%d%H%M.%S')"; \
	touch -t "$date" /usr/src/busybox.SOURCE_DATE_EPOCH; \
# for logging validation/edification
	date --date "@$SOURCE_DATE_EPOCH" --rfc-2822

WORKDIR /usr/src/busybox

{{
	(
		[
			"no-cbq.patch",
			if .version | startswith("1.36.") then empty else
				"sha1_process_block64_shaNI.patch"
			end,
			empty # trailing comma
		]
		| map("/.patches/" + .)
	) as $patches
	| if $patches | length > 0 then (
-}}
# apply necessary/minimal patches (see /.patches/ in the top level of the repository)
COPY \
{{ $patches | map( -}}
	{{ . }} \
{{ ) | join("") -}}
	./.patches/
RUN set -eux; \
	for patch in .patches/*.patch; do \
		patch -p1 --input="$patch"; \
	done; \
	rm -rf .patches
{{ ) else "" end -}}

RUN set -eux; \
	\
# build date/time gets embedded in the BusyBox binary -- SOURCE_DATE_EPOCH should override that
	SOURCE_DATE_EPOCH="$(cat /usr/src/busybox.SOURCE_DATE_EPOCH)"; \
	export SOURCE_DATE_EPOCH; \
# (has to be set in the config stage for making sure "AUTOCONF_TIMESTAMP" is embedded correctly)
	\
	setConfs=' \
		CONFIG_AR=y \
		CONFIG_FEATURE_AR_CREATE=y \
		CONFIG_FEATURE_AR_LONG_FILENAMES=y \
# CONFIG_LAST_SUPPORTED_WCHAR: see https://github.com/docker-library/busybox/issues/13 (UTF-8 input)
		CONFIG_LAST_SUPPORTED_WCHAR=0 \
{{ if env.variant == "glibc" then ( -}}
# As long as we rely on libnss (see below), we have to have libc.so anyhow, so we've removed CONFIG_STATIC here... 😭
{{ ) else ( -}}
		CONFIG_STATIC=y \
{{ ) end -}}
	'; \
	\
	unsetConfs=' \
		CONFIG_FEATURE_SYNC_FANCY \
{{ if env.variant == "musl" then ( -}}
		\
# see https://wiki.musl-libc.org/wiki/Building_Busybox
		CONFIG_FEATURE_HAVE_RPC \
		CONFIG_FEATURE_INETD_RPC \
		CONFIG_FEATURE_UTMP \
		CONFIG_FEATURE_WTMP \
{{ ) else "" end -}}
	'; \
	\
	make defconfig; \
	\
	for conf in $unsetConfs; do \
		sed -i \
			-e "s!^$conf=.*\$!# $conf is not set!" \
			.config; \
	done; \
	\
	for confV in $setConfs; do \
		conf="${confV%=*}"; \
		sed -i \
			-e "s!^$conf=.*\$!$confV!" \
			-e "s!^# $conf is not set\$!$confV!" \
			.config; \
		if ! grep -q "^$confV\$" .config; then \
			echo "$confV" >> .config; \
		fi; \
	done; \
	\
	make oldconfig; \
	\
# trust, but verify
	for conf in $unsetConfs; do \
		! grep -q "^$conf=" .config; \
	done; \
	for confV in $setConfs; do \
		grep -q "^$confV\$" .config; \
	done

RUN set -eux; \
	nproc="$(nproc)"; \
{{ if env.variant == "uclibc" then ( -}}
	CROSS_COMPILE="$(basename /usr/src/buildroot/output/host/usr/*-buildroot-linux-uclibc*)"; \
	export CROSS_COMPILE="$CROSS_COMPILE-"; \
{{ ) else "" end -}}
	make -j "$nproc" busybox; \
	./busybox --help; \
	mkdir -p rootfs/bin; \
	ln -vL busybox rootfs/bin/; \
	\
{{ if env.variant == "uclibc" then ( -}}
# copy "getconf" from buildroot
	ln -vL ../buildroot/output/target/usr/bin/getconf rootfs/bin/; \
{{ ) elif env.variant == "glibc" then ( -}}
# copy "getconf" from Debian
	getconf="$(which getconf)"; \
	ln -vL "$getconf" rootfs/bin/getconf; \
	\
# hack hack hack hack hack
# with glibc, busybox (static or not) uses libnss for DNS resolution :(
	mkdir -p rootfs/etc; \
	cp /etc/nsswitch.conf rootfs/etc/; \
	mkdir -p rootfs/lib; \
	ln -sT lib rootfs/lib64; \
	gccMultiarch="$(gcc -print-multiarch)"; \
	set -- \
		rootfs/bin/busybox \
		rootfs/bin/getconf \
		/lib/"$gccMultiarch"/libnss*.so.* \
# libpthread is part of glibc: https://stackoverflow.com/a/11210463/433558
		/lib/"$gccMultiarch"/libpthread*.so.* \
	; \
	while [ "$#" -gt 0 ]; do \
		f="$1"; shift; \
		fn="$(basename "$f")"; \
		if [ -e "rootfs/lib/$fn" ]; then continue; fi; \
		if [ "${f#rootfs/}" = "$f" ]; then \
			if [ "${fn#ld-}" = "$fn" ]; then \
				ln -vL "$f" "rootfs/lib/$fn"; \
			else \
				cp -v "$f" "rootfs/lib/$fn"; \
			fi; \
		fi; \
		ldd="$(ldd "$f" | awk ' \
			$1 ~ /^\// { print $1; next } \
			$2 == "=>" && $3 ~ /^\// { print $3; next } \
		')"; \
		set -- "$@" $ldd; \
	done; \
{{ ) elif env.variant == "musl" then ( -}}
# copy simplified getconf port from Alpine
# https://github.com/alpinelinux/aports/commits/HEAD/main/musl/getconf.c
	curl -fsSL \
		"https://github.com/alpinelinux/aports/raw/48b16204aeeda5bc1f87e49c6b8e23d9abb07c73/main/musl/getconf.c" \
		-o /usr/src/getconf.c \
	; \
	echo 'd87d0cbb3690ae2c5d8cc218349fd8278b93855dd625deaf7ae50e320aad247c */usr/src/getconf.c' | sha256sum -c -; \
	gcc -o rootfs/bin/getconf -static -Os /usr/src/getconf.c; \
{{ ) else "" end -}}
	chroot rootfs /bin/getconf _NPROCESSORS_ONLN; \
	\
# TODO make this create symlinks instead so the output tarball is cleaner (but "-s" outputs absolute symlinks which is kind of annoying to deal with -- we should also consider letting busybox determine the "install paths"; see "busybox --list-full")
	chroot rootfs /bin/busybox --install /bin

# install a few extra files from buildroot (/etc/passwd, etc)
RUN set -eux; \
{{ if env.variant == "uclibc" then "" else ( -}}
	buildrootVersion={{ .buildroot.version | @sh }}; \
	for file in \
		system/device_table.txt \
		system/skeleton/etc/group \
		system/skeleton/etc/passwd \
		system/skeleton/etc/shadow \
	; do \
		dir="$(dirname "$file")"; \
		mkdir -p "../buildroot/$dir"; \
		curl -fL -o "../buildroot/$file" "https://gitlab.com/buildroot.org/buildroot/-/raw/$buildrootVersion/$file"; \
		[ -s "../buildroot/$file" ]; \
	done; \
	\
{{ ) end -}}
	mkdir -p rootfs/etc; \
	ln -vL \
		../buildroot/system/skeleton/etc/group \
		../buildroot/system/skeleton/etc/passwd \
		../buildroot/system/skeleton/etc/shadow \
		rootfs/etc/ \
	; \
# CVE-2019-5021, https://github.com/docker-library/official-images/pull/5880#issuecomment-490681907
	grep -E '^root::' rootfs/etc/shadow; \
	sed -ri -e 's/^root::/root:*:/' rootfs/etc/shadow; \
	grep -E '^root:[*]:' rootfs/etc/shadow; \
# set expected permissions, etc too (https://gitlab.com/buildroot.org/buildroot/-/blob/HEAD/system/device_table.txt)
	awk ' \
		!/^#/ { \
			if ($2 != "d" && $2 != "f") { \
				printf "error: unknown type \"%s\" encountered in line %d: %s\n", $2, NR, $0 > "/dev/stderr"; \
				exit 1; \
			} \
			sub(/^\/?/, "rootfs/", $1); \
			if ($2 == "d") { \
				printf "mkdir -p %s\n", $1; \
			} \
			printf "chmod %s %s\n", $3, $1; \
		} \
	' ../buildroot/system/device_table.txt | sh -eux

# create missing home directories and ensure /usr/bin/env exists
RUN set -eux; \
	cd rootfs; \
	for userHome in $(awk -F ':' '{ print $3 ":" $4 "=" $6 }' etc/passwd); do \
		user="${userHome%%=*}"; \
		home="${userHome#*=}"; \
		home="./${home#/}"; \
		if [ ! -d "$home" ]; then \
			mkdir -p "$home"; \
			chown "$user" "$home"; \
			chmod 755 "$home"; \
		fi; \
	done; \
	if [ ! -s usr/bin/env ] && [ -s bin/env ]; then \
		mkdir -p usr/bin; \
		ln -s ../../bin/env usr/bin/; \
	fi

# test and make sure it works
RUN chroot rootfs /usr/bin/env sh -xec 'true'

# ensure correct timezone (UTC)
RUN set -eux; \
	ln -vL /usr/share/zoneinfo/UTC rootfs/etc/localtime; \
	[ "$(chroot rootfs date +%Z)" = 'UTC' ]

# test and make sure DNS works too
RUN set -eux; \
	cp -L /etc/resolv.conf rootfs/etc/; \
	chroot rootfs /bin/sh -xec 'nslookup google.com'; \
	rm rootfs/etc/resolv.conf

# vim:set ft=dockerfile: