NAME¶

geli — control utility for the cryptographic GEOM class

SYNOPSIS¶

To compile GEOM_ELI into your kernel, add the following lines to your kernel configuration file:

Alternatively, to load the GEOM_ELI module at boot time, add the following line to your loader.conf(5):

geom_eli_load="YES"

Usage of the

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-XTS, AES-CBC, Blowfish-CBC, Camellia-CBC and 3DES-CBC).
• 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 User Key from up to two, piecewise components: a passphrase entered via prompt or read from one or more passfiles; a keyfile read from one or more files.
• Allows encryption of the root partition. The user will be asked for the passphrase before the root file system is mounted.
• Strengthens the passphrase component of the User Key with: B. Kaliski, PKCS #5: Password-Based Cryptography Specification, Version 2.0., RFC, 2898.
• Allows the use of two independent User Keys (e.g., a "user key" and a "company key").
• It is fast - geli performs simple sector-to-sector encryption.
• Allows the encrypted Master Key to be backed up and restored, so that if a user has to quickly destroy key material, it is possible to get the data back by restoring keys from 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 attaching a provider with a random, one-time Master Key - useful for swap partitions and temporary file systems.
• Allows verification of data integrity (data authentication).
• Allows suspending and resuming encrypted devices.

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

init

Initialize the provider which needs to be encrypted. Here you can set up the cryptographic algorithm to use, Data Key length, etc. The last sector of the provider is used to store metadata. The init subcommand also automatically writes metadata backups to /var/backups/<prov>.eli file. The metadata can be recovered with the restore subcommand described below.

Additional options include:

-a aalgo

Enable data integrity verification (authentication) using the given algorithm. This will reduce the size of storage available 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. The recommended algorithm is HMAC/SHA256.

-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.

-B backupfile

File name to use for metadata backup instead of the default /var/backups/<prov>.eli. To inhibit backups, you can use none as the backupfile.

-e ealgo

Encryption algorithm to use. Currently supported algorithms are: AES-XTS, AES-CBC, Blowfish-CBC, Camellia-CBC, 3DES-CBC, and NULL. The default and recommended algorithm is AES-XTS. NULL is unencrypted.

-i iterations

Number of iterations to use with PKCS#5v2 when processing User Key passphrase component. 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. PKCS#5v2 processing is performed once, after all parts of the passphrase component have been read.

-J newpassfile

Specifies a file which contains the passphrase component of the User Key (or part of it). If newpassfile is given as -, standard input will be used. Only the first line (excluding new-line character) is taken from the given file. This argument can be specified multiple times, which has the effect of reassembling a single passphrase split across multiple files. Cannot be combined with the -P option.

-K newkeyfile

Specifies a file which contains the keyfile component of the User Key (or part of it). If newkeyfile is given as -, standard input will be used. This argument can be specified multiple times, which has the effect of reassembling a single keyfile split across multiple keyfile parts.

-l keylen

Data Key length to use with the given cryptographic algorithm. If the length is not specified, the selected algorithm uses its default key length.

AES-XTS

128, 256

AES-CBC, Camellia-CBC

128, 192, 256

Blowfish-CBC

128 + n * 32, for n=[0..10]

3DES-CBC

192

-P

Do not use a passphrase as a component of the User Key. Cannot be combined with the -J option.

-s sectorsize

Change decrypted provider's sector size. Increasing the sector size allows increased performance, because encryption/decryption which requires an initialization vector is done per sector; fewer sectors means less computational work.

-V version

Metadata version to use. This option is helpful when creating a provider that may be used by older FreeBSD/GELI versions. Consult the HISTORY section to find which metadata version is supported by which FreeBSD version. Note that using an older version of metadata may limit the number of features available.

attach

Attach the given provider. The encrypted Master Key will be loaded from the metadata and 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 scarce memory so the 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.

-j passfile

Specifies a file which contains the passphrase component of the User Key (or part of it). For more information see the description of the -J option for the init subcommand.

-k keyfile

Specifies a file which contains the keyfile component of the User Key (or part of it). For more information see the description of the -K option for the init subcommand.

-p

Do not use a passphrase as a component of the User Key. Cannot be combined with the -j option.

-r

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

detach

Detach the given providers, which means remove the devfs entry and clear the Master Key and Data 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 while it is open, but will be automatically detached when it is closed for the last time even if it was only opened for reading.

onetime

Attach the given providers with a random, one-time (ephemeral) Master Key. 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: this 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

Data 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

Install a copy of the Master Key into the selected slot, encrypted with a new User Key. If the selected slot is populated, replace the existing copy. A provider has one Master Key, which can be stored in one or both slots, each encrypted with an independent User Key. With the init subcommand, only key number 0 is initialized. The User Key can be changed at any time: 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 existing 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 the setkey subcommand, only one key has to be defined and this key must be changed.

-j passfile

Specifies a file which contains the passphrase component of a current User Key (or part of it).

-J newpassfile

Specifies a file which contains the passphrase component of the new User Key (or part of it).

-k keyfile

Specifies a file which contains the keyfile component of a current User Key (or part of it).

-K newkeyfile

Specifies a file which contains the keyfile component of the new User Key (or part of it).

-n keyno

Specifies the index number of the Master Key copy 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 first Master Key copy to be successfully decrypted with the provided User Key passphrase/keyfile will be changed.

-p

Do not use a passphrase as a component of the current User Key. Cannot be combined with the -j option.

-P

Do not use a passphrase as a component of the new User Key. Cannot be combined with the -J option.

delkey

Destroy (overwrite with random data) the selected Master Key copy. If one is destroying keys for an attached provider, the provider will not be detached even if all copies of the Master Key are destroyed. It can even be rescued with the setkey subcommand because the Master Key is still in memory.

Additional options include:

-a

Destroy all copies of the Master Key (does not need -f option).

-f

Force key destruction. This option is needed to destroy the last copy of the Master Key.

-n keyno

Specifies the index number of the Master Key copy. 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 only in emergency situations. It will destroy all copies of the Master Key on a 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.

Additional options include:

-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.

Additional options include:

-f

Metadata contains the size of the provider to ensure that the correct partition or slice is attached. If an attempt is made to restore metadata to a provider that has a different size, geli will refuse to restore the data unless the -f switch is used. If the partition or slice has been grown, the resize subcommand should be used rather than attempting to relocate the metadata through backup and restore.

suspend

Suspend device by waiting for all inflight requests to finish, clearing all sensitive information (like the Master Key and Data Keys) from kernel memory, and blocking all further I/O requests until the resume subcommand is executed. This functionality is useful for laptops: when one wants to suspend a laptop, one does not want to leave an encrypted device attached. Instead of closing all files and directories opened from a file system located on an encrypted device, unmounting the file system, and detaching the device, the suspend subcommand can be used. Any access to the encrypted device will be blocked until the Master Key is reloaded through the resume subcommand. Thus there is no need to close nor unmount anything. The suspend subcommand does not work with devices created with the onetime subcommand. Please note that sensitive data might still be present in memory after suspending an encrypted device due to the file system cache, etc.

Additional options include:

-a

Suspend all geli devices.

resume

Resume previously suspended device. The caller must ensure that executing this subcommand does not access the suspended device, leading to a deadlock. For example suspending a device which contains the file system where the geli utility is stored is bad idea.

Additional options include:

-j passfile

Specifies a file which contains the passphrase component of the User Key (or part of it). For more information see the description of the -J option for the init subcommand.

-k keyfile

Specifies a file which contains the keyfile component of the User Key (or part of it). For more information see the description of the -K option for the init subcommand.

-p

Do not use a passphrase as a component of the User Key. Cannot be combined with the -j option.

resize

Inform geli that the provider has been resized. The old metadata block is relocated to the correct position at the end of the provider and the provider size is updated.

Additional options include:

-s oldsize

The size of the provider before it was resized.

version

If no arguments are given, the version subcommand will print the version of geli userland utility as well as the version of the ELI GEOM class.

If GEOM providers are specified, the version subcommand will print metadata version used by each of them.

clear

Clear metadata from the given providers. WARNING: This will erase with zeros the encrypted Master Key copies stored in the metadata.

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.

KEY SUMMARY¶

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. Some variables can also be set in /boot/loader.conf.

kern.geom.eli.version

Version number of the ELI GEOM class.

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 are 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 alternative 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 set to 0, a CPU-pinned 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 reduces the number of interrupts by responding to a group of crypto requests with one interrupt. The crypto card and the driver has to support this feature.

kern.geom.eli.key_cache_limit: 8192

Specifies how many Data Keys to cache. The default limit (8192 keys) will allow caching of all keys for a 4TB provider with 512 byte sectors and will take around 1MB of memory.

kern.geom.eli.key_cache_hits

Reports how many times we were looking up a Data Key and it was already in cache. This sysctl is not updated for providers that need fewer Data Keys than the limit specified in kern.geom.eli.key_cache_limit.

kern.geom.eli.key_cache_misses

Reports how many times we were looking up a Data Key and it was not in cache. This sysctl is not updated for providers that need fewer Data Keys than the limit specified in kern.geom.eli.key_cache_limit.

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 User Keys: one for your employee and one for you as the company's security officer (so it is not a tragedy if the employee "accidentally" forgets his passphrase):

# geli init /dev/da2
Enter new passphrase:	(enter security officer's passphrase)
Reenter new passphrase:
# geli setkey -n 1 /dev/da2
Enter passphrase:	(enter security officer's passphrase)
Enter new passphrase:	(let your employee enter his passphrase ...)
Reenter new passphrase:	(... twice)

You are the security officer in your company. Create an encrypted provider for use by the user, but remember that users forget their passphrases, so backup the Master Key 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/ada0s1e
# geli backup /dev/ada0s1e /mnt/pendrive/backups/`hostname`
(use key number 0, so the encrypted Master Key will be re-encrypted by this)
# geli setkey -n 0 -k /mnt/pendrive/keys/`hostname` /dev/ada0s1e
(allow the user to enter his passphrase)
Enter new passphrase:
Reenter new passphrase:

Encrypted swap partition setup:

# dd if=/dev/random of=/dev/ada0s1b bs=1m
# geli onetime -d -e 3des ada0s1b
# swapon /dev/ada0s1b.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 keyfile parts and the other is using only a keyfile in one part:

# 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
# geli init -b -K /boot/keys/da0.key0 -K /boot/keys/da0.key1 -K /boot/keys/da0.key2 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 these 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

geli writes the metadata backup by default to the /var/backups/<prov>.eli file. If the metadata is lost in any way (e.g., by accidental overwrite), it can be restored. Consider the following situation:

# geli init /dev/da0
Enter new passphrase:
Reenter new passphrase:

Metadata backup can be found in /var/backups/da0.eli and
can be restored with the following command:

	# geli restore /var/backups/da0.eli /dev/da0

# geli clear /dev/da0
# geli attach /dev/da0
geli: Cannot read metadata from /dev/da0: Invalid argument.
# geli restore /var/backups/da0.eli /dev/da0
# geli attach /dev/da0
Enter passphrase:

If an encrypted file system is extended, it is necessary to relocate and update the metadata:

# gpart create -s GPT ada0
# gpart add -s 1g -t freebsd-ufs -i 1 ada0
# geli init -K keyfile -P ada0p1
# gpart resize -s 2g -i 1 ada0
# geli resize -s 1g ada0p1
# geli attach -k keyfile -p ada0p1

Initialize provider with the passphrase split into two files. The provider can be attached using those two files or by entering “foobar” as the passphrase at the geli prompt:

# echo foo > da0.pass0
# echo bar > da0.pass1
# geli init -J da0.pass0 -J da0.pass1 da0
# geli attach -j da0.pass0 -j da0.pass1 da0
# geli detach da0
# geli attach da0
Enter passphrase: foobar

Suspend all geli devices on a laptop, suspend the laptop, then resume devices one by one after resuming the laptop:

# geli suspend -a
# zzz
<resume your laptop>
# geli resume -p -k keyfile gpt/secret
# geli resume gpt/private
Enter passphrase:

ENCRYPTION MODES¶

geli supports two encryption modes: XTS, which was standardized as IEEE P1619 and CBC with unpredictable IV. The CBC mode used by geli is very similar to the mode ESSIV.

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 it being noticed. In other words geli will not protect your data against replay attacks.

It is recommended to write to the whole provider before first use, in order to make sure that all sectors and their corresponding checksums are properly initialized into a consistent state. One can safely ignore data authentication errors that occur immediately after the first time a provider is attached and before it is initialized in this way.

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 the Camellia block cipher is implemented by Yoshisato Yanagisawa in FreeBSD 7.0.

Highest GELI metadata version supported by the given FreeBSD version:

AUTHORS¶

Pawel Jakub Dawidek ⟨pjd@FreeBSD.org⟩