1NDCTL-SANITIZE-DIMM(1)           ndctl Manual           NDCTL-SANITIZE-DIMM(1)
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NAME

6       ndctl-sanitize-dimm - Perform a cryptographic destruction or overwrite
7       of the contents of the given NVDIMM(s)
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SYNOPSIS

10       ndctl sanitize-dimm <nmem0> [<nmem1>..<nmemN>] [<options>]
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DESCRIPTION

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.
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19       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
24       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.
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OPTIONS

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
37       -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
43       -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
48       -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
55       -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
59       -z, --zero-key
60           Passing in a key with payload that is just 0’s.
61
62       --verbose
63           Emit debug messages.
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THEORY OF OPERATION

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
72       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
80       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
86       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
94       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:
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99           # 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
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105       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
110       [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf
111       [2]
112       https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
113
114       The following sub-sections describe specifics of each security feature.
115
116   UNLOCK
117       Unlock is performed by the kernel, however a preparation step must
118       happen before the unlock DSM can be issued by the kernel. It is
119       expected that from the initramfs, a setup command (ndctl load-keys) is
120       executed before the libnvdimm module is loaded by modprobe. This
121       command will inject the kek and the encrypted passphrases into the
122       kernel’s user keyring. During the probe of the libnvdimm driver, it
123       will:
124
125        1. Check the security state of the device and see if the DIMM is
126           locked
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128        2. Request the associated encrypted passphrase from the kernel’s user
129           key ring
130
131        3. Use the kek to decrypt the passphrase
132
133        4. Create the unlock DSM, copy the decrypted payload into the DSM
134
135        5. Issue the DSM to unlock the DIMM
136
137       If the DIMM is already unlocked, the kernel will attempt to revalidate
138       the passphrase. If we fail to revalidate the passphrase, the kernel
139       will freeze the security and disallow any further security
140       configuration changes. A kernel module parameter is available to
141       override this behavior.
142
143   SETUP USER PASSPHRASE
144       To setup the passphrase for a DIMM, it is expected that the kek to be
145       used is present in the kernel’s user keyring. The kek encrypts the DIMM
146       passphrase using the enc32 key format. The plaintext passphrase is
147       never provided by or made visible to the user. It is instead randomly
148       generated by the kernel and userspace does not have access to it. Upon
149       encryption, a binary blob of the passphrase is written to the
150       passphrase blob storage directory (/etc/ndctl/keys). The user is
151       responsible for backing up the passphrase blobs to a secure location.
152
153   UPDATE USER PASSPHRASE
154       The update user passphrase operation uses the same DSM command as
155       enable user passphrase. Most of the work is done on the key management
156       side. The user has the option of providing a new kek for the new
157       passphrase, but continuing to use the existing kek is also acceptable.
158       The following operations are performed for update-passphrase:
159
160        1. Remove the encrypted passphrase from the kernel’s user keyring.
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162        2. Rename the passphrase blob to old.
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164        3. Load this old passphrase blob into the keyring with an "old" name.
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166        4. Create the new passphrase and encrypt with the  kek.
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168        5. Send DSM with the old and new decrypted passphrases.
169
170        6. Remove old passphrase and the passphrase blob from the keyring.
171
172   REMOVE USER PASSPHRASE
173       The key-ID for the passphrase to be removed is written to sysfs. The
174       kernel then sends the DSM to disable security, and the passphrase is
175       then removed from the keyring, and the associated passphrase blob is
176       deleted.
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178   CRYPTO (SECURE) ERASE
179       This operation is similar to remove-passphrase. The kernel issues a
180       WBINVD instruction before and after the operation to ensure no data
181       corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
182       with the --crypto-erase option to perform this operation.
183
184   OVERWRITE
185       This is invoked using --overwrite option for ndctl sanitize-dimm. The
186       overwrite operation wipes the entire NVDIMM. The operation can take a
187       significant amount of time. NOTE: When the command returns
188       successfully, it just means overwrite has been successfully started,
189       and not that the overwrite is complete. Subsequently, 'ndctl
190       wait-overwrite’can be used to wait for the NVDIMMs that are performing
191       overwrite. Upon successful completion of an overwrite, the WBINVD
192       instruction is issued by the kernel. If both --crypto-erase and
193       --overwrite options are supplied, then crypto-erase is performed before
194       overwrite.
195
196   SECURITY FREEZE
197       This operation does not require a passphrase. This will cause any
198       security command other than a status query to be locked out until the
199       next boot.
200
201   MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
202       These operations are similar to the user passphrase enable and update.
203       The only difference is that a different passphrase is used. The master
204       passphrase has no relation to the master key (kek) which is used for
205       encryption of either passphrase.
206
208       Copyright (c) 2016 - 2019, Intel Corporation. License GPLv2: GNU GPL
209       version 2 http://gnu.org/licenses/gpl.html. This is free software: you
210       are free to change and redistribute it. There is NO WARRANTY, to the
211       extent permitted by law.
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SEE ALSO

214       ndctl-wait-overwrite(1),
215       https://trustedcomputinggroup.org/wp-content/uploads/TCG_SWG_SIIS_Version_1_07_Revision_1_00.pdf
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219ndctl                             2020-03-24            NDCTL-SANITIZE-DIMM(1)
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