1NDCTL-SANITIZE-DIM(1) NDCTL-SANITIZE-DIM(1)
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6 ndctl-sanitize-dimm - Perform a cryptographic destruction or overwrite
7 of the contents of the given NVDIMM(s)
8
10 ndctl sanitize-dimm <nmem0> [<nmem1>..<nmemN>] [<options>]
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13 The sanitize-dimm command performs a cryptographic destruction of the
14 contents of the given NVDIMM. It scrambles the data, and any metadata
15 or info-blocks, but it doesn’t modify namespace labels. Therefore, any
16 namespaces on regions associated with the given NVDIMM will be
17 retained, but they will end up in the raw mode.
18 Additionally, after completion of this command, the security and
20 passphrase for the given NVDIMM will be disabled, and the passphrase
21 and any key material will also be removed from the keyring and the
22 ndctl keys directory at /etc/ndctl/keys
23 The command supports two different methods of performing the
25 cryptographic erase. The default is crypto-erase, but additionally, an
26 overwrite option is available which overwrites not only the data area,
27 but also the label area, thus losing record of any namespaces the given
28 NVDIMM participates in.
29
31 <dimm>
32 A nmemX device name, or a dimm id number. Restrict the operation to
33 the specified dimm(s). The keyword all can be specified to indicate
34 the lack of any restriction, however this is the same as not
35 supplying a --dimm option at all.
36 -b, --bus=
38 A bus id number, or a provider string (e.g. "ACPI.NFIT"). Restrict
39 the operation to the specified bus(es). The keyword all can be
40 specified to indicate the lack of any restriction, however this is
41 the same as not supplying a --bus option at all.
42 -c, --crypto-erase
44 Replace the media encryption key on the NVDIMM causing all existing
45 data to read as cipher text with the new key. This does not change
46 label data. Namespaces get reverted to raw mode.
47 -o, --ovewrite
49 Wipe the entire DIMM, including label data. This can take
50 significant time, and the command is non-blocking. With this
51 option, the overwrite request is merely submitted to the NVDIMM,
52 and the completion is asynchronous. Depending on the medium and
53 capacity, overwrite may take tens of minutes to many hours.
54 -m, --master-passphrase
56 Indicate that we are using the master passphrase to perform the
57 erase. This only is applicable to the crypto-erase option.
58 -z, --zero-key
60 Passing in a key with payload that is just 0’s.
61 --verbose
63 Emit debug messages.
64
66 The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
67 introduced the following security management operations: enable
68 passhprase, update passphrase, unlock DIMM, disable security, freeze
69 security, secure (crypto) erase, overwrite, master passphrase enable,
70 master passphrase update, and master passphrase secure erase.
71 The security management for NVDIMMs is comprised of two parts. The
73 front end uses the Linux key management framework (trusted and
74 encrypted keys [2]) to store the encrypted passphrases in the
75 kernel-managed keyring. The interface for this is the keyutils utility
76 which uses the key management APIs in the Linux kernel. The back end
77 takes the decrypted payload (which is the DIMM passphrase) and passes
78 it to the DIMM.
79 Unlike other DSMs which are composed by libndctl and sent to the kernel
81 via an ioctl, the security DSMs are managed through the security sysfs
82 attribute under the dimm device. A key-ID is written to the security
83 attribute and the kernel pulls the associated key material from the
84 user keyring that is maintained by the kernel.
85 The security process begins with the generation of a master key that is
87 used to seal (encrypt) the passphrase for the DIMM. There can either be
88 one common master key that is used to encrypt every DIMM’s passphrase,
89 or a separate key can be generated for each DIMM. The master key is
90 also referred to as the key-encryption-key (kek). The kek can either be
91 generated by the TPM (Trusted Platform Module) on the system, or
92 alternatively, the System Master Key can also be used as the kek
93 For testing purposes a user key with randomized payload can also be
95 used as a kek. See [2] for details. To perform any security operations,
96 it is expected that the kek has been added to the kernel’s user keyring
97 as shown in example below:
98 # keyctl show
100 Session Keyring
101 736023423 --alswrv 0 0 keyring: _ses
102 675104189 --alswrv 0 65534 \_ keyring: _uid.0
103 680187394 --alswrv 0 0 \_ trusted: nvdimm-master
104 Before performing any of the security operations, all the regions
106 associated with the DIMM in question need to be disabled. For the
107 overwrite operation, in addition to the regions, the dimm also needs to
108 be disabled.
109 [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
111 https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
112 The following sub-sections describe specifics of each security feature.
114 UNLOCK
116 Unlock is performed by the kernel, however a preparation step must
117 happen before the unlock DSM can be issued by the kernel. It is
118 expected that from the initramfs, a setup command (ndctl load-keys) is
119 executed before the libnvdimm module is loaded by modprobe. This
120 command will inject the kek and the encrypted passphrases into the
121 kernel’s user keyring. During the probe of the libnvdimm driver, it
122 will:
123 1. Check the security state of the device and see if the DIMM is
125 locked
126 2. Request the associated encrypted passphrase from the kernel’s user
128 key ring
129 3. Use the kek to decrypt the passphrase
131 4. Create the unlock DSM, copy the decrypted payload into the DSM
133 5. Issue the DSM to unlock the DIMM
135 If the DIMM is already unlocked, the kernel will attempt to revalidate
137 the passphrase. If we fail to revalidate the passphrase, the kernel
138 will freeze the security and disallow any further security
139 configuration changes. A kernel module parameter is available to
140 override this behavior.
141 SETUP USER PASSPHRASE
143 To setup the passphrase for a DIMM, it is expected that the kek to be
144 used is present in the kernel’s user keyring. The kek encrypts the DIMM
145 passphrase using the enc32 key format. The plaintext passphrase is
146 never provided by or made visible to the user. It is instead randomly
147 generated by the kernel and userspace does not have access to it. Upon
148 encryption, a binary blob of the passphrase is written to the
149 passphrase blob storage directory (/etc/ndctl/keys). The user is
150 responsible for backing up the passphrase blobs to a secure location.
151 UPDATE USER PASSPHRASE
153 The update user passphrase operation uses the same DSM command as
154 enable user passphrase. Most of the work is done on the key management
155 side. The user has the option of providing a new kek for the new
156 passphrase, but continuing to use the existing kek is also acceptable.
157 The following operations are performed for update-passphrase:
158 1. Remove the encrypted passphrase from the kernel’s user keyring.
160 2. Rename the passphrase blob to old.
162 3. Load this old passphrase blob into the keyring with an "old" name.
164 4. Create the new passphrase and encrypt with the kek.
166 5. Send DSM with the old and new decrypted passphrases.
168 6. Remove old passphrase and the passphrase blob from the keyring.
170 REMOVE USER PASSPHRASE
172 The key-ID for the passphrase to be removed is written to sysfs. The
173 kernel then sends the DSM to disable security, and the passphrase is
174 then removed from the keyring, and the associated passphrase blob is
175 deleted.
176 CRYPTO (SECURE) ERASE
178 This operation is similar to remove-passphrase. The kernel issues a
179 WBINVD instruction before and after the operation to ensure no data
180 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
181 with the --crypto-erase option to perform this operation.
182 OVERWRITE
184 This is invoked using --overwrite option for ndctl sanitize-dimm. The
185 overwrite operation wipes the entire NVDIMM. The operation can take a
186 significant amount of time. NOTE: When the command returns
187 successfully, it just means overwrite has been successfully started,
188 and not that the overwrite is complete. Subsequently, 'ndctl
189 wait-overwrite’can be used to wait for the NVDIMMs that are performing
190 overwrite. Upon successful completion of an overwrite, the WBINVD
191 instruction is issued by the kernel. If both --crypto-erase and
192 --overwrite options are supplied, then crypto-erase is performed before
193 overwrite.
194 SECURITY FREEZE
196 This operation does not require a passphrase. This will cause any
197 security command other than a status query to be locked out until the
198 next boot.
199 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
201 These operations are similar to the user passphrase enable and update.
202 The only difference is that a different passphrase is used. The master
203 passphrase has no relation to the master key (kek) which is used for
204 encryption of either passphrase.
205
207 Copyright © 2016 - 2022, Intel Corporation. License GPLv2: GNU GPL
208 version 2 http://gnu.org/licenses/gpl.html. This is free software: you
209 are free to change and redistribute it. There is NO WARRANTY, to the
210 extent permitted by law.
211
213 linkndctl:ndctl-wait-overwrite[1],
214 https://trustedcomputinggroup.org/wp-content/uploads/TCG_SWG_SIIS_Version_1_07_Revision_1_00.pdf
215 03/08/2022 NDCTL-SANITIZE-DIM(1)