1NDCTL-UPDATE-PASSPHRASE(1) ndctl Manual NDCTL-UPDATE-PASSPHRASE(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>]
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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".
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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>
41 e.g. trusted:nvdimm-master
42 NOTE: The kek is expected to have been loaded into the user
43 keyring.
44 -m, --master-passphrase
46 Indicates that we are managing the master passphrase instead of the
47 user passphrase.
48 -v, --verbose
50 Emit debug messages.
51
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 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 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 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 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 # 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
91 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 [1] <http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf>
98 [2] <https://www.kernel.org/doc/Documentation/security/keys/
99 trusted-encrypted.rst>
100 The following sub-sections describe specifics of each security feature.
102 UNLOCK
104 Unlock is performed by the kernel, however a preparation step must
105 happen before the unlock DSM can be issued by the kernel. It is
106 expected that from the initramfs, a setup command (ndctl load-keys) is
107 executed before the libnvdimm module is loaded by modprobe. This
108 command will inject the kek and the encrypted passphrases into the
109 kernel’s user keyring. During the probe of the libnvdimm driver, it
110 will:
111 1. Check the security state of the device and see if the DIMM is
113 locked
114 2. Request the associated encrypted passphrase from the kernel’s user
116 key ring
117 3. Use the kek to decrypt the passphrase
119 4. Create the unlock DSM, copy the decrypted payload into the DSM
121 5. Issue the DSM to unlock the DIMM
123 If the DIMM is already unlocked, the kernel will attempt to revalidate
125 the passphrase. If we fail to revalidate the passphrase, the kernel
126 will freeze the security and disallow any further security
127 configuration changes. A kernel module parameter is available to
128 override this behavior.
129 SETUP USER PASSPHRASE
131 To setup the passphrase for a DIMM, it is expected that the kek to be
132 used is present in the kernel’s user keyring. The kek encrypts the DIMM
133 passphrase using the enc32 key format. The plaintext passphrase is
134 never provided by or made visible to the user. It is instead randomly
135 generated by the kernel and userspace does not have access to it. Upon
136 encryption, a binary blob of the passphrase is written to the
137 passphrase blob storage directory (/etc/ndctl/keys). The user is
138 responsible for backing up the passphrase blobs to a secure location.
139 UPDATE USER PASSPHRASE
141 The update user passphrase operation uses the same DSM command as
142 enable user passphrase. Most of the work is done on the key management
143 side. The user has the option of providing a new kek for the new
144 passphrase, but continuing to use the existing kek is also acceptable.
145 The following operations are performed for update-passphrase:
146 1. Remove the encrypted passphrase from the kernel’s user keyring.
148 2. Rename the passphrase blob to old.
150 3. Load this old passphrase blob into the keyring with an "old" name.
152 4. Create the new passphrase and encrypt with the kek.
154 5. Send DSM with the old and new decrypted passphrases.
156 6. Remove old passphrase and the passphrase blob from the keyring.
158 REMOVE USER PASSPHRASE
160 The key-ID for the passphrase to be removed is written to sysfs. The
161 kernel then sends the DSM to disable security, and the passphrase is
162 then removed from the keyring, and the associated passphrase blob is
163 deleted.
164 CRYPTO (SECURE) ERASE
166 This operation is similar to remove-passphrase. The kernel issues a
167 WBINVD instruction before and after the operation to ensure no data
168 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
169 with the --crypto-erase option to perform this operation.
170 OVERWRITE
172 This is invoked using --overwrite option for ndctl sanitize-dimm. The
173 overwrite operation wipes the entire NVDIMM. The operation can take a
174 significant amount of time. NOTE: When the command returns
175 successfully, it just means overwrite has been successfully started,
176 and not that the overwrite is complete. Subsequently, 'ndctl
177 wait-overwrite’can be used to wait for the NVDIMMs that are performing
178 overwrite. Upon successful completion of an overwrite, the WBINVD
179 instruction is issued by the kernel. If both --crypto-erase and
180 --overwrite options are supplied, then crypto-erase is performed before
181 overwrite.
182 SECURITY FREEZE
184 This operation does not require a passphrase. This will cause any
185 security command other than a status query to be locked out until the
186 next boot.
187 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
189 These operations are similar to the user passphrase enable and update.
190 The only difference is that a different passphrase is used. The master
191 passphrase has no relation to the master key (kek) which is used for
192 encryption of either passphrase.
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195 Copyright (c) 2016 - 2019, Intel Corporation. License GPLv2: GNU GPL
196 version 2 <http://gnu.org/licenses/gpl.html>. This is free software:
197 you are free to change and redistribute it. There is NO WARRANTY, to
198 the extent permitted by law.
199
201 ndctl-setup-passphrase(1), ndctl-remove-passphrase(1)
202ndctl 2019-10-28 NDCTL-UPDATE-PASSPHRASE(1)