Tor: Finding the Hidden Shallots Jo ao Marques University of - - PowerPoint PPT Presentation

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Tor: Finding the Hidden Shallots Jo ao Marques University of - - PowerPoint PPT Presentation

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Tor: Finding the Hidden Shallots Jo ao Marques University of Amsterdam joao.marques@os3.nl July 5, 2018 Jo ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 1 / 24 Overview Introduction 1 Project Idea and Motivation

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Tor: Finding the Hidden Shallots

Jo˜ ao Marques

University of Amsterdam joao.marques@os3.nl

July 5, 2018

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 1 / 24

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Overview

1

Introduction Project Idea and Motivation Previous Research Research Question

2

Theoretical Background The Onion Routing Network Hidden Services

3

Project Method Findings

4

Conclusion Discussion Future work

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 2 / 24

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Why this project?

Hidden Services importance (for the service provider): Anonymity Freedom

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Why this project?

Hidden Services importance (for the service provider): Anonymity Freedom Consequences of above values: legitimate - Uncensored news website/blog - important to secure illegitimate - C&C Servers / Uncontrolled markets - Extract intel / monitor

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 3 / 24

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Previous Research

In 2013 a paper by Alex Biryukov, Ivan Pustogarov, and Ralf-Philipp Weinmann was published, titled: Trawling for tor hidden services: Detection, measurement, deanonymization They were very successful and gave recommendations to stop the acquisition of Hidden services, and targeted attacks

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 4 / 24

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Previous Research

In 2013 a paper by Alex Biryukov, Ivan Pustogarov, and Ralf-Philipp Weinmann was published, titled: Trawling for tor hidden services: Detection, measurement, deanonymization They were very successful and gave recommendations to stop the acquisition of Hidden services, and targeted attacks Despite the work done: No extraction method No tools Requires verification for changes

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Research Question

How feasible is the acquisition of hidden service links (onion links)?

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Research Question

How feasible is the acquisition of hidden service links (onion links)? What is the state of the current specification? How are protection mechanisms used/applied? What protocols are still used in the wild? Are these protocols safe? How can we extract from unsafe ones?

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 5 / 24

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Tor Network

What is the The Onion Rounting (Tor) Network?

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Tor Network The tor network is an Overlay Network that aims to provide the user with: Privacy Anonymity

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Tor Network The tor network is an Overlay Network that aims to provide the user with: Privacy Anonymity

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Tor: How does it work?

For the Tor network to work it makes use of 3 types of relays/nodes:

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 7 / 24

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Tor: How does it work?

For the Tor network to work it makes use of 3 types of relays/nodes: Guard Node - First node of the circuit created by the client and where traffic enters the Tor Network Middle Node Exit Node

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 7 / 24

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Tor: How does it work?

For the Tor network to work it makes use of 3 types of relays/nodes: Guard Node Middle Node - Second node of the circuit, it relays the traffic between the guard node and the exit node Exit Node

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 7 / 24

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Tor: How does it work?

For the Tor network to work it makes use of 3 types of relays/nodes: Guard Node Middle Node Exit Node - Third and last Node of the circuit, where the traffic gets unencrypted and sent to the destination

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 7 / 24

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Tor: How does it work?

Figure: Tor browser requests page to proxy

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Tor: How does it work?

Figure: Tor proxy negotiates encryption layer with each node

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Tor: How does it work?

Figure: Exit node communicates on the user’s behalf

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Tor: How does it work?

Figure: Data gets relayed back to the client

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How does it work?

This provides anonymity to the client... but what about the server?

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 9 / 24

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HS: How does it work?

Distributed Hash Table (DHT): Group of servers Each server holds a list of descriptors Descriptors contain information on how to contact the service

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HS: How does it work?

The publishing of the Hidden Service

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HS: How does it work?

Figure: Server selection of Introduction Points

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HS: How does it work?

Figure: Server publishing descriptor to DHT

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Client connection to hidden service

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Figure: From browser request to receiving the descriptor from the DHT

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Figure: Rendezvous Point selection and contacting the Hidden Service

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Figure: Server connection to RP and bridging of both circuits

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HS: The protocol specified

Protocol received several changes through out the project lifetime. The protocol versions are: V0 V2 (0.2.0.10-alpha+) V3 (0.3.0.8)

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 15 / 24

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HS: The protocol specified

Protocol received several changes through out the project lifetime. The protocol versions are: V0

First version No encryption Requests made to HSDir directly with onion link (Supposed to be Hidden!!) Deprecated in 0.2.2.1-alpha...no more V0 legacy ;-)

V2 (0.2.0.10-alpha+) V3 (0.3.0.8)

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 15 / 24

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HS: The protocol specified

Protocol received several changes through out the project lifetime. The protocol versions are: V0 V2 (0.2.0.10-alpha+)

Second version Encrypted Introduction points, but link still encoded in the clear text part 16 characters link - yyhws9optuwiwsns.onion

V3 (0.3.0.8)

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 15 / 24

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HS: The protocol specified

Protocol received several changes through out the project lifetime. The protocol versions are: V0 V2 (0.2.0.10-alpha+) V3 (0.3.0.8)

Current version Clear text metadata for identification of descriptor Rest encrypted using a derivation of the onion link 56 characters link - l5satjgud6gucryazcyvyvhuxhr74u6ygigiuyixe3a6ysis67ororad.onion

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HS: The protocol specified

Figure: Differences between V2 and V3 descriptor

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Method

Several routes to acquire the onion links: Scrapping Bruteforcing Sniffing Dumping Memory from the HSDir

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Method

Several routes to acquire the onion links: Scrapping

Time consuming Only links that have been shared in public domain

Bruteforcing Sniffing Dumping Memory from the HSDir

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Method

Several routes to acquire the onion links: Scrapping Bruteforcing

Infeasible - V3 Time - V2

Sniffing Dumping Memory from the HSDir

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Method

Several routes to acquire the onion links: Scrapping Bruteforcing Sniffing

Impossible

Dumping Memory from the HSDir

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Method

Several routes to acquire the onion links: Scrapping Bruteforcing Sniffing Dumping Memory from the HSDir

Requires HSDir (flag acquired 4 days from last down (Requires Stable flag which takes 5 days)) Impossible - V3

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Memory Dumps

Dumping Memory - Very fruitful, V2 descriptors successfully extracted and decoded to acquire the onion link

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Memory Dumps

Dumping Memory - Very fruitful, V2 descriptors successfully extracted and decoded to acquire the onion link Created a proof of concept program for automating hourly memory dumps

  • f multiple Tor proxys

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Memory Dumps

Figure: Process flow diagram of the link extraction PoC

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Figure: Graph showing the number of unique descriptors extracted in 5 days

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Figure: Graph showing tor versions currently being run: V2≥0.2.0.10 - V3≥0.3.0.8 (15/18)

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 20 / 24

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In conclusion...

How feasible is the acquisition of hidden service links (onion links)? We can conclude from the findings that: 2104 unique V2 links five days of running memory dumps from the 105069 reported by tor metrics 1 Two relays for less than 26 euros - Very good cost/efficiency balance V2: Even though IP encryption enabled, the encoded links are always present on the clear V3 Enabled Relays != V3 > V2

1https://metrics.torproject.org/hidserv-dir-onions-seen.html Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 21 / 24

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In conclusion...

But hidden services are supposed to be hidden unless specifically gived the address. So to solve this the recommendation is to simply: Use the latest features of the software Deprecate the V2 protocol If not possible use V2 IP encryption

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 21 / 24

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What can still be done

With results aggregated, this stage becomes a stepping stone for targeted intel extraction such as: Verifying which links are alive (big portion could be on demand file sharing, short lived hidden services) Identifying type of service running behind the onion link

Jo˜ ao Marques (UvA) Finding the Hidden Shallots July 5, 2018 22 / 24

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What can still be done

With results aggregated, this stage becomes a stepping stone for targeted intel extraction such as: Verifying which links are alive (big portion could be on demand file sharing, short lived hidden services) Identifying type of service running behind the onion link With some research into how to capture the requests for V2 descriptors: Easy to convert from from link to id Correlate id captured to addresses acquired

Possibly discerning traffic to previously discovered C&Cs

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Questions?

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References

Biryukov, Alex and Pustogarov, Ivan and Weinmann, Ralf-Philipp (2013) Trawling for tor hidden services: Detection, measurement, deanonymization Security and Privacy (SP), 2013 IEEE Symposium on pp.80 – 94.

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