[RFC PATCH v5 1/1] Add dm verity root hash pkcs7 sig validation.

[Mike Snitzer]

On Wed, Jun 19 2019 at  3:10pm -0400,
Jaskaran Khurana <jaskarankhurana at linux.microsoft.com> wrote:

> The verification is to support cases where the roothash 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.
> 
> Kernel commandline parameter will indicate whether to check (only if 
> specified) or force (for all dm verity volumes) roothash signature 
> verification.
> 
> Kernel commandline: dm_verity.verify_sig=1 or 2 for check/force root hash
> signature validation respectively.
> 
> Signed-off-by: Jaskaran Khurana <jaskarankhurana at linux.microsoft.com>

Milan and/or others: could you please provide review and if you're OK
with this patch respond accordingly?

Thanks,
Mike