1NDCTL-FREEZE-SECURITY(1) ndctl Manual NDCTL-FREEZE-SECURITY(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 freezed 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":"frozen"
41 }
42 ]
43
45 <dimm>
46 A 'nmemX' device name, or a dimm id number. The keyword 'all' can
48 be specified to carry out the operation on every dimm in the system,
49 optionally filtered by bus id (see --bus= option).
50 -b, --bus=
52 Enforce that the operation only be carried on devices that are
53 attached to the given bus. Where bus can be a provider name or a
54 bus id number.
55 -v, --verbose
57 Emit debug messages.
58
60 The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
61 introduced the following security management operations: enable
62 passhprase, update passphrase, unlock DIMM, disable security, freeze
63 security, secure (crypto) erase, overwrite, master passphrase enable,
64 master passphrase update, and master passphrase secure erase.
65 The security management for NVDIMMs is comprised of two parts. The
67 front end uses the Linux key management framework (trusted and
68 encrypted keys [2]) to store the encrypted passphrases in the
69 kernel-managed keyring. The interface for this is the keyutils utility
70 which uses the key management APIs in the Linux kernel. The back end
71 takes the decrypted payload (which is the DIMM passphrase) and passes
72 it to the DIMM.
73 Unlike other DSMs which are composed by libndctl and sent to the kernel
75 via an ioctl, the security DSMs are managed through the security sysfs
76 attribute under the dimm device. A key-ID is written to the security
77 attribute and the kernel pulls the associated key material from the
78 user keyring that is maintained by the kernel.
79 The security process begins with the generation of a master key that is
81 used to seal (encrypt) the passphrase for the DIMM. There can either be
82 one common master key that is used to encrypt every DIMM’s passphrase,
83 or a separate key can be generated for each DIMM. The master key is
84 also referred to as the key-encryption-key (kek). The kek can either be
85 generated by the TPM (Trusted Platform Module) on the system, or
86 alternatively, the System Master Key can also be used as the kek
87 For testing purposes a user key with randomized payload can also be
89 used as a kek. See [2] for details. To perform any security operations,
90 it is expected that the kek has been added to the kernel’s user keyring
91 as shown in example below:
92 # keyctl show
94 Session Keyring
95 736023423 --alswrv 0 0 keyring: _ses
96 675104189 --alswrv 0 65534 \_ keyring: _uid.0
97 680187394 --alswrv 0 0 \_ trusted: nvdimm-master
98 Before performing any of the security operations, all the regions
100 associated with the DIMM in question need to be disabled. For the
101 overwrite operation, in addition to the regions, the dimm also needs to
102 be disabled.
103 [1] <http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf>
105 [2] <https://www.kernel.org/doc/Documentation/security/keys/
106 trusted-encrypted.rst>
107 The following sub-sections describe specifics of each security feature.
109 UNLOCK
111 Unlock is performed by the kernel, however a preparation step must
112 happen before the unlock DSM can be issued by the kernel. It is
113 expected that from the initramfs, a setup command (ndctl load-keys) is
114 executed before the libnvdimm module is loaded by modprobe. This
115 command will inject the kek and the encrypted passphrases into the
116 kernel’s user keyring. During the probe of the libnvdimm driver, it
117 will:
118 1. Check the security state of the device and see if the DIMM is
120 locked
121 2. Request the associated encrypted passphrase from the kernel’s user
123 key ring
124 3. Use the kek to decrypt the passphrase
126 4. Create the unlock DSM, copy the decrypted payload into the DSM
128 5. Issue the DSM to unlock the DIMM
130 If the DIMM is already unlocked, the kernel will attempt to revalidate
132 the passphrase. If we fail to revalidate the passphrase, the kernel
133 will freeze the security and disallow any further security
134 configuration changes. A kernel module parameter is available to
135 override this behavior.
136 SETUP USER PASSPHRASE
138 To setup the passphrase for a DIMM, it is expected that the kek to be
139 used is present in the kernel’s user keyring. The kek encrypts the DIMM
140 passphrase using the enc32 key format. The plaintext passphrase is
141 never provided by or made visible to the user. It is instead randomly
142 generated by the kernel and userspace does not have access to it. Upon
143 encryption, a binary blob of the passphrase is written to the
144 passphrase blob storage directory (/etc/ndctl/keys). The user is
145 responsible for backing up the passphrase blobs to a secure location.
146 UPDATE USER PASSPHRASE
148 The update user passphrase operation uses the same DSM command as
149 enable user passphrase. Most of the work is done on the key management
150 side. The user has the option of providing a new kek for the new
151 passphrase, but continuing to use the existing kek is also acceptable.
152 The following operations are performed for update-passphrase:
153 1. Remove the encrypted passphrase from the kernel’s user keyring.
155 2. Rename the passphrase blob to old.
157 3. Load this old passphrase blob into the keyring with an "old" name.
159 4. Create the new passphrase and encrypt with the kek.
161 5. Send DSM with the old and new decrypted passphrases.
163 6. Remove old passphrase and the passphrase blob from the keyring.
165 REMOVE USER PASSPHRASE
167 The key-ID for the passphrase to be removed is written to sysfs. The
168 kernel then sends the DSM to disable security, and the passphrase is
169 then removed from the keyring, and the associated passphrase blob is
170 deleted.
171 CRYPTO (SECURE) ERASE
173 This operation is similar to remove-passphrase. The kernel issues a
174 WBINVD instruction before and after the operation to ensure no data
175 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
176 with the --crypto-erase option to perform this operation.
177 OVERWRITE
179 This is invoked using --overwrite option for ndctl sanitize-dimm. The
180 overwrite operation wipes the entire NVDIMM. The operation can take a
181 significant amount of time. NOTE: When the command returns
182 successfully, it just means overwrite has been successfully started,
183 and not that the overwrite is complete. Subsequently, 'ndctl
184 wait-overwrite’can be used to wait for the NVDIMMs that are performing
185 overwrite. Upon successful completion of an overwrite, the WBINVD
186 instruction is issued by the kernel. If both --crypto-erase and
187 --overwrite options are supplied, then crypto-erase is performed before
188 overwrite.
189 SECURITY FREEZE
191 This operation does not require a passphrase. This will cause any
192 security command other than a status query to be locked out until the
193 next boot.
194 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
196 These operations are similar to the user passphrase enable and update.
197 The only difference is that a different passphrase is used. The master
198 passphrase has no relation to the master key (kek) which is used for
199 encryption of either passphrase.
200
202 Copyright (c) 2016 - 2019, Intel Corporation. License GPLv2: GNU GPL
203 version 2 <http://gnu.org/licenses/gpl.html>. This is free software:
204 you are free to change and redistribute it. There is NO WARRANTY, to
205 the extent permitted by law.
206ndctl 2019-05-10 NDCTL-FREEZE-SECURITY(1)