On Tue, 2012-07-24 at 02:01 -0700, Alex Netes wrote:
> Hi Jim,
>
> On 17:55 Mon 25 Jun , Jim Foraker wrote:
> > If mkeys are protected, sweep should always be enabled and
> > set to an interval < the lease timeout, to ensure a missed trap
> > doesn't lead to mkey exposure.
>
> This is a minimal requirement, but it might not be enough to avoid mkey
> exposure completely. In noisy fabrics, sweep duration may take more
> time than sweep interval (and lease timeout), so theoretically we can still
> get mkey exposure. However, I don't know how can we completely avoid this.
I thought about this a bit while writing the patch, and
fundamentally we can't. Particularly if we assume that an attacker can
wield some control over the amount of time a sweep takes, which I think
is very reasonable.
The primary defense against mkey exposure is the TrapRepress that
the SM sends in response to mkey violation traps, which will reset the
lease timer. Setting sweep interval < mkey timeout just provides some
complementary backup in case a Trap/TrapRepress somehow gets missed.
Fundamentally however, if an mkey timeout is set, an attacker who
knows how to confuse/DOS/crash the SM will always be able to recover
keys on the subnet.
Jim
>
> >
> > Signed-off-by: Jim Foraker <[email protected]>
> > ---
> > opensm/osm_subnet.c | 20 ++++++++++++++++++++
> > 1 file changed, 20 insertions(+)
> >
> > diff --git a/opensm/osm_subnet.c b/opensm/osm_subnet.c
> > index ddee955..3f336d8 100644
> > --- a/opensm/osm_subnet.c
> > +++ b/opensm/osm_subnet.c
> > @@ -1502,6 +1502,26 @@ int osm_subn_verify_config(IN osm_subn_opt_t *
> > p_opts)
> > "instead\n", p_opts->m_key_protect_bits, 2);
> > p_opts->m_key_protect_bits = 2;
> > }
> > + if (p_opts->m_key_protect_bits && p_opts->m_key_lease_period) {
> > + if (!p_opts->sweep_interval) {
> > + log_report(" Sweep disabled with protected mkey "
> > + "leases in effect; re-enabling sweeping "
> > + "with interval %u\n",
> > + cl_ntoh16(p_opts->m_key_lease_period) - 1);
> > + p_opts->sweep_interval =
> > + cl_ntoh16(p_opts->m_key_lease_period) - 1;
> > + }
> > + if (p_opts->sweep_interval >=
> > + cl_ntoh16(p_opts->m_key_lease_period)) {
> > + log_report(" Sweep interval %u >= mkey lease period "
> > + "%u. Setting lease period to %u\n",
> > + p_opts->sweep_interval,
> > + cl_ntoh16(p_opts->m_key_lease_period),
> > + p_opts->sweep_interval + 1);
> > + p_opts->m_key_lease_period =
> > + cl_hton16(p_opts->sweep_interval + 1);
> > + }
> > + }
> >
> > if (p_opts->root_guid_file != NULL) {
> > FILE *root_file = fopen(p_opts->root_guid_file, "r");
> > --
> > 1.7.9.2
> >
> > --
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