[PATCH 04/16] integrity: Allow digital signature verification with a given keyring ptr

[Mimi Zohar]

On Tue, 2013-09-10 at 17:44 -0400, Vivek Goyal wrote:
> Currently digital signature verification code assumes that it can be
> used only with 3 keyrings. IMA, EVM and MODULE keyring. Provide another
> variant where one can pass in a pointer to keyring (struct key *), and
> integrity code can try to find key in that keyring and verify signature.
> 
> This will be useful at two places.
> 
> - elf binary loader can use system keyring and call into integrity
>   subsystem for signature verification.
> - In later patches I am extending keyctl() to allow signature of
>   a user buffer against specified keyring. That logic can make use
>   of this code too.
> 
> Signed-off-by: Vivek Goyal <vgoyal at redhat.com>

My original thought was to use the system keyring, in lieu of having the
multiple keyrings.  Unfortunately, the scope of a key's usage needs to
be limited, which can not be done safely with a single keyring.

Mimi