Cатсн²² (in)sесuяitу / ChrisJohnRiley

Because we're damned if we do, and we're damned if we don't!

Shmoocon 2011: Attacking 3G and 4G mobile telecommunications networks

Attacking 3G and 4G mobile telecommunications networks

Enno Rey, Rene Graf & Daniel Mende

 

No demos today due to shipping materials and the like. TSA don’t like big electronic devices being shipped after all.

Still, that doesn’t mean there was no practical research.

Fundamentals

Standards

In mobile telco world everything is standardized by 3GPP

  • 3GPP: collaboration between groups of telco standards orgs
  • 3GPP: standard structured as/bundled in releases
    • 1992: Phase 1
    • 2000: Release 99 (incl first spec of 3G UMTS)
    • 2008: Release 8

2 Elements. 1 facing the internet and the other facing the mobile network

4G Network

4G networks change the names and functions of some devices.

Transport Layer: UDP or SCTP (mostly)

There could be some TCP elements, but none that have been seen in this research.

Generic Packed Tunneling: GTP

All types of signaling:

  • S1AP
  • X2AP
  • GTP-C

Authentication: DIAMETER

Others:

  • L2TP
  • DSMIPv6

SCTP Overview

Stream Control Transmission Protocol

General purpose layer 4 protocol

Specified by the IETF

Uses elements from TCP and UDP to cover all required functionality of both.

SCTP – 4 way handshake

INIT – INIT ACK – COOKIE ECHO – COOKIE ACK

Several different RFCs covering SCTP (starting with RFC2960).

Current tools don’t work very well due to SCTP rewrites in RFC5206 and RFC4960

  • NMAP SCTP doesn’t work “in a satisfactory manner”
  • SCTPscan no long work

Attacks from within the mobile telco networks

  • Attacks from the backhaul networks
  • Attacks from the Core network
  • Attacks from Management networks

Backhaul networks

Mobile backhaul

Carries data from the RAN to the management network and back

4G specific requirement laid out by 3GPP

Includes

  • eNodeB
  • MME
  • SGW

Can be implemented with different technologies

Originally ATM (in the early years of GSM), PDH/SDH, IP/MPLS, “Hybrid Approach” offloading to DSL, Carrier Ethernet

4G Assumes gigabit connections between elements to give sufficient bandwidth (mainly ethernet based)

How to get into backhaul

Physical intrusion to some cage located “in the somewhere”

Get Access to the network segment

  • Microwave
  • DSL
  • Carrier Ethernet

4G Aggregates “dumb” BTS and BSC/RNC functions on the one device –> eNB is not dumb anymore!

Once your in, what to do!

Attacking components

  • 3G: SGSNm RNC, NodeB
  • 4G: MME, eNB, SAE.GW
  • Routers/Switches

Eavesdropping

  • Pretty much everything is unencrypted
  • 3GPP insists on using IPsec Gateways
    • Which operators implement this?
  • Some countries argue against this standard

ARP spoofing still works smoothly

  • Apparently not on the security radar!

4G ALL-IP approach comes in handy

Let’s get practical

These notes are from in lab testing (i.e no firewalls, IPsec, etc…)

Real world attacks may be different due to this!

“Standard attack approach” did not yield anything interesting

SCTP Scanning via nmap or SCTPscan showed nothing

Using custom SCTP scanning tool showed some open ports

  • some of those “obscure signaling protocols”

Fuzzing the protocols

After starting the fuzzing, things got really slow.

When checking the server was sending SCTP ABORT leading us to believe something had crashed!

The main function of the device was no longer available

It recovered after a few minutes

Changed scripts and continued to fuzz

Final result…. system went down!

Business impact?

 

The first field of the protocol was causing the device crash!

Targeted code was running in the kernel

All that glitters is not gold however!

This isn’t old code! It’s newly developed for 4G! Make your own conclusions…

<NDA>

Continued testing is planned to really find the impact of this and other issues.

</NDA>

Attacks from the internet

Public space might mean the terminal (not covered) or the internet

Some interfaces must be made available to entities outside the network

  • e.g. S8 on PDN-GW for roaming
  • 3G: SGSNs must be able to connect to GGSNs of other countries
  • Standards say: Use NDS (IPsec of equiv. security) for these cases
  • So GTP should never be visible from the internet

Reality check!

GTP

Used to carry IP-based data traffic between network elements. There is also some other elements

Variants: GTP-C, GTP-U, and GTP’

TEID

Tunnel Endpoint IDentifier

Not very random

Not protected

Reality is that scanning for GTP in the wild does find results.

GTP Echo mechanism (port 2123) can be used to discover real GTP speakers in the internet waiting for communications

GTP-scan.py will be released soon to show this!

Many of the systems listening on GTP ports are also listening on other ports (21, 22, 23, 80) !

Various countries, many in Europe.

Whois information points to major mobile operators in these countries.

So why would they do this?

Sometimes having a working network is more important than following the standards to the letter!

Conclusions

From what the research shows, it looks like many attacks are coming against these networks.

Walled telco gardens are disappearing

All IP in the future

Terminals are getting more and more powerful

Misconception that people don’t understand these complex IP landscapes

Links:

Advertisements

Comments are closed.

%d bloggers like this: