Encryption branch / BSC-MSC split
zecke at selfish.org
Wed Jun 9 10:56:46 CEST 2010
On 06/09/2010 03:43 PM, Sylvain Munaut wrote:
Hi both of you,
> I guess I must read on on what exactly is MSC domain and what is BSC
> domain, so far I mostly focused on 04.08 without paying attention to
> who is supposed to handle what ...
I have not read the code but the split is actual quite easy. Most of it
is not in the BSC domain at all. The MSC will send a GSM08.08 message
called Cipher Mode Command. It contains the key we will embed into the
RSL message. E.g. this is when the subscriber has been authenticated
(e.g. the IMSI still in the VLR, or the TMSI making sense).
The Authentication Request is simply wrapped in DTAP and there is
nothing special with it from the BSC point of view. Actually everything
that is needed for the BSC/MSC split is already inside the GSM 04.08
utils, so anything you put into gsm_04_08.c does not create a problem...
(at one point i will replace the gsm48_sendmsg with bsc_dtap_send).
In regard to the MSC side... what will/should change is:
1.) no ref counting for lchan (maybe I start/finish it today)
2.) no direct paging calls, it should go through the subscriber
code I had already checked-in..
3.) better lchan management and this is where encyrption comes
in. When we have a new connection, we should run it through
auth first... and then hand it to the subsystem.
please poke me if that does not make sense to you...
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