1NDCTL-LOAD-KEYS(1) NDCTL-LOAD-KEYS(1)
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6 ndctl-load-keys - load the kek and encrypted passphrases into the
7 keyring
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10 ndctl load-keys [<options>]
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13 The load-keys command loads the master key (kek) and the encrypted
14 passphrases for all NVDIMMs into the user keyring maintained by the
15 kernel. The command is expected to be called during initialization and
16 before the libnvdimm kernel module is loaded, typically from an initrd.
17 This is typically set up using a modprobe config that calls the command
18 before module load.
19 Note
21 All key files are expected to be in the format:
22 nvdimm_<id>_hostname The ‘'_’ character is used to delimit the
23 different components in the file name. Within the hostname, the
24 ‘'_’ character is allowed since it is the last component of the
25 file name.
26 Note
28 This command is typically never called directly by a user.
29
31 -p, --key-path=
32 Path to where key related files reside. This parameter is optional
33 and the default location is /etc/ndctl/keys.
34 -t, --tpm-handle=
36 Provide a TPM handle (should be a string such as 0x81000001). If
37 the key path (/etc/ndctl/keys) contains a file called tpm.handle
38 which contains the handle string, then this option may be left out,
39 and the tpm handle will be obtained from the file. If both are
40 present, then this option will override (but not overwrite)
41 anything that is in the file.
42
44 The Intel Device Specific Methods (DSM) specification v1.7 and v1.8 [1]
45 introduced the following security management operations: enable
46 passphrase, update passphrase, unlock DIMM, disable security, freeze
47 security, secure (crypto) erase, overwrite, master passphrase enable,
48 master passphrase update, and master passphrase secure erase.
49 The security management for NVDIMMs is comprised of two parts. The
51 front end uses the Linux key management framework (trusted and
52 encrypted keys [2]) to store the encrypted passphrases in the
53 kernel-managed keyring. The interface for this is the keyutils utility
54 which uses the key management APIs in the Linux kernel. The back end
55 takes the decrypted payload (which is the DIMM passphrase) and passes
56 it to the DIMM.
57 Unlike other DSMs which are composed by libndctl and sent to the kernel
59 via an ioctl, the security DSMs are managed through the security sysfs
60 attribute under the dimm device. A key-ID is written to the security
61 attribute and the kernel pulls the associated key material from the
62 user keyring that is maintained by the kernel.
63 The security process begins with the generation of a master key that is
65 used to seal (encrypt) the passphrase for the DIMM. There can either be
66 one common master key that is used to encrypt every DIMM’s passphrase,
67 or a separate key can be generated for each DIMM. The master key is
68 also referred to as the key-encryption-key (kek). The kek can either be
69 generated by the TPM (Trusted Platform Module) on the system, or
70 alternatively, the System Master Key can also be used as the kek
71 For testing purposes a user key with randomized payload can also be
73 used as a kek. See [2] for details. To perform any security operations,
74 it is expected that the kek has been added to the kernel’s user keyring
75 as shown in example below:
76 # keyctl show
78 Session Keyring
79 736023423 --alswrv 0 0 keyring: _ses
80 675104189 --alswrv 0 65534 \_ keyring: _uid.0
81 680187394 --alswrv 0 0 \_ trusted: nvdimm-master
82 Before performing any of the security operations, all the regions
84 associated with the DIMM in question need to be disabled. For the
85 overwrite operation, in addition to the regions, the dimm also needs to
86 be disabled.
87 [1] http://pmem.io/documents/NVDIMM_DSM_Interface-V1.8.pdf [2]
89 https://www.kernel.org/doc/Documentation/security/keys/trusted-encrypted.rst
90 The following sub-sections describe specifics of each security feature.
92 UNLOCK
94 Unlock is performed by the kernel, however a preparation step must
95 happen before the unlock DSM can be issued by the kernel. It is
96 expected that from the initramfs, a setup command (ndctl load-keys) is
97 executed before the libnvdimm module is loaded by modprobe. This
98 command will inject the kek and the encrypted passphrases into the
99 kernel’s user keyring. During the probe of the libnvdimm driver, it
100 will:
101 1. Check the security state of the device and see if the DIMM is
103 locked
104 2. Request the associated encrypted passphrase from the kernel’s user
106 key ring
107 3. Use the kek to decrypt the passphrase
109 4. Create the unlock DSM, copy the decrypted payload into the DSM
111 5. Issue the DSM to unlock the DIMM
113 If the DIMM is already unlocked, the kernel will attempt to revalidate
115 the passphrase. If we fail to revalidate the passphrase, the kernel
116 will freeze the security and disallow any further security
117 configuration changes. A kernel module parameter is available to
118 override this behavior.
119 SETUP USER PASSPHRASE
121 To setup the passphrase for a DIMM, it is expected that the kek to be
122 used is present in the kernel’s user keyring. The kek encrypts the DIMM
123 passphrase using the enc32 key format. The plaintext passphrase is
124 never provided by or made visible to the user. It is instead randomly
125 generated by the kernel and userspace does not have access to it. Upon
126 encryption, a binary blob of the passphrase is written to the
127 passphrase blob storage directory (/etc/ndctl/keys). The user is
128 responsible for backing up the passphrase blobs to a secure location.
129 UPDATE USER PASSPHRASE
131 The update user passphrase operation uses the same DSM command as
132 enable user passphrase. Most of the work is done on the key management
133 side. The user has the option of providing a new kek for the new
134 passphrase, but continuing to use the existing kek is also acceptable.
135 The following operations are performed for update-passphrase:
136 1. Remove the encrypted passphrase from the kernel’s user keyring.
138 2. Rename the passphrase blob to old.
140 3. Load this old passphrase blob into the keyring with an "old" name.
142 4. Create the new passphrase and encrypt with the kek.
144 5. Send DSM with the old and new decrypted passphrases.
146 6. Remove old passphrase and the passphrase blob from the keyring.
148 REMOVE USER PASSPHRASE
150 The key-ID for the passphrase to be removed is written to sysfs. The
151 kernel then sends the DSM to disable security, and the passphrase is
152 then removed from the keyring, and the associated passphrase blob is
153 deleted.
154 CRYPTO (SECURE) ERASE
156 This operation is similar to remove-passphrase. The kernel issues a
157 WBINVD instruction before and after the operation to ensure no data
158 corruption from a stale CPU cache. Use ndctl’s sanitize-dimm command
159 with the --crypto-erase option to perform this operation.
160 OVERWRITE
162 This is invoked using --overwrite option for ndctl sanitize-dimm. The
163 overwrite operation wipes the entire NVDIMM. The operation can take a
164 significant amount of time. NOTE: When the command returns
165 successfully, it just means overwrite has been successfully started,
166 and not that the overwrite is complete. Subsequently, ndctl
167 wait-overwrite can be used to wait for the NVDIMMs that are performing
168 overwrite. Upon successful completion of an overwrite, the WBINVD
169 instruction is issued by the kernel. If both --crypto-erase and
170 --overwrite options are supplied, then crypto-erase is performed before
171 overwrite.
172 SECURITY FREEZE
174 This operation does not require a passphrase. This will cause any
175 security command other than a status query to be locked out until the
176 next boot.
177 MASTER PASSPHRASE SETUP, UPDATE, and CRYPTO ERASE
179 These operations are similar to the user passphrase enable and update.
180 The only difference is that a different passphrase is used. The master
181 passphrase has no relation to the master key (kek) which is used for
182 encryption of either passphrase.
183
185 Copyright © 2016 - 2022, Intel Corporation. License GPLv2: GNU GPL
186 version 2 http://gnu.org/licenses/gpl.html. This is free software: you
187 are free to change and redistribute it. There is NO WARRANTY, to the
188 extent permitted by law.
189 08/03/2023 NDCTL-LOAD-KEYS(1)