Script for loop-AES key generation
Max Vozeler
max at nusquama.org
Sat Nov 18 15:35:47 CET 2006
Hi Jari,
On Tue, Nov 14, 2006 at 09:58:43AM +0200, Jari Ruusu wrote:
> There have been few cases where v3 key file and v2 losetup/mount were
> used to set up a file system, and after upgrade to v3 losetup/mount,
> mounting the file system failed. There is a warning about this problem
> in loop-AES README file, but not everyone reads README files.
>
> May I suggest adding a check that losetup is recent enough. Something
> like this:
> strings /sbin/losetup | grep -q -s multi-key-v3
> if [ $? != 0 ] ; then
> echo "too old losetup version"
> fi
Indeed, that's a useful check. Given that strings(1) is part
of binutils, which may not be installed on all systems, I made it
run only if strings can be found. Thanks for your suggestion.
cheers,
Max
-------------- next part --------------
Index: debian/loop-aes-keygen
===================================================================
--- debian/loop-aes-keygen (Revision 1325)
+++ debian/loop-aes-keygen (Revision 1326)
@@ -137,6 +137,11 @@
return 0
}
+check_multikey_support ()
+{
+ strings /sbin/losetup | grep -q -s multi-key-v$1
+}
+
keygen()
{
version=$1
@@ -174,6 +179,12 @@
exit 1
fi
+if [ "$version" -gt 1 ] && [ -x /usr/bin/strings ]; then
+ if ! check_multikey_support $version; then
+ echo "Warning: /sbin/losetup too old for v$version keys."
+ fi
+fi
+
if [ -e $keyfile ]; then
echo "Keyfile $keyfile exists. Aborting."
exit 1
-------------- next part --------------
#!/bin/sh
#
# loop-aes-keygen - Create loop-AES encryption keys
#
# 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; version 2 dated June, 1991.
#
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
#
# Copyright 2005-2006, Max Vozeler <xam at debian.org>
#
# $Id: loop-aes-keygen 1326 2006-11-18 14:03:56Z xam $
#
set -e
umask 077
cipher=
userids=
rnd=/dev/random
version=3
usage()
{
cat << USAGE
usage: loop-aes-keygen [opts] <keyfile>
-v <1|2|3> Key format (Default: $version)
-u userid Encrypt for GnuPG pubkey <userid>
-c cipher Use GnuPG cipher <cipher>
USAGE
}
get_options()
{
while getopts 'v:s:c:u:h' f
do
case $f in
v)
version=$OPTARG
;;
c)
cipher=$OPTARG
;;
s)
rnd=$OPTARG
;;
u)
userids="$userids $OPTARG"
;;
h)
usage
exit 0
;;
esac
done
shift `expr $OPTIND - 1`
keyfile=$1
if [ -z $keyfile ]; then
echo No output file. Aborting
usage
exit 1
fi
if [ $version -lt 1 ] || [ $version -gt 3 ]; then
echo Unsupported key format: $version
exit 1
fi
}
check_safe_loop()
{
loopdev=$1
opts=$(/sbin/losetup $loopdev 2>&1)
if [ $? -ne 0 ]; then
echo "Error: Check for $loopdev failed ($opts)"
exit 1
fi
# If loop entry has an encryption= option assume it's safe
if echo "$opts" | grep -q encryption=; then
return 0
fi
return 1
}
check_safe_swap()
{
if [ ! -r /proc/swaps ]; then
echo Error: Cannot read /proc/swaps
exit 1
fi
unsafe=
while read line
do
set -- $line
case $1 in
/dev/loop*)
if ! check_safe_loop $1; then
unsafe=$1
break
fi
;;
Filename*)
;;
*)
unsafe=$1
break
;;
esac
done < /proc/swaps
if [ $unsafe ]; then
echo Fatal: Unsafe swap detected: $unsafe
exit 1
fi
return 0
}
check_multikey_support ()
{
strings /sbin/losetup | grep -q -s multi-key-v$1
}
keygen()
{
version=$1
keyfile=$2
gpgargs=$3
# These are the known loop-AES key formats:
# v1.x 1 45 bytes AES key
# v2.x 64 2880 bytes(45 * 64) AES keys
# v3.x 65 2925 bytes(45 * 65) #65 is md5 seed
case $version in
1) nkeys=1 ;;
2) nkeys=64 ;;
3) nkeys=65 ;;
*) return 1 ;;
esac
bytes=$((45*$nkeys))
head -c $bytes $rnd | uuencode -m - | head -n $(($nkeys+1)) | tail -n $nkeys | gpg $gpgargs > $keyfile
}
get_options $*
if ! check_safe_swap; then
exit 1
fi
if ! [ -x /usr/bin/gpg ]; then
echo "Error: gpg not found"
exit 1
fi
if ! [ -x /usr/bin/uuencode ]; then
echo "Error: uuencode not found - see package sharutils"
exit 1
fi
if [ "$version" -gt 1 ] && [ -x /usr/bin/strings ]; then
if ! check_multikey_support $version; then
echo "Warning: /sbin/losetup too old for v$version keys."
fi
fi
if [ -e $keyfile ]; then
echo "Keyfile $keyfile exists. Aborting."
exit 1
fi
gpgargs="--armor"
if [ "$userids" ]; then
gpgargs="$gpgargs --encrypt"
for id in $userids; do
gpgargs="$gpgargs --recipient $id"
done
else
gpgargs="$gpgargs --symmetric"
fi
if [ $cipher ]; then
gpgargs="$gpgargs --cipher-algo=$cipher"
fi
if ! keygen $version $keyfile "$gpgargs"; then
echo An error occured while creating the key file.
exit 1
fi
exit 0
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