geli

GELI(8) FreeBSD System Manager's Manual GELI(8)

NAME
geli -- control utility for cryptographic GEOM class

SYNOPSIS
To compile GEOM_ELI into your kernel, place the following lines in your
kernel configuration file:

device crypto
options GEOM_ELI

Alternately, to load the GEOM_ELI module at boot time, place the follow-
ing line in your loader.conf(5):

geom_eli_load="YES"

Usage of the geli(8) utility:

geli init [-bPv] [-a aalgo] [-e ealgo] [-i iterations] [-K newkeyfile]
[-l keylen] [-s sectorsize] prov
geli label - an alias for init
geli attach [-dprv] [-k keyfile] prov
geli detach [-fl] prov ...
geli stop - an alias for detach
geli onetime [-d] [-a aalgo] [-e ealgo] [-l keylen] [-s sectorsize] prov
...
geli configure [-bB] prov ...
geli setkey [-pPv] [-i iterations] [-k keyfile] [-K newkeyfile]
[-n keyno] prov
geli delkey [-afv] [-n keyno] prov
geli kill [-av] [prov ...]
geli backup [-v] prov file
geli restore [-v] file prov
geli clear [-v] prov ...
geli dump [-v] prov ...
geli list
geli status
geli load
geli unload

DESCRIPTION
The geli utility is used to configure encryption on GEOM providers.

The following is a list of the most important features:

o Utilizes the crypto(9) framework, so when there is crypto hard-
ware available, geli will make use of it automatically.
o Supports many cryptographic algorithms (currently AES, Blowfish
and 3DES).
o Can optionally perform data authentication (integrity verifica-
tion) utilizing one of the following algorithms: HMAC/MD5,
HMAC/SHA1, HMAC/RIPEMD160, HMAC/SHA256, HMAC/SHA384 or
HMAC/SHA512.
o Can create a key from a couple of components (user entered
passphrase, random bits from a file, etc.).
o Allows to encrypt the root partition - the user will be asked
for the passphrase before the root file system is mounted.
o The passphrase of the user is strengthened with: B. Kaliski,
PKCS #5: Password-Based Cryptography Specification, Version
2.0., RFC, 2898.
o Allows to use two independent keys (e.g. "user key" and
"company key").
o It is fast - geli performs simple sector-to-sector encryption.
o Allows to backup/restore Master Keys, so when a user has to
quickly destroy his keys, it is possible to get the data back
by restoring keys from the backup.
o Providers can be configured to automatically detach on last
close (so users do not have to remember to detach providers
after unmounting the file systems).
o Allows to attach a provider with a random, one-time key - use-
ful for swap partitions and temporary file systems.
o Allows to verify data integrity (data authentication).

The first argument to geli indicates an action to be performed:

init Initialize provider which needs to be encrypted. Here you can
set up the cryptographic algorithm to use, key length, etc.
The last provider's sector is used to store metadata.

Additional options include:

-a aalgo Enable data integrity verification (authentication)
using the given algorithm. This will reduce size of
available storage and also reduce speed. For exam-
ple, when using 4096 bytes sector and HMAC/SHA256
algorithm, 89% of the original provider storage will
be available for use. Currently supported algo-
rithms are: HMAC/MD5, HMAC/SHA1, HMAC/RIPEMD160,
HMAC/SHA256, HMAC/SHA384 and HMAC/SHA512. If the
option is not given, there will be no authentica-
tion, only encryption.

-e ealgo Encryption algorithm to use. Currently supported
algorithms are: AES, Blowfish and 3DES. The default
is AES.

-b Ask for the passphrase on boot, before the root par-
tition is mounted. This makes it possible to use an
encrypted root partition. One will still need
bootable unencrypted storage with a /boot/ direc-
tory, which can be a CD-ROM disc or USB pen-drive,
that can be removed after boot.

-i iterations
Number of iterations to use with PKCS#5v2. If this
option is not specified, geli will find the number
of iterations which is equal to 2 seconds of crypto
work. If 0 is given, PKCS#5v2 will not be used.

-K newkeyfile
Specifies a file which contains part of the key. If
newkeyfile is given as -, standard input will be
used. Here is how more than one file with a key
component can be used:

# cat key1 key2 key3 | geli init -K - /dev/da0

-l keylen
Key length to use with the given cryptographic algo-
rithm. If not given, the default key length for the
given algorithm is used, which is: 128 for AES, 128
for Blowfish and 192 for 3DES.

-s sectorsize
Change decrypted provider's sector size. Increasing
sector size allows to increase performance, because
we need to generate an IV and do encrypt/decrypt for
every single sector - less number of sectors means
less work to do.

-P Do not use passphrase as the key component.

attach Attach the given provider. The master key will be decrypted
using the given passphrase/keyfile and a new GEOM provider
will be created using the given provider's name with an ".eli"
suffix.

Additional options include:

-d If specified, a decrypted provider will be detached
automatically on last close. This can help with
short memory - user does not have to remember to
detach the provider after unmounting the file system.
It only works when the provider was opened for writ-
ing, so it will not work if the file system on the
provider is mounted read-only. Probably a better
choice is the -l option for the detach subcommand.

-r Attach read-only provider. It will not be opened for
writing.

-k keyfile
Specifies a file which contains part of the key. For
more information see the description of the -K option
for the init subcommand.

-p Do not use passphrase as the key component.

detach Detach the given providers, which means remove the devfs entry
and clear the keys from memory.

Additional options include:

-f Force detach - detach even if the provider is open.

-l Mark provider to detach on last close. If this
option is specified, the provider will not be
detached until it is open, but when it will be closed
last time, it will be automatically detached (even if
it was only opened for reading).

onetime Attach the given providers with random, one-time keys. The
command can be used to encrypt swap partitions or temporary
file systems.

Additional options include:

-a aalgo Enable data integrity verification (authentication).
For more information, see the description of the
init subcommand.

-e ealgo Encryption algorithm to use. For more information,
see the description of the init subcommand.

-d Detach on last close. Note, the option is not
usable for temporary file systems as the provider
will be detached after creating the file system on
it. It still can (and should be) used for swap par-
titions. For more information, see the description
of the attach subcommand.

-l keylen
Key length to use with the given cryptographic algo-
rithm. For more information, see the description of
the init subcommand.

-s sectorsize
Change decrypted provider's sector size. For more
information, see the description of the init subcom-
mand.

configure Change configuration of the given providers.

Additional options include:

-b Set the BOOT flag on the given providers. For more infor-
mation, see the description of the init subcommand.

-B Remove the BOOT flag from the given providers.

setkey Change or setup (if not yet initialized) selected key. There
is one master key, which can be encrypted with two independent
user keys. With the init subcommand, only key number 0 is
initialized. The key can always be changed: for an attached
provider, for a detached provider or on the backup file. When
a provider is attached, the user does not have to provide an
old passphrase/keyfile.

Additional options include:

-i iterations
Number of iterations to use with PKCS#5v2. If 0 is
given, PKCS#5v2 will not be used. To be able to use
this option with setkey subcommand, only one key have
to be defined and this key has to be changed.

-k keyfile
Specifies a file which contains part of the old key.

-K newkeyfile
Specifies a file which contains part of the new key.

-n keyno
Specifies the number of the key to change (could be 0
or 1). If the provider is attached and no key number
is given, the key used for attaching the provider
will be changed. If the provider is detached (or we
are operating on a backup file) and no key number is
given, the key decrypted with the passphrase/keyfile
will be changed.

-p Do not use passphrase as the old key component.

-P Do not use passphrase as the new key component.

delkey Destroy (overwrite with random data) the selected key. If one
is destroying keys for an attached provider, the provider will
not be detached even if all keys will be destroyed. It can be
even rescued with the setkey subcommand.

-a Destroy all keys (does not need -f option).

-f Force key destruction. This option is needed to
destroy the last key.

-n keyno
Specifies the key number. If the provider is
attached and no key number is given, the key used for
attaching the provider will be destroyed. If
provider is detached (or we are operating on a backup
file) the key number has to be given.

kill This command should be used in emergency situations. It will
destroy all keys on the given provider and will detach it
forcibly (if it is attached). This is absolutely a one-way
command - if you do not have a metadata backup, your data is
gone for good. In case provider was attached with the -r
flag, the keys won't be destroyed, only the provider will be
detached.

-a If specified, all currently attached providers will
be killed.

backup Backup metadata from the given provider to the given file.

restore Restore metadata from the given file to the given provider.

clear Clear metadata from the given providers.

dump Dump metadata stored on the given providers.

list See geom(8).

status See geom(8).

load See geom(8).

unload See geom(8).

Additional options include:

-v Be more verbose.

SYSCTL VARIABLES
The following sysctl(8) variables can be used to control the behavior of
the ELI GEOM class. The default value is shown next to each variable.
All variables can also be set in /boot/loader.conf.

kern.geom.eli.debug: 0
Debug level of the ELI GEOM class. This can be set to a number
between 0 and 3 inclusive. If set to 0, minimal debug informa-
tion is printed. If set to 3, the maximum amount of debug infor-
mation is printed.

kern.geom.eli.tries: 3
Number of times a user is asked for the passphrase. This is only
used for providers which should be attached on boot (before the
root file system is mounted). If set to 0, attaching providers
on boot will be disabled. This variable should be set in
/boot/loader.conf.

kern.geom.eli.overwrites: 5
Specifies how many times the Master-Key will be overwritten with
random values when it is destroyed. After this operation it is
filled with zeros.

kern.geom.eli.visible_passphrase: 0
If set to 1, the passphrase entered on boot (before the root file
system is mounted) will be visible. This possibility should be
used with caution as the entered passphrase can be logged and
exposed via dmesg(8). This variable should be set in
/boot/loader.conf.

kern.geom.eli.threads: 0
Specifies how many kernel threads should be used for doing soft-
ware cryptography. Its purpose is to increase performance on SMP
systems. If hardware acceleration is available, only one thread
will be started. If set to 0, CPU-bound thread will be started
for every active CPU.

kern.geom.eli.batch: 0
When set to 1, can speed-up crypto operations by using batching.
Batching allows to reduce number of interrupts by responding on a
group of crypto requests with one interrupt. The crypto card and
the driver has to support this feature.

EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.

EXAMPLES
Initialize a provider which is going to be encrypted with a passphrase
and random data from a file on the user's pen drive. Use 4kB sector
size. Attach the provider, create a file system and mount it. Do the
work. Unmount the provider and detach it:

# dd if=/dev/random of=/mnt/pendrive/da2.key bs=64 count=1
# geli init -s 4096 -K /mnt/pendrive/da2.key /dev/da2
Enter new passphrase:
Reenter new passphrase:
# geli attach -k /mnt/pendrive/da2.key /dev/da2
Enter passphrase:
# dd if=/dev/random of=/dev/da2.eli bs=1m
# newfs /dev/da2.eli
# mount /dev/da2.eli /mnt/secret
...
# umount /mnt/secret
# geli detach da2.eli

Create an encrypted provider, but use two keys: one for your girlfriend
and one for you (so there will be no tragedy if she forgets her
passphrase):

# geli init /dev/da2
Enter new passphrase: (enter your passphrase)
Reenter new passphrase:
# geli setkey -n 1 /dev/da2
Enter passphrase: (enter your passphrase)
Enter new passphrase: (let your girlfriend enter her passphrase ...)
Reenter new passphrase: (... twice)

You are the security-person in your company. Create an encrypted
provider for use by the user, but remember that users forget their
passphrases, so back Master Key up with your own random key:

# dd if=/dev/random of=/mnt/pendrive/keys/`hostname` bs=64 count=1
# geli init -P -K /mnt/pendrive/keys/`hostname` /dev/ad0s1e
# geli backup /dev/ad0s1e /mnt/pendrive/backups/`hostname`
(use key number 0, so the encrypted Master Key by you will be overwritten)
# geli setkey -n 0 -k /mnt/pendrive/keys/`hostname` /dev/ad0s1e
(allow the user to enter his passphrase)
Enter new passphrase:
Reenter new passphrase:

Encrypted swap partition setup:

# dd if=/dev/random of=/dev/ad0s1b bs=1m
# geli onetime -d -e 3des ad0s1b
# swapon /dev/ad0s1b.eli

The example below shows how to configure two providers which will be
attached on boot (before the root file system is mounted). One of them
is using passphrase and three keyfiles and the other is using only a key-
file:

# dd if=/dev/random of=/dev/da0 bs=1m
# dd if=/dev/random of=/boot/keys/da0.key0 bs=32k count=1
# dd if=/dev/random of=/boot/keys/da0.key1 bs=32k count=1
# dd if=/dev/random of=/boot/keys/da0.key2 bs=32k count=1
# cat /boot/keys/da0.key0 /boot/keys/da0.key1 /boot/keys/da0.key2 | geli init -b -K - da0
Enter new passphrase:
Reenter new passphrase:
# dd if=/dev/random of=/dev/da1s3a bs=1m
# dd if=/dev/random of=/boot/keys/da1s3a.key bs=128k count=1
# geli init -b -P -K /boot/keys/da1s3a.key da1s3a

The providers are initialized, now we have to add those lines to
/boot/loader.conf:

geli_da0_keyfile0_load="YES"
geli_da0_keyfile0_type="da0:geli_keyfile0"
geli_da0_keyfile0_name="/boot/keys/da0.key0"
geli_da0_keyfile1_load="YES"
geli_da0_keyfile1_type="da0:geli_keyfile1"
geli_da0_keyfile1_name="/boot/keys/da0.key1"
geli_da0_keyfile2_load="YES"
geli_da0_keyfile2_type="da0:geli_keyfile2"
geli_da0_keyfile2_name="/boot/keys/da0.key2"

geli_da1s3a_keyfile0_load="YES"
geli_da1s3a_keyfile0_type="da1s3a:geli_keyfile0"
geli_da1s3a_keyfile0_name="/boot/keys/da1s3a.key"

Not only configure encryption, but also data integrity verification using
HMAC/SHA256.

# geli init -a hmac/sha256 -s 4096 /dev/da0
Enter new passphrase:
Reenter new passphrase:
# geli attach /dev/da0
Enter passphrase:
# dd if=/dev/random of=/dev/da0.eli bs=1m
# newfs /dev/da0.eli
# mount /dev/da0.eli /mnt/secret

DATA AUTHENTICATION
geli can verify data integrity when an authentication algorithm is speci-
fied. When data corruption/modification is detected, geli will not
return any data, but instead will return an error (EINVAL). The offset
and size of the corrupted data will be printed on the console. It is
important to know against which attacks geli provides protection for your
data. If data is modified or copied from one place on the disk to
another, geli should be able to detect such a modification. If an
attacker can remember the encrypted data, modify them and write them back
to the same place, the modification will not be detected. geli will not
protect your data against replay attacks.

SEE ALSO
crypto(4), gbde(4), geom(4), loader.conf(5), gbde(8), geom(8), crypto(9)

HISTORY
The geli utility appeared in FreeBSD 6.0.

AUTHORS
Pawel Jakub Dawidek <pjdATFreeBSD.org>

FreeBSD 6.2 September 16, 2006 FreeBSD 6.2

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