From: guido@trentalancia.com (Guido Trentalancia)
Date: Thu, 10 Aug 2017 19:30:11 +0200
Subject: [refpolicy] [PATCH v2 1/1] Add module_load permission to self
 when loading modules is allowed
In-Reply-To: <20170810151142.GA29463@julius.enp8s0.d30>
References: <20170808065956.10200-1-nicolas.iooss@m4x.org>
	<142b7928-8d41-f552-a471-73cb2707832a@ieee.org>
	<1502384990.5184.2.camel@trentalancia.com>
	<20170810151142.GA29463@julius.enp8s0.d30>
Message-ID: <1502386211.5184.4.camel@trentalancia.com>
To: refpolicy@oss.tresys.com
List-Id: refpolicy.oss.tresys.com

Hello and thanks for getting back.

On Thu, 10/08/2017 at 17.11 +0200, Dominick Grift via
refpolicy wrote:
> On Thu, Aug 10, 2017 at 07:09:50PM +0200, Guido Trentalancia via
> refpolicy wrote:
> > On Tue, 08/08/2017 at 20.03 -0400, Chris PeBenito via
> > refpolicy wrote:
> > > On 08/08/2017 02:59 AM, Nicolas Iooss via refpolicy wrote:
> > > > When a program uses init_module() to load a module, the kernel
> > > > checks
> > > > for system:load_module permission in the process type [1].
> > > > For example when systemd loads ip_tables modules (since
> > > > https://github.com/systemd/systemd/commit/1d3087978a8ee23107cb6
> > > > 4aa5
> > > > 5ca97aefe9531e2),
> > > > the following AVC denial gets reported:
> > > > 
> > > >     avc:  denied  { module_load } for  pid=1 comm="systemd"
> > > >     scontext=system_u:system_r:init_t
> > > > tcontext=system_u:system_r:init_t
> > > >     tclass=system permissive=1
> > > > 
> > > > [1] The relevant kernel code is
> > > > selinux_kernel_module_from_file()
> > > > in
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.
> > > > git/
> > > > tree/security/selinux/hooks.c?h=v4.11#n3836
> > > > 
> > > >     /* init_module */
> > > >     if (file == NULL)
> > > >         return avc_has_perm(sid, sid, SECCLASS_SYSTEM,
> > > >                     SYSTEM__MODULE_LOAD, NULL);
> > > > 
> > > > In this code, both source and target SIDs are current_sid().
> > > > ---
> > > >  policy/modules/kernel/kernel.te | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/policy/modules/kernel/kernel.te
> > > > b/policy/modules/kernel/kernel.te
> > > > index 424a4b511262..e2d3073b4260 100644
> > > > --- a/policy/modules/kernel/kernel.te
> > > > +++ b/policy/modules/kernel/kernel.te
> > > > @@ -474,6 +474,7 @@ optional_policy(`
> > > > 
> > > >  if( ! secure_mode_insmod ) {
> > > >  	allow can_load_kernmodule self:capability sys_module;
> > > > +	allow can_load_kernmodule self:system module_load;
> > > > 
> > > >  	files_load_kernel_modules(can_load_kernmodule)
> > > 
> > > Merged.
> > 
> > Hello.
> > 
> > Sorry for my late reply...
> > 
> > I believe this only applies to systemd.
> 
> It doesnt. it applies to systems that have kernel modules compressed.

Confirmed.

> > So, is there any reason why it hasn't been enclosed in the
> > appropriate
> > ifdef(init_systemd) ?

Regards,

Guido