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cryptroot-unlock	5.51 KB	-rwxr-xr-x

Code Editor : cryptroot-unlock

#!/bin/busybox ash

# Remotely unlock encrypted volumes.
#
# Copyright © 2015-2017 Guilhem Moulin <guilhem@debian.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

set -ue
PATH=/sbin:/bin

TIMEOUT=10
PASSFIFO=/lib/cryptsetup/passfifo
ASKPASS=/lib/cryptsetup/askpass
UNLOCK_ALL=n

# The list of configured devices to unlock.
# TODO refactor: this code should be shared with the cryptroot boot script
if grep -qE '^(.*\s)?cryptopts=' /proc/cmdline; then
	CRYPTDEVS=$(tr ' ' '\n' </proc/cmdline | sed -nr 's/^cryptopts=(.*,)?target=([^[:blank:],]+)(,.*)?$/\2/p')
else
	CRYPTDEVS=$(sed -nr 's/^(.*,)?target=([^[:blank:],]+)(,.*)?$/\2/p' /conf/conf.d/cryptroot)
fi

# Print the list of PIDs the executed command of which is $exe.
pgrep_exe() {
	local exe="$1" pid
	ps | awk '{print $1, $5}' | while read LINE; do
		set $LINE
		local pid=$1
		local cmd=$2
		if [ "$cmd" == "$exe" ]; then
			echo $pid
			break
		fi
	done
}

# Return 0 if $pid has a file descriptor pointing to $name, and 1
# otherwise.
in_fds() {
	local pid="$1" name="$2" fd
	for fd in $(find "/proc/$pid/fd" -type l); do
		[ "$(readlink -f "$fd")" != "$name" ] || return 0
	done
	return 1
}

# Print the PID of the askpass process with a file descriptor opened to
# /lib/cryptsetup/passfifo.
get_askpass_pid() {
	local pid
	for pid in $(pgrep_exe "$ASKPASS"); do
		if in_fds "$pid" "$PASSFIFO"; then
			echo "$pid"
			return 0
		fi
	done
	return 1
}

# Print the number of configured crypt devices that have not been unlocked yet.
count_locked_devices() {
	local dev n=0
	for dev in $CRYPTDEVS; do
		[ -b "/dev/mapper/$dev" ] || n=$(( $n + 1 ))
	done
	echo $n
}

# Return 0 if the $target is in $CRYPTDEVS, and 1 otherwise.
is_device_known() {
	local dev target="$1"
	for dev in $CRYPTDEVS; do
		[ "$dev" != "$target" ] || return 0
	done
	return 1
}

# Wait for askpass, then set $PID (resp. $BIRTH) to the PID (resp.
# birth date) of the cryptsetup process with same $CRYPTTAB_NAME.
wait_for_prompt() {
	local pid timer num_locked_devices=-1 n

# wait for the fifo
	while :; do
		n=$(count_locked_devices)
		if [ $n -eq 0 ]; then
			# all configured devices have been unlocked, we're done
			exit 0
		elif [ $num_locked_devices -lt 0 ] || [ $n -lt $num_locked_devices ]; then
			# reset $timer if a device was unlocked (for instance using
			# a keyscript) while we were waiting
			timer=$(( 10 * $TIMEOUT ))
		fi
		num_locked_devices=$n

if pid=$(get_askpass_pid) && [ -p "$PASSFIFO" ]; then
			break
		fi

sleep 0.1
		timer=$(( $timer - 1 ))
		if [ $timer -le 0 ]; then
			echo "Error: Timeout reached while waiting for askpass." >&2
			exit 1
		fi
	done

# find the cryptsetup process with same $CRYPTTAB_NAME
	eval $(tr '\0' '\n' < "/proc/$pid/environ" | grep -E '^CRYPTTAB_(NAME|TRIED|SOURCE)=')
	if ! is_device_known "$CRYPTTAB_NAME"; then
		echo "Error: Refusing to process unknown device $CRYPTTAB_NAME" >&2
		exit 1
	fi

for pid in $(pgrep_exe '/sbin/cryptsetup'); do
		if tr '\0' '\n' < "/proc/$pid/environ" | grep -Fxq "CRYPTTAB_NAME=$CRYPTTAB_NAME"; then
			PID=$pid
			BIRTH=$(stat -c'%Z' "/proc/$PID")
			return 0;
		fi
	done

PID=
	BIRTH=
}

# Wait until $PID no longer exists or has a birth date greater that
# $BIRTH (ie was reallocated).  Then return with exit value 0 if
# /dev/mapper/$CRYPTTAB_NAME exists, and with exit value 1 if the
# maximum number of tries exceeded.  Otherwise (if the unlocking
# failed), return with value 1.
wait_for_answer() {
	local timer=$(( 10 * $TIMEOUT )) dev
	until [ ! -d "/proc/$PID" ] || [ $(stat -c'%Z' "/proc/$PID") -gt $BIRTH ]; do
		sleep 0.1
		timer=$(( $timer - 1 ))
		if [ $timer -le 0 ]; then
			echo "Error: Timeout reached while waiting for PID $PID." >&2
			exit 1
		fi
	done

if [ -b "/dev/mapper/$CRYPTTAB_NAME" ]; then
		echo "cryptsetup: $CRYPTTAB_NAME set up successfully" >&2
		[ "$UNLOCK_ALL" = y ] && return 0 || exit 0
	elif [ $CRYPTTAB_TRIED -ge 2 ]; then
		echo "cryptsetup: maximum number of tries exceeded for $CRYPTTAB_NAME" >&2
		exit 1
	else
		echo "cryptsetup: cryptsetup failed, bad password or options?" >&2
		return 1
	fi
}

if [ -t 0 ] && [ -x "$ASKPASS" ]; then
	# interactive mode on a TTY: keep trying until all configured devices have
	# been unlocked or the maximum number of tries exceeded
	UNLOCK_ALL=y
	while :; do
		# note: if the script is not killed before pivot_root it should
		# exit on its own once $TIMEOUT is reached
		wait_for_prompt
		diskname="$CRYPTTAB_NAME"
		[ "${CRYPTTAB_SOURCE#/dev/disk/by-uuid/}" != "$CRYPTTAB_SOURCE" ] || diskname="$diskname ($CRYPTTAB_SOURCE)"
		read -rs -p "Please unlock disk $diskname: "; echo
		printf '%s' "$REPLY" >"$PASSFIFO"
		wait_for_answer || true
	done
else
	# non-interactive mode: slurp the passphrase from stdin and exit
	wait_for_prompt
	diskname="$CRYPTTAB_NAME"
	# TODO: refactor $CRYPTTAB_NAME/$CRYPTTAB_SOURCE to prompt mapping
	[ "${CRYPTTAB_SOURCE#/dev/disk/by-uuid/}" != "$CRYPTTAB_SOURCE" ] || diskname="$diskname ($CRYPTTAB_SOURCE)"
	echo "Please unlock disk $diskname"
	cat >"$PASSFIFO"
	wait_for_answer || exit 1
fi

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Code Editor : cryptroot-unlock