Re: [RFC PATCH 1/1] kernel: Add SELinux SCTP protocol support

[Richard Haines <richard_c_haines@btinternet.com>]

On Fri, 2016-12-16 at 11:40 -0200, Marcelo Ricardo Leitner wrote:
> On Wed, Dec 14, 2016 at 02:01:35PM +0000, David Laight wrote:
> > From: Richard Haines
> > > Sent: 14 December 2016 13:40
> > > Add SELinux support for the SCTP protocol. The SELinux-sctp.txt
> > > document
> > > describes how the patch has been implemented with an example
> > > policy and
> > > tests using lkstcp-tools.
> > 
> > ...
> > > +SCTP_SOCKOPT_BINDX_ADD - Allows additional bind addresses to be
> > > +                         associated after (optionally) calling
> > > bind(2)
> > > +                         if given the "bind_add" permission.
> > 
> > Does restricting bindx make any sense at all?
> > The only addresses than can be specified are those of local
> > interfaces.
> > If bindx isn't called then the default is to include the addresses
> > of
> > all local interfaces.
> > So bindx only actually removes local addresses, it doesn't add
> > them.
> 
> You could bind the socket while on a priviledged process and then
> drop
> the priviledges, like daemons do for binding on lower ports. Then the
> application wouldn't be able to bind on another address that it's not
> expected to.
> 
>   Marcelo
> 

It appears from Marcelo's comments that keeping bindx_add/bindx_rem
would be useful. However I will rename the permissions to a single
permission of "bindx_addr" if that's okay.

Any more sctp specific comments gratefully received (SELinux/LSM as
well of course). I plan to issue an updated patch mid-late Jan '17.

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