Public bug reported:
I'm speaking about ubuntu 20.04.4 with cryptsetup 2:2.2.2-3ubuntu2.4.
The behaviour is the same in ubuntu 22.04. I havent tried 18.04 and
older LTS, probably the same problem there as well.
So I have your usual setup with luks encrypted root. I've installed
dropbear-initramfs to make it remotely unlockable, set everything up and
tried to unlock it connecting from termux with my phone. When I ran
cryptroot-unlock it kept silent (not even the prompt) for some secs and
quit with such error:
Error: Timeout reached while waiting for askpass.
Long story short: if I rotated the phone everything worked as supposed.
I tracked it down to this piece in cryptroot-unlock:
# Print the list of PIDs the executed command of which is $exe.
pgrep_exe() {
local exe pid
exe="$(readlink -f -- "$1" 2>/dev/null)" && [ -f "$exe" ] || return 0
ps | awk '{print $1, $5}' | while read LINE; do
set $LINE
local pid=$1
local cmd=$(readlink -f -- "$2")
if [ "$cmd" == "$exe" ]; then
echo $pid
break
fi
done
}
Notice it walks through "ps" (busybox one) lines which adapts its output
to the terminal width. Check out this shell session:
> stty size
40 115
> /usr/lib/initramfs-tools/bin/busybox ps | grep '[b]usybox'
18944 account 2804 R /usr/lib/initramfs-tools/bin/busybox ps
## resize the terminal width to 50
> stty size
40 50
> /usr/lib/initramfs-tools/bin/busybox ps | grep '[b]usybox'
18947 account 2804 R {busybox} /usr/lib/ini
Look at the last line above. "ps" ensures one terminal line per process,
no wrapping. If a line is too long, cut it. If the full binary path is
to be cut, prepend the binary basename in curly braces.
Here is a shell session over dropbear connection:
> stty size
40 115
> ps | grep '[a]skpass'
285 root 2364 S /lib/cryptsetup/askpass Please unlock disk
dm_crypt-0:
## resize the terminal width to 50
> stty size
40 50
> ps | grep '[a]skpass'
285 root 2364 S {askpass} /lib/cryptse
As you can see askpass cmdline is a total mess now and because of that
pgrep_exe cant find askpass PID.
A quick fix could be "ps -w" instead of just "ps" in pgrep_exe. It would make
ps assume the terminal width 132 which is enough for askpass line to be printed
pristine.
Currently one cant unlock encrypted root with terminal width up to and
including 50.
** Affects: cryptsetup (Ubuntu)
Importance: Undecided
Status: New
** Tags: cryptsetup cryptsetup-initramfs
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https://bugs.launchpad.net/bugs/1968636
Title:
cryptroot-unlock doesn't work at all when terminal width is below 51
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