Encryption branch / BSC-MSC split

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Sylvain Munaut 246tnt at gmail.com
Wed Jun 9 09:45:58 UTC 2010


Hi,


> 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).

Ok, when I look back at the code, most of it was gsm_04_08.c only. But
not all of it. I needed some change in the paging system because once
a paging succeded, I needed to be able to 'inject' myself before the
callback was called. (So that I could secure the channel in the
meantime).


>        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.

One thing that makes a 'transparent' implementation tricky is that a
CIPHER MODE COMMAND is considered to be an implicit CM SERVICE ACCEPT.
So what the code did it to offer a simple function to call whenever
you wanted to secure the channel and offer a callback with the result.

    Sylvain




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