1NDCTL-FREEZE-SECUR(1)                                    NDCTL-FREEZE-SECUR(1)
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NAME

6       ndctl-freeze-security - Set the given DIMM(s) to reject future security
7       operations
8

SYNOPSIS

10       ndctl freeze-security <nmem0> [<nmem1>..<nmemN>] [<options>]
11

DESCRIPTION

13       Prevent any further security operations on the given DIMMs until the
14       next reboot. This is used in scenarios where the administrator has
15       taken all expected security actions for the current boot and wants the
16       DIMM to enforce / lock the current state.
17

EXAMPLES

19           $ ndctl list -d nmem0
20           [
21             {
22               "dev":"nmem0",
23               "id":"cdab-0a-07e0-ffffffff",
24               "handle":0,
25               "phys_id":0,
26               "security":"unlocked"
27             }
28           ]
29
30           $ ndctl freeze-security  nmem0
31           security froze 1 nmem.
32
33           $ ndctl list -d nmem0
34           [
35             {
36               "dev":"nmem0",
37               "id":"cdab-0a-07e0-ffffffff",
38               "handle":0,
39               "phys_id":0,
40               "security":"unlocked",
41               "security_frozen":true
42             },
43           ]
44

OPTIONS

46       <dimm>
47           A nmemX device name, or a dimm id number. Restrict the operation to
48           the specified dimm(s). The keyword all can be specified to indicate
49           the lack of any restriction, however this is the same as not
50           supplying a --dimm option at all.
51
52       -b, --bus=
53           A bus id number, or a provider string (e.g. "ACPI.NFIT"). Restrict
54           the operation to the specified bus(es). The keyword all can be
55           specified to indicate the lack of any restriction, however this is
56           the same as not supplying a --bus option at all.
57
58       -v, --verbose
59           Emit debug messages.
60

THEORY OF OPERATION

62       The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
63       introduced the following security management operations: enable
64       passphrase, update passphrase, unlock DIMM, disable security, freeze
65       security, secure (crypto) erase, overwrite, master passphrase enable,
66       master passphrase update, and master passphrase secure erase.
67
68       The security management for NVDIMMs is comprised of two parts. The
69       front end uses the Linux key management framework (trusted and
70       encrypted keys [2]) to store the encrypted passphrases in the
71       kernel-managed keyring. The interface for this is the keyutils utility
72       which uses the key management APIs in the Linux kernel. The back end
73       takes the decrypted payload (which is the DIMM passphrase) and passes
74       it to the DIMM.
75
76       Unlike other DSMs which are composed by libndctl and sent to the kernel
77       via an ioctl, the security DSMs are managed through the security sysfs
78       attribute under the dimm device. A key-ID is written to the security
79       attribute and the kernel pulls the associated key material from the
80       user keyring that is maintained by the kernel.
81
82       The security process begins with the generation of a master key that is
83       used to seal (encrypt) the passphrase for the DIMM. There can either be
84       one common master key that is used to encrypt every DIMM’s passphrase,
85       or a separate key can be generated for each DIMM. The master key is
86       also referred to as the key-encryption-key (kek). The kek can either be
87       generated by the TPM (Trusted Platform Module) on the system, or
88       alternatively, the System Master Key can also be used as the kek
89
90       For testing purposes a user key with randomized payload can also be
91       used as a kek. See [2] for details. To perform any security operations,
92       it is expected that the kek has been added to the kernel’s user keyring
93       as shown in example below:
94
95           # keyctl show
96           Session Keyring
97            736023423 --alswrv      0     0  keyring: _ses
98            675104189 --alswrv      0 65534   \_ keyring: _uid.0
99            680187394 --alswrv      0     0       \_ trusted: nvdimm-master
100
101       Before performing any of the security operations, all the regions
102       associated with the DIMM in question need to be disabled. For the
103       overwrite operation, in addition to the regions, the dimm also needs to
104       be disabled.
105
106       [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
107       https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
108
109       The following sub-sections describe specifics of each security feature.
110
111   UNLOCK
112       Unlock is performed by the kernel, however a preparation step must
113       happen before the unlock DSM can be issued by the kernel. It is
114       expected that from the initramfs, a setup command (ndctl load-keys) is
115       executed before the libnvdimm module is loaded by modprobe. This
116       command will inject the kek and the encrypted passphrases into the
117       kernel’s user keyring. During the probe of the libnvdimm driver, it
118       will:
119
120        1. Check the security state of the device and see if the DIMM is
121           locked
122
123        2. Request the associated encrypted passphrase from the kernel’s user
124           key ring
125
126        3. Use the kek to decrypt the passphrase
127
128        4. Create the unlock DSM, copy the decrypted payload into the DSM
129
130        5. Issue the DSM to unlock the DIMM
131
132       If the DIMM is already unlocked, the kernel will attempt to revalidate
133       the passphrase. If we fail to revalidate the passphrase, the kernel
134       will freeze the security and disallow any further security
135       configuration changes. A kernel module parameter is available to
136       override this behavior.
137
138   SETUP USER PASSPHRASE
139       To setup the passphrase for a DIMM, it is expected that the kek to be
140       used is present in the kernel’s user keyring. The kek encrypts the DIMM
141       passphrase using the enc32 key format. The plaintext passphrase is
142       never provided by or made visible to the user. It is instead randomly
143       generated by the kernel and userspace does not have access to it. Upon
144       encryption, a binary blob of the passphrase is written to the
145       passphrase blob storage directory (/etc/ndctl/keys). The user is
146       responsible for backing up the passphrase blobs to a secure location.
147
148   UPDATE USER PASSPHRASE
149       The update user passphrase operation uses the same DSM command as
150       enable user passphrase. Most of the work is done on the key management
151       side. The user has the option of providing a new kek for the new
152       passphrase, but continuing to use the existing kek is also acceptable.
153       The following operations are performed for update-passphrase:
154
155        1. Remove the encrypted passphrase from the kernel’s user keyring.
156
157        2. Rename the passphrase blob to old.
158
159        3. Load this old passphrase blob into the keyring with an "old" name.
160
161        4. Create the new passphrase and encrypt with the kek.
162
163        5. Send DSM with the old and new decrypted passphrases.
164
165        6. Remove old passphrase and the passphrase blob from the keyring.
166
167   REMOVE USER PASSPHRASE
168       The key-ID for the passphrase to be removed is written to sysfs. The
169       kernel then sends the DSM to disable security, and the passphrase is
170       then removed from the keyring, and the associated passphrase blob is
171       deleted.
172
173   CRYPTO (SECURE) ERASE
174       This operation is similar to remove-passphrase. The kernel issues a
175       WBINVD instruction before and after the operation to ensure no data
176       corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
177       with the --crypto-erase option to perform this operation.
178
179   OVERWRITE
180       This is invoked using --overwrite option for ndctl sanitize-dimm. The
181       overwrite operation wipes the entire NVDIMM. The operation can take a
182       significant amount of time. NOTE: When the command returns
183       successfully, it just means overwrite has been successfully started,
184       and not that the overwrite is complete. Subsequently, ndctl
185       wait-overwrite can be used to wait for the NVDIMMs that are performing
186       overwrite. Upon successful completion of an overwrite, the WBINVD
187       instruction is issued by the kernel. If both --crypto-erase and
188       --overwrite options are supplied, then crypto-erase is performed before
189       overwrite.
190
191   SECURITY FREEZE
192       This operation does not require a passphrase. This will cause any
193       security command other than a status query to be locked out until the
194       next boot.
195
196   MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
197       These operations are similar to the user passphrase enable and update.
198       The only difference is that a different passphrase is used. The master
199       passphrase has no relation to the master key (kek) which is used for
200       encryption of either passphrase.
201
203       Copyright © 2016 - 2022, Intel Corporation. License GPLv2: GNU GPL
204       version 2 http://gnu.org/licenses/gpl.html. This is free software: you
205       are free to change and redistribute it. There is NO WARRANTY, to the
206       extent permitted by law.
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210                                  08/03/2023             NDCTL-FREEZE-SECUR(1)
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