1NDCTL-SETUP-PASSPHRASE(1) ndctl Manual NDCTL-SETUP-PASSPHRASE(1)
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6 ndctl-setup-passphrase - setup and enable the security passphrase for
7 an NVDIMM
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10 ndctl setup-passphrase <nmem0> [<nmem1>..<nmemN>] -k <key_handle> [<options>]
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13 Setup and enable a security passphrase for one or more NVDIMMs.
14 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: <https://
18 www.kernel.org/doc/html/latest/security/keys/trusted-encrypted.html>
19 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 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
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 -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 -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>
43 e.g. trusted:nvdimm-master
44 NOTE: The kek is expected to have been loaded into the user
45 keyring.
46 -m, --master-passphrase
48 Indicates that we are managing the master passphrase instead of the
49 user passphrase.
50 -v, --verbose
52 Emit debug messages.
53
55 The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
56 introduced the following security management operations: enable
57 passhprase, update passphrase, unlock DIMM, disable security, freeze
58 security, secure (crypto) erase, overwrite, master passphrase enable,
59 master passphrase update, and master passphrase secure erase.
60 The security management for NVDIMMs is comprised of two parts. The
62 front end uses the Linux key management framework (trusted and
63 encrypted keys [2]) to store the encrypted passphrases in the
64 kernel-managed keyring. The interface for this is the keyutils utility
65 which uses the key management APIs in the Linux kernel. The back end
66 takes the decrypted payload (which is the DIMM passphrase) and passes
67 it to the DIMM.
68 Unlike other DSMs which are composed by libndctl and sent to the kernel
70 via an ioctl, the security DSMs are managed through the security sysfs
71 attribute under the dimm device. A key-ID is written to the security
72 attribute and the kernel pulls the associated key material from the
73 user keyring that is maintained by the kernel.
74 The security process begins with the generation of a master key that is
76 used to seal (encrypt) the passphrase for the DIMM. There can either be
77 one common master key that is used to encrypt every DIMM’s passphrase,
78 or a separate key can be generated for each DIMM. The master key is
79 also referred to as the key-encryption-key (kek). The kek can either be
80 generated by the TPM (Trusted Platform Module) on the system, or
81 alternatively, the System Master Key can also be used as the kek
82 For testing purposes a user key with randomized payload can also be
84 used as a kek. See [2] for details. To perform any security operations,
85 it is expected that the kek has been added to the kernel’s user keyring
86 as shown in example below:
87 # keyctl show
89 Session Keyring
90 736023423 --alswrv 0 0 keyring: _ses
91 675104189 --alswrv 0 65534 \_ keyring: _uid.0
92 680187394 --alswrv 0 0 \_ trusted: nvdimm-master
93 Before performing any of the security operations, all the regions
95 associated with the DIMM in question need to be disabled. For the
96 overwrite operation, in addition to the regions, the dimm also needs to
97 be disabled.
98 [1] <http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf>
100 [2] <https://www.kernel.org/doc/Documentation/security/keys/
101 trusted-encrypted.rst>
102 The following sub-sections describe specifics of each security feature.
104 UNLOCK
106 Unlock is performed by the kernel, however a preparation step must
107 happen before the unlock DSM can be issued by the kernel. It is
108 expected that from the initramfs, a setup command (ndctl load-keys) is
109 executed before the libnvdimm module is loaded by modprobe. This
110 command will inject the kek and the encrypted passphrases into the
111 kernel’s user keyring. During the probe of the libnvdimm driver, it
112 will:
113 1. Check the security state of the device and see if the DIMM is
115 locked
116 2. Request the associated encrypted passphrase from the kernel’s user
118 key ring
119 3. Use the kek to decrypt the passphrase
121 4. Create the unlock DSM, copy the decrypted payload into the DSM
123 5. Issue the DSM to unlock the DIMM
125 If the DIMM is already unlocked, the kernel will attempt to revalidate
127 the passphrase. If we fail to revalidate the passphrase, the kernel
128 will freeze the security and disallow any further security
129 configuration changes. A kernel module parameter is available to
130 override this behavior.
131 SETUP USER PASSPHRASE
133 To setup the passphrase for a DIMM, it is expected that the kek to be
134 used is present in the kernel’s user keyring. The kek encrypts the DIMM
135 passphrase using the enc32 key format. The plaintext passphrase is
136 never provided by or made visible to the user. It is instead randomly
137 generated by the kernel and userspace does not have access to it. Upon
138 encryption, a binary blob of the passphrase is written to the
139 passphrase blob storage directory (/etc/ndctl/keys). The user is
140 responsible for backing up the passphrase blobs to a secure location.
141 UPDATE USER PASSPHRASE
143 The update user passphrase operation uses the same DSM command as
144 enable user passphrase. Most of the work is done on the key management
145 side. The user has the option of providing a new kek for the new
146 passphrase, but continuing to use the existing kek is also acceptable.
147 The following operations are performed for update-passphrase:
148 1. Remove the encrypted passphrase from the kernel’s user keyring.
150 2. Rename the passphrase blob to old.
152 3. Load this old passphrase blob into the keyring with an "old" name.
154 4. Create the new passphrase and encrypt with the kek.
156 5. Send DSM with the old and new decrypted passphrases.
158 6. Remove old passphrase and the passphrase blob from the keyring.
160 REMOVE USER PASSPHRASE
162 The key-ID for the passphrase to be removed is written to sysfs. The
163 kernel then sends the DSM to disable security, and the passphrase is
164 then removed from the keyring, and the associated passphrase blob is
165 deleted.
166 CRYPTO (SECURE) ERASE
168 This operation is similar to remove-passphrase. The kernel issues a
169 WBINVD instruction before and after the operation to ensure no data
170 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
171 with the --crypto-erase option to perform this operation.
172 OVERWRITE
174 This is invoked using --overwrite option for ndctl sanitize-dimm. The
175 overwrite operation wipes the entire NVDIMM. The operation can take a
176 significant amount of time. NOTE: When the command returns
177 successfully, it just means overwrite has been successfully started,
178 and not that the overwrite is complete. Subsequently, 'ndctl
179 wait-overwrite’can be used to wait for the NVDIMMs that are performing
180 overwrite. Upon successful completion of an overwrite, the WBINVD
181 instruction is issued by the kernel. If both --crypto-erase and
182 --overwrite options are supplied, then crypto-erase is performed before
183 overwrite.
184 SECURITY FREEZE
186 This operation does not require a passphrase. This will cause any
187 security command other than a status query to be locked out until the
188 next boot.
189 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
191 These operations are similar to the user passphrase enable and update.
192 The only difference is that a different passphrase is used. The master
193 passphrase has no relation to the master key (kek) which is used for
194 encryption of either passphrase.
195
197 Copyright (c) 2016 - 2019, Intel Corporation. License GPLv2: GNU GPL
198 version 2 <http://gnu.org/licenses/gpl.html>. This is free software:
199 you are free to change and redistribute it. There is NO WARRANTY, to
200 the extent permitted by law.
201
203 ndctl-update-passphrase(1), ndctl-remove-passphrase(1)
204ndctl 2019-10-28 NDCTL-SETUP-PASSPHRASE(1)