Cellular Network Infrastructure » Core Network (CN) » OsmoMSC

"BSSMAP CIPHER MODE REQUEST" doesn't seem to exist.
You probably meant BSSMAP CIPHER MODE CMD instead?

This proposed patch adds a TTCN3 test for this issue:
https://gerrit.osmocom.org/#/c/osmo-ttcn3-hacks/+/12332

At present the MSC responds with a LU reject after receiving a CIPHER MODE COMPLETE with an invalid cipher.
The test looks for this LU reject and passes when it is received.

Is this the correct behaviour? Should the MSC respond in some other way?

re "command" vs "request": the things can be named differently on the layers, e.g. there's the Cipher Mode Command on BSSMAP, but Cipher Mode Request on 04.08...

The above test has been merged. neels says the current osmo-msc behaviour which the test checks for (expect a LU reject) is correct as it is.
Can this issue be closed?

this issue says that osmo-msc should check that the cipher matches the request,
and the issue implies that osmo-msc doesn't check that.
If it turns out that osmo-msc does indeed reject a mismatch already, that's nice.

How about the side thing there, if the chosen algorithm is not provided in the response?
I guess osmo-msc should accept then. Does it? (If they mismatch then, the ciphered data will not be decipherable anyway.)
Maybe duplicate the test for that situation.

See https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/12347 for additional tests,
and https://gerrit.osmocom.org/c/osmo-msc/+/12349 for related osmo-msc changes.

The tests are not complete yet -- they pass both with and without the osmo-msc changes
because they don't verify which cipher the MSC really ends up using. Could you suggest
a good way of doing that?

the patch back then was not merged. neels: Is this still an issue in the "new msc" ?

IIRC there were some problems in those patches.
Current OsmoMSC doesn't verify the chosen cipher AFAIR, only stores it. So it should still be an open issue.