Re: [PATCH 1/1] Implement cryptographic initialization control.

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Tue, Apr 07, 2020 at 04:20:39AM -0500, Dr. Greg wrote:
> This patch introduces the ability of the platform owner to
> implement cryptographically controlled enclave initialization
> policy.  This functionality provides the platform owner with the
> ability to use the identity modulus signature of an enclave
> signer (SHA256 hash of the modulus of the signing key) to gate
> access to enclave initialization, rather then simply relying
> on discretionary access controls that are applied to the SGX
> relevant device driver nodes.
> 
> The following policy functionality is introduced in this commit:
> 
> 1.) Control over which keys are allowed to initialize an
> enclave.
> 
> 2.) Control over which keys are allowed to implement launch
> enclaves.
> 
> 3.) Control over which keys are allowed to initialize enclaves
> that have access to the PROVISION_KEY attribute.
> 
> For each policy type a plurality of key signatures are allowed.
> 
> Absent an intent by the platform owner/administrator to use
> cryptographic initialization policies, this functionality does
> not change the standard behavior of the driver, which is to
> allow any enclave presented to the driver to be initialized.
> 
> Cryptographic initialization policy is accessed through the
> following three pseudo-files that are implemented by this patch:
> 
> /sys/kernel/security/signing_keys
> 
> /sys/kernel/security/launch_keys
> 
> /sys/kernel/security/provisioning_keys
> 
> Policy keys are registered with the driver by writing the identity
> modulus signature to these files in simple hexadecimal format, ie:
> 
> 0000000000000000000000000000000000000000000000000000000000000000
> 
> The current list of policy keys can be displayed by reading the
> contents of the pseudo-files.
> 
> In addition to a key signature, the following keywords are
> accepted as valid entries for a policy file:
> 
> clear
> 
> lock
> 
> The 'clear' keyword causes all existing entries in a policy list
> to be deleted.
> 
> The 'lock' keyword causes any further modifications or access to
> a policy list to be denied.
> 
> All of the policy code is implemented in a single file, policy.c,
> with minimal impact to the driver at large.  Since the calculation
> of the identity modulus signature needed to program a launch control
> register is effectively a policy decision, the code to compute the
> signature was moved from the ioctl.c file to the policy.c file.
> 
> In order to support a plurality of launch keys the code that
> loops over initialization attempts was pushed downward into a new
> function that is named as follows:
> 
> sgx_try_init()
> 
> Primarily to avoid excessive indentation that would otherwise be
> needed in the sgx_encl_init() function.
> 
> Signed-off-by: Dr. Greg Wettstein <greg@enjellic.com>

Sorry, would have responded earlier but forgot to check the
folder where fdm pulls mailing list email's. For shorter
latency I recommend CC'ing.

This comes down to the fact that we are not doing anything
that would prevent doing something similar post upstreaming
(e.g. add a new ioctl for token version of EINIT or whatever)
but is not something that we want to include right now. It is
an additional feature (like other features e.g. virtualization)

/Jarkko