man/man8/zfs-change-key.8

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.\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org>
.\" Copyright (c) 2011, 2019 by Delphix. All rights reserved.
.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
.\" Copyright (c) 2014 by Adam Stevko. All rights reserved.
.\" Copyright (c) 2014 Integros [integros.com]
.\" Copyright 2019 Richard Laager. All rights reserved.
.\" Copyright 2018 Nexenta Systems, Inc.
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.Dd January 13, 2020
.Dt ZFS-LOAD-KEY 8
.Os
.
.Sh NAME
.Nm zfs-load-key
.Nd load, unload, or change encryption key of ZFS dataset
.Sh SYNOPSIS
.Nm zfs
.Cm load-key
.Op Fl nr
.Op Fl L Ar keylocation
.Fl a Ns | Ns Ar filesystem
.Nm zfs
.Cm unload-key
.Op Fl r
.Fl a Ns | Ns Ar filesystem
.Nm zfs
.Cm change-key
.Op Fl l
.Op Fl o Ar keylocation Ns = Ns Ar value
.Op Fl o Ar keyformat Ns = Ns Ar value
.Op Fl o Ar pbkdf2iters Ns = Ns Ar value
.Ar filesystem
.Nm zfs
.Cm change-key
.Fl i
.Op Fl l
.Ar filesystem
.
.Sh DESCRIPTION
.Bl -tag -width ""
.It Xo
.Nm zfs
.Cm load-key
.Op Fl nr
.Op Fl L Ar keylocation
.Fl a Ns | Ns Ar filesystem
.Xc
Load the key for
.Ar filesystem ,
allowing it and all children that inherit the
.Sy keylocation
property to be accessed.
The key will be expected in the format specified by the
.Sy keyformat
and location specified by the
.Sy keylocation
property.
Note that if the
.Sy keylocation
is set to
.Sy prompt
the terminal will interactively wait for the key to be entered.
Loading a key will not automatically mount the dataset.
If that functionality is desired,
.Nm zfs Cm mount Fl l
will ask for the key and mount the dataset
.Po
see
.Xr zfs-mount 8
.Pc .
Once the key is loaded the
.Sy keystatus
property will become
.Sy available .
.Bl -tag -width "-r"
.It Fl r
Recursively loads the keys for the specified filesystem and all descendent
encryption roots.
.It Fl a
Loads the keys for all encryption roots in all imported pools.
.It Fl n
Do a dry-run
.Pq Qq No-op
.Cm load-key .
This will cause
.Nm zfs
to simply check that the provided key is correct.
This command may be run even if the key is already loaded.
.It Fl L Ar keylocation
Use
.Ar keylocation
instead of the
.Sy keylocation
property.
This will not change the value of the property on the dataset.
Note that if used with either
.Fl r
or
.Fl a ,
.Ar keylocation
may only be given as
.Sy prompt .
.El
.It Xo
.Nm zfs
.Cm unload-key
.Op Fl r
.Fl a Ns | Ns Ar filesystem
.Xc
Unloads a key from ZFS, removing the ability to access the dataset and all of
its children that inherit the
.Sy keylocation
property.
This requires that the dataset is not currently open or mounted.
Once the key is unloaded the
.Sy keystatus
property will become
.Sy unavailable .
.Bl -tag -width "-r"
.It Fl r
Recursively unloads the keys for the specified filesystem and all descendent
encryption roots.
.It Fl a
Unloads the keys for all encryption roots in all imported pools.
.El
.It Xo
.Nm zfs
.Cm change-key
.Op Fl l
.Op Fl o Ar keylocation Ns = Ns Ar value
.Op Fl o Ar keyformat Ns = Ns Ar value
.Op Fl o Ar pbkdf2iters Ns = Ns Ar value
.Ar filesystem
.Xc
.It Xo
.Nm zfs
.Cm change-key
.Fl i
.Op Fl l
.Ar filesystem
.Xc
Changes the user's key (e.g. a passphrase) used to access a dataset.
This command requires that the existing key for the dataset is already loaded.
This command may also be used to change the
.Sy keylocation ,
.Sy keyformat ,
and
.Sy pbkdf2iters
properties as needed.
If the dataset was not previously an encryption root it will become one.
Alternatively, the
.Fl i
flag may be provided to cause an encryption root to inherit the parent's key
instead.
.Pp
If the user's key is compromised,
.Nm zfs Cm change-key
does not necessarily protect existing or newly-written data from attack.
Newly-written data will continue to be encrypted with the same master key as
the existing data.
The master key is compromised if an attacker obtains a
user key and the corresponding wrapped master key.
Currently,
.Nm zfs Cm change-key
does not overwrite the previous wrapped master key on disk, so it is
accessible via forensic analysis for an indeterminate length of time.
.Pp
In the event of a master key compromise, ideally the drives should be securely
erased to remove all the old data (which is readable using the compromised
master key), a new pool created, and the data copied back.
This can be approximated in place by creating new datasets, copying the data
.Pq e.g. using Nm zfs Cm send | Nm zfs Cm recv ,
and then clearing the free space with
.Nm zpool Cm trim Fl -secure
if supported by your hardware, otherwise
.Nm zpool Cm initialize .
.Bl -tag -width "-r"
.It Fl l
Ensures the key is loaded before attempting to change the key.
This is effectively equivalent to running
.Nm zfs Cm load-key Ar filesystem ; Nm zfs Cm change-key Ar filesystem
.It Fl o Ar property Ns = Ns Ar value
Allows the user to set encryption key properties
.Pq Sy keyformat , keylocation , No and Sy pbkdf2iters
while changing the key.
This is the only way to alter
.Sy keyformat
and
.Sy pbkdf2iters
after the dataset has been created.
.It Fl i
Indicates that zfs should make
.Ar filesystem
inherit the key of its parent.
Note that this command can only be run on an encryption root
that has an encrypted parent.
.El
.El
.Ss Encryption
Enabling the
.Sy encryption
feature allows for the creation of encrypted filesystems and volumes.
ZFS will encrypt file and volume data, file attributes, ACLs, permission bits,
directory listings, FUID mappings, and
.Sy userused Ns / Ns Sy groupused
data.
ZFS will not encrypt metadata related to the pool structure, including
dataset and snapshot names, dataset hierarchy, properties, file size, file
holes, and deduplication tables (though the deduplicated data itself is
encrypted).
.Pp
Key rotation is managed by ZFS.
Changing the user's key (e.g. a passphrase)
does not require re-encrypting the entire dataset.
Datasets can be scrubbed,
resilvered, renamed, and deleted without the encryption keys being loaded (see
the
.Cm load-key
subcommand for more info on key loading).
.Pp
Creating an encrypted dataset requires specifying the
.Sy encryption No and Sy keyformat
properties at creation time, along with an optional
.Sy keylocation No and Sy pbkdf2iters .
After entering an encryption key, the
created dataset will become an encryption root.
Any descendant datasets will
inherit their encryption key from the encryption root by default, meaning that
loading, unloading, or changing the key for the encryption root will implicitly
do the same for all inheriting datasets.
If this inheritance is not desired, simply supply a
.Sy keyformat
when creating the child dataset or use
.Nm zfs Cm change-key
to break an existing relationship, creating a new encryption root on the child.
Note that the child's
.Sy keyformat
may match that of the parent while still creating a new encryption root, and
that changing the
.Sy encryption
property alone does not create a new encryption root; this would simply use a
different cipher suite with the same key as its encryption root.
The one exception is that clones will always use their origin's encryption key.
As a result of this exception, some encryption-related properties
.Pq namely Sy keystatus , keyformat ,  keylocation , No and Sy pbkdf2iters
do not inherit like other ZFS properties and instead use the value determined
by their encryption root.
Encryption root inheritance can be tracked via the read-only
.Sy encryptionroot
property.
.Pp
Encryption changes the behavior of a few ZFS
operations.
Encryption is applied after compression so compression ratios are preserved.
Normally checksums in ZFS are 256 bits long, but for encrypted data
the checksum is 128 bits of the user-chosen checksum and 128 bits of MAC from
the encryption suite, which provides additional protection against maliciously
altered data.
Deduplication is still possible with encryption enabled but for security,
datasets will only deduplicate against themselves, their snapshots,
and their clones.
.Pp
There are a few limitations on encrypted datasets.
Encrypted data cannot be embedded via the
.Sy embedded_data
feature.
Encrypted datasets may not have
.Sy copies Ns = Ns Em 3
since the implementation stores some encryption metadata where the third copy
would normally be.
Since compression is applied before encryption, datasets may
be vulnerable to a CRIME-like attack if applications accessing the data allow
for it.
Deduplication with encryption will leak information about which blocks
are equivalent in a dataset and will incur an extra CPU cost for each block
written.
.
.Sh SEE ALSO
.Xr zfsprops 7 ,
.Xr zfs-create 8 ,
.Xr zfs-set 8