Q:

How to make suspend to RAM secure on Ubuntu with full disk encryption (LVM on top of LUKS)?

I'm on Ubuntu 13.04 using full disk encryption (LVM on top of LUKS).
I would like to incorporate luksSuspend into the suspend procedure (and later use luksResume) so that I can suspend to RAM without leaving key material on memory and the root unlocked.
I've been trying for the last 7 hours to port a script for Arch Linux, so far without success: I honestly have no idea of what I'm doing...
Can anyone help me port this (or create something like this from scratch)? Or, at least, can anyone point me to documentation about how to hook stuff into the suspend procedures and how to keep the necessary binaries and scripts (such as cryptsetup) available even after all IO to root has been blocked (by luksSuspend)?
Concerning how to keep the necessary binaries and scripts available for resume, this other blog post (also for Arch) copied them to /boot; I would like however to use something more in the lines what Vianney used in the script I mentioned before, because that approach appears to be a bit more elegant in this aspect.

A:

I've come across the same problem, so I took another shot at porting the same script, which you can see here. It doesn't touch any non-volatile storage after luksSuspend, so it works even with real full-disk encryption with an encrypted /boot. However, you'll need to be careful -- it might not work as expected occasionally!
The ported script does the following:

Create a ramfs mount somewhere
Extract the contents of initramfs there (including the initramfs suspend script)
Bind mount relevant directories (e.g. /sys, /proc, /dev, /run) to the ramfs mount
Stop any services that may interfere (systemd-udevd, systemd-journald)
Remount the root filesystem (ext4 or btrfs) with nobarrier so Linux doesn't hang while trying to go into S3, then sync
Chroot into the initramfs mount, which syncs again, runs luksSuspend, and puts the computer to sleep
After wake, luksResume, remount filesystems, restart services, unmount bind mounts in the initramfs mount
Finally, unmount the initramfs mount so that we free the RAM used for the initramfs files

I've yet to do extensive testing on my script, but it seems to work reliably for me. If you use another filesystem (i.e. not ext4 or btrfs), then you might experience issues with barrier, so you'll need to modify the script too.
Either way, it's good to test and verify that the scripts work first. If you experience hangs while attempting to put Linux into S3 (i.e. at echo mem > /sys/power/state), then you should be able to recover:

Before suspending, open a tty or other terminal (that will be accessible, so ideally a tty)
Load cryptsetup and relevant libraries into RAM: sudo cryptsetup luksResume anything_here
Suspend using the script
If it hangs after the chroot (e.g. after starting version xxx is displayed on the new vt), switch to the tty you opened earlier and run sudo cryptsetup luksResume your_luks_device_name_here
If that hangs too, open another vt and chroot into /run/initramfs: sudo chroot /run/initramfs /bin/ash
Try to run luksResume: cryptsetup luksResume your_luks_device_name_here && exit
Your computer should then suspend. You can then wake it up, kill the script(s) if they are still running, unmount the bind mounts and /run/initramfs, and remount your root filesystem with barrier if applicable.

