Use supermin in unprivileged environments

Dockerfile

@@ -2,7 +2,7 @@ FROM registry.fedoraproject.org/fedora:28
 WORKDIR /root/containerbuild
 
 # Only need a few of our scripts for the first few steps
-COPY ./build.sh ./deps.txt ./build-deps.txt /root/containerbuild/
+COPY ./build.sh ./deps.txt ./vmdeps.txt ./build-deps.txt /root/containerbuild/
 RUN ./build.sh configure_yum_repos
 RUN ./build.sh install_rpms
 
@@ -15,6 +15,10 @@ RUN ./build.sh configure_user
 WORKDIR /srv/
 RUN rm -rf /root/containerbuild
 
+# allow writing to /etc/passwd from arbitrary UID
+# https://docs.openshift.com/container-platform/3.10/creating_images/guidelines.html
+RUN chmod g=u /etc/passwd
+
 # run as `builder` user
 USER builder
 ENTRYPOINT ["/usr/bin/dumb-init", "/usr/bin/coreos-assembler"]

coreos-assembler

@@ -4,9 +4,24 @@ set -euo pipefail
 # Currently this just wraps the two binaries we have today
 # under a global entrypoint with subcommands.
 
-# docker/podman don't run through PAM, but we want this set
+# docker/podman don't run through PAM, but we want this set for the privileged
+# (non-virtualized) path
 export USER=${USER:-$(id -nu)}
 
+# When trying to connect to libvirt we get "Failed to find user record
+# for uid" errors if there is no entry for our UID in /etc/passwd.
+# This was taken from 'Support Arbitrary User IDs' section of:
+#   https://docs.openshift.com/container-platform/3.10/creating_images/guidelines.html
+if ! whoami &> /dev/null; then
+  # We need to make sure we set $HOME in the /etc/passwd file because
+  # if we don't libvirt will try to use `/` and we will get permission
+  # issues
+  export HOME="/var/tmp/${USER_NAME:-default}" && mkdir -p $HOME
+  if [ -w /etc/passwd ]; then
+      echo "${USER_NAME:-default}:x:$(id -u):0:${USER_NAME:-default} user:${HOME}:/sbin/nologin" >> /etc/passwd
+  fi
+fi
+
 # Ensure we've unshared our mount namespace so
 # the later umount doesn't affect the host potentially
 if [ -e /sys/fs/selinux/status ]; then

src/cmd-build

@@ -69,7 +69,7 @@ fi
 
 previous_commit=
 if [ -n "${ref:-}" ]; then
-    previous_commit=$(ostree --repo=${workdir}/repo rev-parse ${ref} || true)
+    previous_commit=$(ostree --repo=${workdir}/repo rev-parse ${ref} 2>/dev/null || true)
 fi
 # If the ref was unset or missing, look at the previous build
 if [ -z "${previous_commit}" ] && [ -n "${previous_build}" ]; then
@@ -145,13 +145,13 @@ else
 fi
 
 if [ -n "${previous_build}" ]; then
-    rpm-ostree --repo=${workdir}/repo-build db diff ${previous_commit} ${commit}
+    rpm-ostree --repo=${workdir}/repo db diff ${previous_commit} ${commit}
 fi
 
 image_input_checksum=$((echo ${commit} && echo ${kickstart_checksum}) | sha256sum_str)
 echo "New image input checksum: ${image_input_checksum}"
-version=$(ostree --repo=${workdir}/repo-build show --print-metadata-key=version ${commit} | sed -e "s,',,g")
-if [ "${previous_commit}" = "${commit}" ]; then
+version=$(ostree --repo=${workdir}/repo show --print-metadata-key=version ${commit} | sed -e "s,',,g")
+if [ "${previous_commit}" = "${commit}" ] && [ -n "${previous_image_genver:-}" ]; then
     image_genver=$((${previous_image_genver} + 1))
     buildid=${version}-${image_genver}
 else
@@ -160,15 +160,6 @@ else
 fi
 echo "New build ID: ${buildid}"
 
-# https://github.com/ostreedev/ostree/issues/1562#issuecomment-385393872
-# The passwd files (among others) don't have world readability.  This won't
-# actually corrupt the repository as the *canonical* permissions are stored
-# as xattrs.  Probably what we should do is have an ostree option to specify
-# a permission mask for objects.
-sudo chmod -R a+rX ${workdir}/repo-build/objects
-ostree --repo=${workdir}/repo pull-local ${workdir}/repo-build "${ref:-${commit}}"
-ostree --repo=${workdir}/repo summary -u
-
 # Generate JSON
 if [ -n "${previous_commit}" ]; then
     previous_commit_json='"'"${previous_commit}"'"'

src/cmd-clean

@@ -49,8 +49,7 @@ prepare_build
 
 # But go back to the toplevel
 cd ${workdir}
-# Note we don't prune the cache/ dir or the objects
-# in the repos.  If you want that, just rm -rf them.
+# Note we don't prune the cache.qcow2 or the objects
+# in the repo.  If you want that, just rm -rf them.
 rm -rf repo/refs/heads/* builds/* tmp/*
 ostree --repo=repo summary -u
-sudo rm -rf repo-build/refs/heads/*

src/cmd-init

@@ -66,13 +66,16 @@ if [ "$FORCE" != "1" -a ! -z "$(ls -A ./)" ]; then
    fatal "init: current directory is not empty, override with --force"
 fi
 
-set -x
 source=$1; shift
 subdir=${1:-}
 
 preflight
 
-sudo chown $USER: .
+if has_privileges; then
+    sudo chown $USER: .
+elif [ ! -w . ]; then
+    fatal "init: running unprivileged, and current directory not writable"
+fi
 
 INSTALLER=https://download.fedoraproject.org/pub/fedora/linux/releases/28/Everything/x86_64/iso/Fedora-Everything-netinst-x86_64-28-1.1.iso
 INSTALLER_CHECKSUM=https://download.fedoraproject.org/pub/fedora/linux/releases/28/Everything/x86_64/iso/Fedora-Everything-28-1.1-x86_64-CHECKSUM
@@ -116,4 +119,7 @@ mkdir -p cache
 mkdir -p builds
 mkdir -p tmp
 ostree --repo=repo init --mode=archive
-ostree --repo=repo-build init --mode=bare-user
+if ! has_privileges; then
+    qemu-img create -f qcow2 cache/cache.qcow2 10G
+    LIBGUESTFS_BACKEND=direct virt-format --filesystem=xfs -a cache/cache.qcow2
+fi

src/cmdlib.sh

@@ -1,7 +1,32 @@
 # Shared shell script library
 
+DIR=$(dirname $0)
+
+info() {
+    echo "info: $@" 1>&2
+}
+
 fatal() {
-    echo "error: $@" 1>&2; exit 1
+    info "$@"; exit 1
+}
+
+_privileged=
+has_privileges() {
+    if [ -z "${_privileged:-}" ]; then
+        if [ -n "${FORCE_UNPRIVILEGED:-}" ]; then
+            info "Detected FORCE_UNPRIVILEGED; using virt"
+            _privileged=0
+        elif ! capsh --print | grep -q 'Current.*cap_sys_admin'; then
+            info "Missing CAP_SYS_ADMIN; using virt"
+            _privileged=0
+        elif ! sudo true; then
+            info "Missing sudo privs; using virt"
+            _privileged=0
+        else
+            _privileged=1
+        fi
+    fi
+    [ ${_privileged} == 1 ]
 }
 
 preflight() {
@@ -28,27 +53,25 @@ preflight() {
         fatal "Unable to find /dev/kvm"
     fi
 
-    if ! capsh --print | grep -q 'Current.*cap_sys_admin'; then
-        fatal "This container must currently be run with --privileged"
-    fi
-
-    if ! sudo true; then
-        fatal "The user must currently have sudo privileges"
-    fi
-
     # permissions on /dev/kvm vary by (host) distro.  If it's
     # not writable, recreate it.
     if ! [ -w /dev/kvm ]; then
-        sudo rm -f /dev/kvm
-        sudo mknod /dev/kvm c 10 232
-        sudo setfacl -m u:$USER:rw /dev/kvm
+        if ! has_privileges; then
+            fatal "running unprivileged, and /dev/kvm not writable"
+        else
+            sudo rm -f /dev/kvm
+            sudo mknod /dev/kvm c 10 232
+            sudo setfacl -m u:$USER:rw /dev/kvm
+        fi
     fi
 }
 
 prepare_build() {
     preflight
     if ! [ -d repo ]; then
         fatal "No $(pwd)/repo found; did you run coreos-assembler init?"
+    elif ! has_privileges && [ ! -f cache/cache.qcow2 ]; then
+        fatal "No cache.qcow2 found; did you run coreos-assembler init?"
     fi
 
     export workdir=$(pwd)
@@ -95,10 +118,6 @@ prepare_build() {
 }
 
 runcompose() {
-    local treecompose_args=""
-    if ! grep -q '^# disable-unified-core' "${manifest}"; then
-        treecompose_args="${treecompose_args} --unified-core"
-    fi
     # Implement support for automatic local overrides:
     # https://github.com/coreos/coreos-assembler/issues/118
     local overridesdir=${workdir}/overrides/
@@ -126,10 +145,86 @@ EOF
     fi
 
     rm -f ${changed_stamp}
-    set -x
-    sudo rpm-ostree compose tree --repo=${workdir}/repo-build --cachedir=${workdir}/cache \
-         --touch-if-changed "${changed_stamp}" \
-         ${treecompose_args} \
-         ${TREECOMPOSE_FLAGS:-} ${manifest} "$@"
-    set +x
+
+    set - rpm-ostree compose tree --repo=${workdir}/repo \
+            --cachedir=${workdir}/cache --touch-if-changed "${changed_stamp}" \
+            ${manifest} "$@"
+
+    if ! grep -q '^# disable-unified-core' "${manifest}"; then
+        set - "$@" --unified-core
+    fi
+
+    echo "Running: $@"
+
+    # this is the heart of the privs vs no privs dual path
+    if has_privileges; then
+        sudo "$@"
+    else
+        runvm "$@"
+    fi
+}
+
+runvm() {
+    local vmpreparedir=${workdir}/tmp/supermin.prepare
+    local vmbuilddir=${workdir}/tmp/supermin.build
+
+    # use REBUILDVM=1 if e.g. hacking on rpm-ostree/ostree and wanting to get
+    # the new bits in the VM
+    if [ ! -f ${vmbuilddir}/.done ] || [ -n "${REBUILDVM:-}" ]; then
+        rm -rf ${vmpreparedir} ${vmbuilddir}
+        mkdir -p ${vmpreparedir} ${vmbuilddir}
+
+        local rpms=
+        # then add all the base deps
+        for dep in $(grep -v '^#' ${DIR}/vmdeps.txt); do
+            rpms+="$dep "
+        done
+
+        supermin --prepare --use-installed $rpms -o "${vmpreparedir}"
+
+        # the reason we do a heredoc here is so that the var substition takes
+        # place immediately instead of having to proxy them through to the VM
+        cat > "${vmpreparedir}/init" <<EOF
+#!/bin/bash
+set -xeuo pipefail
+workdir=${workdir}
+$(cat ${DIR}/supermin-init-prelude.sh)
+rc=0
+sh ${TMPDIR}/cmd.sh || rc=\$?
+echo \$rc > ${workdir}/tmp/rc
+/sbin/fstrim -v ${workdir}/cache
+/sbin/reboot -f
+EOF
+        chmod a+x ${vmpreparedir}/init
+        (cd ${vmpreparedir} && tar -czf init.tar.gz --remove-files init)
+        supermin --build "${vmpreparedir}" --size 5G -f ext2 -o "${vmbuilddir}"
+        touch "${vmbuilddir}/.done"
+    fi
+
+    echo "$@" > ${TMPDIR}/cmd.sh
+
+    # support local dev cases where src/config is a symlink
+    srcvirtfs=
+    if [ -L "${workdir}/src/config" ]; then
+        # qemu follows symlinks
+        srcvirtfs="-virtfs local,id=source,path=${workdir}/src/config,security_model=none,mount_tag=source"
+    fi
+
+    qemu-kvm -nodefaults -nographic -m 2048 -no-reboot \
+        -kernel "${vmbuilddir}/kernel" \
+        -initrd "${vmbuilddir}/initrd" \
+        -netdev user,id=eth0,hostname=supermin \
+        -device virtio-net-pci,netdev=eth0 \
+        -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x3 \
+        -drive if=none,id=drive-scsi0-0-0-0,snapshot=on,file="${vmbuilddir}/root" \
+        -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1 \
+        -drive if=none,id=drive-scsi0-0-0-1,discard=unmap,file="${workdir}/cache/cache.qcow2" \
+        -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=1,drive=drive-scsi0-0-0-1,id=scsi0-0-0-1 \
+        -virtfs local,id=workdir,path="${workdir}",security_model=none,mount_tag=workdir \
+        ${srcvirtfs} -serial stdio -append "root=/dev/sda console=ttyS0 selinux=1 enforcing=0 autorelabel=1"
+
+    if [ ! -f ${workdir}/tmp/rc ]; then
+        fatal "Couldn't find rc file, something went terribly wrong!"
+    fi
+    return $(cat ${workdir}/tmp/rc)
 }

src/deps.txt

@@ -1,3 +1,6 @@
+# For privileged ops
+supermin
+
 # We default to builder user, but sudo where necessary
 sudo
 

src/prune_builds

@@ -102,4 +102,3 @@ def ostree_prune(repo_name, sudo=False):
     subprocess.run(argv, check=True)
 
 ostree_prune('repo')
-ostree_prune('repo-build', sudo=True)

src/supermin-init-prelude.sh

@@ -0,0 +1,27 @@
+mount -t proc /proc /proc
+mount -t sysfs /sys /sys
+mount -t devtmpfs devtmpfs /dev
+
+# load selinux policy
+LANG=C /sbin/load_policy  -i
+
+# load kernel module for 9pnet_virtio for 9pfs mount
+/sbin/modprobe 9pnet_virtio
+
+# need fuse module for rofiles-fuse/bwrap during post scripts run
+/sbin/modprobe fuse
+
+# set up networking
+/usr/sbin/dhclient eth0
+
+# set up workdir
+mkdir -p ${workdir}
+mount -t 9p -o rw,trans=virtio,version=9p2000.L workdir ${workdir}
+if [ -L ${workdir}/src/config ]; then
+    mkdir -p $(readlink ${workdir}/src/config)
+    mount -t 9p -o rw,trans=virtio,version=9p2000.L source ${workdir}/src/config
+fi
+mkdir -p ${workdir}/cache
+mount /dev/sdb1 ${workdir}/cache
+
+cd ${workdir}

src/vmdeps.txt

@@ -0,0 +1,16 @@
+# Base deps for a viable VM environment.
+
+# bare essentials
+bash vim-minimal coreutils util-linux procps-ng kmod kernel-modules
+
+# for composes
+rpm-ostree distribution-gpg-keys jq
+
+# for clean reboot
+systemd
+
+# networking
+dhcp-client bind-export-libs iproute
+
+# SELinux
+selinux-policy selinux-policy-targeted policycoreutils

vmdeps.txt

@@ -0,0 +1 @@
+./src/vmdeps.txt