Base Jumping Attacking the GSM baseband and base station - - PowerPoint PPT Presentation

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Base Jumping Attacking the GSM baseband and base station - - PowerPoint PPT Presentation

Base Jumping Attacking the GSM baseband and base station grugq@coseinc.com Tuesday, 20 July 2010 Overview GSM Base Station Base Band Conclusion 2 Tuesday, 20 July 2010 GSM: The Protocol 3 Tuesday, 20 July 2010 Documents


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SLIDE 1

Base Jumping

Attacking the GSM baseband and base station grugq@coseinc.com

Tuesday, 20 July 2010

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SLIDE 2

Overview

❖GSM ❖Base Station ❖Base Band ❖Conclusion

2 Tuesday, 20 July 2010

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SLIDE 3

GSM: The Protocol

3 Tuesday, 20 July 2010

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Documents

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❖Dozens of docs ❖Thousands of pages ❖Important one (defines L3)

❖GSM 04 08

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SLIDE 5

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Logical Channels

Broadcast Channels (BCH) Broadcast Control Channel (BCCH) Frequency Correction Channel (FCCH) Synchronization Channel (SCH) Cell Broadcast Channel (CBCH)

Tuesday, 20 July 2010

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Logical Channels, cont.

❖ Common Control Channels (CCCH)

Paging Channel (PCH) Random Access Channel (RACH) Access Grant Channel (AGCH)

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Logical Channels, cont.

Standalone Dedicated Control Channel (SDCCH) Associated Control Channel (ACCH) Fast Associated Control Channel (FACCH) Slow Associated Control Channel (SACCH)

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GSM Channels

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❖Opening a channel is slow

❖Can take seconds

❖Specific channels for specific uses

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Opening a channel

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RACH

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RACH AGCH

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RACH AGCH LCH

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PCH

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RACH PCH

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RACH PCH AGCH

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RACH PCH AGCH LCH

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14

MS BTS BTS BSC MSC ARFCN

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Base Transceiver Station BTS Base Station Controller BSC Mobile Station Controller MSC Mobile Station MS Base Station Sub-System BSS

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MS BSS MSC HLR VLR

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Mobile Identifiers

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IMSI

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IMSI IMEI

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GSM Attacks

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RACHell

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❖Request channel allocation ❖Flood the BSS with requests ❖First announced by Dieter Spaar at

DeepSec

❖Prevent everyone from using that cell

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RACHell

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RACHell

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RACHell

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RACHell

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RACHell

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RACHell

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?

RACHell

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Our Target

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Demo - RACHell

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IMSI Flood

❖Send IMSI ATTACH messages ❖pre-authentication ❖Overload the HLR/VLR infrastructure ❖Prevent everyone using the network

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IMSI Flood

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IMSI Flood

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IMSI Flood

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IMSI Flood

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IMSI Flood

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IMSI Flood

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IMSI Flood

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How hard to get an IMSI?

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IMSI DETACH

❖Send multiple Location Update

Requests including a spoofed IMSI

❖Unauthenticated

❖Prevent SIM from receiving calls and

SMS

❖Discovered by Sylvain Munaut

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IMSI DETACH

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IMSI DETACH

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IMSI DETACH

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IMSI DETACH

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IMSI DETACH

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IMSI DETACH

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IMSI DETACH

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Baseband Fuzzing

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= +

How to make a smartphone

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Two separate computers

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Two separate computers

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Baseband

❖Controls the radio ❖Separate CPU and code base ❖RTOS ❖Written in C ❖Typically legacy code base (decades)

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Coseinc GSM FuzzFarm

❖OpenBTS based fuzzer delivery

engine

❖Targetting

❖iPhone ❖HTC (Android) ❖Palm Pre ❖Blackberry ❖Nokia

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Conclusion

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GSM Trouble

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❖GSM is no longer a walled garden ❖GSM spec has security problems ❖Expect many more issues as OSS

reduces costs for entry

Tuesday, 20 July 2010

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Future work

❖More GSM stack fuzzing ❖Next gen protocol stacks

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Thanks to

Harald Walte, Osmocom-bb & OpenBTS

Tuesday, 20 July 2010

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Questions?

40 Tuesday, 20 July 2010