tomb

the crypto undertaker
git clone git://parazyd.org/tomb.git
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commit 825f7ed687c6a0facc8bad7ccc14e3d10e52015f
parent 12a7760895753baddf4d05ec114cc6c4980daa3a
Author: Jaromil <jaromil@dyne.org>
Date:   Sat, 30 Mar 2013 18:44:05 +0100

Security check for extra keyslots

when a tomb is opened we check if other slots besides the master (0)
are enabled and if so we warn the user that there can be a backdoor.
LUKS permits the presence of multiple keys that can open a single
volume, but this weakens the security of it and we are not really
interested in implementing it.

Diffstat:
Msrc/tomb | 14+++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/tomb b/src/tomb @@ -931,7 +931,7 @@ lock_tomb_with_key() { _message "formatting Luks mapped device" get_lukskey "${tombpass}" ${tombkey} | \ cryptsetup --key-file - --batch-mode \ - --cipher ${cipher} --key-size 256 \ + --cipher ${cipher} --key-size 256 --key-slot 0 \ luksFormat ${nstloop} if ! [ $? = 0 ]; then _warning "cryptsetup luksFormat returned an error" @@ -1173,7 +1173,6 @@ mount_tomb() { fi losetup -f ${tombdir}/${tombfile} - _message "check for a valid LUKS encrypted device" cryptsetup isLuks ${nstloop} if [ $? != 0 ]; then # is it a LUKS encrypted nest? see cryptsetup(1) @@ -1181,13 +1180,21 @@ mount_tomb() { $norm || rmdir $tombmount 2>/dev/null return 1 fi + say "this tomb is a valid LUKS encrypted device" - tombdump=(`cryptsetup luksDump ${nstloop} | awk ' + luksdump="`cryptsetup luksDump ${nstloop}`" + tombdump=(`print $luksdump | awk ' /^Cipher name/ {print $3} /^Cipher mode/ {print $3} /^Hash spec/ {print $3}'`) say "cipher is \"$tombdump[1]\" mode \"$tombdump[2]\" hash \"$tombdump[3]\"" + slotwarn=`print $luksdump | awk ' + BEGIN { zero=0 } + /^Key slot 0/ { zero=1 } + /^Key slot.*ENABLED/ { if(zero==1) print "WARN" }'` + { test "$slotwarn" = "WARN" } && { + _warning "Multiple key slots are enabled on this tomb. Beware: there can be a backdoor." } # save date of mount in minutes since 1970 mapdate=`date +%s` @@ -1756,6 +1763,7 @@ list_tombs() { tombmount=${t[(ws:;:)2]} tombfs=${t[(ws:;:)3]} tombfsopts=${t[(ws:;:)4]} + tombloop=${mapper[(ws:.:)4]} # calculate tomb size ts=`df -hP /dev/mapper/$mapper |