1NDCTL-UPDATE-PASSPHRASE(1) ndctl Manual NDCTL-UPDATE-PASSPHRASE(1)
2
6 ndctl-update-passphrase - update the security passphrase for an NVDIMM
7
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
41 NOTE: The kek is expected to have been loaded into the user
42 keyring.
43 -m, --master-passphrase
45 Indicates that we are managing the master passphrase instead of the
46 user passphrase.
47 -v, --verbose
49 Emit debug messages.
50
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.
57 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 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.
71 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
79 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 # 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
90 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.
95 [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
99 The following sub-sections describe specifics of each security feature.
101 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 1. Check the security state of the device and see if the DIMM is
112 locked
113 2. Request the associated encrypted passphrase from the kernel’s user
115 key ring
116 3. Use the kek to decrypt the passphrase
118 4. Create the unlock DSM, copy the decrypted payload into the DSM
120 5. Issue the DSM to unlock the DIMM
122 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 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 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 1. Remove the encrypted passphrase from the kernel’s user keyring.
147 2. Rename the passphrase blob to old.
149 3. Load this old passphrase blob into the keyring with an "old" name.
151 4. Create the new passphrase and encrypt with the kek.
153 5. Send DSM with the old and new decrypted passphrases.
155 6. Remove old passphrase and the passphrase blob from the keyring.
157 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 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 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 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 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 (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.
198
200 ndctl-setup-passphrase(1), ndctl-remove-passphrase(1)
201ndctl 2020-03-24 NDCTL-UPDATE-PASSPHRASE(1)