Re: [PATCH v4 00/14] security: digest_cache LSM

Paul Moore
2024-06-19T15:49:18Z

On Wed, Jun 19, 2024 at 3:59 AM Roberto Sassu
<roberto.sassu@huaweicloud.com> wrote:
> On Tue, 2024-06-18 at 19:20 -0400, Paul Moore wrote:
> > On Mon, Apr 15, 2024 at 10:25 AM Roberto Sassu
> > <roberto.sassu@huaweicloud.com> wrote:
> > >
> > > From: Roberto Sassu <roberto.sassu@huawei.com>
> > >
> > > Integrity detection and protection has long been a desirable feature, to
> > > reach a large user base and mitigate the risk of flaws in the software
> > > and attacks.
> > >
> > > However, while solutions exist, they struggle to reach the large user
> > > base, due to requiring higher than desired constraints on performance,
> > > flexibility and configurability, that only security conscious people are
> > > willing to accept.
> > >
> > > This is where the new digest_cache LSM comes into play, it offers
> > > additional support for new and existing integrity solutions, to make
> > > them faster and easier to deploy.
> > >
> > > The full documentation with the motivation and the solution details can be
> > > found in patch 14.
> > >
> > > The IMA integration patch set will be introduced separately. Also a PoC
> > > based on the current version of IPE can be provided.
> >
> > I'm not sure we want to implement a cache as a LSM. I'm sure it would
> > work, but historically LSMs have provided some form of access control,
> > measurement, or other traditional security service. A digest cache,
> > while potentially useful for a variety of security related
> > applications, is not a security service by itself, it is simply a file
> > digest storage mechanism.
>
> Uhm, currently the digest_cache LSM is heavily based on the LSM
> infrastructure:

I understand that, but as I said previously, I don't believe that we
want to support a LSM which exists solely to provide a file digest
cache. LSMs should be based around the idea of some type of access
control, security monitoring, etc.

Including a file digest cache in IMA, or implementing it as a
standalone piece of kernel functionality, are still options. If you
want to pursue this, I would suggest that including the digest cache
as part of IMA would be the easier of the two options; if it proves to
be generally useful outside of IMA, it can always be abstracted out to
a general kernel module/subsystem.

--
paul-moore.com