1NDCTL-UPDATE-PASSP(1)            ndctl Manual            NDCTL-UPDATE-PASSP(1)
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NAME

6       ndctl-update-passphrase - update the security passphrase for an NVDIMM
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SYNOPSIS

9       ndctl update-passphrase <nmem0> [<nmem1>..<nmemN>] [<options>]
10

DESCRIPTION

12       Update the security passphrase for one or more NVDIMMs. Prerequisites
13       for command to succeed:
14
15        1. The kek has been loaded into the kernel’s user keyring.
16
17        2. setup-passphrase has successfully been executed on the NVDIMM.
18
19           ·   Alternatively, the NVDIMM is unlocked.
20
21       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

OPTIONS

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.
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31       -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.
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37       -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 NOTE: The
41           kek is expected to have been loaded into the user keyring.
42
43       -m, --master-passphrase
44           Indicates that we are managing the master passphrase instead of the
45           user passphrase.
46
47       -v, --verbose
48           Emit debug messages.
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THEORY OF OPERATION

51       The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
52       introduced the following security management operations: enable
53       passhprase, update passphrase, unlock DIMM, disable security, freeze
54       security, secure (crypto) erase, overwrite, master passphrase enable,
55       master passphrase update, and master passphrase secure erase.
56
57       The security management for NVDIMMs is comprised of two parts. The
58       front end uses the Linux key management framework (trusted and
59       encrypted keys [2]) to store the encrypted passphrases in the
60       kernel-managed keyring. The interface for this is the keyutils utility
61       which uses the key management APIs in the Linux kernel. The back end
62       takes the decrypted payload (which is the DIMM passphrase) and passes
63       it to the DIMM.
64
65       Unlike other DSMs which are composed by libndctl and sent to the kernel
66       via an ioctl, the security DSMs are managed through the security sysfs
67       attribute under the dimm device. A key-ID is written to the security
68       attribute and the kernel pulls the associated key material from the
69       user keyring that is maintained by the kernel.
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71       The security process begins with the generation of a master key that is
72       used to seal (encrypt) the passphrase for the DIMM. There can either be
73       one common master key that is used to encrypt every DIMM’s passphrase,
74       or a separate key can be generated for each DIMM. The master key is
75       also referred to as the key-encryption-key (kek). The kek can either be
76       generated by the TPM (Trusted Platform Module) on the system, or
77       alternatively, the System Master Key can also be used as the kek
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79       For testing purposes a user key with randomized payload can also be
80       used as a kek. See [2] for details. To perform any security operations,
81       it is expected that the kek has been added to the kernel’s user keyring
82       as shown in example below:
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84
85           .ft C
86           # 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           .ft
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93
94       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
99       [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
100       https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
101
102       The following sub-sections describe specifics of each security feature.
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104   UNLOCK
105       Unlock is performed by the kernel, however a preparation step must
106       happen before the unlock DSM can be issued by the kernel. It is
107       expected that from the initramfs, a setup command (ndctl load-keys) is
108       executed before the libnvdimm module is loaded by modprobe. This
109       command will inject the kek and the encrypted passphrases into the
110       kernel’s user keyring. During the probe of the libnvdimm driver, it
111       will:
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113        1. Check the security state of the device and see if the DIMM is
114           locked
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116        2. Request the associated encrypted passphrase from the kernel’s user
117           key ring
118
119        3. Use the kek to decrypt the passphrase
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121        4. Create the unlock DSM, copy the decrypted payload into the DSM
122
123        5. Issue the DSM to unlock the DIMM
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125       If the DIMM is already unlocked, the kernel will attempt to revalidate
126       the passphrase. If we fail to revalidate the passphrase, the kernel
127       will freeze the security and disallow any further security
128       configuration changes. A kernel module parameter is available to
129       override this behavior.
130
131   SETUP USER PASSPHRASE
132       To setup the passphrase for a DIMM, it is expected that the kek to be
133       used is present in the kernel’s user keyring. The kek encrypts the DIMM
134       passphrase using the enc32 key format. The plaintext passphrase is
135       never provided by or made visible to the user. It is instead randomly
136       generated by the kernel and userspace does not have access to it. Upon
137       encryption, a binary blob of the passphrase is written to the
138       passphrase blob storage directory (/etc/ndctl/keys). The user is
139       responsible for backing up the passphrase blobs to a secure location.
140
141   UPDATE USER PASSPHRASE
142       The update user passphrase operation uses the same DSM command as
143       enable user passphrase. Most of the work is done on the key management
144       side. The user has the option of providing a new kek for the new
145       passphrase, but continuing to use the existing kek is also acceptable.
146       The following operations are performed for update-passphrase:
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148        1. Remove the encrypted passphrase from the kernel’s user keyring.
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150        2. Rename the passphrase blob to old.
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152        3. Load this old passphrase blob into the keyring with an "old" name.
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154        4. Create the new passphrase and encrypt with the kek.
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156        5. Send DSM with the old and new decrypted passphrases.
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158        6. Remove old passphrase and the passphrase blob from the keyring.
159
160   REMOVE USER PASSPHRASE
161       The key-ID for the passphrase to be removed is written to sysfs. The
162       kernel then sends the DSM to disable security, and the passphrase is
163       then removed from the keyring, and the associated passphrase blob is
164       deleted.
165
166   CRYPTO (SECURE) ERASE
167       This operation is similar to remove-passphrase. The kernel issues a
168       WBINVD instruction before and after the operation to ensure no data
169       corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
170       with the --crypto-erase option to perform this operation.
171
172   OVERWRITE
173       This is invoked using --overwrite option for ndctl sanitize-dimm. The
174       overwrite operation wipes the entire NVDIMM. The operation can take a
175       significant amount of time. NOTE: When the command returns
176       successfully, it just means overwrite has been successfully started,
177       and not that the overwrite is complete. Subsequently, 'ndctl
178       wait-overwrite’can be used to wait for the NVDIMMs that are performing
179       overwrite. Upon successful completion of an overwrite, the WBINVD
180       instruction is issued by the kernel. If both --crypto-erase and
181       --overwrite options are supplied, then crypto-erase is performed before
182       overwrite.
183
184   SECURITY FREEZE
185       This operation does not require a passphrase. This will cause any
186       security command other than a status query to be locked out until the
187       next boot.
188
189   MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
190       These operations are similar to the user passphrase enable and update.
191       The only difference is that a different passphrase is used. The master
192       passphrase has no relation to the master key (kek) which is used for
193       encryption of either passphrase.
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196       Copyright © 2016 - 2020, Intel Corporation. License GPLv2: GNU GPL
197       version 2 http://gnu.org/licenses/gpl.html. This is free software: you
198       are free to change and redistribute it. There is NO WARRANTY, to the
199       extent permitted by law.
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SEE ALSO:

202       ndctl-setup-passphrase(1), ndctl-remove-passphrase(1)
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206ndctl 71.1                        12/22/2020             NDCTL-UPDATE-PASSP(1)
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