#!/bin/bash
# Script to check whether a Debian/Ubuntu system will experience boot problems from https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1889556 / https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1889509
# https://www.redradishtech.com/display/~jturner/2020/07/30/symbol+%27grub_calloc%27+not+found+--+how+to+fix+on+AWS

pass()
{
	echo "All good. $*"
	exit
}

fail()
{
	echo >&2 "Reboot may fail! $*"
	exit 1
}

if [[ -d /sys/firmware/efi ]]; then
	pass "System uses EFI, not BIOS, so is not affected"
fi

if zgrep -q "LP: #1889556" /usr/share/doc/grub-pc/changelog.Debian.gz; then
	pass "grub version has fixed the bug #1889556"
fi

command -v debconf-get-selections >/dev/null || sudo apt-get install debconf-utils
devices="$(sudo debconf-get-selections | awk '$1=="grub-pc" && $2 == "grub-pc/install_devices" {print $4}')"

if [[ -z $devices ]]; then
	pass "Although your grub is vulnerable to the bug, your debconf system has no preset devices to install grub onto. You will be prompted for a device when next running dpkg-reconfigure grub-pc"
fi

for device in $devices; do
	[[ -e $device ]] || fail "Your grub version does not fix the bug, and grub is configured to install to nonexistent device $device. Please upgrade grub and/or 'dpkg-reconfigure grub-pc' until you are sure grub is installed on the correct boot device"
done

fail "Your grub version does not fix the bug. Please run 'dpkg-reconfigure grub-pc', select the correct boot device, and verify that grub gets installed on it without error."