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Encrypted iSCSI devices using NetBSD
One of the problems with iSCSI devices is that they can be located
remotely, where complete control over the physical hardware cannot be
guaranteed.
One other use case is that of a laptop - by running a target and
initiator on the same machine, a flat file can be created within an
existing file system, presented as storage by the iSCSI target
process, and accessed as an encrypted device by the initiator. So
that smaller encrypted directories and sub-directories can be used.
I thought I'd write a short document on some experience I've had in
setting up the NetBSD iSCSI initiator to use the NetBSD cgd device
to secure the contents of the iSCSI volume. No changes or different
set up is required at the target end, just the initiator.
I've attached it to this mail, and there's also a copy in
ftp://ftp.netbsd.org/pub/NetBSD/misc/agc/HOWTO-iSCSI-encrypt.txt
Regards,
Alistair
Encrypted iSCSI Devices on NetBSD
=================================
This document shows how to set up and run an encrypted iSCSI device on
NetBSD. Encryption of devices can be used for maintaining privacy on
devices located remotely, possibly on co-located hardware, for
instance, or on machines which could be stolen, or to which others
could gain access.
To encrypt the iSCSI device, we use the NetBSD iSCSI initiator,
available in NetBSD-current, and the standard cgd device. In all,
setting up an encrypted device in this manner should take less than 15
minutes, even for someone unfamiliar with iSCSI or cgd.
The approach is to layer a vnd on top of the "storage" file presented
by the iSCSI target. This is exactly the same as normal. On top of that
vnd, we layer a cgd device, which ensures that all data is encrypted
on the iSCSI device.
1. Device Initialisation
========================
This first section shows how to initialise the device, a one-time
operation.
Firstly, the initiator is started, pointing at the machine which is
presenting the iSCSI storage (i.e. the machine on which the iSCSI
target is running). In this example, the target is running on the
same machine as the initiator (a laptop called, in a moment of
inspiration, inspiron1300). A 50 MB iSCSI target is being presented
as target1.
# obj/iscsifs -u agc -h inspiron1300.wherever.co.uk /mnt &
[1] 11196
#
# df
Filesystem 1K-blocks Used Avail %Cap Mounted on
/dev/dk0 28101396 20862004 5834324 78% /
kernfs 1 1 0 100% /kern
procfs 4 4 0 100% /proc
ptyfs 1 1 0 100% /dev/pts
/dev/puffs 0 0 0 100% /mnt
#
Looking at the last line, we can see that the initiator is running
via the puffs device.
We now add a vnd device on top of the storage which the target is
presenting:
# vnconfig vnd0 /mnt/inspiron1300.wherever.co.uk/target1/storage
#
We now add a disklabel, which is offset 63 blocks into the iSCSI device.
This is so that the encrypted device which we shall put on top of the vnd
does not clash with the vnd's label. Chapter 14 of the NetBSD guide, on
setting up a cgd device, recommends that the cgd's type be "ccd".
# disklabel -e vnd0
# /dev/rvnd0d:
type: vnd
disk: vnd
label: fictitious
flags:
bytes/sector: 512
sectors/track: 32
tracks/cylinder: 64
sectors/cylinder: 2048
cylinders: 50
total sectors: 102400
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0 # microseconds
track-to-track seek: 0 # microseconds
drivedata: 0
4 partitions:
# size offset fstype [fsize bsize cpg/sgs]
a: 102336 63 ccd 2048 16384 28360 # (Cyl. 0 -
49)
d: 102400 0 unused 0 0 # (Cyl. 0 -
49)
~
=== EdDk.a11098a [confmode] is /tmp/EdDk.a11098a
================(22,11) 95% ==
#
We now set up the cgd device, pointing it at the vnd device.
# priv cgdconfig -s cgd0 /dev/vnd0a aes-cbc 128 < /dev/urandom
#
and then zero the cgd device's storage.
# dd if=/dev/zero of=/dev/rcgd0d bs=32k
dd: /dev/rcgd0d: Invalid argument
1601+0 records in
1600+0 records out
52428800 bytes transferred in 16.633 secs (3152095 bytes/sec)
#
We now unconfigure the cgd device.
# cgdconfig -u cgd0
#
and then write using the disklabel verification method onto the cgd. Sometimes,
this process does not always complete properly, and so it has to be repeated.
# cgdconfig -g -V disklabel -o /etc/cgd/vnd0a aes-cbc 256
cgdconfig: could not calibrate pkcs5_pbkdf2
cgdconfig: Failed to generate defaults for keygen
# cgdconfig -g -V disklabel -o /etc/cgd/vnd0a aes-cbc 256
#
Now we have to add the password to the cgd device
# cgdconfig -V re-enter cgd0 /dev/vnd0a
/dev/vnd0a's passphrase:
re-enter device's passphrase:
#
and disklabel inside the cgd itself:
# disklabel -I -e cgd0
# /dev/rcgd0d:
type: cgd
disk: cgd
label: fictitious
flags:
bytes/sector: 512
sectors/track: 2048
tracks/cylinder: 1
sectors/cylinder: 2048
cylinders: 49
total sectors: 102336
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0 # microseconds
track-to-track seek: 0 # microseconds
drivedata: 0
4 partitions:
# size offset fstype [fsize bsize cpg/sgs]
a: 102336 0 4.2BSD 2048 16384 28360 # (Cyl. 0 -
49*)
d: 102336 0 unused 0 0 # (Cyl. 0 -
49*)
~
~
=== EdDk.a11253a [confmode] is /tmp/EdDk.a11253a
=================(22,53) 95% ==
#
Having placed a disklabel inside the cgd, we can now make a filesystem on there:
# newfs /dev/rcgd0a
/dev/rcgd0a: 50.0MB (102336 sectors) block size 8192, fragment size 1024
using 4 cylinder groups of 12.49MB, 1599 blks, 3136 inodes.
super-block backups (for fsck_ffs -b #) at:
32, 25616, 51200, 76784,
#
we can then mount the new file system in the cgd on the /iscsi mount
point:
# df
Filesystem 1K-blocks Used Avail %Cap Mounted on
/dev/dk0 28101396 20910216 5786112 78% /
kernfs 1 1 0 100% /kern
procfs 4 4 0 100% /proc
ptyfs 1 1 0 100% /dev/pts
/dev/puffs 0 0 0 100% /mnt
# mount /dev/cgd0a /iscsi
# df
Filesystem 1K-blocks Used Avail %Cap Mounted on
/dev/dk0 28101396 20910216 5786112 78% /
kernfs 1 1 0 100% /kern
procfs 4 4 0 100% /proc
ptyfs 1 1 0 100% /dev/pts
/dev/puffs 0 0 0 100% /mnt
/dev/cgd0a 49519 1 47043 0% /iscsi
#
The new file system, mounted on /iscsi, can now be used as normal.
2. Unmounting the Encrypted Device
==================================
The device can be freed up using the following commands:
# umount /iscsi
# cgdconfig -u cgd0
# vnconfig -u vnd0
3. Normal Usage
===============
In normal usage, the device can be mounted. Firstly, the initiator
must be configured to connect to the device:
# vnconfig vnd0 /mnt/inspiron1300.wherever.co.uk/target1/storage
# cgdconfig cgd0 /dev/vnd0a
/dev/vnd0a's passphrase:
#
I'm using dk devices on this machine, so I now have to access the cgd
device using the dk that was assigned in the cgdconfig step. If I
wasn't using dk devices, then I'd use the cgd device.
!!!SO PICK ONE OF THE FOLLOWING TWO COMMANDS!!!
# mount /dev/cgd0a /iscsi OR
# mount /dev/dk3 /iscsi
# ls -al /iscsi
total 3
drwxr-xr-x 2 root wheel 512 Jan 1 1970 .
drwxr-xr-x 35 root wheel 1536 Jan 5 08:59 ..
# df
Filesystem 1K-blocks Used Avail %Cap Mounted on
/dev/dk0 28101396 20910100 5786228 78% /
kernfs 1 1 0 100% /kern
procfs 4 4 0 100% /proc
ptyfs 1 1 0 100% /dev/pts
/dev/puffs 0 0 0 100% /mnt
/dev/dk3 49519 1 47043 0% /iscsi
#
4. Conclusion
=============
An iSCSI disk can be in a location over which complete control
cannot be assured. In order to ensure privacy, the cgd device
can be used to encrypt the data on the iSCSI device.
This document has shown how to set up a cgd device on top of the
iSCSI device, and how to mount and unmount on a regular basis.
Alistair Crooks
Sat Jan 5 22:08:32 GMT 2008
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