Re: [RFC PATCH v3 5/5] selinux: introduce kdbus access controls

Paul Moore
2015-10-09T20:29:27Z

On Friday, October 09, 2015 04:17:17 PM Stephen Smalley wrote:
> On 10/09/2015 11:39 AM, Paul Moore wrote:
> > On Friday, October 09, 2015 11:05:58 AM Stephen Smalley wrote:
> >> On 10/07/2015 07:08 PM, Paul Moore wrote:
> >>> +static int selinux_kdbus_init_inode(struct inode *inode,
> >>> + const struct cred *creds)
> >>> +{
> >>> + struct inode_security_struct *isec = inode->i_security;
> >>> + u32 sid = cred_sid(creds);
> >>> +
> >>> + /* XXX - this is very simple, e.g. no transitions, no special object
> >>> + * class, etc. since this inode is basically an IPC socket ...
> >>> + * however, is this too simple? do we want transitions? if
we
> >>> + * do, we should do the transition in kdbus_node_init() and
not
> >>> + * here so that endpoint is labeled correctly and not just
this
> >>> + * inode */
> >>> +
> >>> + isec->inode = inode;
> >>> + isec->task_sid = sid;
> >>> + isec->sid = sid;
> >>> + isec->sclass = SECCLASS_FILE;
> >>> + isec->initialized = 1;
> >>
> >> These are used for files exposed in the filesystem namespace, unlike
> >> sockets (sockfs can't be mounted by userspace, and the socket objects
> >> themselves have their own class, so there is no ambiguity). Currently
> >> the only such files that are labeled with the same SID as the associated
> >> task are /proc files. So if we label the kdbusfs files with the same
> >> SID, then you can't allow read/write to kdbusfs nodes owned by another
> >> task without also exposing its /proc/pid files in the same manner.
> >> Doubt we want that. Probably should compute a transition from the task
> >> SID and the kdbusfs SID.
> >
> > Okay, that was one of my main concerns; your suggestion makes sense to me.
> >
> > I'm also thinking that is we do a file transition using the task label and
> > the kdbusfs superblock label we should limit it to just the inode label
> > and not the kdbus endpoint as I suggested in the comment above (the bit
> > about kdbus_node_init()), yes?
>
> Yes, it only needs to be done for the inode, not the endpoint.
> Analogy with sockets: Can I write to the socket file (kdbus file) bound
> to the socket (endpoint)? Can I connectto/sendto the socket (endpoint)?

Yep.

I'll make these changes and work to get another draft out next week.

--
paul moore
security @ redhat