Re: [GIT PULL] selinux/selinux-pr-20250323

[Casey Schaufler <casey@schaufler-ca.com>]

On 3/27/2025 1:59 AM, Jeffrey Vander Stoep wrote:
> On Thu, Mar 27, 2025 at 5:10 AM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>> On Wed, 26 Mar 2025 at 20:28, Thiébaud Weksteen <tweek@google.com> wrote:
>>> That is not quite right. If you look at commit 581dd6983034 [1], when
>>> a firmware is about to be loaded, the kernel credentials are used.
>> Ahh, that's good, at least there's no "random state" to check.
>>
>> But it does still mean that the security check is pointless - there
>> aren't any other credentials that would validly be used for firmware
>> loading, so what was the point of checking them again?
> The value here isn't so much about checking the source context
> "kernel", but rather about checking the target context and enforcing
> that firmware can only come from trusted filesystems. So even a
> compromised privileged process that sets firmware_class.path cannot
> cause the kernel to load firmware from an arbitrary source.
>
> These restrictions reduce our reliance on (1) individual component
> manufacturers (e.g. NFC chips) implementing signature verification
> correctly in their firmware loading procedure, or (2) the fallout for
> the Android ecosystem if a component manufacturer's private key leaks
> because even firmware signed with the leaked key will not be trusted
> if it doesn't come from the trusted filesystem signed by the Android
> device manufacturer. Leaked keys is a very real problem. Restrictions
> like those added here can significantly reduce the severity of such
> incidences.
>
> With this, we can write policies for Android devices that enforce that
> firmware only comes from trusted filesystems. For example:
>
> allow kernel vendor_file:system firmware_load;

Am I missing something, or isn't that what loadpin is for?