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Testing Tor bridge assignments
by Jodi Spacek 20 Mar '19

20 Mar '19

Hi! I'm seeking advice on simulating Tor's consistent hashing, bridge ring distributor. I'm finishing up my Master's thesis on proxy distribution :) I run BridgeDB through my Python simulator to analyze the https distributor's bridge assignments over multiple bridge pool sizes and trials. So far, it follows a uniform random distribution (as expected). I'm using https distributor's prepopulateRings() example as a guideline on how the rings should be populated. Besides the default ring settings, are there any other test scenarios that I should cover? For instance, is there a possibility that the behaviour might change if there are quality of service limitations? Aside from the reserved set, are there any cases where it may not assign bridges uniform randomly that I should consider? I attempted to use the descriptors from leekspin, but ran into some hurdles integrating it with my simulator. My simulator doesn't need to persist or store state, since I only need the assignment information of proxies to clients until all proxies are enumerated. I hope the pared down version using the test data from generateFakeBridges() in test/util.py is adequate. Any advice is greatly appreciated!

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Tor Friendliness Scanner
by Kevin Gallagher 18 Mar '19

18 Mar '19

Hello tor-dev! My name is Kevin and I'm a PhD student at NYU. Recently I've been working on creating a "Tor Friendliness Scanner" (TFS), or a scanner that will measure what features of a given website are broken (non-functional) when accessed on the Tor Browser (TB), along with actionable suggestions to improve it. In order to do this, we first must get an approximation of ground-truth data of how a given website should work. We then need to compare it to how the website works on the TB to determine any changes. To generate a method of determining ground-truth, we decided to modify* the Firefox (FF) browser to log all of the steps of the creation of the Content Tree (also called the DOM tree), and to log the execution of all JavaScript functions (currently underway). We then will apply these changes to the TB as well, and run a scan of popular Web sites using the modified FF and the modified TB on all three of the TB security slider settings. We will then compare the resulting logs to determine where the tree creation processes differed* and why. These differences could potentially help us illuminate two things: 1. what functionality issues the Tor Browser encounters on popular Web sites, and 2. what threats (beyond metadata surveillance) the TB is protecting its users from in-the-wild. As far as I have considered, this method seems to capture a lot, but it's far from complete. For one thing, it obviously won't detect any difference that's spawned from user interaction or input (such as a script launched by an OnClick event). However, it does seem to make automation of scanning for Tor Friendliness possible, and can allow for wide-scale use. We have moved ahead with development (though have not yet finished it) and are (hopefully) very close to a working prototype. I was wondering if there was feedback on this method, or if anyone can consider an angle we have not that would either make the TFS more robust, easier to create, or both. Thanks for your time and consideration! Kevin *Note 1: Unfortunately we cannot just rely on JavaScript for examining the content tree, since this needs to work on all 3 security settings of the TB's security slider, and the "safest" setting deactivates JavaScript by default on all Web pages. *Note 2: There can be non-functional differences in Web pages, such as different ads showing or the display of the current time. We are working on methods to distinguish these from functional differences, such as using ad blacklists to determine if a given request or script is part of an ad, and ignoring it as part of the difference between the two trees. -- Kevin Gallagher Ph.D. Candidate Center For Cybersecurity NYU Tandon School of Engineering Key Fingerprint: D02B 25CB 0F7D E276 06C3 BF08 53E4 C50F 8247 4861

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Proposal: Don't include package fingerprints in consensus documents
by Iain Learmonth 13 Mar '19

13 Mar '19

Hi All, #28465 [0] needed a proposal. Feedback is welcome and encouraged. I've not written a proposal before, so if someone could let me know if I'm following the process OK (or not) then that is useful too. Thanks, Iain. [0] https://trac.torproject.org/projects/tor/ticket/28465

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#3600 tech doc
by Richard Pospesel 13 Mar '19

13 Mar '19

Hey y'all, For the past little while I've been working on a technical overview doc for #3600 (Prevent redirects from transmitting+storing cookies+identifiers) detailing the problems, scenarios and possible solutions. Please take a look and feel free to comment, edit or add! Link: https://storm.torproject.org/grain/X4nhdNqR9fGRc7sgTefFkg/ best, -Richard

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Updating Proposal 299 (Preferring IPv4 or IPv6 based on IP Version Failure Count)
by Neel Chauhan 12 Mar '19

12 Mar '19

Hi tor-dev@ mailing list, I have Proposal 299, also known as "Preferring IPv4 or IPv6 based on IP Version Failure Count" which makes ClientAutoIPv6ORPort take into account IPv4 and IPv6 failures. An older version of this document is available here: https://gitweb.torproject.org/torspec.git/tree/proposals/299-ip-failure-cou… I have attached an updated copy of this proposal to this message. This includes the changes recommended by teor at https://lists.torproject.org/pipermail/tor-dev/2019-February/013673.html. Would someone be able to update torspec to include the updated (and attached) proposal? Also, if any of you have opinions on this proposal, please share them with me. -Neel === https://www.neelc.org/

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download consensus from mirrors based on frequency options in torrc
by Pouya Miralaee 08 Mar '19

08 Mar '19

Hello to the community. according to these frequency options below, how should i specify that tor does not or if it has to, only in necessary times downloads consensus from directory servers and in all other cases, download them from mirrors or fallbacks. "ClientBootstrapConsensusAuthorityDownloadSchedule": "6, 11, 3600, 10800, 25200, 54000, 111600, 262800", "ClientBootstrapConsensusFallbackDownloadSchedule": "0, 1, 4, 11, 3600, 10800, 25200, 54000, 111600,262800", "ClientBootstrapConsensusAuthorityOnlyDownloadSchedule": "0, 3, 7, 3600, 10800, 25200, 54000, 111600,262800", I just intend to complete the decentralized situation in here. but i can not figure out how these frequency options work together. thanks in advance. Cheers. -- *Pouya Miralayi* -- *Pouya Miralayi*

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March Network Team Meeting Schedule
by teor 01 Mar '19

01 Mar '19

Hi, Next week's network team meeting is at a different time. We'll be meeting at Tuesday 5 March at 2300 UTC on #tor-meeting on OFTC. Here is our March schedule: * Tuesday 5 March at 2300 UTC * Monday 11 March at 1800 UTC * Monday 18 March at 1800 UTC * Monday 25 March at 1800 UTC We'll have a similar schedule in April, except for the company holiday on April 22. T -- teor ----------------------------------------------------------------------

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Anti-censorship discussion with Briar devs
by Cecylia Bocovich 28 Feb '19

28 Feb '19

Hi, I just had a really great conversation with some of the developers at Briar about the recent work they've done in integrating some pluggable transports into their messaging application. I thought I would summarize some key points from the conversation here. In particular, this information might prove useful for both the metrics and anti-censorship teams to know how other projects are using our tools and what they would like help with. This summary is organized as follows: I. How they used metrics data II. Independent reachability tests they performed III. What they did to integrate pluggable transports into Briar IV. What they want help with I. How they used metrics data One goal the Briar project had was to automatically detect where bridges are needed so they can be enabled automatically and for Briar to "work out of the box" with minimal developer overhead as they do not currently have dedicated anti-censorship funding. Here is the related ticket with a lot of useful discussion: https://code.briarproject.org/briar/briar/issues/1266 They wrote a collection of analytics scripts that use both OONI and Tor Project metrics data to determine where bridges are being blocked. Source code for the scripts: https://code.briarproject.org/briar/tor-circumvention-analytics/ Results (outdated): https://grobox.de/tor/bridges.html They rely mostly on OONI data but also use some Tor metrics to look at the ratio of bridge users in a country. Their reasoning being that while OONI shows what doesn't work, Tor metrics data shows what is currently working. Source code for Tor metrics script: https://code.briarproject.org/briar/tor-circumvention-analytics/blob/master… The ticket linked above has more discussion that might be useful to the metrics team as well. II. Independent reachability tests they performed To validate some of the results from OONI and Tor metrics, they ran a private bridge and did some reachability tests to it from China. They found that the bridge was not blocked, however they did not perform bandwidth tests to determine whether or not obfs4 bridges are being throttled. This makes sense as briar produces probably fairly low bandwidth traffic. When I asked them about it they suggested performing the following test: Set up obfs4 to forward connections to a local http server that servers a large, static file. Have a contact in China set up a cron job that periodically downloads the file from the bridge via obfs4. Their original reachability test was not running for very long, so it's still possible that prolonged use would result in its discovery but the fact that it wasn't blocked suggests that China might be enumerating bridges through the distribution mechanism rather than by something identifiable from obfs4 itself. We should perform our own tests to verify this, and to check for throttling. III. What they did to integrate pluggable transports into Briar My understanding from the issue text and commit messages about how briar decides whether to use pluggable transports is to use the output of their reachability analysis to determine user needs by country. If Tor is not blocked, users just use vanilla Tor If it is they use obfs4. If obfs4 is blocked, then they use meek (meek lite). Right now the countries that use meek in briar are: China, Iran, Egypt, Belarus, Turkey, Syria, and Venezuela. As far as the integration, they wrote some code that makes reproducible builds of obfs4 and meek and spits out a java/android library: https://code.briarproject.org/briar/go-reproducer Briar already uses Tor, so they configure these bridges in the usual way using a torrc file and a hardcoded, shipped file of bridge information (which I believe are also the default bridges used by Tor Browser). They decided they didn't want to maintain any private bridges like the one they used for their reachability tests. One of the concerns there was the ability to fingerprint Briar traffic by bridge connection and differentiate it from other Tor traffic. IV. What they want help with Because they do not have dedicated anti-censorship funding, they mentioned a few things that would help them maintain their pluggable transport use going forward and ease the integration of pluggable transports. The main thing they would like on the metrics side is up-to-date information about which PT works in which country and where PTs are needed at all in order to make quick and easy decisions based on location about which transports to use. They started to work with OONI to expand their tests but it turned out to be too much work for their time/funding: https://code.briarproject.org/briar/briar/issues/1414 It's on our roadmap to work with OONI and other censorship measurement tools (like Censored Planet) to expand our tests so we should get into contact with them again once we have gotten farther with this. On the PT development side, they expressed a desire to transfer maintenance of their reproducible builds of obfs4 and meek to someone else (that's the go-reproducer code linked above).

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Speeding up your Tor Appveyor Builds
by teor 27 Feb '19

27 Feb '19

Hi, We have made some changes to speed up Tor's Appveyor builds: https://bugs.torproject.org/29601 They should be merged soon. If you have Appveyor set up on your personal tor git repository, you can change Appveyor's configuration so that it's a bit faster. (We can't make these changes in the .appveyor.yaml config.) 0. Log in to Appveyor: https://ci.appveyor.com/ I use GitHub to log in to Appveyor. 1. Go to Appveyor's project settings page. Mine is: https://ci.appveyor.com/project/teor2345/tor/settings 2. Set "Build timeout, minutes" to 30. The default timeout is 60 minutes. Tor's jobs usually take about 10 minutes, unless they hang. 3. Set the "Rolling builds" checkbox. The default is: "build all versions of a branch/pull request". Rolling builds means: "when a branch or pull request is updated, cancel the previous build, and start a build with the latest changes." That's it. Your builds will be a bit faster! T -- teor ----------------------------------------------------------------------

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Sending multiple streams throuh a single Tor circuit
by Piyush Kumar Sharma 26 Feb '19

26 Feb '19

Hello all, I am a PhD student, and am working on some measurements in Tor. I am stuck at a point where i need to send multiple applications(streams) traffic through a single circuit. I am currently using torsocks/torify to send traffic of these multiple applications through Tor. The main problem is that, despite trying many different ways to achieve the same (sending multiple streams through a single circuit), i am not successful. Things i have tried : 1.) Force Tor process to create only a single circuit at a time preventing any new circuit creation, so that any new stream would be attached to this only available circuit. To acheive this i have set the following Tor options : set __DisablePredictedCircuits to 1 set MaxClientCircuitsPending to 1 set newcircuitperiod to 999999999 set maxcircuitdirtiness to 999999999 The problem with the above method is that it seems to work sometimes randomly. But most of the times for some reason, a new circuit is still created. 2.) Next, i assumed that maybe running torify multiple times for each application is the culprit, as it may try to create new circuit for each run. So i created a new bidirectional stream using socat, which listens on a local TCP port, and forwards the data to the Tor SOCKS port assuming that it will lead to a singe connection to local SOCKS. Even this did not work and still new circuits were created randomly. 3.) Next i tried to attach streams to circuits manually, using the stem library following the link : https://stem.torproject.org/tutorials/to_russia_with_love.html#custom-path-… . This seemed to work initially, but then after every 4-5 runs, the streams seemed to detach automatically. Moreover, the original circuit crashed too. It would be great, if someone could tell a simple way to achieve the same, or would point me to any mistakes that can be improved in the above methodologies to make them work. Regards Piyush

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