volume_key(8)volume_key(8)NAMEvolume_key - work with volume encryption secrets and escrow packets
SYNOPISvolume_key [OPTION]... OPERAND...
DESCRIPTIONvolume_key extracts "secrets" used for volume encryption (for example
keys or passphrases) and stores them into separate encrypted "escrow
packets", uses a previously created escrow packet to restore access to
a volume (e.g. if the user forgets a passphrase), or manipulates the
information in escrow packets.
The mode of operation and operands of volume_key are determined by
specifying one of the --save, --restore, --setup-volume, --reencrypt,
--dump or --secrets options. See the OPTIONS sections for details.
OPTIONS
In all options described below, VOLUME is a LUKS device, not the plain‐
text device containted within:
blkid -s TYPE VOLUME
should report TYPE="crypto_LUKS".
The following options determine the mode of operation and expected op‐
erands of volume_key:
--save Expects operands VOLUME [PACKET]. Open VOLUME. If PACKET is
provided, load the secrets from it. Otherwise, extract secrets
from VOLUME, prompting the user if necessary. In any case,
store secrets in one or more output packets.
--restore
Expects operands VOLUME PACKET. Open VOLUME and use the secrets
in PACKET to make VOLUME accessible again, prompting the user if
necessary (e.g. by letting the user enter a new passphrase).
--setup-volume
Expects operands VOLUME PACKET NAME. Open VOLUME and use the
secrets in PACKET to set up VOLUME for use of the decrypted data
as NAME.
Currently NAME is a name of a dm-crypt volume, and this opera‐
tion makes the decrypted volume available as /dev/mapper/NAME.
This operation should not permanently alter VOLUME (e.g. by
adding a new passphrase); the user can of course access and mod‐
ify the decrypted volume, modifying VOLUME in the process.
--reencrypt
Expects operand PACKET. Open PACKET, decrypting it if neces‐
sary, and store the information in one or more new output pack‐
ets.
--dump Expects operand PACKET. Open PACKET, decrypting it if neces‐
sary, and output the contents of PACKET. The secrets are not
output by default.
--secrets
Expects operand PACKET. Open PACKET, decrypting it if neces‐
sary, and output secrets contained in PACKET.
--help Show usage information.
--version
Show version of volume_key.
The following options alter the behavior of the specified operation:
-b, --batch
Run in batch mode. Read passwords and passphrases from standard
input, each terminated by a NUL character. If a packet does not
match a volume exactly, fail instead of prompting the user.
-d, --nss-dir DIR
Use private keys in NSS database in DIR to decrypt public key-
encrypted packets.
-o, --output PACKET
Write the default secret to PACKET.
Which secret is the default depends on volume format: it should
not be likely to expire, and it should allow restoring access to
the volume using --restore.
--output-data-encryption-key PACKET
Write the data encryption key (the key directly used to encrypt
the actual volume data) to PACKET.
--output-passphrase PACKET
Write a passphrase that can be used to access the volume to
PACKET.
--create-random-passphrase PACKET
Generate a random alphanumeric passphrase, add it to VOLUME
(without affecting other passphrases) and store the random
passphrase into PACKET.
-c, --certificate CERT
Load a certificate from the file specified by CERT and encrypt
all output packets using the public key contained in the cer‐
tificate. If this option is not specified, all output packets
are encrypted using a passphrase.
Note that CERT is a certificate file name, not a NSS certificate
nickname.
--output-format FORMAT
Use FORMAT for all output packets. FORMAT can currently be one
of asymmetric (use CMS to encrypt the whole packet, requires a
certificate), asymmetric_wrap_secret_only (wrap only the secret,
requires a certificate), passphrase (use GPG to encrypt the
whole packet, requires a passphrase).
--with-secrets
Include secrets in the output of --dump
EXIT STATUSvolume_key returns with exit status 0 on success, 1 on error.
NOTES
The only currently supported volume format is LUKS.
EXAMPLE
Typical usage of volume_key proceeds as follows. During system instal‐
lation or soon after, back up the default secret of a volume, and add a
system-specific random passphrase. Encrypt both using a certificate:
volume_key--save VOLUME -c CERT -o PACKET_DEFAULT --create-ran‐
dom-passphrase PACKET_PASSPHRASE
Store PACKET_DEFAULT and PACKET_PASSPHRASE outside of the computer.
If the user forgets a passphrase, and the you can access the computer,
decrypt PACKET_DEFAULT using the certificate private key (which should
never leave a secure machine):
volume_key--reencrypt-d NSS_DB PACKET_DEFAULT -o
PACKET_DEFAULT_PW
Then boot the computer (e.g. using a "rescue mode"), copy
PACKET_DEFAULT_PW to it, and restore access to the volume:
volume_key--restore VOLUME PACKET_DEFAULT_PW
If the user forgets the passphrase, and you cannot access the computer,
decrypt the backup passphrase:
volume_key--secrets PACKET_PASSPHRASE
and tell the backup passphrase to the user. (You can later generate a
new backup passphrase.)
volume_key Sep 2010 volume_key(8)
