[srslte-users] RRC Security Mode Command Failure

[David Rupprecht]

Hi Pedro,

the issue was that the NAS uplink count is 1 when the key enodeb is
computed, but the NAS upnlink count should be 0. I fixed the problem and
issued a pull request https://github.com/srsLTE/srsLTE/pull/172

Best regards,
David

On 27.04.2018 14:11, David Rupprecht wrote:
> Hi Pedro,
> 
> finally I got some time to record the cases. I attach you the log and
> pcap files. In the first folder you find the trace of case 1 and 2. In
> the second folder you find the traces of the 3 case. You are right, it
> fails at the 3 case. I guess the k_enb is out of sync.
> 
> Best regards,
> David
> 
> On 05.04.2018 11:53, Pedro Alvarez wrote:
>> Hi David,
>>
>> Thanks for reporting, I'll look into this.
>> You're probably right, it's probably  a mis-match between the UE's and
>> the EPC's UL NAS COUNT.
>>
>> Could you try to do the following, just so I can be sure the problem
>> is what I think it is:
>>
>>   1 - Force an IMSI attach. You should be able to do this by taking
>> out the SIM and putting it in again, or by putting the . (This should
>> work fine.)
>>   2 - Do a GUTI attach without restarting the EPC. You can do this by
>> going in and out of  flight mode. (This should still work fine.)
>>   3 - Re-start the eNB and the EPC and try the GUTI attach again.
>> (This is probably where it's failing.)
>>
>> Regards,
>> Pedro
>>
>> On Wed, Apr 4, 2018 at 1:45 PM, David Rupprecht <david.rupprecht at rub.de> wrote:
>>> Hi,
>>>
>>> I'm using srsepc and srsenb in the latest version (1803). When trying to
>>> connect a commercial UE with a programmable SIM card to the enB and EPC,
>>> I get a RRC Security Mode Failure from the UE. My first guess, was that
>>> the key_enb was not correctly transmitted, but this is not the case.
>>> Maybe the k_enb is not correctly derived (NAS_UL_COUNT?), but I have not
>>> checked that. Do you have any suggestions?
>>>
>>> With an older version of the srsEPC and the latest eNodeB the attach
>>> works without any problems.
>>>
>>> I have attached the logs.
>>>
>>>
>>> Best regards,
>>> David
>>> --
>>> M.Sc. David Rupprecht
>>>
>>> Ruhr-University Bochum
>>> Research Group Information Security
>>> Universitätsstraße 150
>>> ID 2/130
>>> 44780 Bochum / Germany
>>>
>>> Phone: +49 234 / 32 - 23508
>>> Web: www.infsec.rub.de
>>>
>>> _______________________________________________
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>>> srslte-users at lists.softwareradiosystems.com
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>>>
> 
> 
> 
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-- 
M.Sc. David Rupprecht

Ruhr-University Bochum
Research Group Information Security
Universitätsstraße 150
ID 2/130
44780 Bochum / Germany

Phone: +49 234 / 32 - 23508
Web: www.infsec.rub.de