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>
Add pvebc tool for parsing and verifying EBC Add-Secret-Request structures
Introduce pvebc, a CLI tool that parses and verifies the integrity of
Add-Secret-Request (ASR) structures used in Early Boot Customization for
SEL guests.
The tool processes an integrity-protected ASR structure consisting of:
- toc.asr: Meta secret that links to toc.pol via relative filepath and
SHA512 hash, integrity-protected by its AES GCM authentication tag
- toc.pol: Policy file containing AES GCM authentication tags (last 16
bytes) of all user-provided ASRs
- User ASRs: Individual Add-Secret-Requests containing encrypted secrets
This structure guarantees:
- Prevents ASR removal: toc.pol lists all expected ASR authentication tags
- Prevents ASR insertion: Unlisted ASRs are rejected
- Prevents ASR modification: AES GCM authentication tags provide
cryptographic integrity
- Prevents toc.pol tampering: toc.asr's integrity protection secures the
link
The tool verifies completeness by checking that all ASRs listed in toc.pol
are present and their AES GCM authentication tags match. This prevents
attackers from removing, inserting, or modifying ASRs during transport over
unsecured channels.
After verification, pvebc adds all ASRs to the Ultravisor (UV), which
decrypts them using the guest's secret key and makes them available to
the guest during early boot.
Assisted-by: IBM Bob:1.0.1
Acked-by: Holger Dengler <dengler@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Finn Callies <fcallies@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Finn Callies