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Neels Hofmeyr nhofmeyr at sysmocom.deOn Wed, Apr 18, 2018 at 01:21:27PM +0000, Bruckner Jan (ETAS-SEC/ECT-Mu) wrote: > Hi, > > I migrated my setup to the new Network In The Box configuration with separated components (from latest, not nightly). I tested whether the described issue with A5/3 is resolved, but it still does not work. Though, the behavior has changed. > > In the old setup a Ciphering Mode Command for A5/3 was sent, but a Ciphering Mode Complete was never received. Probably, what was happening is the following: > > The details there are that the Ciphering Mode Command is asking to start ciphering on the air, and the Ciphering Mode Complete is already sent > ciphered. > > So it might be received, but the received data may be discarded as gibberish. > > In the new setup not even the Ciphering Mode Command is sent to the MS. Commented in OS#3043 on the reason why A5/3 gets rejected. I'm continuing discussion there instead of duplicating on the mailing list. > Instead the BSC sends a Cipher Mode Reject to the MSC, if I am reading the logs correctly: > > <000a> a_iface_bssap.c:629 Rx MSC DT1 BSSMAP CIPHER MODE REJECT > <000a> a_iface_bssap.c:453 BSC sends cipher mode reject (conn_id=65) This bit confuses me: how can the BSC reject a Cipher Mode if the MSC never sent a Cipher Mode Command? The BSC would send a Cipher Mode Reject if it finds the algorithm requested by the MSC not supported in the osmo-bsc.cfg. Maybe we also do that if A5/0 (no encryption) is not listed in osmo-bsc.cfg?? > <000a> a_iface_bssap.c:457 Cause code is missing -- discarding message! Interesting. I have identified https://osmocom.org/issues/3186 and https://osmocom.org/issues/3187 > A5/1 continues to work without any problems. The root cause for all of this is most probably above missing-classmark problem, but it turns out to be a good thing that it helped us uncover a bunch of errors in error handling. Thanks for your reports! ~N -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/openbsc/attachments/20180419/7438f34b/attachment.bin>