Re: [PATCH v18 16/21] fsverity: expose verified fsverity built-in signatures to LSMs

Paul Moore
2024-05-14T19:55:13Z

On Fri, May 3, 2024 at 6:32 PM Fan Wu <wufan@linux.microsoft.com> wrote:
>
> This patch enhances fsverity's capabilities to support both integrity and
> authenticity protection by introducing the exposure of built-in
> signatures through a new LSM hook. This functionality allows LSMs,
> e.g. IPE, to enforce policies based on the authenticity and integrity of
> files, specifically focusing on built-in fsverity signatures. It enables
> a policy enforcement layer within LSMs for fsverity, offering granular
> control over the usage of authenticity claims. For instance, a policy
> could be established to permit the execution of all files with verified
> built-in fsverity signatures while restricting kernel module loading
> from specified fsverity files via fsverity digests.
>
> The introduction of a security_inode_setintegrity() hook call within
> fsverity's workflow ensures that the verified built-in signature of a file
> is exposed to LSMs. This enables LSMs to recognize and label fsverity files
> that contain a verified built-in fsverity signature. This hook is invoked
> subsequent to the fsverity_verify_signature() process, guaranteeing the
> signature's verification against fsverity's keyring. This mechanism is
> crucial for maintaining system security, as it operates in kernel space,
> effectively thwarting attempts by malicious binaries to bypass user space
> stack interactions.
>
> The second to last commit in this patch set will add a link to the IPE
> documentation in fsverity.rst.
>
> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@linux.microsoft.com>

Eric, are you okay with the fs-verity patches in v18? If so, it would
be nice to get your ACK on this patch at the very least.

While it looks like there may be a need for an additional respin to
address some new/different feedback from the device-mapper folks, that
shouldn't affect the fs-verity portions of the patchset.

--
paul-moore.com