1NDCTL-UPDATE-PASSP(1) NDCTL-UPDATE-PASSP(1)
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6 ndctl-update-passphrase - update the security passphrase for an NVDIMM
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9 ndctl update-passphrase <nmem0> [<nmem1>..<nmemN>] [<options>]
10
12 Update the security passphrase for one or more NVDIMMs. Prerequisites
13 for command to succeed:
14 1. The kek has been loaded into the kernel’s user keyring.
16 2. setup-passphrase has successfully been executed on the NVDIMM.
18 • Alternatively, the NVDIMM is unlocked.
20 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".
23
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.
30 -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.
36 -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 NOTE: The
41 kek is expected to have been loaded into the user keyring.
42 -m, --master-passphrase
44 Indicates that we are managing the master passphrase instead of the
45 user passphrase.
46 -v, --verbose
48 Emit debug messages.
49
51 The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
52 introduced the following security management operations: enable
53 passhprase, update passphrase, unlock DIMM, disable security, freeze
54 security, secure (crypto) erase, overwrite, master passphrase enable,
55 master passphrase update, and master passphrase secure erase.
56 The security management for NVDIMMs is comprised of two parts. The
58 front end uses the Linux key management framework (trusted and
59 encrypted keys [2]) to store the encrypted passphrases in the
60 kernel-managed keyring. The interface for this is the keyutils utility
61 which uses the key management APIs in the Linux kernel. The back end
62 takes the decrypted payload (which is the DIMM passphrase) and passes
63 it to the DIMM.
64 Unlike other DSMs which are composed by libndctl and sent to the kernel
66 via an ioctl, the security DSMs are managed through the security sysfs
67 attribute under the dimm device. A key-ID is written to the security
68 attribute and the kernel pulls the associated key material from the
69 user keyring that is maintained by the kernel.
70 The security process begins with the generation of a master key that is
72 used to seal (encrypt) the passphrase for the DIMM. There can either be
73 one common master key that is used to encrypt every DIMM’s passphrase,
74 or a separate key can be generated for each DIMM. The master key is
75 also referred to as the key-encryption-key (kek). The kek can either be
76 generated by the TPM (Trusted Platform Module) on the system, or
77 alternatively, the System Master Key can also be used as the kek
78 For testing purposes a user key with randomized payload can also be
80 used as a kek. See [2] for details. To perform any security operations,
81 it is expected that the kek has been added to the kernel’s user keyring
82 as shown in example below:
83 # keyctl show
85 Session Keyring
86 736023423 --alswrv 0 0 keyring: _ses
87 675104189 --alswrv 0 65534 \_ keyring: _uid.0
88 680187394 --alswrv 0 0 \_ trusted: nvdimm-master
89 Before performing any of the security operations, all the regions
91 associated with the DIMM in question need to be disabled. For the
92 overwrite operation, in addition to the regions, the dimm also needs to
93 be disabled.
94 [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
96 https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
97 The following sub-sections describe specifics of each security feature.
99 UNLOCK
101 Unlock is performed by the kernel, however a preparation step must
102 happen before the unlock DSM can be issued by the kernel. It is
103 expected that from the initramfs, a setup command (ndctl load-keys) is
104 executed before the libnvdimm module is loaded by modprobe. This
105 command will inject the kek and the encrypted passphrases into the
106 kernel’s user keyring. During the probe of the libnvdimm driver, it
107 will:
108 1. Check the security state of the device and see if the DIMM is
110 locked
111 2. Request the associated encrypted passphrase from the kernel’s user
113 key ring
114 3. Use the kek to decrypt the passphrase
116 4. Create the unlock DSM, copy the decrypted payload into the DSM
118 5. Issue the DSM to unlock the DIMM
120 If the DIMM is already unlocked, the kernel will attempt to revalidate
122 the passphrase. If we fail to revalidate the passphrase, the kernel
123 will freeze the security and disallow any further security
124 configuration changes. A kernel module parameter is available to
125 override this behavior.
126 SETUP USER PASSPHRASE
128 To setup the passphrase for a DIMM, it is expected that the kek to be
129 used is present in the kernel’s user keyring. The kek encrypts the DIMM
130 passphrase using the enc32 key format. The plaintext passphrase is
131 never provided by or made visible to the user. It is instead randomly
132 generated by the kernel and userspace does not have access to it. Upon
133 encryption, a binary blob of the passphrase is written to the
134 passphrase blob storage directory (/etc/ndctl/keys). The user is
135 responsible for backing up the passphrase blobs to a secure location.
136 UPDATE USER PASSPHRASE
138 The update user passphrase operation uses the same DSM command as
139 enable user passphrase. Most of the work is done on the key management
140 side. The user has the option of providing a new kek for the new
141 passphrase, but continuing to use the existing kek is also acceptable.
142 The following operations are performed for update-passphrase:
143 1. Remove the encrypted passphrase from the kernel’s user keyring.
145 2. Rename the passphrase blob to old.
147 3. Load this old passphrase blob into the keyring with an "old" name.
149 4. Create the new passphrase and encrypt with the kek.
151 5. Send DSM with the old and new decrypted passphrases.
153 6. Remove old passphrase and the passphrase blob from the keyring.
155 REMOVE USER PASSPHRASE
157 The key-ID for the passphrase to be removed is written to sysfs. The
158 kernel then sends the DSM to disable security, and the passphrase is
159 then removed from the keyring, and the associated passphrase blob is
160 deleted.
161 CRYPTO (SECURE) ERASE
163 This operation is similar to remove-passphrase. The kernel issues a
164 WBINVD instruction before and after the operation to ensure no data
165 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
166 with the --crypto-erase option to perform this operation.
167 OVERWRITE
169 This is invoked using --overwrite option for ndctl sanitize-dimm. The
170 overwrite operation wipes the entire NVDIMM. The operation can take a
171 significant amount of time. NOTE: When the command returns
172 successfully, it just means overwrite has been successfully started,
173 and not that the overwrite is complete. Subsequently, 'ndctl
174 wait-overwrite’can be used to wait for the NVDIMMs that are performing
175 overwrite. Upon successful completion of an overwrite, the WBINVD
176 instruction is issued by the kernel. If both --crypto-erase and
177 --overwrite options are supplied, then crypto-erase is performed before
178 overwrite.
179 SECURITY FREEZE
181 This operation does not require a passphrase. This will cause any
182 security command other than a status query to be locked out until the
183 next boot.
184 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
186 These operations are similar to the user passphrase enable and update.
187 The only difference is that a different passphrase is used. The master
188 passphrase has no relation to the master key (kek) which is used for
189 encryption of either passphrase.
190
192 Copyright © 2016 - 2022, Intel Corporation. License GPLv2: GNU GPL
193 version 2 http://gnu.org/licenses/gpl.html. This is free software: you
194 are free to change and redistribute it. There is NO WARRANTY, to the
195 extent permitted by law.
196
198 linkndctl:ndctl-setup-passphrase[1],
199 linkndctl:ndctl-remove-passphrase[1]
200 03/08/2022 NDCTL-UPDATE-PASSP(1)