zfs-change-key.8

ZFS-LOAD-KEY(8) System Manager's Manual ZFS-LOAD-KEY(8)

zfs-load-key — load, unload, or change encryption key of ZFS dataset

zfs load-key [-nr] [-L keylocation] -a|filesystem

zfs unload-key [-r] -a|filesystem

zfs change-key [-l] [-o keylocation=value] [-o keyformat=value] [-o pbkdf2iters=value] filesystem

zfs change-key -i [-l] filesystem

zfs load-key [-nr] [-L keylocation] -a|filesystem
Load the key for filesystem, allowing it and all children that inherit the keylocation property to be accessed. The key will be expected in the format specified by the keyformat and location specified by the keylocation property. Note that if the keylocation is set to 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, zfs mount -l will ask for the key and mount the dataset (see zfs-mount(8)). Once the key is loaded the keystatus property will become .
Recursively loads the keys for the specified filesystem and all descendent encryption roots.
Loads the keys for all encryption roots in all imported pools.
Do a dry-run ("No-op") load-key. This will cause zfs to simply check that the provided key is correct. This command may be run even if the key is already loaded.
keylocation
Use keylocation instead of the keylocation property. This will not change the value of the property on the dataset. Note that if used with either -r or -a, keylocation may only be given as prompt.
zfs unload-key [-r] -a|filesystem
Unloads a key from ZFS, removing the ability to access the dataset and all of its children that inherit the keylocation property. This requires that the dataset is not currently open or mounted. Once the key is unloaded the keystatus property will become .
Recursively unloads the keys for the specified filesystem and all descendent encryption roots.
Unloads the keys for all encryption roots in all imported pools.
zfs change-key [-l] [-o keylocation=value] [-o keyformat=value] [-o pbkdf2iters=value] filesystem
 
zfs change-key -i [-l] filesystem
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 keylocation, keyformat, and pbkdf2iters properties as needed. If the dataset was not previously an encryption root it will become one. Alternatively, the -i flag may be provided to cause an encryption root to inherit the parent's key instead.

If the user's key is compromised, zfs 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, zfs 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.

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 (e.g. using zfs send | zfs recv), and then clearing the free space with zpool trim --secure if supported by your hardware, otherwise zpool initialize.

Ensures the key is loaded before attempting to change the key. This is effectively equivalent to running zfs load-key filesystem; zfs change-key filesystem
property=value
Allows the user to set encryption key properties (keyformat, keylocation, and pbkdf2iters) while changing the key. This is the only way to alter keyformat and pbkdf2iters after the dataset has been created.
Indicates that zfs should make filesystem inherit the key of its parent. Note that this command can only be run on an encryption root that has an encrypted parent.

Enabling the 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 / 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).

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 load-key subcommand for more info on key loading).

Creating an encrypted dataset requires specifying the encryption and keyformat properties at creation time, along with an optional keylocation and 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 keyformat when creating the child dataset or use zfs change-key to break an existing relationship, creating a new encryption root on the child. Note that the child's keyformat may match that of the parent while still creating a new encryption root, and that changing the 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 (namely keystatus, keyformat, keylocation, and 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 property.

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.

There are a few limitations on encrypted datasets. Encrypted data cannot be embedded via the feature. Encrypted datasets may not have = 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.

zfsprops(7), zfs-create(8), zfs-set(8)

January 13, 2020 Debian