svn commit: r359797 - in head/sys: net netinet netinet6

[Ian Lepore]

On Sat, 2020-04-11 at 13:02 -0700, Conrad Meyer wrote:
> Hi Alexander,
> 
> On Sat, Apr 11, 2020 at 12:37 AM Alexander V. Chernikov
> <melifaro at freebsd.org> wrote:
> > 
> > Author: melifaro
> > Date: Sat Apr 11 07:37:08 2020
> > New Revision: 359797
> > URL: https://svnweb.freebsd.org/changeset/base/359797
> > 
> > Log:
> >   Remove per-AF radix_mpath initializtion functions.
> > 
> >   Split their functionality by moving random seed allocation
> >    to SYSINIT and calling (new) generic multipath function from
> >    standard IPv4/IPv5 RIB init handlers.
> > ...
> > --- head/sys/net/radix_mpath.c  Sat Apr 11 07:31:16
> > 2020        (r359796)
> > +++ head/sys/net/radix_mpath.c  Sat Apr 11 07:37:08
> > 2020        (r359797)
> > @@ -290,38 +290,18 @@ rtalloc_mpath_fib(struct route *ro, uint32_t
> > hash, u_i
> > ...
> > +static void
> > +mpath_init(void)
> >  {
> > -       struct rib_head *rnh;
> > 
> >         hashjitter = arc4random();
> > -       if (in6_inithead(head, off, fibnum) == 1) {
> > -               rnh = (struct rib_head *)*head;
> > -               rnh->rnh_multipath = 1;
> > -               return 1;
> > -       } else
> > -               return 0;
> >  }
> > +SYSINIT(mpath_init, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY, mpath_init,
> > NULL);
> 
> This is pretty early in boot to be asking for random numbers.  We
> don't have interrupts yet, for example.  If the system doesn't have a
> saved /boot/entropy loaded (PPC, or installer, or some other embedded
> system perhaps), we will either deadlock boot or get not especially
> random numbers here (depending on availability behavior of arc4random
> — currently we err on the side of low quality random numbers).
> 
> If this number is predictable to an attacker, is it easier to DoS the
> system?  Do we need the random number before userspace starts?  (I
> would imagine networking does not really start chatting with remote
> hosts prior to userspace boot, but this is just a guess.)
> 
> Best,
> Conrad
> 

I believe the earliest use of networking during boot is for mounting
the rootfs using nfs.  So SI_SUB_ROOT_CONF-1 might be good.

-- Ian