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GSoC'16 proposal: the Torprinter project (a Panopticlick-like website)
by Pierre Laperdrix 22 Mar '16

22 Mar '16

Hi Tor Community, My name is Pierre and I'm really interested in participating in a GSoC project this year with the Tor organization. Since I've been working on browser fingerprinting for the past two years, I'd love to build a Panopticlick-like website to improve the fingerprinting defenses of the Tor browser. I've included below my proposal in case anyone has ideas or suggestions, especially on the technical section or on some of the open questions that I have. (It should be noted that the Torprinter name is subject to change). ****************************************************** Summary - The Torprinter project: a browser fingerprinting website to improve Tor fingerprinting defenses The capabilities of browser fingerprinting as a tool to track users online has been demonstrated by Panopticlick and other research papers since 2010. The Tor community is fully aware of the problem and the Tor browser has been modified to follow the "one fingerprint for all" approach. Spoofing HTTP headers, removing plugins, including bundled fonts, preventing canvas image extraction: these are a few examples of the progress made by Tor developers to protect their users against such threat. However, due to the constant evolution of the web and its underlying technologies, it has become a true challenge to always stay ahead of the latest fingerprinting techniques. I'm deeply interested in privacy and I've been studying browser fingerprinting for the past 2 years. I've launched 18 months ago the AmIUnique.org website to investigate the latest fingerprinting techniques. Collecting data on thousands of devices is one of the keys to understand and counter the fingerprinting problem. For this Google Summer of Code project, I propose to develop the Torprinter website that will run a fingerprinting test suite and collect data from Tor browsers to help developers design and test new defenses against browser fingerprinting. The website will be similar to AmIUnique or Panopticlick for users where they will get a complete summary with statistics after the test suite has been executed. It can be used to test new fingerprinting protection as well as making sure that fingerprinting-related bugs were correctly fixed with specific regression tests. The expected long-term impact of this project is to reduce the differences between Tor users and reinforce their privacy and anonymity online. In a second step, the website could open its doors to more browsers so that it could become a platform where vendors can implement significant changes in their browsers with regards to privacy and see the impact first-hand on the website. With the strong expertise I have acquired on the fingerprinting subject and the experience I have gained by developing the AmIUnique website, I believe I'm fully qualified to see such a project through to completion. Website features The main feature of the website is to collect a set of fingerprintable attributes on the client and calculate the distribution of values for each attribute like Panopticlick or AmIUnique. The set of tests would not only include known fingerprinting techniques but also ones developed specifically for the Tor browser. The second main feature of the website would be for Tor users to check how close their current fingerprint is from the ideal unique fingerprint that most users should share. A list of actions should be added to help users configure their browser to reach this ideal fingerprint. The third main feature would be an API for automated tests as detailed by this page : https://people.torproject.org/~boklm/automation/tor-automation-proposals.ht… . This would enable automatic verification of Tor protection features with regard to fingerprinting. When a new version is released, the output of specific tests will be verified to check for any evolution/changes/regressions from previous versions. The fourth main feature I'd like to include is a complete stats page where the user can go through every attribute and filter by OS, browser version and more. The inclusion of additional features that go beyond the core functionnalities of the site should be driven by the needs of the developers and the Tor community. Still, a lot of open questions remain that should be addressed during the bonding period to define precisely how each of these features should ultimately work. Some of these open questions include: - How closed/private/transparent should the website be about its tests and the results? Should every tests be clearly indicated on the webpage with their own description? or should some tests stay hidden to prevent spreading usable tests to fingerprint Tor users? - Should a statistics page exist? Should we give a read access to the database to every user (like in the form of a REST API or other solutions)? - Where the data should be stored? How long should the data be kept? If tests are performed by versions, should the data from an old TBB version be removed? Should the data be kept a week, a month or more? - How new tests should be added: A pull request? A form where submissions are reviewed by admins? A link to the Tor tracker? - Should the website only be accessible through Tor? Technical choices In my opinion, the website must be accessible and modular. It should have the ability to cope with an important number of connections/data. With this in mind and the experience gained from developing AmIUnique, I plan on using the Play framework with a MongoDB database. Developing the website in Java opens the door to many developers to make the website better and more robust after its initial launch since it is one of most used programming language in the world. On the storage and statistics side, MongoDB is a good fit because it is now a mature technology that can scale well with an important number of data and connections. Moreover, the use of SQL databases for AmIUnique proved to be really powerful but the maintenance after the website was launched became a tedious task, especially when modifying the underlying model of a fingerprint to collect new attributes. The choice of a more flexible and modular database seems a better choice for maintenance and for adding/removing tests. Estimated timeline You will find below a rough estimate of the timeline for the three months of the GSoC. Community bonding period - Discuss with the mentors and the community the set of features that should be included in the very first version of the website and clarify the open questions raised in one of the previous paragraphs. 23 May - 27 June : Development of the first version of the website with the core features Week 1 - Development of the first version of the fingerprinting script with the core set of attributes. Special attention will be given so that it is fully compatible with the most recent version of the Tor browser (and older ones too). Week 2 - Start developing the front-end and the back-end to store fingerprints with a page containing data on your current fingerprint (try adding a view to see how close/far you are from the ideal fingerprint). Week 3 - Start developing the statistics page with the necessary visualization for the users. Modification of the back-end to improve statistics computation to lessen the server load. Week 4 - Finishing the front-end development and refining the statistics page to get back the most relevant information. Adding and testing an API to support automated tests. Week 5 - Finishing the first version so that it is ready for deployment. Start developing additional features requested by the community (rest API? account management?) 27 June - Mid July : Deployment of the first version online for a beta-test with bug fixing. Finishing development of additional features requested by the mentors/community. Defining the list of new features for the second version. Mid July - 23th August : Adding a system to make the website as flexible as possible to add/remove tests easily (A pull-request system? A test submission form where admins review tests before they are included in the test suite?) Developing additional features for the website. Making sure that the website can be opened to more browsers (work done at design time to support any browsers will be tested here) Bug fixing Code sample In 2014, I developed the entire AmIUnique.org website from scratch. Its aim is to collect fingerprints to study the current diversity of fingerprints on the Internet while providing full details to users on this subject. It was the first time that I built a complete website from the design phase to its deployment online. One of the first challenge that I encountered was to build a script that would not only use state-of-the-art techniques but that could simply work on the widest variety of browsers. Testing a script for a recent version of a major browser like Chrome and Firefox is an easy task since they implement the latest HTML and JavaScript technologies but making sure that the script runs correctly on older browsers like Internet Explorer is another story. Juggling with a dozen different virtual machines was necessary to obtain a bug-free and stable version of the script. A small beta-test was required to make sure that everything was good to go for what is now the foundations of the AmIUnique website. The totality of the source code for AmIUnique and my other projects can be found on GitHub. A second challenge that I faced was to deal with the increasing load of users so that the server could return personalized statistics to visitors in a timely manner (less than 2/3s). By having a separate entity that updates statistics in real time on top of the database, I managed to drastically reduce the server load. With the number of Tor users around the world, the website needs from the get go to handle a high load of visitors and statistics computation and my previous experience on that specific task will prove useful. For the very first version of Torprinter, I plan on testing well-known and widespread fingerprinting techniques to make sure that there is no variation among Tor users. These include HTTP headers and known JavaScript objects. There should be no need for any Flash attributes since plugins are not present in the Tor browser (thus removing complex code in charge of correctly loading the Flash object). For this proposal, I have also developed a special page with 7 different tests that are mainly targeted at the Tor browser to give an idea of what tests can be included that are more suited to the Tor users. Tests n°5, n°6 and n°7 are broader and also concerns the Firefox browser. You can found a working version of the script on a special webpage (need to scroll to make the results appear): https://plaperdr.github.io/torScript.html The script can be found here: https://plaperdr.github.io/assets/tor/tor.js Test n°1 Test the size of the current window - As reported by ticket n°14098 https://trac.torproject.org/projects/tor/ticket/14098 Test n°2 Test the support of emoji - As reported by ticket n°18172 https://trac.torproject.org/projects/tor/ticket/18172 Test n°3 Analysis of the "scroll" behavior of the window - As investiagted by http://jcarlosnorte.com/security/2016/03/06/advanced-tor-browser-fingerprin… Test n°4 Test the size of current fallback font by using the canvas API to render some text (no need for user permission like canvas extraction) - Custom test Test n°5 Test the difference between OS on the maximum font size - Custom test Test n°6 Test the difference between OS on the Date API - As reported by ticket n°15473 https://trac.torproject.org/projects/tor/ticket/15473 Test n°7 Test the difference between OS on the Math class - As reported by ticket n° 13018 https://trac.torproject.org/projects/tor/ticket/13018 ****************************************************** Any remarks, suggestions or ideas are very welcome! Pierre

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New weekly IRC tor development/network team meeting times start next week
by Nick Mathewson 22 Mar '16

22 Mar '16

Hello! Starting on March 28, we will have two weekly meetings in #tor-dev to talk about developing Tor stuff. NETWORK TEAM MEETING: * Please make this one if you can, and if you work on Tor or some other network team project. It'll be fun. * It is Monday, at 1700 UTC. (That's 1pm EDT and 10am PDT.) * This replaces the old Wednesday meetings. We'll each check in briefly, then discuss stuff that we need to discuss. * The meeting time has been chosen by picking the time at which the most folks could make it. PATCH PARTY: * Patch Party will be extra fun. We'll talk about code and tickets. It will be later in the day for a lot of us, and some will still be waking up, so we'll try to have a pretty chill atmosphere. * If Patch Party is not fun, we are doing something wrong. * It'll be Tuesday, at 2300 UTC. (That's 7pm EDT and 4pm PDT.) * This replaces the old Monday meetings. We'll have a freewheeling chat about patches and upcoming stuff. * If you come and feel like talking about Tor stuff, I'll do my best to make sure it is fun. This all starts next Monday. For this week, we are on the same old times. cheers, -- Nick

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How to build a Router that will only allow Tor users
by Martin Kepplinger 20 Mar '16

20 Mar '16

Hi, I try to configure OpenWRT in a way that it will only allow outgoing connections if it is Tor. Basically it is the opposite of "blacklisting exit relays on servers": "whitelisting (guard) relays for clients". It should *not* run Tor itself. A first test setup (onionoo document, ipset and iptables) kind of worked. It's definitely doable, but not totally trivial in the end. What did *not* work, was starting Torbrowser. That's a hard requirement, and before bebugging it through I ask: Do I miss something when I just allow outgoing connections to * Guard, * Authority, * and HSDir flagged relays (do I *need* them? that's a different question probably) I don't restrict ports for now, even though I really should, and it's all only IPv4 addresses I care about for now, and I easily could just have OpenWRT configured wrongly, but: DNS is not an issue I think, what else could be? So far I only see Torbrowser talking to one Authority while starting. thanks martin

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Scheduling next proposal discussion meetings
by Isabela 20 Mar '16

20 Mar '16

Hello there, on today's irc meeting we choose 2 proposals to discuss: #224 and #267. I took a look at people's availability in the wiki and picked the following date&time for both meetings: * Proposal 224: Next-Generation Hidden Services in Tor o Wednesday, March 16th 2200 UTC (teor can join) o Must-have attendees: special, dgoulet, asn, teor o Conflicts: (If you are noting a conflict, please include a big bunch of times when you COULD make it.) + ??? o Can-attend: * Proposal 267: Tor Consensus Transparency o Friday, March 18th 1600 UTC o Must-have attendees: ln5, leif o Conflicts: (If you are noting a conflict, please include a big bunch of times when you COULD make it.) + ???? o Can-attend: Please update in the wiki with your options for them. If this date and time does not work, let me know what is a good one in the 'conflicts' notes. https://trac.torproject.org/projects/tor/wiki/org/teams/NetworkTeam/Meeting… Let me know if you have any questions! cheers, Isabela -- PM at TorProject.org gpg fingerprint = 8F2A F9B6 D4A1 4D03 FDF1 B298 3224 4994 1506 4C7B @isa

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Core Tor / Network Team meeting time updates.
by Nick Mathewson 19 Mar '16

19 Mar '16

Hi, all! I've got a doodle poll open on http://doodle.com/poll/nvx26m4cxspryf3e to try to find the best time for a network team meeting. So far, it looks like our options are somewhat constrained, since we have people who are living from UTC-7 through UTC+11, and a wide range of time zones in between. (Karsten has said he's okay with us picking a time he can only-sorta make. Isabela claims she has no sleep schedule and can meet whenever.) In particular, we're going to have a hard time having both George and Teor on the same meeting, since whenever they're both available, all the west-coast-US people are asleep. Asking people to start meetings before 0800 or after 2200 in their personal time zones is not IMO nice or okay, so let's not try to do that. So, my favorite option ("Find some magical time when everybody can make it") is out. So, as I see it here are our options: A. Pick a time when as many people as possible can attend. Include people who can't make that time by doing one or more of these: A1. Encourage everybody to catch up informally with everybody who can't attend. A2. Work with the people who can't attend, and whoever has a schedule closest to theirs, to make sure that there is a supplemental topic meeting on topics of their joint interest. A3. In addition to meetbot logs, keep minutes of the meetings and send them to tor-dev. B. Try to pick two or more times such that everybody can make one or the other. Try to solve disconnectedness by doing one or more of these: B1. Encourage everybody who can attend both to do so. B2. Make Nick and Isabela attend both. B3. Try to make sure there are at least 3 times, with several people shared pairwise between each. B4. Minutes as above. C. We all move to a nice tropical island. Thoughts? Especially from regular attendees or would-be-regular attendees? peace, -- Nick

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Meeting about the new guard algorithm proposal (prop259)
by George Kadianakis 19 Mar '16

19 Mar '16

Hello there, seems like the prop259 algorithm has kind of stabilized and you guys have jumped into implementation. That's great! A small problem in this process is that I'm probably the only person in Tor who understands the new algorithm right now. We could fix this by doing a small proposal IRC meeting where you guys could summarize the current state of the algorithm, as well as provide some simulation results. I think that folks like Nick, Mike and isis could provide valuable feedback at this point. Would you guys be interested in something like this? I'm fine with doing it next week at some point. Maybe Wednesday or Thursday? Maybe at 15:00 UTC? Let me know if that's convenient for you. Cheers!

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Introducing Snowflake (webrtc pt)
by Serene 18 Mar '16

18 Mar '16

Hi all, Snowflake is a webrtc pluggable transport inspired by flashproxy. (https://gitweb.torproject.org/pluggable-transports/snowflake.git) Arlo, David, and I have made lots of progress on it lately, and it now appears to have reached minimum viability. The following should result in a 100% bootstrap over WebRTC: ``` git clone https://git.torproject.org/pluggable-transports/snowflake.git cd snowflake/client go get go build tor -f torrc ``` In case you have a moment, it'd be cool if you tried it out and let us know whether it works for you. I'd really appreciate hearing about all the thoughts / concerns / issues before we move forward. -- More info -- Q: What are the benefits of this PT compared with other PTs? Snowflake combines the advantages of flashproxy and meek. Primarily: - It has the convenience of Meek, but can support magnitudes more users with negligible CDN costs. (Domain fronting only used for brief signalling / NAT-piercing to setup P2P webrtc which handles the actual traffic) - Arbitrarily high numbers of volunteer proxies are possible like in flashproxy, but NATs are no longer a usability barrier - no need for manual port forwarding! Q: How does it work? 1. Volunteers visit websites which host the "snowflake" proxy. (just like flashproxy) 2. Tor clients automatically find available browser proxies over the domain fronted signaling channel. 3. Tor client and browser proxy establish a WebRTC peer connection. 4. Proxy connects to some relay. 5. Tor occurs. Q: Why is it called Snowflake? There's a bunch of "ICE" negotiation happening for WebRTC, and it also involves a great abundance of ephemeral and short-lived (and special!) volunteer proxies... Anyhow, if Snowflake seems like it would be useful / desired here, it would be awesome if we had more help getting it stable, polished, audited, deployable, etc... Plenty of work to do! <3, ~serene P.S. Make sure you're using a recent version of Go (1.5+) P.P.S. The repo is available in these locations: - https://gitweb.torproject.org/pluggable-transports/snowflake.git - https://github.com/keroserene/snowflake

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[GSoC '16] Exitmap project - Introduction and request for comments
by Mridul Malpotra 18 Mar '16

18 Mar '16

Hi everyone! I'm Mridul. I wish to apply for the Exitmap improvements project mentored by Dr. Philipp Winter for the Google Summer of Code 2016. My current IRC handle is mtyamantau. Contents -------- 1. Introduction - About myself and experience with Tor 2. Exitmap - Current progress and questions 3. GSoC - Rough proposal structure and questions 1. Introduction - About myself and experience with Tor ------------------------------------------------------ I'm Mridul Malpotra, currently in my senior year pursuing bachelors in Computer Science from IIIT Delhi, India. My interests primarily lie in computer networks and network security, specifically anonymous networks like Tor and I2P. Through my now 1-year long undergraduate thesis work under Dr. Sambuddho Chakravarty, I have had exposure to the Tor network, relevant literature and some related projects, which helped me better understand and appreciate the current research and development going on. My work involved manually setting up testbeds through testing Tor networks on our institute intranet as well as on PlanetLab (for those wondering, I had recommended Chutney and Shadow). The current private testing Tor network is running on a PlanetLab slice (iiitd_mridul2) with ~170 nodes globally and 3 directory authorities. I used the control protocol through the Stem library to help in multiple circuit creation and stream attachments for measuring performance of a software over Tor. I have also had experience with open source software, by contributing to the Non intrusive load-monitoring toolkit (NILMTK) which is based on Python and Pandas. While working there, I helped contribute code for additional features, fixed a few bugs and also worked with a few of Python's package management and documentation systems. Relevant links: github.com/nilmtk/nilmtk/commits?author=mridulmalpotra 2. Exitmap - Current progress and questions ------------------------------------------- I recently read about Exitmap in the 'Differential Treatment of Anonymous Users' paper by Khattak et. al. The use case for fast automated scanning through Exitmap to evaluate ~1000 exit nodes was really interesting. On top of that, it fitted my use case of testing a particular software's performance over Tor. Familiarizing myself with the source code, I think I understand the basic layout for how the scanner works and appreciate the modularity of task executions. I followed the project's progress on github and have read the 'Spoiled Onions' paper by Winter et. al. In the coming 2 days, I plan to tinker around more with the code, discuss concerns, issues and/or suggestions if any, and get myself properly familiarized with the codebase. I also have certain ideas regarding what modules could be added and improvements made, some of which I have mentioned in the next section. I will also be reading the tech report on Exitmap and would be grateful if you can recommend any other resource(s) that I should be referring to. Lastly, I had a few queries related to the project and/or paper and apologize for the naivety in the questions if any. a. How was the bifurcation between stand-alone and same-process modules decided? Are there any advantages to allow for multiple forked processes for specific modules? b. For testing active attacks, can there be modules developed keeping other cleartext protocols like SNMP and Telnet in mind? Alternatively, is there a way to determine what protocols are being used over Tor and their popularity? c. How is Exitmap being crowdsourced currently? I'm interested to know how data is being collected from volunteers running the scanner. 3. GSoC - Rough proposal structure and questions ------------------------------------------------ Here I am listing the possible objectives that my project will be focusing on. I request your feedback and comments on the chosen topics and their descriptions. 1. Achieve autonomous scanning in Exitmap with periodic scans that, based on a certain algorithm, fetches relay descriptors and automates various subtasks for consistent data collection and verification. The main challenges that I expect will be intelligently recognizing which tasks to automate and when, and making the entire background process execution efficient in resource consumption. 2. Emulating multiple user interaction in individual modules and in Exitmap overall to provide indistinguishability to Exitmap from regular users. I will try to explore libraries for this purpose like Splinter with Selenium or BeautifulSoup with Requests that help dynamically interaction with the web resource. The main challenges that I expect will be to scale this automated testing alongside the running asynchronous jobs and making the entire scans look like genuine user interactions. Any suggestions on better ways to do this will be helpful. 3. Making the codebase more robust by adding unit test cases. I plan on using either the plain unittest/unittest2 framework or nose/nose2/pytest tools or any other alternatives that I may find or be recommended. I plan to simultaneously write the unit test cases for new code added and improve upon the exiting testing programs. 4. (Optional) I read from the mail threads on the tor-dev mailing list that the code needs to be converted to be Python3 compatible. Would like your opinion on whether it is a viable option and if it is possible, would like to include this in my list of tasks. 5. (Optional) If I can spare time in the milestone timeline and if discussion leads to some clarity, I would like to add another module for more cleartext protocols that could be implemented like SNMP or Telnet. I am also looking at possible local to remote attacks that are active at the application layer and could be tested in Exitmap. I'll update if I find anything. Next, I am drafting a week-wise timeline of what I plan to do over the duration of ~3 months. I will be dividing task 1 and 2 before and after the mid-term, with the optional tasks done in either of the slots and testing done alongside for everything. This is to ensure incremental milestones that can be useful to the community as I develop. Also, as I gain clarity on my objectives, I plan to refine this timeline to a week-wise format with buffers placed accordingly and present it in 2 days time. Lastly, I would appreciate any suggestions, criticism or feedback on this proposal regarding content, volume or specificities. I am looking forward to contributing to the Tor Project organization and interacting with developers here. Thanking you, (long mail I know, sorry) Sincerely, -- Mridul Malpotra Undergrad @ IIIT-Delhi <https://www.iiitd.ac.in/> mridulmalpotra.github.io ============================= PGP keyID: 0xb716e33ab6d0a653 <http://pgp.mit.edu/pks/lookup?op=get&search=0xb716e33ab6d0a653>

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"Not our bug" bugs
by Griffin Boyce 18 Mar '16

18 Mar '16

Hey all, There have been quite a few bug reports that discuss incompatibility with various Firefox extensions and with websites. In most cases, I can't replicate these bugs -- either because the extension in question has been patched, the website reported no longer exists, or the issue can't be replicated (which could be due to site updates and past Firefox incompatibility). Occasionally, the issue is real and still in effect, but isn't really a Tor bug (such as #7279, where a forum restricts logins by Tor users). We've all worked very hard to reduce overly-restrictive blacklist policies, but can't be everything for everyone. In these cases, I'd propose rejecting these bugs as either invalid or `not a bug`. These are all varying degrees of "not our bug" or "actually not a bug at all." Open to more thoughts on this. ~Griffin

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Notes from the prop267 meeting 2016-03-17
by Linus Nordberg 18 Mar '16

18 Mar '16

Hi, Here's a summary of what happened in the prop267 meeting in #tor-dev yesterday with Nick, Tom, Sebastian and myself. Sebastian started by summarising the proposal nicely. Topics discussed: - for bootstrap reasons we can't mandate using tor for all communication - SCT's or not: using SCT's instead of inclusion proofs would lower the burden on operating a log and save bytes on the wire - pushback on suggestion of turning all relays into auditors, reason being increased (code) complexity - there are some differences between "MITM:ing tor" and "MITM:ing on the internet", one being that a tor mitm is the controlling of a majority of the dirauth keys, which in many cases is more persistent than an IP layer MITM - the "eventually you escape a MITM" hand waving is problematic - we need a story on how a perfectly tor-MITM:ed TAILS user get back to the real network - relays and clients must check consensus documents the same way - hard fail or not when consensus isn't shown to be in a log? - handling of changes in the set of dirauths Identified next steps: - add text about what needs to be and what should be anonymised, taking bootstrapping issues into account - decide on replacing SHA2-256 with SHA3-512 or SHA2-512||SHA3-512 (taking availability of implementations into account) - decide on using SCT's or not - analyse the "TAILS user under MITM" case - analyse "set of dirauths changing" What did I miss? Full logs can be found at http://meetbot.debian.net/tor-dev/2016/tor-dev.2016-03-17-14.58.log.html

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