Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

On 8/13/20 10:58 AM, Stephen Smalley wrote:
> On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
> <nramas@xxxxxxxxxxxxxxxxxxx> wrote:
> > On 8/13/20 10:42 AM, Stephen Smalley wrote:
> >
> > > > diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> > > > new file mode 100644
> > > > index 000000000000..f21b7de4e2ae
> > > > --- /dev/null
> > > > +++ b/security/selinux/measure.c
> > > > @@ -0,0 +1,204 @@
> > > > +static int selinux_hash_buffer(void *buf, size_t buf_len,
> > > > +                   void **buf_hash, int *buf_hash_len)
> > > > +{
> > > > +    struct crypto_shash *tfm;
> > > > +    struct shash_desc *desc = NULL;
> > > > +    void *digest = NULL;
> > > > +    int desc_size;
> > > > +    int digest_size;
> > > > +    int ret = 0;
> > > > +
> > > > +    tfm = crypto_alloc_shash("sha256", 0, 0);
> > > > +    if (IS_ERR(tfm))
> > > > +        return PTR_ERR(tfm);
> > > Can we make the algorithm selectable via kernel parameter and/or writing
> > > to a new selinuxfs node?
> >
> > I can add a kernel parameter to select this hash algorithm.
>
> Also can we provide a Kconfig option for the default value like IMA does?

Would we need both - Kconfig and kernel param?

The other option is to provide an IMA function to return the current 
hash algorithm used for measurement. That way a consistent hash 
algorithm can be employed by both IMA and the callers. Would that be better?

 -lakshmi