[Openbts-discuss] OpenBTS-UMTS auth issues

[Sipos C. <sip...@kv...>]

Dear Michael & list,

Finally I figured it out how to add subscribers to the database:

./nmcli.py sipauthserve subscribers create "Test-1" IMSI901550000000000 1234567 d360c2591de1bf61a11014c33d012246

The subscriber is created with the proper data, but when i try to register with a UE, I got the following:

Dec 10 12:37:50 TH-SDR1 openbts-umts: ERR 2982665024 12:37:50.9 Sgsn.cpp:603:sendAuthenticationRequest: SGSN:No Kc found for MS in TMSI table during Attach procedure UE#7 URNTI=2a23 stCELL_FACH imsi=901550000000000

When I check the database, the subscriber is in there, but the Kc, SRES and RAND fields are empty.

I also checked the OpenBTS-UMTS-TMSI table and the subscribers are there, but no Kc there neither.

At this point it is safe to say that the Kc, SRES and RAND values are not generated in the subscriber database and therefor not copied to the TMSI table and because of that the Auth process is going to fail. I checked the comp128 binary is working and it is in its correct place, the link to this file is also correctly configured. I also tried to reattach, restart openbts-umts and the sipatuhserve multiple times, but the Kc, SRES and RAND values are not there.

I am using a Sysmocom UMTS test sim (USIM). I understand that the current implementation is only doing GSM level auth and no ciphering at all (especialy not supporting the USIMs Milenage protocol), but still: it is an important question if USIMs can be used to pass the current implementation of OpenBTS-UMTS in some sort of compatibility or fallback mode, or not. It would be lovely to clarify this.

You probably know about this, but Ben already impleneted Milenage capability in the OpenLTE project, probably it is not that hard to take that and use it in OpenBTS-UMTS. That implementation already wokrs, I can pass both auth and security mode command steps successfully with my test USIM.

Regards,
Csaba