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Security check for extra keyslots

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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.
This commit is contained in:
Jaromil 2013-03-30 18:44:05 +01:00
parent 12a7760895
commit 825f7ed687
1 changed files with 11 additions and 3 deletions
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14
src/tomb
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@ -931,7 +931,7 @@ lock_tomb_with_key() {
_message "formatting Luks mapped device" _message "formatting Luks mapped device"
get_lukskey "${tombpass}" ${tombkey} | \ get_lukskey "${tombpass}" ${tombkey} | \
cryptsetup --key-file - --batch-mode \ cryptsetup --key-file - --batch-mode \
--cipher ${cipher} --key-size 256 \ --cipher ${cipher} --key-size 256 --key-slot 0 \
luksFormat ${nstloop} luksFormat ${nstloop}
if ! [ $? = 0 ]; then if ! [ $? = 0 ]; then
_warning "cryptsetup luksFormat returned an error" _warning "cryptsetup luksFormat returned an error"
@ -1173,7 +1173,6 @@ mount_tomb() {
fi fi
losetup -f ${tombdir}/${tombfile} losetup -f ${tombdir}/${tombfile}
_message "check for a valid LUKS encrypted device"
cryptsetup isLuks ${nstloop} cryptsetup isLuks ${nstloop}
if [ $? != 0 ]; then if [ $? != 0 ]; then
# is it a LUKS encrypted nest? see cryptsetup(1) # is it a LUKS encrypted nest? see cryptsetup(1)
@ -1181,13 +1180,21 @@ mount_tomb() {
$norm || rmdir $tombmount 2>/dev/null $norm || rmdir $tombmount 2>/dev/null
return 1 return 1
fi 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 name/ {print $3}
/^Cipher mode/ {print $3} /^Cipher mode/ {print $3}
/^Hash spec/ {print $3}'`) /^Hash spec/ {print $3}'`)
say "cipher is \"$tombdump[1]\" mode \"$tombdump[2]\" hash \"$tombdump[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 # save date of mount in minutes since 1970
mapdate=`date +%s` mapdate=`date +%s`
@ -1756,6 +1763,7 @@ list_tombs() {
tombmount=${t[(ws:;:)2]} tombmount=${t[(ws:;:)2]}
tombfs=${t[(ws:;:)3]} tombfs=${t[(ws:;:)3]}
tombfsopts=${t[(ws:;:)4]} tombfsopts=${t[(ws:;:)4]}
tombloop=${mapper[(ws:.:)4]}
# calculate tomb size # calculate tomb size
ts=`df -hP /dev/mapper/$mapper | ts=`df -hP /dev/mapper/$mapper |