GELI(8) MidnightBSD 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 following 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:

Utilizes the crypto(9) framework, so when there is crypto hardware available, geli will make use of it automatically.

Supports many cryptographic algorithms (currently AES, Blowfish, Camellia and 3DES).

Can optionally perform data authentication (integrity verification) utilizing one of the following algorithms: HMAC/MD5, HMAC/SHA1, HMAC/RIPEMD160, HMAC/SHA256, HMAC/SHA384 or HMAC/SHA512.

Can create a key from a couple of components (user entered passphrase, random bits from a file, etc.).

Allows to encrypt the root partition - the user will be asked for the passphrase before the root file system is mounted.

The passphrase of the user is strengthened with:

B. Kaliski ,
PKCS #5: Password-Based Cryptography Specification, Version 2.0.
,
RFC ,
2898 .

Allows to use two independent keys (e.g. "user key" and "company key").

It is fast - geli performs simple sector-to-sector encryption.

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.

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).

Allows to attach a provider with a random, one-time key - useful for swap partitions and temporary file systems.

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 example, when using 4096 bytes sector and HMAC/SHA256 algorithm, 89% of the original provider storage will be available for use. Currently supported algorithms are: HMAC/MD5, HMAC/SHA1, HMAC/RIPEMD160, HMAC/SHA256, HMAC/SHA384 and HMAC/SHA512. If the option is not given, there will be no authentication, only encryption.

−e ealgo

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

−b

Ask for the passphrase on boot, before the root partition is mounted. This makes it possible to use an encrypted root partition. One will still need bootable unencrypted storage with a /boot/ directory, 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 algorithm. If not given, the default key length for the given algorithm is used, which is: 128 for AES, 128 for Blowfish, 128 for Camellia 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 writing, 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 partitions. For more information, see the description of the attach subcommand.

−l keylen

Key length to use with the given cryptographic algorithm. 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 subcommand.

configure

Change configuration of the given providers.

Additional options include:

−b

Set the BOOT flag on the given providers. For more information, 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 the provider was attached with the −r flag, the keys will not 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 information is printed. If set to 3, the maximum amount of debug information 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 software 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 keyfile:

# 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 specified. 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 in-place or copied from one place on the disk to another even without modification, geli should be able to detect such a change. If an attacker can remember the encrypted data, he can overwrite any future changes with the data he owns without notice. In other words 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. Support for Camellia block cipher is implemented by Yoshisato Yanagisawa in FreeBSD 7.0.

AUTHORS

Pawel Jakub Dawidek 〈pjd@FreeBSD.org〉

MidnightBSD 0.3 September 16, 2006 MidnightBSD 0.3