Revert PR #3534 "sysext: Add OS-dependent sysext compression"

Revert PR #3162 "Signed OS-dependent sysexts"

Signed-off-by: Daniel Zatovic <daniel.zatovic@gmail.com>

build_library/prod_image_util.sh

@@ -170,10 +170,6 @@ EOF
   # Remove source locale data, only need to ship the compiled archive.
   sudo rm -rf ${root_fs_dir}/usr/share/i18n/
 
-  # Inject ephemeral sysext signing certificate
-  sudo mkdir -p "${root_fs_dir}/usr/lib/verity.d"
-  sudo cp "${SYSEXT_SIGNING_KEY_DIR}/sysexts.crt" "${root_fs_dir}/usr/lib/verity.d"
-
   # Finish image will move files from /etc to /usr/share/flatcar/etc.
   # Note that image filesystem contents generated by finish_image will not
   # include sysext contents (only the sysext squashfs files themselves).

build_library/sysext_prod_builder

@@ -63,15 +63,11 @@ create_prod_sysext() {
   # The --install_root_basename="${name}-base-sysext-rootfs" flag is
   # important - it sets the name of a rootfs directory, which is used
   # to determine the package target in coreos/base/profile.bashrc
-  #
-  # Built-in sysexts are stored in the compressed /usr partition, so we
-  # disable compression to avoid double-compression.
-  sudo -E "FLATCAR_BUILD_ID=$FLATCAR_BUILD_ID" "${SCRIPTS_DIR}/build_sysext" \
+  sudo "FLATCAR_BUILD_ID=$FLATCAR_BUILD_ID" "${SCRIPTS_DIR}/build_sysext" \
             --board="${BOARD}" \
             --image_builddir="${workdir}/sysext-build" \
             --squashfs_base="${base_sysext}" \
             --generate_pkginfo \
-            --compression=none \
             --install_root_basename="${name}-base-sysext-rootfs" \
             "${build_sysext_opts[@]}" \
             "${name}" "${grp_pkg[@]}"
@@ -103,14 +99,6 @@ sysext_mountdir="${BUILD_DIR}/prod-sysext-work/mounts"
 sysext_base="${sysext_workdir}/base-os.squashfs"
 
 function cleanup() {
-  IFS=':' read -r -a mounted_sysexts <<< "$sysext_lowerdirs"
-  # skip the rootfs
-  mounted_sysexts=("${mounted_sysexts[@]:1}")
-
-  for sysext in "${mounted_sysexts[@]}"; do
-    sudo systemd-dissect --umount --rmdir "$sysext"
-  done
-
   sudo umount "${sysext_mountdir}"/* || true
   rm -rf "${sysext_workdir}" || true
 }
@@ -128,7 +116,6 @@ sudo mksquashfs "${root_fs_dir}" "${sysext_base}" -noappend -xattrs-exclude '^bt
 # for combined overlay later.
 prev_pkginfo=""
 sysext_lowerdirs="${sysext_mountdir}/rootfs-lower"
-mkdir -p "${sysext_mountdir}"
 for sysext in ${sysexts_list//,/ }; do
   # format is "<name>:<group>/<package>"
   name="${sysext%|*}"
@@ -142,21 +129,12 @@ for sysext in ${sysexts_list//,/ }; do
                      "${grp_pkg}" \
                      "${prev_pkginfo}"
 
-  sudo systemd-dissect \
-    --read-only \
-    --mount \
-    --mkdir \
-    --image-policy='root=encrypted+unprotected+absent:usr=encrypted+unprotected+absent' \
-    "${sysext_output_dir}/${name}.raw" \
-    "${sysext_mountdir}/${name}"
-
-  sudo systemd-dissect \
-    --read-only \
-    --mount \
-    --mkdir \
-    --image-policy='root=encrypted+unprotected+absent:usr=encrypted+unprotected+absent' \
-    "${sysext_output_dir}/${name}_pkginfo.raw" \
-    "${sysext_mountdir}/${name}_pkginfo"
+  mkdir -p "${sysext_mountdir}/${name}" \
+           "${sysext_mountdir}/${name}_pkginfo"
+  sudo mount -rt squashfs -o loop,nodev "${sysext_output_dir}/${name}.raw" \
+                                    "${sysext_mountdir}/${name}"
+  sudo mount -rt squashfs -o loop,nodev "${sysext_output_dir}/${name}_pkginfo.raw" \
+                                    "${sysext_mountdir}/${name}_pkginfo"
 
   sysext_lowerdirs="${sysext_lowerdirs}:${sysext_mountdir}/${name}"
   sysext_lowerdirs="${sysext_lowerdirs}:${sysext_mountdir}/${name}_pkginfo"

build_library/vm_image_util.sh

@@ -585,15 +585,11 @@ install_oem_sysext() {
     # important - it sets the name of a rootfs directory, which is
     # used to determine the package target in
     # coreos/base/profile.bashrc
-    #
-    # OEM sysexts are stored in the compressed partition, so we disable
-    # compression to avoid double-compression.
     local build_sysext_flags=(
         --board="${BOARD}"
         --squashfs_base="${VM_SRC_SYSEXT_IMG}"
         --image_builddir="${built_sysext_dir}"
         --metapkgs="${metapkg}"
-        --compression=none
         --install_root_basename="${VM_IMG_TYPE}-oem-sysext-rootfs"
     )
     local overlay_path mangle_fs
@@ -606,7 +602,7 @@ install_oem_sysext() {
     fi
 
     mkdir -p "${built_sysext_dir}"
-    sudo -E "${build_sysext_env[@]}" "${SCRIPT_ROOT}/build_sysext" "${build_sysext_flags[@]}" "${oem_sysext}"
+    sudo "${build_sysext_env[@]}" "${SCRIPT_ROOT}/build_sysext" "${build_sysext_flags[@]}" "${oem_sysext}"
 
     local installed_sysext_oem_dir='/oem/sysext'
     local installed_sysext_file_prefix="${oem_sysext}-${version}"

build_sysext

@@ -35,10 +35,10 @@ DEFINE_boolean generate_pkginfo "${FLAGS_FALSE}" \
   "Generate an additional squashfs '<sysext_name>_pkginfo.raw' with portage package meta-information (/var/db ...). Useful for creating sysext dependencies; see 'base_pkginfo' below."
 DEFINE_string base_pkginfo "" \
   "Colon-separated list of pkginfo squashfs paths / files generated via 'generate_pkginfo' to base this sysext on. The corresponding base sysexts are expected to be merged with the sysext generated."
-DEFINE_string compression "lz4hc" \
-  "Compression to use for sysext EROFS image. Options: 'lz4', 'lz4hc', 'zstd', or 'none'. Default is 'lz4hc'."
-DEFINE_string mkerofs_opts "" \
-  "Additional mkfs.erofs options to pass via SYSTEMD_REPART_MKFS_OPTIONS_EROFS. If not specified, defaults are used based on compression type."
+DEFINE_string compression "zstd" \
+  "Compression to use for sysext squashfs. One of 'gzip', 'lzo', 'lz4', 'xz', or 'zstd'. Must be supported by the Flatcar squashfs kernel module in order for the sysext to work."
+DEFINE_string mksquashfs_opts "" \
+  "Additional command line options to pass to mksquashfs. See 'man 1 mksquashfs'. If <compression> is 'zstd' (the default), this option defaults to '-Xcompression-level 22 -b 512K'. Otherwise the default is empty."
 DEFINE_boolean ignore_version_mismatch "${FLAGS_FALSE}" \
   "Ignore version mismatch between SDK board packages and base squashfs. DANGEROUS."
 DEFINE_string install_root_basename "${default_install_root_basename}" \
@@ -112,6 +112,10 @@ fi
 BUILD_DIR=$(realpath "${FLAGS_image_builddir}")
 mkdir -p "${BUILD_DIR}"
 
+if [[ "${FLAGS_compression}" = "zstd" && -z "${FLAGS_mksquashfs_opts}" ]] ; then
+    FLAGS_mksquashfs_opts="-Xcompression-level 22 -b 512k"
+fi
+
 source "${BUILD_LIBRARY_DIR}/toolchain_util.sh" || exit 1
 source "${BUILD_LIBRARY_DIR}/board_options.sh" || exit 1
 source "${BUILD_LIBRARY_DIR}/reports_util.sh" || exit 1
@@ -244,7 +248,7 @@ if [[ "$FLAGS_generate_pkginfo" = "${FLAGS_TRUE}" ]] ; then
   mkdir -p "${BUILD_DIR}/img-pkginfo/var/db"
   cp -R "${BUILD_DIR}/${FLAGS_install_root_basename}/var/db/pkg" "${BUILD_DIR}/img-pkginfo/var/db/"
   mksquashfs "${BUILD_DIR}/img-pkginfo" "${BUILD_DIR}/${SYSEXTNAME}_pkginfo.raw" \
-              -noappend -xattrs-exclude '^btrfs.' -comp zstd -Xcompression-level 22 -b 512k
+              -noappend -xattrs-exclude '^btrfs.' -comp "${FLAGS_compression}" ${FLAGS_mksquashfs_opts}
 fi
 
 info "Writing ${SYSEXTNAME}_packages.txt"
@@ -300,44 +304,14 @@ if [[ -n "${invalid_files}" ]]; then
   die "Invalid file ownership: ${invalid_files}"
 fi
 
-# Set up EROFS compression options based on compression type
-if [[ "${FLAGS_compression}" != "none" ]]; then
-  export SYSTEMD_REPART_MKFS_OPTIONS_EROFS="-z${FLAGS_compression}"
-
-  if [[ -n "${FLAGS_mkerofs_opts}" ]]; then
-    # User provided custom options
-    export SYSTEMD_REPART_MKFS_OPTIONS_EROFS="${SYSTEMD_REPART_MKFS_OPTIONS_EROFS} ${FLAGS_mkerofs_opts}"
-  elif [[ "${FLAGS_compression}" = "lz4hc" ]]; then
-    # Default options for lz4hc
-    export SYSTEMD_REPART_MKFS_OPTIONS_EROFS="${SYSTEMD_REPART_MKFS_OPTIONS_EROFS},12 -C65536 -Efragments,ztailpacking"
-  elif [[ "${FLAGS_compression}" = "zstd" ]]; then
-    # Default options for zstd
-    export SYSTEMD_REPART_MKFS_OPTIONS_EROFS="${SYSTEMD_REPART_MKFS_OPTIONS_EROFS},level=22 -C524288 -Efragments,ztailpacking"
-  fi
-  info "Building sysext with ${FLAGS_compression} compression"
-else
-  info "Building sysext without compression (built-in sysexts)"
-fi
-
-systemd-repart \
-  --private-key="${SYSEXT_SIGNING_KEY_DIR}/sysexts.key" \
-  --certificate="${SYSEXT_SIGNING_KEY_DIR}/sysexts.crt" \
-  --make-ddi=sysext \
-  --copy-source="${BUILD_DIR}/${FLAGS_install_root_basename}" \
-  "${BUILD_DIR}/${SYSEXTNAME}.raw"
-
+mksquashfs "${BUILD_DIR}/${FLAGS_install_root_basename}" "${BUILD_DIR}/${SYSEXTNAME}.raw" \
+               -noappend -xattrs-exclude '^btrfs.' -comp "${FLAGS_compression}" ${FLAGS_mksquashfs_opts}
 rm -rf "${BUILD_DIR}"/{fs-root,"${FLAGS_install_root_basename}",workdir}
 
 # Generate reports
 mkdir "${BUILD_DIR}/img-rootfs"
-systemd-dissect --read-only \
-  --mount \
-  --mkdir \
-  --image-policy='root=encrypted+unprotected+absent:usr=encrypted+unprotected+absent' \
-  "${BUILD_DIR}/${SYSEXTNAME}.raw" \
-  "${BUILD_DIR}/img-rootfs"
-
+mount -rt squashfs -o loop,nodev "${BUILD_DIR}/${SYSEXTNAME}.raw" "${BUILD_DIR}/img-rootfs"
 write_contents "${BUILD_DIR}/img-rootfs" "${BUILD_DIR}/${SYSEXTNAME}_contents.txt"
 write_contents_with_technical_details "${BUILD_DIR}/img-rootfs" "${BUILD_DIR}/${SYSEXTNAME}_contents_wtd.txt"
 write_disk_space_usage_in_paths "${BUILD_DIR}/img-rootfs" "${BUILD_DIR}/${SYSEXTNAME}_disk_usage.txt"
-systemd-dissect --umount --rmdir "${BUILD_DIR}/img-rootfs"
+umount "${BUILD_DIR}/img-rootfs"

changelog/changes/2025-11-05-signed-os-dependent-sysexts.md

@@ -1 +0,0 @@
-- OS-dependent sysexts (e.g., docker-flatcar, containerd-flatcar) are now cryptographically signed using dm-verity roothash signatures. This enables stricter sysext policies via systemd-sysext and provides a foundation for verifying user-provided extensions in future releases. The format changed from squashfs to erofs-based Discoverable Disk Images (DDI). ([scripts#3162](https://github.com/flatcar/scripts/pull/3162))

sdk_container/src/third_party/coreos-overlay/profiles/coreos/targets/sdk/package.use

@@ -32,6 +32,3 @@ x11-libs/pixman static-libs
 
 # Get latest EDK2 firmware for Secure Boot on arm64.
 app-emulation/qemu -pin-upstream-blobs
-
-# Needed for signed sysexts using systemd-repart
-sys-apps/systemd cryptsetup

sdk_lib/sdk_entry.sh

@@ -88,43 +88,6 @@ if ! grep -q 'export MODULE_SIGNING_KEY_DIR=' /home/sdk/.bashrc; then
     fi
 fi
 
-# Ensure sysext signing keys exist; regenerate if directory or files missing
-if grep -q 'export SYSEXT_SIGNING_KEY_DIR' /home/sdk/.bashrc; then
-    _existing_sysext_dir=$(source /home/sdk/.bashrc 2>/dev/null; echo "$SYSEXT_SIGNING_KEY_DIR")
-    if [[ -z "$_existing_sysext_dir" || ! -d "$_existing_sysext_dir" || ! -s "$_existing_sysext_dir/sysexts.key" || ! -s "$_existing_sysext_dir/sysexts.crt" ]]; then
-        # Drop stale export so block below regenerates
-        sed -i -e '/export SYSEXT_SIGNING_KEY_DIR=/d' /home/sdk/.bashrc
-    fi
-fi
-grep -q 'export SYSEXT_SIGNING_KEY_DIR' /home/sdk/.bashrc || {
-    if [[ ${COREOS_OFFICIAL:-0} -eq 1 ]]; then
-        SYSEXT_SIGNING_KEY_DIR=$(su sdk -c "mktemp -d")
-    else
-        SYSEXT_SIGNING_KEY_DIR="/home/sdk/.sysext-signing-keys"
-        su sdk -c "mkdir -p ${SYSEXT_SIGNING_KEY_DIR@Q}"
-    fi
-    if [[ ! "$SYSEXT_SIGNING_KEY_DIR" || ! -d "$SYSEXT_SIGNING_KEY_DIR" ]]; then
-        echo "Failed to create directory for sysext signing keys."
-    else
-        echo "export SYSEXT_SIGNING_KEY_DIR='$SYSEXT_SIGNING_KEY_DIR'" >> /home/sdk/.bashrc
-    fi
-    pushd "$SYSEXT_SIGNING_KEY_DIR" > /dev/null
-    build_id=$(source "/mnt/host/source/.repo/manifests/version.txt"; echo "$FLATCAR_BUILD_ID")
-    # Generate sysext signing key only if missing or empty
-    if [[ ! -s sysexts.key || ! -s sysexts.crt ]]; then
-      su sdk -c "openssl req -new -nodes -utf8 \
-        -x509 -batch -sha256 \
-        -days 36000 \
-        -outform PEM \
-        -out sysexts.crt \
-        -keyout sysexts.key \
-        -newkey 4096 \
-        -subj '/CN=Flatcar sysext key/OU=$build_id'" \
-          || echo "Generating sysext signing key failed"
-    fi
-    popd > /dev/null
-}
-
 # This is ugly.
 #   We need to sudo su - sdk -c so the SDK user gets a fresh login.
 #    'sdk' is member of multiple groups, and plain docker USER only