1NDCTL-UPDATE-PASSPHRASE(1)       ndctl Manual       NDCTL-UPDATE-PASSPHRASE(1)
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NAME

6       ndctl-update-passphrase - update the security passphrase for an NVDIMM
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SYNOPSIS

9       ndctl update-passphrase <nmem0> [<nmem1>..<nmemN>] [<options>]
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DESCRIPTION

12       Update the security passphrase for one or more NVDIMMs. Prerequisites
13       for command to succeed:
14
15        1. The kek has been loaded into the kernel’s user keyring.
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17        2. setup-passphrase has successfully been executed on the NVDIMM.
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19           ·   Alternatively, the NVDIMM is unlocked.
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21       The updated key blobs will be created in the /etc/ndctl/keys directory
22       with a file name format of "nvdimm_<dimm-unique-id>_<hostname>.blob".
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OPTIONS

25       <dimm>
26           A nmemX device name, or a dimm id number. Restrict the operation to
27           the specified dimm(s). The keyword all can be specified to indicate
28           the lack of any restriction, however this is the same as not
29           supplying a --dimm option at all.
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31       -b, --bus=
32           A bus id number, or a provider string (e.g. "ACPI.NFIT"). Restrict
33           the operation to the specified bus(es). The keyword all can be
34           specified to indicate the lack of any restriction, however this is
35           the same as not supplying a --bus option at all.
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37       -k, --key_handle=
38           Handle for the master kek (key-encryption-key) that will be used
39           for sealing the passphrase(s) for the given DIMM(s). The format is:
40           <key type>:<key description> e.g. trusted:nvdimm-master
41           NOTE: The kek is expected to have been loaded into the user
42           keyring.
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44       -m, --master-passphrase
45           Indicates that we are managing the master passphrase instead of the
46           user passphrase.
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48       -v, --verbose
49           Emit debug messages.
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THEORY OF OPERATION

52       The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
53       introduced the following security management operations: enable
54       passhprase, update passphrase, unlock DIMM, disable security, freeze
55       security, secure (crypto) erase, overwrite, master passphrase enable,
56       master passphrase update, and master passphrase secure erase.
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58       The security management for NVDIMMs is comprised of two parts. The
59       front end uses the Linux key management framework (trusted and
60       encrypted keys [2]) to store the encrypted passphrases in the
61       kernel-managed keyring. The interface for this is the keyutils utility
62       which uses the key management APIs in the Linux kernel. The back end
63       takes the decrypted payload (which is the DIMM passphrase) and passes
64       it to the DIMM.
65
66       Unlike other DSMs which are composed by libndctl and sent to the kernel
67       via an ioctl, the security DSMs are managed through the security sysfs
68       attribute under the dimm device. A key-ID is written to the security
69       attribute and the kernel pulls the associated key material from the
70       user keyring that is maintained by the kernel.
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72       The security process begins with the generation of a master key that is
73       used to seal (encrypt) the passphrase for the DIMM. There can either be
74       one common master key that is used to encrypt every DIMM’s passphrase,
75       or a separate key can be generated for each DIMM. The master key is
76       also referred to as the key-encryption-key (kek). The kek can either be
77       generated by the TPM (Trusted Platform Module) on the system, or
78       alternatively, the System Master Key can also be used as the kek
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80       For testing purposes a user key with randomized payload can also be
81       used as a kek. See [2] for details. To perform any security operations,
82       it is expected that the kek has been added to the kernel’s user keyring
83       as shown in example below:
84
85           # keyctl show
86           Session Keyring
87            736023423 --alswrv      0     0  keyring: _ses
88            675104189 --alswrv      0 65534   \_ keyring: _uid.0
89            680187394 --alswrv      0     0       \_ trusted: nvdimm-master
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91       Before performing any of the security operations, all the regions
92       associated with the DIMM in question need to be disabled. For the
93       overwrite operation, in addition to the regions, the dimm also needs to
94       be disabled.
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96       [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf
97       [2]
98       https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
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100       The following sub-sections describe specifics of each security feature.
101
102   UNLOCK
103       Unlock is performed by the kernel, however a preparation step must
104       happen before the unlock DSM can be issued by the kernel. It is
105       expected that from the initramfs, a setup command (ndctl load-keys) is
106       executed before the libnvdimm module is loaded by modprobe. This
107       command will inject the kek and the encrypted passphrases into the
108       kernel’s user keyring. During the probe of the libnvdimm driver, it
109       will:
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111        1. Check the security state of the device and see if the DIMM is
112           locked
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114        2. Request the associated encrypted passphrase from the kernel’s user
115           key ring
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117        3. Use the kek to decrypt the passphrase
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119        4. Create the unlock DSM, copy the decrypted payload into the DSM
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121        5. Issue the DSM to unlock the DIMM
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123       If the DIMM is already unlocked, the kernel will attempt to revalidate
124       the passphrase. If we fail to revalidate the passphrase, the kernel
125       will freeze the security and disallow any further security
126       configuration changes. A kernel module parameter is available to
127       override this behavior.
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129   SETUP USER PASSPHRASE
130       To setup the passphrase for a DIMM, it is expected that the kek to be
131       used is present in the kernel’s user keyring. The kek encrypts the DIMM
132       passphrase using the enc32 key format. The plaintext passphrase is
133       never provided by or made visible to the user. It is instead randomly
134       generated by the kernel and userspace does not have access to it. Upon
135       encryption, a binary blob of the passphrase is written to the
136       passphrase blob storage directory (/etc/ndctl/keys). The user is
137       responsible for backing up the passphrase blobs to a secure location.
138
139   UPDATE USER PASSPHRASE
140       The update user passphrase operation uses the same DSM command as
141       enable user passphrase. Most of the work is done on the key management
142       side. The user has the option of providing a new kek for the new
143       passphrase, but continuing to use the existing kek is also acceptable.
144       The following operations are performed for update-passphrase:
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146        1. Remove the encrypted passphrase from the kernel’s user keyring.
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148        2. Rename the passphrase blob to old.
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150        3. Load this old passphrase blob into the keyring with an "old" name.
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152        4. Create the new passphrase and encrypt with the  kek.
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154        5. Send DSM with the old and new decrypted passphrases.
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156        6. Remove old passphrase and the passphrase blob from the keyring.
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158   REMOVE USER PASSPHRASE
159       The key-ID for the passphrase to be removed is written to sysfs. The
160       kernel then sends the DSM to disable security, and the passphrase is
161       then removed from the keyring, and the associated passphrase blob is
162       deleted.
163
164   CRYPTO (SECURE) ERASE
165       This operation is similar to remove-passphrase. The kernel issues a
166       WBINVD instruction before and after the operation to ensure no data
167       corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
168       with the --crypto-erase option to perform this operation.
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170   OVERWRITE
171       This is invoked using --overwrite option for ndctl sanitize-dimm. The
172       overwrite operation wipes the entire NVDIMM. The operation can take a
173       significant amount of time. NOTE: When the command returns
174       successfully, it just means overwrite has been successfully started,
175       and not that the overwrite is complete. Subsequently, 'ndctl
176       wait-overwrite’can be used to wait for the NVDIMMs that are performing
177       overwrite. Upon successful completion of an overwrite, the WBINVD
178       instruction is issued by the kernel. If both --crypto-erase and
179       --overwrite options are supplied, then crypto-erase is performed before
180       overwrite.
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182   SECURITY FREEZE
183       This operation does not require a passphrase. This will cause any
184       security command other than a status query to be locked out until the
185       next boot.
186
187   MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
188       These operations are similar to the user passphrase enable and update.
189       The only difference is that a different passphrase is used. The master
190       passphrase has no relation to the master key (kek) which is used for
191       encryption of either passphrase.
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194       Copyright (c) 2016 - 2019, Intel Corporation. License GPLv2: GNU GPL
195       version 2 http://gnu.org/licenses/gpl.html. This is free software: you
196       are free to change and redistribute it. There is NO WARRANTY, to the
197       extent permitted by law.
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SEE ALSO:

200       ndctl-setup-passphrase(1), ndctl-remove-passphrase(1)
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204ndctl                             2020-03-24        NDCTL-UPDATE-PASSPHRASE(1)
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