safer/simpler uid/gid mapping w/ reduced build privs

Makefile

@@ -111,7 +111,7 @@ sign: $(RELEASE_DIR)/*.rom $(RELEASE_DIR)/*.iso
 .PHONY: shell
 shell:
 	$(docker) inspect "$(NAME)" \
-	&& $(docker) exec --interactive --tty "$(NAME)" shell \
+	&& $(docker) exec --interactive --user=root --tty "$(NAME)" shell \
 	|| $(contain) shell
 
 
@@ -119,7 +119,7 @@ shell:
 menuconfig:
 	$(contain) menuconfig
 
-.PHONY: menuconfig
+.PHONY: linux-menuconfig
 linux-menuconfig:
 	$(contain) linux-menuconfig
 
@@ -163,7 +163,6 @@ contain := \
 		--interactive \
 		--name "$(NAME)" \
 		--hostname "$(NAME)" \
-		--user $(userid):$(groupid) \
 		--env TARGET="$(TARGET)" \
 		--env DEVICES="$(DEVICES)" \
 		--env GIT_DATETIME="$(GIT_DATETIME)" \
@@ -172,7 +171,8 @@ contain := \
 		--env GIT_AUTHOR="$(GIT_AUTHOR)" \
 		--env GIT_KEY="$(GIT_KEY)" \
 		--env GIT_STATE="$(GIT_STATE)" \
-		--security-opt seccomp=unconfined \
+		--env UID="$(shell id -u)" \
+		--env GID="$(shell id -g)" \
 		--volume $(PWD)/build:/home/build/build \
 		--volume $(PWD)/config:/home/build/config \
 		--volume $(PWD)/release:/home/build/release \

config/container/Dockerfile

@@ -1,39 +1,4 @@
 ARG DEBIAN_IMAGE_HASH=4ab3309ba955211d1db92f405be609942b595a720de789286376f030502ffd6f
-ARG GOLANG_IMAGE_HASH=84349ee862d8bafff35e0d2bfd539da565b536b4dfce654773fc21a1db2da6d7
-
-FROM golang@sha256:${GOLANG_IMAGE_HASH} as gotools
-
-ARG FIXUID_GIT_REF="0ec93d22e52bde5b7326e84cb62fd26a3d20cead"
-ARG OZZOCONFIG_GIT_REF="0ff174cf5aa6480026e0b40c14fd9cfb61c4abf6"
-ARG JSONPREPROCESS_GIT_REF="a4e954386171be645f1eb7c41865d2624b69259d"
-ARG TOML_GIT_REF="3012a1dbe2e4bd1391d42b32f0577cb7bbc7f005"
-ARG YAMLV2_GIT_REF="51d6538a90f86fe93ac480b35f37b2be17fef232"
-ARG GLIDE_GIT_REF="b94b39d657d8abcccba6545e148f1201aee6ffec"
-
-RUN apk add bash git make
-
-RUN printf "\
-github.com/boxboat/fixuid.git github.com/boxboat/fixuid ${FIXUID_GIT_REF} \n\
-github.com/go-ozzo/ozzo-config github.com/go-ozzo/ozzo-config ${OZZOCONFIG_GIT_REF} \n\
-github.com/hnakamur/jsonpreprocess github.com/hnakamur/jsonpreprocess ${JSONPREPROCESS_GIT_REF} \n\
-github.com/BurntSushi/toml github.com/BurntSushi/toml ${TOML_GIT_REF} \n\
-github.com/go-yaml/yaml gopkg.in/yaml.v2 ${YAMLV2_GIT_REF} \n" \
-> /go/src/repos
-
-RUN echo ' \
-    set -o nounset -o pipefail -o errexit; \
-    cat /go/src/repos | while read -r line; do \
-        repo=$(echo $line | awk "{ print \$1 }"); \
-        folder=$(echo $line | awk "{ print \$2 }"); \
-        ref=$(echo $line | awk "{ print \$3 }"); \
-        git clone "https://${repo}" "/go/src/${folder}"; \
-        git -C "/go/src/${folder}" checkout ${ref};  \
-    done' \
-| bash
-
-RUN go build -o /usr/local/bin/fixuid github.com/boxboat/fixuid
-
-
 FROM debian@sha256:${DEBIAN_IMAGE_HASH} as debian
 
 ENV DEBIAN_FRONTEND=noninteractive \
@@ -43,14 +8,6 @@ ENV DEBIAN_FRONTEND=noninteractive \
     HOME=/home/build \
     PATH=/home/build/scripts:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 
-## Setup fixuid for mounting host-dirs with correct permissions during dev
-COPY --from=gotools /usr/local/bin/ /usr/local/bin/
-RUN chown root:root /usr/local/bin/fixuid \
-    && chmod 4755 /usr/local/bin/fixuid \
-    && mkdir -p /etc/fixuid \
-    && printf "user: build\ngroup: build\npaths:\n  - /\n  - /home/build/build\n" > /etc/fixuid/config.yml
-ENTRYPOINT ["/usr/local/bin/fixuid", "-q"]
-
 ADD scripts/ /usr/local/bin/
 
 ## Install packages from packages.list with retry
@@ -59,11 +16,6 @@ ADD config/container/packages.list /etc/apt/packages.list
 ADD config/container/apt.conf /etc/apt/apt.conf
 RUN apt-install
 
-## Create build user with sudo privs
-RUN useradd -G plugdev,sudo -ms /bin/bash build \
-    && chown -R build:build /home/build \
-    && echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
-
 WORKDIR /home/build
 
-USER build
+ENTRYPOINT ["/usr/local/bin/host-env"]

scripts/host-env

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e
+set -x
+
+uid=${UID?}
+gid=${GID?}
+user=${USER:-"build"}
+export HOME="/home/${user}"
+
+groupadd -g "$gid" "${user}"
+useradd \
+	-g "$gid" \
+	-u "$uid" \
+	-md "/home/${user}" \
+	-s /bin/bash \
+	"${user}"
+
+mkdir -p "$HOME"
+chown -R "$uid:$gid" "$HOME"
+cd "$HOME"
+setpriv --reuid="$uid" --regid="$gid" --init-groups "$@"