NAME

zfs-tpm2-change-key — change ZFS dataset key to one stored on the TPM

SYNOPSIS

zfs-tpm2-change-key [-b backup-file] dataset

DESCRIPTION

To normalise dataset, zfs-tpm2-change-key will open its encryption root in its stead. zfs-tpm2-change-key will never create or destroy encryption roots; use zfs-change-key(8) for that.

First, a connection is made to the TPM, which must be TPM-2.0-compatible.

If dataset was previously encrypted with tzpfms and the TPM2 back-end was used, the previous key will be freed from the TPM. Otherwise, or in case of an error, data required for manual intervention will be printed to the standard error stream.

Next, a new wrapping key is be generated on the TPM, optionally backed up (see OPTIONS), and sealed to a persistent object on the TPM under the owner hierarchy; if there is a passphrase set on the owner hierarchy, the user is prompted for it; the user is always prompted for an optional passphrase to protect the sealed object with.

The following properties are set on dataset:

xyz.nabijaczleweli:tzpfms.backend=TPM2
xyz.nabijaczleweli:tzpfms.key=ID of persistent object

tzpfms.backend identifies this dataset for work with TPM2-back-ended tzpfms tools (namely zfs-tpm2-change-key(8), zfs-tpm2-load-key(8), and zfs-tpm2-clear-key(8)).

tzpfms.key is an integer representing the sealed object; if needed, it can be passed to tpm2_unseal -c ${tzpfms.key} [-p ${password}] or equivalent for back-up (see OPTIONS). If you have a sealed key you can access with that or equivalent tool and set both of these properties, it will funxion seamlessly.

Finally, the equivalent of zfs change-key -o keylocation=prompt -o keyformat=raw dataset is performed with the new key. If an error occurred, best effort is made to clean up the persistent object and properties, or to issue a note for manual intervention into the standard error stream.

A final verification should be made by running zfs-tpm2-load-key -n dataset. If that command succeeds, all is well, but otherwise the dataset can be manually rolled back to a password with zfs-tpm2-clear-key dataset (or, if that fails to work, zfs change-key -o keyformat=passphrase dataset), and you are hereby asked to report a bug, please.

zfs-tpm2-clear-key dataset can be used to free the TPM persistent object and go back to using a password.

OPTIONS

-b backup-file: Save a back-up of the key to backup-file, which must not exist beforehand. This back-up must be stored securely, off-site. In case of a catastrophic event, the key can be loaded by running
zfs load-key dataset < backup-file

TPM2 back-end configuration

Environment variables

TSS2_LOG: Any of: NONE, ERROR, WARNING, INFO, DEBUG, TRACE. Default: WARNING.

TPM selection

The library libtss2-tcti-default.so can be linked to any of the libtss2-tcti-*.so libraries to select the default, otherwise /dev/tpmrm0, then /dev/tpm0, then localhost:2321 will be tried, in order (see ESYS_CONTEXT(3)).