cryptsetup-suspend[edit]

(Bold added.)

Package: cryptsetup-suspend [...] Description: disk encryption support - suspend mode integration Cryptsetup provides an interface for configuring encryption on block devices (such as /home or swap partitions), using the Linux kernel device mapper target dm-crypt. It features integrated Linux Unified Key Setup (LUKS) support. . This package provides suspend mode integration for cryptsetup. It takes care of removing LUKS master key from memory before system suspend. . Please note that the supsend mode integration is limited to LUKS devices and requires systemd.

Potential cryptsetup-suspend Security Issue[edit]

Might not suspend and wipe cryptsetup key.

Not enough memory available. Please close some programs or add swap space to suspend successfully.

/lib/cryptsetup/scripts/suspend/cryptsetup-suspend-wrapper ^[archive]

        if [ $((MemAvailable+SwapFree)) -lt $((300*1024*1024)) ]; then
            log_error "Not enough memory available. Please close some programs or add swap space to suspend successfully."
            exit 1
        fi

cryptsetup[edit]

Quote cryptsetup luksSuspend, cryptsetup close (previously cryptsetup lukseClose) man page ^[archive]. (Bold added.)

luksSuspend suspends active device (all IO operations are frozen) and wipes encryption key from kernel.

close Removes the existing mapping <name> and wipes the key from kernel memory.

Does systemd run cryptsetup luksSuspend, cryptsetup close or cryptsetup lukseClose on the root device and thereby wipe the cryptsetup encryption key from kernel memory?

Quote https://www.freedesktop.org/software/systemd/man/systemd-halt.service.html ^[archive]

When these services are run, they ensure that PID 1 is replaced by the /usr/lib/systemd/systemd-shutdown tool which is then responsible for the actual shutdown. Before shutting down, this binary will try to unmount all remaining file systems, disable all remaining swap devices, detach all remaining storage devices and kill all remaining processes.

https://manpages.debian.org/systemd-shutdown ^[archive]
https://github.com/systemd/systemd/blob/master/src/shutdown/shutdown.c ^[archive]
- mentions need_dm_detach, dm_detach_all
  - https://github.com/systemd/systemd/blob/master/src/shutdown/umount.c#L815 ^[archive] implements dm_detach_all
    - https://lists.freedesktop.org/archives/systemd-devel/2012-June/005443.html ^[archive] might imply that dm_detach_all refers to dm-crypt

/lib/cryptsetup/cryptdisks-functions

# Removes all mappings in crypttab, except the ones holding the root
# file system or /usr
do_stop() {

systemd[edit]

initramfs[edit]

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=778849 ^[archive]

Inspiration[edit]

Forum Discussion[edit]

https://forums.whonix.org/t/is-ram-wipe-possible-inside-whonix-cold-boot-attack-defense/5596 ^[archive]

Footnotes[edit]

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RAM Wipe Development Notes

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