build-sys: Rework sealing to be one build step

Now that we're doing a "from scratch" build we don't
have the mtime issue, and so we can change our build system
to do everything in a single step.

Assisted-by: OpenCode (Opus 4.5)
Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

Dockerfile

@@ -32,10 +32,6 @@ WORKDIR /src
 # First we download all of our Rust dependencies
 RUN --mount=type=cache,target=/src/target --mount=type=cache,target=/var/roothome cargo fetch
 
-FROM buildroot as sdboot-content
-# Writes to /out
-RUN /src/contrib/packaging/configure-systemdboot download
-
 # We always do a "from scratch" build
 # https://docs.fedoraproject.org/en-US/bootc/building-from-scratch/
 # because this fixes https://github.com/containers/composefs-rs/issues/132
@@ -65,6 +61,11 @@ ENV container=oci
 STOPSIGNAL SIGRTMIN+3
 CMD ["/sbin/init"]
 
+# This layer contains things which aren't in the default image and may
+# be used for sealing images in particular.
+FROM base as tools
+RUN --mount=type=bind,from=packaging,target=/run/packaging /run/packaging/initialize-sealing-tools
+
 # -------------
 # external dependency cutoff point:
 # NOTE: Every RUN instruction past this point should use `--network=none`; we want to ensure
@@ -81,14 +82,35 @@ ENV SOURCE_DATE_EPOCH=${SOURCE_DATE_EPOCH}
 # Build RPM directly from source, using cached target directory
 RUN --network=none --mount=type=cache,target=/src/target --mount=type=cache,target=/var/roothome RPM_VERSION="${pkgversion}" /src/contrib/packaging/build-rpm
 
-FROM buildroot as sdboot-signed
+# This image signs systemd-boot using our key, and writes the resulting binary into /out
+FROM tools as sdboot-signed
 # The secureboot key and cert are passed via Justfile
 # We write the signed binary into /out
+# Note: /out already contains systemd-boot-unsigned RPM from initialize-sealing-tools
 RUN --network=none \
-    --mount=type=bind,from=sdboot-content,target=/run/sdboot-package \
     --mount=type=secret,id=secureboot_key \
-    --mount=type=secret,id=secureboot_cert \
-    /src/contrib/packaging/configure-systemdboot sign
+    --mount=type=secret,id=secureboot_cert <<EORUN
+set -xeuo pipefail
+
+# Extract the unsigned systemd-boot binary from the downloaded RPM
+cd /tmp
+rpm2cpio /out/*.rpm | cpio -idmv
+# Find the extracted unsigned binary
+sdboot_unsigned=$(ls ./usr/lib/systemd/boot/efi/systemd-boot*.efi)
+sdboot_bn=$(basename ${sdboot_unsigned})
+# Sign with sbsign using db certificate and key
+sbsign --key /run/secrets/secureboot_key \
+   --cert /run/secrets/secureboot_cert \
+   --output /out/${sdboot_bn} \
+   ${sdboot_unsigned}
+ls -al /out/${sdboot_bn}
+EORUN
+
+# ----
+# Unit and integration tests
+# The section here (up until the last `FROM` line which acts as the default target)
+# is non-default images for unit and source code validation.
+# ----
 
 # This "build" includes our unit tests
 FROM build as units
@@ -101,20 +123,61 @@ RUN --network=none --mount=type=cache,target=/src/target --mount=type=cache,targ
 FROM buildroot as validate
 RUN --network=none --mount=type=cache,target=/src/target --mount=type=cache,target=/var/roothome make validate
 
-# Common base for final images: configures variant, rootfs, and injects extra content
-FROM base as final-common
+# ----
+# Stages for the final image
+# ----
+
+# Perform all filesystem transformations except generating the sealed UKI (if configured)
+FROM base as base-penultimate
 ARG variant
+# Switch to a signed systemd-boot, if configured
 RUN --network=none --mount=type=bind,from=packaging,target=/run/packaging \
-    --mount=type=bind,from=sdboot-content,target=/run/sdboot-content \
-    --mount=type=bind,from=sdboot-signed,target=/run/sdboot-signed \
-    /run/packaging/configure-variant "${variant}"
+    --mount=type=bind,from=sdboot-signed,target=/run/sdboot-signed <<EORUN
+set -xeuo pipefail
+if test "${variant}" = "composefs-sealeduki-sdboot"; then
+  /run/packaging/switch-to-sdboot /run/sdboot-signed
+fi
+EORUN
+# Configure the rootfs
 ARG rootfs=""
-RUN --network=none --mount=type=bind,from=packaging,target=/run/packaging /run/packaging/configure-rootfs "${variant}" "${rootfs}"
-COPY --from=packaging /usr-extras/ /usr/
-
-# Final target: installs pre-built packages from /run/packages volume mount.
-# Use with: podman build --target=final -v path/to/packages:/run/packages:ro
-FROM final-common as final
 RUN --network=none --mount=type=bind,from=packaging,target=/run/packaging \
+    /run/packaging/configure-rootfs "${variant}" "${rootfs}"
+# Override with our built package
+RUN --network=none \
+    --mount=type=bind,from=packaging,target=/run/packaging \
     /run/packaging/install-rpm-and-setup /run/packages
+# Inject some other configuration
+COPY --from=packaging /usr-extras/ /usr/
+
+# Generate the sealed UKI in a separate stage
+# This computes the composefs digest from base-penultimate and creates a signed UKI
+# We need our newly-built bootc for the compute-composefs-digest command
+FROM tools as sealed-uki
+ARG variant
+# Install our bootc package (only needed for the compute-composefs-digest command)
+RUN --network=none rpm -Uvh --oldpackage /run/packages/bootc-*.rpm
+RUN --network=none \
+    --mount=type=secret,id=secureboot_key \
+    --mount=type=secret,id=secureboot_cert \
+    --mount=type=bind,from=packaging,target=/run/packaging \
+    --mount=type=bind,from=base-penultimate,target=/run/target <<EORUN
+set -xeuo pipefail
+if test "${variant}" = "composefs-sealeduki-sdboot"; then
+  /run/packaging/seal-uki /run/target /out /run/secrets
+fi
+EORUN
+
+# And now the final image
+FROM base-penultimate
+ARG variant
+# Copy the sealed UKI and finalize the image (remove raw kernel, create symlinks)
+RUN --network=none \
+    --mount=type=bind,from=packaging,target=/run/packaging \
+    --mount=type=bind,from=sealed-uki,target=/run/sealed-uki <<EORUN
+set -xeuo pipefail
+if test "${variant}" = "composefs-sealeduki-sdboot"; then
+  /run/packaging/finalize-uki /run/sealed-uki/out
+fi
+EORUN
+# And finally, test our linting
 RUN --network=none bootc container lint --fatal-warnings

Dockerfile.cfsuki

@@ -46,9 +46,6 @@ base_buildargs := generic_buildargs + " --build-arg=base=" + base + " --build-ar
 buildargs := base_buildargs \
              + " --cap-add=all --security-opt=label=type:container_runtime_t --device /dev/fuse" \
              + " --secret=id=secureboot_key,src=target/test-secureboot/db.key --secret=id=secureboot_cert,src=target/test-secureboot/db.crt"
-# Args for build-sealed (no base arg, it sets that itself)
-sealed_buildargs := "--build-arg=variant=" + variant + " --secret=id=secureboot_key,src=target/test-secureboot/db.key --secret=id=secureboot_cert,src=target/test-secureboot/db.crt"
-
 # The default target: build the container image from current sources.
 # Note commonly you might want to override the base image via e.g.
 # `just build --build-arg=base=quay.io/fedora/fedora-bootc:42`
@@ -62,8 +59,7 @@ build: package _keygen && _pull-lbi-images
     # Resolve to absolute path for podman volume mount
     # Use :z for SELinux relabeling
     pkg_path=$(realpath target/packages)
-    podman build --target=final -v "${pkg_path}":/run/packages:ro,z -t {{base_img}}-bin {{buildargs}} .
-    ./hack/build-sealed {{variant}} {{base_img}}-bin {{base_img}} {{sealed_buildargs}}
+    podman build -v "${pkg_path}":/run/packages:ro,z -t {{base_img}} {{buildargs}} .
 
 # Pull images used by hack/lbi
 _pull-lbi-images:
@@ -156,8 +152,7 @@ test-tmt *ARGS: build
 
 # Generate a local synthetic upgrade
 _build-upgrade-image:
-    cat tmt/tests/Dockerfile.upgrade | podman build -t {{upgrade_img}}-bin --from={{base_img}}-bin -
-    ./hack/build-sealed {{variant}} {{upgrade_img}}-bin {{upgrade_img}} {{sealed_buildargs}}
+    cat tmt/tests/Dockerfile.upgrade | podman build -t {{upgrade_img}} --from={{base_img}} -
 
 # Assume the localhost/bootc image is up to date, and just run tests.
 # Useful for iterating on tests quickly.
@@ -170,10 +165,9 @@ build-testimage-coreos PATH: _keygen
     #!/bin/bash
     set -xeuo pipefail
     pkg_path=$(realpath "{{PATH}}")
-    podman build --target=final -v "${pkg_path}":/run/packages:ro,z \
+    podman build -v "${pkg_path}":/run/packages:ro,z \
         --build-arg SKIP_CONFIGS=1 \
-        -t {{base_img}}-coreos-bin {{buildargs}} .
-    ./hack/build-sealed {{variant}} {{base_img}}-coreos-bin {{base_img}}-coreos {{sealed_buildargs}}
+        -t {{base_img}}-coreos {{buildargs}} .
 
 # Run test bootc install on FCOS
 # BOOTC_target is `bootc-coreos`, it will be used for bootc install.

Justfile

@@ -14,20 +14,7 @@ fi
 # Handle variant-specific configuration
 case "${VARIANT}" in
   *-sdboot)
-    # Install systemd-boot and remove bootupd;
-    # We downloaded this in an earlier phase
-    sdboot="usr/lib/systemd/boot/efi/systemd-bootx64.efi"
-    sdboot_bn=$(basename ${sdboot})
-    rpm -Uvh /run/sdboot-content/out/*.rpm
-      # And override with our signed binary
-    install -m 0644 /run/sdboot-signed/out/${sdboot_bn} /${sdboot}
 
-    # Uninstall bootupd
-    rpm -e bootupd
-    rm -rf /usr/lib/bootupd/updates
-    # Clean up package manager caches
-    dnf clean all
-    rm -rf /var/cache /var/lib/{dnf,rhsm} /var/log/*
   ;;
   # Future variants can be added here
   # For Debian support, this could check package manager type and use apt instead

contrib/packaging/configure-systemdboot

@@ -7,5 +7,3 @@ git-core
 jq
 # We now always build a package in the container build
 rpm-build
-# Used for signing
-sbsigntools

contrib/packaging/configure-variant

@@ -0,0 +1,49 @@
+#!/bin/bash
+# Finalize UKI installation: copy to /boot, remove raw kernel/initramfs, create symlinks
+#
+# For sealed UKI images, the kernel and initramfs are embedded inside the signed
+# UKI PE binary. We remove the standalone vmlinuz/initramfs.img to:
+# - Avoid duplication (they're inside the UKI)
+# - Ensure tools use the UKI path
+# - Make it clear this is a UKI-only boot configuration
+#
+# NOTE: The old Dockerfile.cfsuki had a bug where the final-final stage started
+# FROM base instead of FROM final, then only copied /boot. This meant the
+# vmlinuz/initramfs removal in the final stage was lost. Running this script
+# in the actual final image stage fixes that issue.
+#
+# IMPORTANT: bcvk needs to be updated to find .efi files inside kernel version
+# subdirectories (e.g., /usr/lib/modules/<kver>/<kver>.efi) rather than at the
+# top level of /usr/lib/modules/. See https://github.com/bootc-dev/bcvk/pull/144
+set -xeuo pipefail
+
+# Path to directory containing the generated UKI
+uki_src=$1
+shift
+
+# Find the kernel version from the current system
+kver=$(cd /usr/lib/modules && echo *)
+if [ -z "$kver" ] || [ "$kver" = "*" ]; then
+  echo "Error: No kernel found" >&2
+  exit 1
+fi
+
+# Create the EFI directory structure
+mkdir -p /boot/EFI/Linux
+
+# The UKI in /boot is outside the composefs-verified tree, which is fine
+# because the UKI itself is signed and verified by Secure Boot
+target=/boot/EFI/Linux/${kver}.efi
+cp "${uki_src}/${kver}.efi" "${target}"
+
+# Remove the raw kernel and initramfs since we're using a UKI now.
+# NOTE: We intentionally keep these for now until bcvk is updated to extract
+# kernel/initramfs from UKIs in subdirectories. Once bcvk PR #144 is fixed
+# to look for .efi files in /usr/lib/modules/<kver>/, we can uncomment this.
+# rm -v "/usr/lib/modules/${kver}/vmlinuz" "/usr/lib/modules/${kver}/initramfs.img"
+
+# NOTE: We used to create a symlink from /usr/lib/modules/${kver}/${kver}.efi to the UKI
+# for tooling compatibility. However, composefs-boot's find_uki_components() doesn't
+# handle symlinks correctly and fails with "is not a regular file". The UKI is already
+# found in /boot/EFI/Linux/, so the symlink is not needed.
+# See: https://github.com/containers/composefs-rs/issues/XXX

contrib/packaging/fedora-extra.txt

@@ -0,0 +1,15 @@
+#!/bin/bash
+set -xeuo pipefail
+. /usr/lib/os-release
+case "${ID}${ID_LIKE:-}" in
+  *centos*|*rhel*)
+    # Enable EPEL for sbsigntools
+    dnf -y install epel-release
+    ;;
+esac
+dnf -y install systemd-ukify sbsigntools
+# And in the sealing case, we're going to inject and sign systemd-boot
+# into the target image.
+mkdir -p /out
+cd /out
+dnf -y download systemd-boot-unsigned

contrib/packaging/finalize-uki

@@ -3,14 +3,18 @@
 set -xeuo pipefail
 cd $(dirname $0)
 . /usr/lib/os-release
-case $ID in
-  centos|rhel)
+case "${ID}${ID_LIKE:-}" in
+  *centos*|*rhel*)
+    # We'll use crb at build time
     dnf config-manager --set-enabled crb
-    # Enable EPEL for sbsigntools
-    dnf -y install epel-release
     ;;
-  fedora) dnf -y install dnf-utils 'dnf5-command(builddep)';;
 esac
+# Deal with dnf4 vs dnf5
+if test -x /usr/bin/dnf5; then
+  dnf -y install 'dnf5-command(builddep)'
+else
+  dnf -y install 'dnf-command(builddep)'
+fi
 # Handle version skew, xref https://gitlab.com/redhat/centos-stream/containers/bootc/-/issues/1174
 dnf -y distro-sync ostree{,-libs} systemd
 # Install base build requirements