1NDCTL-SETUP-PASSPH(1)                                    NDCTL-SETUP-PASSPH(1)
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NAME

6       ndctl-setup-passphrase - setup and enable the security passphrase for
7       an NVDIMM
8

SYNOPSIS

10       ndctl setup-passphrase <nmem0> [<nmem1>..<nmemN>] -k <key_handle> [<options>]
11

DESCRIPTION

13       Setup and enable a security passphrase for one or more NVDIMMs.
14
15       For this command to succeed, it is expected that the master key has
16       previously been loaded into the user keyring. More information on how
17       this can be done can be found in the kernel documentation at:
18       https://www.kernel.org/doc/html/latest/security/keys/trusted-encrypted.html
19
20       The passphrase blobs are created in the /etc/ndctl/keys directory with
21       a file name format of "nvdimm_<dimm-unique-id>_<hostname>.blob"
22
23       The command will fail if the passphrase is already in the user keyring
24       or if a passphrase blob already exists in /etc/ndctl/keys.
25

OPTIONS

27       <dimm>
28           A nmemX device name, or a dimm id number. Restrict the operation to
29           the specified dimm(s). The keyword all can be specified to indicate
30           the lack of any restriction, however this is the same as not
31           supplying a --dimm option at all.
32
33       -b, --bus=
34           A bus id number, or a provider string (e.g. "ACPI.NFIT"). Restrict
35           the operation to the specified bus(es). The keyword all can be
36           specified to indicate the lack of any restriction, however this is
37           the same as not supplying a --bus option at all.
38
39       -k, --key_handle=
40           Handle for the master kek (key-encryption-key) that will be used
41           for sealing the passphrase(s) for the given DIMM(s). The format is:
42           <key type>:<key description> e.g.  trusted:nvdimm-master NOTE: The
43           kek is expected to have been loaded into the user keyring.
44
45       -m, --master-passphrase
46           Indicates that we are managing the master passphrase instead of the
47           user passphrase.
48
49       -v, --verbose
50           Emit debug messages.
51

THEORY OF OPERATION

53       The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
54       introduced the following security management operations: enable
55       passhprase, update passphrase, unlock DIMM, disable security, freeze
56       security, secure (crypto) erase, overwrite, master passphrase enable,
57       master passphrase update, and master passphrase secure erase.
58
59       The security management for NVDIMMs is comprised of two parts. The
60       front end uses the Linux key management framework (trusted and
61       encrypted keys [2]) to store the encrypted passphrases in the
62       kernel-managed keyring. The interface for this is the keyutils utility
63       which uses the key management APIs in the Linux kernel. The back end
64       takes the decrypted payload (which is the DIMM passphrase) and passes
65       it to the DIMM.
66
67       Unlike other DSMs which are composed by libndctl and sent to the kernel
68       via an ioctl, the security DSMs are managed through the security sysfs
69       attribute under the dimm device. A key-ID is written to the security
70       attribute and the kernel pulls the associated key material from the
71       user keyring that is maintained by the kernel.
72
73       The security process begins with the generation of a master key that is
74       used to seal (encrypt) the passphrase for the DIMM. There can either be
75       one common master key that is used to encrypt every DIMM’s passphrase,
76       or a separate key can be generated for each DIMM. The master key is
77       also referred to as the key-encryption-key (kek). The kek can either be
78       generated by the TPM (Trusted Platform Module) on the system, or
79       alternatively, the System Master Key can also be used as the kek
80
81       For testing purposes a user key with randomized payload can also be
82       used as a kek. See [2] for details. To perform any security operations,
83       it is expected that the kek has been added to the kernel’s user keyring
84       as shown in example below:
85
86           # keyctl show
87           Session Keyring
88            736023423 --alswrv      0     0  keyring: _ses
89            675104189 --alswrv      0 65534   \_ keyring: _uid.0
90            680187394 --alswrv      0     0       \_ trusted: nvdimm-master
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92       Before performing any of the security operations, all the regions
93       associated with the DIMM in question need to be disabled. For the
94       overwrite operation, in addition to the regions, the dimm also needs to
95       be disabled.
96
97       [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
98       https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
99
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:
110
111        1. Check the security state of the device and see if the DIMM is
112           locked
113
114        2. Request the associated encrypted passphrase from the kernel’s user
115           key ring
116
117        3. Use the kek to decrypt the passphrase
118
119        4. Create the unlock DSM, copy the decrypted payload into the DSM
120
121        5. Issue the DSM to unlock the DIMM
122
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.
128
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:
145
146        1. Remove the encrypted passphrase from the kernel’s user keyring.
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148        2. Rename the passphrase blob to old.
149
150        3. Load this old passphrase blob into the keyring with an "old" name.
151
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.
155
156        6. Remove old passphrase and the passphrase blob from the keyring.
157
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.
169
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.
181
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.
192
194       Copyright © 2016 - 2022, 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       linkndctl:ndctl-update-passphrase[1],
201       linkndctl:ndctl-remove-passphrase[1]
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205                                  01/13/2023             NDCTL-SETUP-PASSPH(1)
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