ebc: Add ibm-sel-ebc dracut module

Add 95ibm-sel-ebc dracut module for secure boot-time customization of
SEL guests.

Introduce the IBM SEL EBC dracut module (95ibm-sel-ebc) that enables
Early Boot Customization for SEL guests during the initramfs phase.

The module implements a critical security architecture to prevent
injection attacks: all EBC resources (.asr and .pol files) are copied from
/boot/sics (which resides in the qcow2 image on the host filesystem) to
/run/ibm-sel-ebc (a tmpfs/RAM-backed directory). Since guest RAM is
protected by the Ultravisor, this prevents malicious hosts from modifying
EBC resources during boot.

Systemd units and their purposes:
 - ibm-sel-ebc.target: Groups all EBC-related units
 - boot.mount: Mounts /dev/disk/by-label/boot to /boot
 - ibm-sel-ebc-ensure-sics.service: Fallback to create /boot/sics/ if boot
   partition mount fails (supports Kata VM scenarios)
 - ibm-sel-ebc-pvebc.service: Main unit that copies EBC resources to RAM,
   invokes pvebc tool to verify integrity and add ASRs to UV, retrieves
   LUKS passphrase from UV secret store
 - ibm-sel-ebc-override-crypttab.service: Replaces /etc/crypttab with
   prepared IBM SEL EBC crypttab, reloads systemd daemon, starts cryptsetup
   service
 - ibm-sel-ebc-paes-enforce.service: Verifies root filesystem uses PAES
   encryption to prevent root filesystem substitution attacks

All units write logs to /boot/sics/log for debugging, accessible even if
root filesystem fails to mount. Units are triggered by rd.ibm-sel-ebc
kernel parameter and only execute in initramfs
(ConditionPathExists=/etc/initrd-release).

Assisted-by: IBM Bob:1.0.1
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Finn Callies <fcallies@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/Makefile

@@ -10,6 +10,8 @@ CARGO_TARGETS :=
 PV_TARGETS :=
 CARGO_TEST_TARGETS :=
 
+SEL_EBC_MODDIR := 95sel-ebc
+
 ifneq (${HAVE_CARGO},0)
 	CARGO_TARGETS := pvebc
 
@@ -29,6 +31,7 @@ ifneq (${HAVE_LIBCURL},0)
 
 ifeq ($(HOST_ARCH),s390x)
 	PV_TARGETS += pvapconfig pvinfo
+	INSTALL_TARGETS += install-ebc-dracut-module
 else
 	BUILD_TARGETS += skip-pvapconfig skip-pvinfo
 endif #HOSTARCH
@@ -104,6 +107,23 @@ endif # CARGO
 
 rust-test: $(CARGO_TEST_TARGETS)
 
+install-ebc-dracut-module:
+ifneq ($(HAVE_DRACUT),0)
+	$(INSTALL) -m 755 -d $(DESTDIR)$(DRACUTMODDIR)/
+	$(INSTALL) -m 755 -d $(DESTDIR)$(DRACUTMODDIR)/$(SEL_EBC_MODDIR)
+	$(INSTALL) -m 755 pvebc/$(SEL_EBC_MODDIR)/module-setup.sh \
+		pvebc/$(SEL_EBC_MODDIR)/override-crypttab.sh \
+		pvebc/$(SEL_EBC_MODDIR)/pvebc-wrapper.sh \
+		$(DESTDIR)$(DRACUTMODDIR)/$(SEL_EBC_MODDIR)
+	$(INSTALL) -m 644 pvebc/$(SEL_EBC_MODDIR)/boot.mount \
+		pvebc/$(SEL_EBC_MODDIR)/sel-ebc-override-crypttab.service \
+		pvebc/$(SEL_EBC_MODDIR)/sel-ebc-paes-enforce.service \
+		pvebc/$(SEL_EBC_MODDIR)/sel-ebc-pvebc.service \
+		pvebc/$(SEL_EBC_MODDIR)/sel-ebc.crypttab \
+		pvebc/$(SEL_EBC_MODDIR)/sel-ebc.target \
+		$(DESTDIR)$(DRACUTMODDIR)/$(SEL_EBC_MODDIR)
+endif
+
 install-rust-tools: $(BUILD_TARGETS)
 	$(INSTALL) -d -m 755 $(DESTDIR)$(USRBINDIR)
 	$(foreach target,$(CARGO_TARGETS),\

rust/pvebc/95sel-ebc/boot.mount

@@ -0,0 +1,28 @@
+[Unit]
+Description=Mount /boot early in initramfs
+
+# Initramfs requirement
+DefaultDependencies=no
+# Make absolutely sure this only runs in initramfs (and not post-pivot if the
+# unit ever appears there)
+ConditionPathExists=/etc/initrd-release
+ConditionKernelCommandLine=root
+
+# we use /dev/disk/by-label because it identifies the boot partition system
+# independently IF set up correctly
+Requires=dev-disk-by\x2dlabel-boot.device
+
+# Ordering dependencies
+After=dev-disk-by\x2dlabel-boot.device
+Before=sel-ebc-pvebc.service
+
+[Mount]
+# system independent identification of boot partition requires that the label
+# boot is set for the boot partition
+What=/dev/disk/by-label/boot
+Where=/boot
+Type=auto
+Options=defaults
+
+[Install]
+WantedBy=sel-ebc-pvebc.service

rust/pvebc/95sel-ebc/module-setup.sh

@@ -0,0 +1,76 @@
+#!/bin/bash
+# SPDX-License-Identifier: MIT
+#
+# Copyright IBM Corp.
+
+
+# Called by dracut
+check() {
+	# always include
+	return 0
+}
+
+# Called by dracut
+depends() {
+	# We need systemd in the initramfs
+	echo systemd
+	echo systemd-udevd
+	echo crypt
+	echo dm
+	return 0
+}
+
+# Called by dracut
+installkernel() {
+	# kernel modules needed for opening an encrypted rfs
+	instmods -c uvdevice
+	instmods -c paes_s390
+	instmods -c pkey_uv
+	instmods -c pkey_pckmo
+	instmods -c pkey
+}
+
+# Called by dracut
+install() {
+	# shellcheck disable=SC2154
+	# moddir, systemdsystemunitdir, and initdir are provided by dracut
+	# Copy the units into the initramfs' systemd unit dir
+	inst_simple "$moddir/sel-ebc.target" \
+		"$systemdsystemunitdir/sel-ebc.target"
+	inst_simple "$moddir/sel-ebc-pvebc.service" \
+		"$systemdsystemunitdir/sel-ebc-pvebc.service"
+	inst_simple "$moddir/sel-ebc-paes-enforce.service" \
+		"$systemdsystemunitdir/sel-ebc-paes-enforce.service"
+	inst_simple "$moddir/sel-ebc-override-crypttab.service" \
+		"$systemdsystemunitdir/sel-ebc-override-crypttab.service"
+	inst_simple "$moddir/boot.mount" \
+		"$systemdsystemunitdir/boot.mount"
+
+	# already exisitng unit we depend on for kernel modules
+	inst_simple /usr/lib/systemd/system/systemd-modules-load.service \
+		"$systemdsystemunitdir/systemd-modules-load.service"
+
+	# wrapper for sel-ebc.service
+	inst_simple "$moddir/pvebc-wrapper.sh" \
+		"/etc/sel-ebc/pvebc-wrapper.sh"
+
+	# override crypttab
+	inst_simple "$moddir/override-crypttab.sh" \
+		"/etc/sel-ebc/override-crypttab.sh"
+
+	# copy main application
+	inst_binary "/usr/bin/pvebc"
+	inst_binary "/usr/bin/pvsecret"
+
+	inst_simple "$moddir/sel-ebc.crypttab" "/etc/sel-ebc/crypttab"
+
+	# Create the enablement symlinks in the image using host systemctl:
+	# shellcheck disable=SC2154
+	inst_dir "$initdir/etc/systemd/system"
+	systemctl --root "$initdir" --no-reload --quiet enable sel-ebc.target
+	systemctl --root "$initdir" --no-reload --quiet enable sel-ebc-pvebc.service
+	systemctl --root "$initdir" --no-reload --quiet enable sel-ebc-override-crypttab.service
+	systemctl --root "$initdir" --no-reload --quiet enable sel-ebc-paes-enforce.service
+	systemctl --root "$initdir" --no-reload --quiet enable systemd-modules-load.service
+	systemctl --root "$initdir" --no-reload --quiet enable boot.mount
+}

rust/pvebc/95sel-ebc/override-crypttab.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# SPDX-License-Identifier: MIT
+#
+# Copyright IBM Corp.
+
+IBM_RSRC_DIR="/etc/sel-ebc"
+
+if [[ ! -f "${IBM_RSRC_DIR}/crypttab" ]]; then
+	echo "Error: source file $IBM_RSRC_DIR/crypttab does not exist"
+	exit 1
+fi
+
+# Unconditionally override /etc/crypttab to ensure correct EBC configuration
+cp "${IBM_RSRC_DIR}/crypttab" "/etc/crypttab"
+
+systemctl daemon-reload
+
+systemctl restart systemd-cryptsetup@cryptroot_mapper.service
+
+exit 0

rust/pvebc/95sel-ebc/pvebc-wrapper.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+# SPDX-License-Identifier: MIT
+#
+# Copyright IBM Corp.
+
+SYSFS=/sys/firmware/uv/prot_virt_guest
+SICS=/boot/sics
+EBC_TMPFS=/run/sel-ebc
+TOC=toc.asr
+ASR_NAME=luks-rfs-passphrase
+
+# Early exit for non SEL guests
+if [[ ! -e $SYSFS ]]; then
+	echo "Not running in a SEL guest."
+	exit 1
+fi
+if [[ $(cat $SYSFS) -ne 1 ]]; then
+	echo "Not running in a SEL guest."
+	exit 1
+fi
+echo "Running in SEL guest."
+
+# Copy EBC resources from /boot/sics to tmpfs for security
+# This protects against host injection attacks by moving resources to UV-protected RAM
+echo "Copying EBC resources from $SICS to $EBC_TMPFS"
+if ! mkdir -p "$EBC_TMPFS"; then
+	echo "Failed to create $EBC_TMPFS"
+	exit 1
+fi
+
+# Copy only .asr and .pol files
+for file in "$SICS"/*.asr "$SICS"/*.pol; do
+	if [[ -f "$file" && ! -L "$file" ]]; then
+		cp "$file" "$EBC_TMPFS/" || {
+			echo "Failed to copy $file to $EBC_TMPFS"
+			exit 1
+		}
+	fi
+done
+
+# Verify toc.asr was copied
+if [[ ! -f "$EBC_TMPFS/$TOC" ]]; then
+	echo "Error: $EBC_TMPFS/$TOC does not exist after copy"
+	exit 1
+fi
+
+# execute the actual tool with the copied toc.asr
+pvebc --toc "$EBC_TMPFS/$TOC"
+rc=$?
+if [[ $rc -ne 0 ]]; then
+	exit $rc
+fi
+
+# Retrieve and check for dummy LUKS passphrase
+pvsecret retrieve --inform name -o "$EBC_TMPFS/$ASR_NAME" --outform bin "$ASR_NAME"
+
+if [[ ! -f "$EBC_TMPFS/$ASR_NAME" ]]; then
+	echo "$EBC_TMPFS/$ASR_NAME does not exist"
+fi
+
+chmod 400 "$EBC_TMPFS/$ASR_NAME"
+
+exit 0

rust/pvebc/95sel-ebc/sel-ebc-override-crypttab.service

@@ -0,0 +1,37 @@
+[Unit]
+Description=Override crypttab
+
+# boot partition contains SICS
+# Loading of kernel modules is required which are needed for protected keys
+Requires=systemd-modules-load.service
+Requires=boot.mount
+
+# Ensure this runs before the handoff to the real root, if that's required:
+After=boot.mount
+After=systemd-modules-load.service
+Before=cryptsetup-pre.target
+Before=cryptsetup.target
+Before=systemd-cryptsetup@.service
+Before=initrd-root-device.target
+After=sel-ebc-pvebc.service
+
+# Initramfs requirement
+DefaultDependencies=no
+# Make absolutely sure this only runs in initramfs
+ConditionPathExists=/etc/initrd-release
+ConditionKernelCommandLine=rd.sel-ebc
+ConditionKernelCommandLine=root
+
+[Service]
+Type=oneshot
+ExecStart=/bin/bash /etc/sel-ebc/override-crypttab.sh
+RemainAfterExit=yes
+# If pvebc fails immediately abort boot
+FailureAction=poweroff-immediate
+# boot partition is unencrypted and contains SICS so we can get logs out this way
+# logs do not leek any sensitive information
+StandardOutput=file:/boot/sics/log
+StandardError=file:/boot/sics/log
+
+[Install]
+RequiredBy=sel-ebc.target

rust/pvebc/95sel-ebc/sel-ebc-paes-enforce.service

@@ -0,0 +1,27 @@
+[Unit]
+Description=Enforce PAES encrypted root fs for SEL guests
+
+# Ensure this runs before the handoff to the real root, if that's required:
+After=cryptsetup.target
+After=initrd-root-device.target
+Before=sysroot.mount
+
+# Initramfs requirement
+DefaultDependencies=no
+# Make absolutely sure this only runs in initramfs
+ConditionPathExists=/etc/initrd-release
+ConditionKernelCommandLine=rd.sel-ebc
+ConditionKernelCommandLine=root
+
+[Service]
+Type=oneshot
+ExecStart=bash -c 'dmsetup table /dev/disk/by-label/root | grep "paes-xts-plain64"'
+FailureAction=poweroff-immediate
+RemainAfterExit=yes
+
+# logs do not leek any sensitive information
+StandardOutput=file:/boot/sics/log
+StandardError=file:/boot/sics/log
+
+[Install]
+RequiredBy=sel-ebc.target

rust/pvebc/95sel-ebc/sel-ebc-pvebc.service

@@ -0,0 +1,36 @@
+[Unit]
+Description=Run pvebc during early boot to process SICS
+
+# boot partition contains SICS
+# Loading of kernel modules is required which are needed for protected keys
+Requires=systemd-modules-load.service
+Wants=boot.mount
+
+# Ensure this runs before the handoff to the real root, if that's required:
+Before=initrd-root-device.target
+Before=cryptsetup-pre.target
+Before=cryptsetup.target
+After=boot.mount
+After=systemd-modules-load.service
+
+# Initramfs requirement
+DefaultDependencies=no
+# Make absolutely sure this only runs in initramfs
+ConditionPathExists=/etc/initrd-release
+AssertPathIsDirectory=/boot/sics
+ConditionKernelCommandLine=rd.sel-ebc
+
+[Service]
+Type=oneshot
+# execute pvebc
+ExecStart=/bin/bash /etc/sel-ebc/pvebc-wrapper.sh
+RemainAfterExit=yes
+# If pvebc fails immediately abort boot
+FailureAction=poweroff-immediate
+# boot partition is unencrypted and contains SICS so we can get logs out this way
+# logs do not leek any sensitive information
+StandardOutput=file:/boot/sics/log
+StandardError=file:/boot/sics/log
+
+[Install]
+RequiredBy=sel-ebc.target

rust/pvebc/95sel-ebc/sel-ebc.crypttab

@@ -0,0 +1 @@
+cryptroot_mapper /dev/disk/by-label/cryptroot /run/sel-ebc/luks-rfs-passphrase

rust/pvebc/95sel-ebc/sel-ebc.target

@@ -0,0 +1,27 @@
+[Unit]
+Description=Target unit for IBM Secure Execution for Linux early boot customization
+
+# enable for use in initramfs
+DefaultDependencies=no
+
+# if not met start the target without starting its dependencies
+ConditionPathExists=/etc/initrd-release
+ConditionKernelCommandLine=rd.sel-ebc
+
+# if not met the target is considered failed
+# AssertVirtualization=kvm
+
+# if target fails abort immediately
+FailureAction=poweroff-immediate
+
+Requires=sel-ebc-pvebc.service
+Requires=sel-ebc-override-crypttab.service
+Requires=sel-ebc-paes-enforce.service
+
+# ordering dependencies
+After=systemd-modules-load.service
+Before=initrd-root-device.target
+
+[Install]
+# most basic hook to start target by default
+WantedBy=initrd.target