Add a new configuration DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING
to enable dm-verity signatures to be verified against the secondary
trusted keyring. Instead of relying on the builtin trusted keyring
(with hard-coded certificates), the second trusted keyring can include
certificate authorities from the builtin trusted keyring and child
certificates loaded at run time. Using the secondary trusted keyring
enables to use dm-verity disks (e.g. loop devices) signed by keys which
did not exist at kernel build time, leveraging the certificate chain of
trust model. In practice, this makes it possible to update certificates
without kernel update and reboot, aligning with module and kernel
(kexec) signature verification which already use the secondary trusted
keyring.
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The verification is to support cases where the root hash is not secured
by Trusted Boot, UEFI Secureboot or similar technologies.
One of the use cases for this is for dm-verity volumes mounted after
boot, the root hash provided during the creation of the dm-verity volume
has to be secure and thus in-kernel validation implemented here will be
used before we trust the root hash and allow the block device to be
created.
The signature being provided for verification must verify the root hash
and must be trusted by the builtin keyring for verification to succeed.
The hash is added as a key of type "user" and the description is passed
to the kernel so it can look it up and use it for verification.
Adds CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG which can be turned on if root
hash verification is needed.
Kernel commandline dm_verity module parameter 'require_signatures' will
indicate whether to force root hash signature verification (for all dm
verity volumes).
Signed-off-by: Jaskaran Khurana <jaskarankhurana@linux.microsoft.com>
Tested-and-Reviewed-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Mickaël Salaün
Jaskaran Khurana