1NDCTL-FREEZE-SECUR(1) 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 $ 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 $ ndctl freeze-security nmem0
31 security froze 1 nmem.
32 $ 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
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 -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 -v, --verbose
59 Emit debug messages.
60
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 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 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 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 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 # 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 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 [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 The following sub-sections describe specifics of each security feature.
110 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 1. Check the security state of the device and see if the DIMM is
121 locked
122 2. Request the associated encrypted passphrase from the kernel’s user
124 key ring
125 3. Use the kek to decrypt the passphrase
127 4. Create the unlock DSM, copy the decrypted payload into the DSM
129 5. Issue the DSM to unlock the DIMM
131 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 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 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 1. Remove the encrypted passphrase from the kernel’s user keyring.
156 2. Rename the passphrase blob to old.
158 3. Load this old passphrase blob into the keyring with an "old" name.
160 4. Create the new passphrase and encrypt with the kek.
162 5. Send DSM with the old and new decrypted passphrases.
164 6. Remove old passphrase and the passphrase blob from the keyring.
166 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 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 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 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 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.
207 08/03/2023 NDCTL-FREEZE-SECUR(1)