#!/bin/bash

# the cipher is the first command line argument
CIPHER="$1"
# the loop device to use is the second
LOOPDEV="$2"
# the underlying file is third
UNDERLYING="$3"

echo I am going to switch swap off \- we have no means to keep pages
echo locked in memory with shell scripts.
read -p "Continue <y|n>? "

[ $REPLY = 'y' ] || exit 1

echo -n OK, swap off...
swapoff -a
echo done

# until the two passphrases match and are not empty...
until [ "$PASS1" = "$PASS2" -a -n "$PASS1" ]; do
        # the bash read buitlin has to support the -s option.
	# Don't use read without -s!!
	read -s -p "Enter Passphrase: " PASS1; echo
	read -s -p "Re-enter Passphrase: " PASS2; echo
done

# setup the loop device using the passphrase given on STDIN.
echo "$PASS1" | losetup -e "$CIPHER" -p 0 "$LOOPDEV" "$UNDERLYING"

echo -n swap on...
swapon -a
echo done