1NDCTL-FREEZE-SECUR(1) ndctl Manual NDCTL-FREEZE-SECUR(1)
2
6 ndctl-freeze-security - Set the given DIMM(s) to reject future security
7 operations
8
10 ndctl freeze-security <nmem0> [<nmem1>..<nmemN>] [<options>]
11
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
19 .ft C
20 $ ndctl list -d nmem0
21 [
22 {
23 "dev":"nmem0",
24 "id":"cdab-0a-07e0-ffffffff",
25 "handle":0,
26 "phys_id":0,
27 "security":"unlocked"
28 }
29 ]
30 $ ndctl freeze-security nmem0
32 security froze 1 nmem.
33 $ ndctl list -d nmem0
35 [
36 {
37 "dev":"nmem0",
38 "id":"cdab-0a-07e0-ffffffff",
39 "handle":0,
40 "phys_id":0,
41 "security":"unlocked",
42 "security_frozen":true
43 },
44 ]
45 .ft
46
49 <dimm>
50 A nmemX device name, or a dimm id number. Restrict the operation to
51 the specified dimm(s). The keyword all can be specified to indicate
52 the lack of any restriction, however this is the same as not
53 supplying a --dimm option at all.
54 -b, --bus=
56 A bus id number, or a provider string (e.g. "ACPI.NFIT"). Restrict
57 the operation to the specified bus(es). The keyword all can be
58 specified to indicate the lack of any restriction, however this is
59 the same as not supplying a --bus option at all.
60 -v, --verbose
62 Emit debug messages.
63
65 The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
66 introduced the following security management operations: enable
67 passhprase, update passphrase, unlock DIMM, disable security, freeze
68 security, secure (crypto) erase, overwrite, master passphrase enable,
69 master passphrase update, and master passphrase secure erase.
70 The security management for NVDIMMs is comprised of two parts. The
72 front end uses the Linux key management framework (trusted and
73 encrypted keys [2]) to store the encrypted passphrases in the
74 kernel-managed keyring. The interface for this is the keyutils utility
75 which uses the key management APIs in the Linux kernel. The back end
76 takes the decrypted payload (which is the DIMM passphrase) and passes
77 it to the DIMM.
78 Unlike other DSMs which are composed by libndctl and sent to the kernel
80 via an ioctl, the security DSMs are managed through the security sysfs
81 attribute under the dimm device. A key-ID is written to the security
82 attribute and the kernel pulls the associated key material from the
83 user keyring that is maintained by the kernel.
84 The security process begins with the generation of a master key that is
86 used to seal (encrypt) the passphrase for the DIMM. There can either be
87 one common master key that is used to encrypt every DIMM’s passphrase,
88 or a separate key can be generated for each DIMM. The master key is
89 also referred to as the key-encryption-key (kek). The kek can either be
90 generated by the TPM (Trusted Platform Module) on the system, or
91 alternatively, the System Master Key can also be used as the kek
92 For testing purposes a user key with randomized payload can also be
94 used as a kek. See [2] for details. To perform any security operations,
95 it is expected that the kek has been added to the kernel’s user keyring
96 as shown in example below:
97 .ft C
100 # keyctl show
101 Session Keyring
102 736023423 --alswrv 0 0 keyring: _ses
103 675104189 --alswrv 0 65534 \_ keyring: _uid.0
104 680187394 --alswrv 0 0 \_ trusted: nvdimm-master
105 .ft
106 Before performing any of the security operations, all the regions
109 associated with the DIMM in question need to be disabled. For the
110 overwrite operation, in addition to the regions, the dimm also needs to
111 be disabled.
112 [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
114 https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
115 The following sub-sections describe specifics of each security feature.
117 UNLOCK
119 Unlock is performed by the kernel, however a preparation step must
120 happen before the unlock DSM can be issued by the kernel. It is
121 expected that from the initramfs, a setup command (ndctl load-keys) is
122 executed before the libnvdimm module is loaded by modprobe. This
123 command will inject the kek and the encrypted passphrases into the
124 kernel’s user keyring. During the probe of the libnvdimm driver, it
125 will:
126 1. Check the security state of the device and see if the DIMM is
128 locked
129 2. Request the associated encrypted passphrase from the kernel’s user
131 key ring
132 3. Use the kek to decrypt the passphrase
134 4. Create the unlock DSM, copy the decrypted payload into the DSM
136 5. Issue the DSM to unlock the DIMM
138 If the DIMM is already unlocked, the kernel will attempt to revalidate
140 the passphrase. If we fail to revalidate the passphrase, the kernel
141 will freeze the security and disallow any further security
142 configuration changes. A kernel module parameter is available to
143 override this behavior.
144 SETUP USER PASSPHRASE
146 To setup the passphrase for a DIMM, it is expected that the kek to be
147 used is present in the kernel’s user keyring. The kek encrypts the DIMM
148 passphrase using the enc32 key format. The plaintext passphrase is
149 never provided by or made visible to the user. It is instead randomly
150 generated by the kernel and userspace does not have access to it. Upon
151 encryption, a binary blob of the passphrase is written to the
152 passphrase blob storage directory (/etc/ndctl/keys). The user is
153 responsible for backing up the passphrase blobs to a secure location.
154 UPDATE USER PASSPHRASE
156 The update user passphrase operation uses the same DSM command as
157 enable user passphrase. Most of the work is done on the key management
158 side. The user has the option of providing a new kek for the new
159 passphrase, but continuing to use the existing kek is also acceptable.
160 The following operations are performed for update-passphrase:
161 1. Remove the encrypted passphrase from the kernel’s user keyring.
163 2. Rename the passphrase blob to old.
165 3. Load this old passphrase blob into the keyring with an "old" name.
167 4. Create the new passphrase and encrypt with the kek.
169 5. Send DSM with the old and new decrypted passphrases.
171 6. Remove old passphrase and the passphrase blob from the keyring.
173 REMOVE USER PASSPHRASE
175 The key-ID for the passphrase to be removed is written to sysfs. The
176 kernel then sends the DSM to disable security, and the passphrase is
177 then removed from the keyring, and the associated passphrase blob is
178 deleted.
179 CRYPTO (SECURE) ERASE
181 This operation is similar to remove-passphrase. The kernel issues a
182 WBINVD instruction before and after the operation to ensure no data
183 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
184 with the --crypto-erase option to perform this operation.
185 OVERWRITE
187 This is invoked using --overwrite option for ndctl sanitize-dimm. The
188 overwrite operation wipes the entire NVDIMM. The operation can take a
189 significant amount of time. NOTE: When the command returns
190 successfully, it just means overwrite has been successfully started,
191 and not that the overwrite is complete. Subsequently, 'ndctl
192 wait-overwrite’can be used to wait for the NVDIMMs that are performing
193 overwrite. Upon successful completion of an overwrite, the WBINVD
194 instruction is issued by the kernel. If both --crypto-erase and
195 --overwrite options are supplied, then crypto-erase is performed before
196 overwrite.
197 SECURITY FREEZE
199 This operation does not require a passphrase. This will cause any
200 security command other than a status query to be locked out until the
201 next boot.
202 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
204 These operations are similar to the user passphrase enable and update.
205 The only difference is that a different passphrase is used. The master
206 passphrase has no relation to the master key (kek) which is used for
207 encryption of either passphrase.
208
210 Copyright © 2016 - 2020, Intel Corporation. License GPLv2: GNU GPL
211 version 2 http://gnu.org/licenses/gpl.html. This is free software: you
212 are free to change and redistribute it. There is NO WARRANTY, to the
213 extent permitted by law.
214ndctl 71.1 07/22/2021 NDCTL-FREEZE-SECUR(1)