Suspend to RAM and encrypted partitions

Current problem

When using Ubuntu Full Disk Encryption(that is based on dm-crypt with LUKS) to set up full system encryption, the encryption key is kept in memory when suspending the system. This drawback defeats the purpose of encryption if you carry around your suspended laptop a lot. One can use the cryptsetup luksSuspend command to freeze all I/O and flush the key from memory.

Solution

ubuntu-luks-suspend is an attempt to change the default suspend mechanism. The basic idea is to change to a chroot outside of the encrypted root fs and then lock it (withcryptsetup luksSuspend)

here is another example of ubuntu 14.04 cryptsetup luks suspend/resume root partition "almost works" :-)

one reason it works for arch and "almost works" for ubuntu could be that ubuntu kernel as of

  Linux system 3.19.0-25-generic #26~14.04.1-Ubuntu SMP Fri Jul 24 21:16:20 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

is still "too old": the following patch is not there yet:

make sync() on suspend-to-RAM optional

so any pm-utils or user code that issues any form of clear keys & sleep request, such as:

  cryptsetup luksSuspend root
  echo -n "mem" >/sys/power/state

will result in kernel in a call to sys_sync() which in turn causes a deadlock in dm-crypt (by design, after luks suspend)