9.4. Rotating Tang server keys and updating bindings on clients

Procedure

1. Rename all keys in the /var/db/tang key database directory to have a leading . to hide them from advertisement. Note that the file names in the following example differs from unique file names in the key database directory of your Tang server:

   # cd /var/db/tang
   # ls -l
   -rw-r--r--. 1 root root 349 Feb  7 14:55 UV6dqXSwe1bRKG3KbJmdiR020hY.jwk
   -rw-r--r--. 1 root root 354 Feb  7 14:55 y9hxLTQSiSB5jSEGWnjhY8fDTJU.jwk
   # mv UV6dqXSwe1bRKG3KbJmdiR020hY.jwk .UV6dqXSwe1bRKG3KbJmdiR020hY.jwk
   # mv y9hxLTQSiSB5jSEGWnjhY8fDTJU.jwk .y9hxLTQSiSB5jSEGWnjhY8fDTJU.jwk

2. Check that you renamed and therefore hid all keys from the Tang server advertisement:

   # ls -l
   total 0

3. Generate new keys using the /usr/libexec/tangd-keygen command in /var/db/tang on the Tang server:

   # /usr/libexec/tangd-keygen /var/db/tang
   # ls /var/db/tang
   3ZWS6-cDrCG61UPJS2BMmPU4I54.jwk zyLuX6hijUy_PSeUEFDi7hi38.jwk

4. Check that your Tang server advertises the signing key from the new key pair, for example:

   # tang-show-keys 7500
   3ZWS6-cDrCG61UPJS2BMmPU4I54

5. On your NBDE clients, use the clevis luks report command to check if the keys advertised by the Tang server remains the same. You can identify slots with the relevant binding using the clevis luks list command, for example:

   # clevis luks list -d /dev/sda2
   1: tang '{"url":"http://tang.srv"}'
   # clevis luks report -d /dev/sda2 -s 1
   ...
   Report detected that some keys were rotated.
   Do you want to regenerate luks metadata with "clevis luks regen -d /dev/sda2 -s 1"? [ynYN]

6. To regenerate LUKS metadata for the new keys, either press y to the prompt of the previous command or use the clevis luks regen command:

   # clevis luks regen -d /dev/sda2 -s 1

7. When you are sure that all old clients use the new keys, you can remove the old keys from the Tang server, for example:

   # cd /var/db/tang
   # rm .*.jwk