Provided by: ndctl_65-1_amd64 bug

NAME

       ndctl-sanitize-dimm - Perform a cryptographic destruction or overwrite of the contents of
       the given NVDIMM(s)

SYNOPSIS

       ndctl sanitize-dimm <nmem0> [<nmem1>..<nmemN>] [<options>]

DESCRIPTION

       The sanitize-dimm command performs a cryptographic destruction of the contents of the
       given NVDIMM. It scrambles the data, and any metadata or info-blocks, but it doesn’t
       modify namespace labels. Therefore, any namespaces on regions associated with the given
       NVDIMM will be retained, but they will end up in the raw mode.

       Additionally, after completion of this command, the security and passphrase for the given
       NVDIMM will be disabled, and the passphrase and any key material will also be removed from
       the keyring and the ndctl keys directory at /etc/ndctl/keys

       The command supports two different methods of performing the cryptographic erase. The
       default is crypto-erase, but additionally, an overwrite option is available which
       overwrites not only the data area, but also the label area, thus losing record of any
       namespaces the given NVDIMM participates in.

OPTIONS

       <dimm>

               A 'nmemX' device name, or a dimm id number. The keyword 'all' can
               be specified to carry out the operation on every dimm in the system,
               optionally filtered by bus id (see --bus= option).

       -b, --bus=
           Enforce that the operation only be carried on devices that are attached to the given
           bus. Where bus can be a provider name or a bus id number.

       -c, --crypto-erase
           Replace the media encryption key on the NVDIMM causing all existing data to read as
           cipher text with the new key. This does not change label data. Namespaces get reverted
           to raw mode.

       -o, --ovewrite
           Wipe the entire DIMM, including label data. This can take significant time, and the
           command is non-blocking. With this option, the overwrite request is merely submitted
           to the NVDIMM, and the completion is asynchronous. Depending on the medium and
           capacity, overwrite may take tens of minutes to many hours.

       -m, --master-passphrase
           Indicate that we are using the master passphrase to perform the erase. This only is
           applicable to the crypto-erase option.

       -z, --zero-key
           Passing in a key with payload that is just 0’s.

       --verbose
           Emit debug messages.

THEORY OF OPERATION

       The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1] introduced the
       following security management operations: enable passhprase, update passphrase, unlock
       DIMM, disable security, freeze security, secure (crypto) erase, overwrite, master
       passphrase enable, master passphrase update, and master passphrase secure erase.

       The security management for NVDIMMs is comprised of two parts. The front end uses the
       Linux key management framework (trusted and encrypted keys [2]) to store the encrypted
       passphrases in the kernel-managed keyring. The interface for this is the keyutils utility
       which uses the key management APIs in the Linux kernel. The back end takes the decrypted
       payload (which is the DIMM passphrase) and passes it to the DIMM.

       Unlike other DSMs which are composed by libndctl and sent to the kernel via an ioctl, the
       security DSMs are managed through the security sysfs attribute under the dimm device. A
       key-ID is written to the security attribute and the kernel pulls the associated key
       material from the user keyring that is maintained by the kernel.

       The security process begins with the generation of a master key that is used to seal
       (encrypt) the passphrase for the DIMM. There can either be one common master key that is
       used to encrypt every DIMM’s passphrase, or a separate key can be generated for each DIMM.
       The master key is also referred to as the key-encryption-key (kek). The kek can either be
       generated by the TPM (Trusted Platform Module) on the system, or alternatively, the System
       Master Key can also be used as the kek

       For testing purposes a user key with randomized payload can also be used as a kek. See [2]
       for details. To perform any security operations, it is expected that the kek has been
       added to the kernel’s user keyring as shown in example below:

           # keyctl show
           Session Keyring
            736023423 --alswrv      0     0  keyring: _ses
            675104189 --alswrv      0 65534   \_ keyring: _uid.0
            680187394 --alswrv      0     0       \_ trusted: nvdimm-master

       Before performing any of the security operations, all the regions associated with the DIMM
       in question need to be disabled. For the overwrite operation, in addition to the regions,
       the dimm also needs to be disabled.

       [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf
       [2] https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst

       The following sub-sections describe specifics of each security feature.

   UNLOCK
       Unlock is performed by the kernel, however a preparation step must happen before the
       unlock DSM can be issued by the kernel. It is expected that from the initramfs, a setup
       command (ndctl load-keys) is executed before the libnvdimm module is loaded by modprobe.
       This command will inject the kek and the encrypted passphrases into the kernel’s user
       keyring. During the probe of the libnvdimm driver, it will:

        1. Check the security state of the device and see if the DIMM is locked

        2. Request the associated encrypted passphrase from the kernel’s user key ring

        3. Use the kek to decrypt the passphrase

        4. Create the unlock DSM, copy the decrypted payload into the DSM

        5. Issue the DSM to unlock the DIMM

       If the DIMM is already unlocked, the kernel will attempt to revalidate the passphrase. If
       we fail to revalidate the passphrase, the kernel will freeze the security and disallow any
       further security configuration changes. A kernel module parameter is available to override
       this behavior.

   SETUP USER PASSPHRASE
       To setup the passphrase for a DIMM, it is expected that the kek to be used is present in
       the kernel’s user keyring. The kek encrypts the DIMM passphrase using the enc32 key
       format. The plaintext passphrase is never provided by or made visible to the user. It is
       instead randomly generated by the kernel and userspace does not have access to it. Upon
       encryption, a binary blob of the passphrase is written to the passphrase blob storage
       directory (/etc/ndctl/keys). The user is responsible for backing up the passphrase blobs
       to a secure location.

   UPDATE USER PASSPHRASE
       The update user passphrase operation uses the same DSM command as enable user passphrase.
       Most of the work is done on the key management side. The user has the option of providing
       a new kek for the new passphrase, but continuing to use the existing kek is also
       acceptable. The following operations are performed for update-passphrase:

        1. Remove the encrypted passphrase from the kernel’s user keyring.

        2. Rename the passphrase blob to old.

        3. Load this old passphrase blob into the keyring with an "old" name.

        4. Create the new passphrase and encrypt with the  kek.

        5. Send DSM with the old and new decrypted passphrases.

        6. Remove old passphrase and the passphrase blob from the keyring.

   REMOVE USER PASSPHRASE
       The key-ID for the passphrase to be removed is written to sysfs. The kernel then sends the
       DSM to disable security, and the passphrase is then removed from the keyring, and the
       associated passphrase blob is deleted.

   CRYPTO (SECURE) ERASE
       This operation is similar to remove-passphrase. The kernel issues a WBINVD instruction
       before and after the operation to ensure no data corruption from a stale CPU cache. Use
       ndctl’s sanitize-dimm command with the --crypto-erase option to perform this operation.

   OVERWRITE
       This is invoked using --overwrite option for ndctl sanitize-dimm. The overwrite operation
       wipes the entire NVDIMM. The operation can take a significant amount of time. NOTE: When
       the command returns successfully, it just means overwrite has been successfully started,
       and not that the overwrite is complete. Subsequently, 'ndctl wait-overwrite’can be used to
       wait for the NVDIMMs that are performing overwrite. Upon successful completion of an
       overwrite, the WBINVD instruction is issued by the kernel. If both --crypto-erase and
       --overwrite options are supplied, then crypto-erase is performed before overwrite.

   SECURITY FREEZE
       This operation does not require a passphrase. This will cause any security command other
       than a status query to be locked out until the next boot.

   MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
       These operations are similar to the user passphrase enable and update. The only difference
       is that a different passphrase is used. The master passphrase has no relation to the
       master key (kek) which is used for encryption of either passphrase.

COPYRIGHT

       Copyright (c) 2016 - 2019, Intel Corporation. License GPLv2: GNU GPL version 2
       http://gnu.org/licenses/gpl.html. This is free software: you are free to change and
       redistribute it. There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       ndctl-wait-overwrite(1),
       https://trustedcomputinggroup.org/wp-content/uploads/TCG_SWG_SIIS_Version_1_07_Revision_1_00.pdf