13 Jul
2019
13 Jul
'19
8:18 p.m.
Hi Sukchan and list,
I'm currently reading the MME code and I'm having some trouble understanding the handling of the uplink counter for NAS security.
I only see mme_ue->ul_count.i32 ever being set to '0' when a new security context is used. But I don't see it ever being incremented? I only see ul_count.sqn incremented, but then the nas_mac_calculate() always gets ul_count.i32 passed as input.
So I'm somehow not understanding how the MAC can ever verify on any uplink message beyond/after the first one which establishes a new security context.
What am I missing? Thanks for your insight!
--
- Harald Welte laforge@gnumonks.org http://laforge.gnumonks.org/
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"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)