tor-dev October 2018

tor-dev@lists.torproject.org

29 participants
22 discussions

the consequences of deprecating debian alpha repos with every new major branch
by nusenu 21 Dec '21

21 Dec '21

Hi, tldr: - more outdated relays (that is a claim I'm making and you could easily proof me wrong by recreating the 0.3.3.x alpha repos and ship 0.3.3.7 in them and see how things evolve after a week or so) - more work for the tpo website maintainer - less happy relay operators [3][4] - more work for repo maintainers? (since a new repo needs to be created) When the tor 0.3.4 alpha repos (deb.torproject.org) first appeared on 2018-05-23 I was about to submit a PR for the website to include it in the sources.list generator [1] on tpo but didn't do it because I wanted to wait for a previous PR to be merged first. The outstanding PR got merged eventually (2018-06-28) but I still did not submit a PR to update the repo generator for 0.3.4.x nonetheless and here is why. Recently I was wondering why are there so many relays running tor version 0.3.3.5-rc? (see OrNetStats or Relay Search) (> 3.2% CW fraction) Then I realized that this was the last version the tor-experimental-0.3.3.x-* repos were shipping before they got abandoned due to the new 0.3.4.x-* repos (I can no longer verify it since they got removed by now). Peter made it clear in the past that the current way to have per-major-version debian alpha repos (i.e. tor-experimental-0.3.4.x-jessie) will not change [2]: > If you can't be bothered to change your sources.list once or twice a > year, then you probably should be running stable. but maybe someone else would be willing to invoke a "ln" commands everytime a new new alpha repo is born. tor-alpha-jessie -> tor-experimental-0.3.4.x-jessie once 0.3.5.x repos are created the link would point to tor-alpha-jessie -> tor-experimental-0.3.5.x-jessie It is my opinion that this will help reduce the amount of relays running outdated versions of tor. It will certainly avoid having to update the tpo website, which isn't a big task and could probably be automated but it isn't done currently. "..but that would cause relay operators to jump from i.e. 0.3.3.x to 0.3.4.x alphas (and break setups)!" Yes, and I think that is better than relays stuck on an older version because the former repo no longer exists and operators still can choose the old repos which will not jump to newer major versions. [1] https://www.torproject.org/docs/debian.html.en#ubuntu [2] https://trac.torproject.org/projects/tor/ticket/14997#comment:3 [3] https://lists.torproject.org/pipermail/tor-relays/2018-June/015549.html [4] https://trac.torproject.org/projects/tor/ticket/26474 -- https://twitter.com/nusenu_ https://mastodon.social/@nusenu

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DNS-over-HTTPS (DOH) in Firefox/Torbrowser
by nusenu 01 Jul '20

01 Jul '20

Hi, since Mozilla did tests [0] on DOH [1] in Firefox I was wondering if Torbrowser developers have put any thought into that as well? Note: I'm _not_ suggesting to use DOH in torbrowser I'm just asking because the answer probably matters for exit documentation in the relay guide if clients do DNS themselves over TCP connections instead of relying on the exit (even if torbrowser is not the only tor client). thanks, nusenu [0] https://www.ghacks.net/2018/03/20/firefox-dns-over-https-and-a-worrying-shi… [1] https://datatracker.ietf.org/doc/draft-hoffman-dns-over-https/ -- https://mastodon.social/@nusenu twitter: @nusenu_

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Lets give every circuit its own exit IP?
by nusenu 18 Mar '20

18 Mar '20

The unbearable situation with Google's reCAPTCHA motivated this email (but it is not limited to this specific case). This idea came up when seeing a similar functionality in unbound (which has it for a different reason). Assumption: There are systems that block some tor exit IP addresses (most likely the bigger once), but they are not blocked due to the fact that they are tor exits. It just occurred that the IP got flagged because of "automated / malicious" requests and IP reputation systems. What if every circuit had its "own" IP address at the exit relay to avoid causing collateral damage to all users of the exit if one was bad? (until the exit runs out of IPs and starts to recycle previously used IPs again) The goal is to avoid accumulating a bad "reputation" for the single used exit IP address that affects all tor users of that exit. Instead of doing it on the circuit level you could do it based on time. Change the exit IP every 5 minutes (but do _not_ change the exit IPs for _existing_ circuits even if they live longer than 5 minutes). Yes, no one has that many IPv4 addresses but with the increasing availability of IPv6 at exits and destinations, this could be feasible to a certain extend, depending on how many IPv6 addresses the exit operator has. There are exit operators that have entire /48 IPv6 blocks. problems: - will not solve anything since reputation will shift to netblocks as well (How big of a netblock are you willing to block?) - you can tell two tor users easily apart from each other even if they use the same exit (or more generally: you can tell circuits apart). There might be all kinds of bad implications that I'm not thinking off right now. - check.tpo would no longer be feasible - how can do we still provide the list of exit IPs for easy blocking? Exits could signal their used netblock via their descriptor. What if they don't? (that in turn opens new kinds of attacks where an exit claims to be /0 and the target effectively blocks everything) - more state to track and store at the exit -... some random thoughts, nusenu -- https://mastodon.social/@nusenu twitter: @nusenu_

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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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Bandwidth scanner: request for feedback
by teor 20 Nov '18

20 Nov '18

Hi, Juga and pastly have been working hard on sbws. Sbws' results are now similar to torflow's results: https://trac.torproject.org/projects/tor/attachment/ticket/27135/20180826_0… Now that sbws is close to torflow, we want some feedback on its design. We’ll work on the design at the tor meeting in September. Please feel free to give feedback by email, or on the tickets: What happens when sbws doesn't match torflow? https://trac.torproject.org/projects/tor/ticket/27339 We suggest this rule: If an sbws deployment is within X% of an existing bandwidth authority, sbws is ok. (The total consensus weights of the existing bandwidth authorities are within 25% - 50% of each other, see #25459.) How long should sbws keep relay bandwidths? https://trac.torproject.org/projects/tor/ticket/27338 Torflow uses the latest self-reported relay observed bandwidth and bandwidth rate. Torflow uses a complex feedback loop for measured bandwidths. We think sbws can use a simple average or exponentially decaying weighted average. How should we scale sbws consensus weights? https://trac.torproject.org/projects/tor/ticket/27340 If sbws' total consensus weight is different to torflow's total consensus weight, how should we scale sbws? (The weights might differ because the measurement method is different, or because scanners and servers are in different locations.) In the bandwidth file spec, we suggest linear scaling. How should we round sbws consensus weights? https://trac.torproject.org/projects/tor/ticket/27337 Torflow currently rounds to 3 significant figures (which is a maximum of 0.5%). But I suggest 2 significant figures for sbws (or max 5%), because: - tor has a daily usage cycle that varies by 10% - 20% - existing bandwidth authorities vary by 25% - 50% Proposal 276 contains a slightly more complicated rounding algorithm, which we may want to implement in sbws or in tor: https://gitweb.torproject.org/torspec.git/tree/proposals/276-lower-bw-granu… Does sbws need a maximum consensus weight fraction? https://trac.torproject.org/projects/tor/ticket/27336 Torflow uses 5%, but I suggest 1%, because the largest relay right now is only 0.5%. T -- teor Please reply @torproject.org New subkeys 1 July 2018 PGP C855 6CED 5D90 A0C5 29F6 4D43 450C BA7F 968F 094B ----------------------------------------------------------------------

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Proposal 298: Putting family lines in canonical form
by Nick Mathewson 31 Oct '18

31 Oct '18

Filename: 298-canonical-families.txt Title: Putting family lines in canonical form Author: Nick Mathewson Created: 31-Oct-2018 Status: Open Target: 0.3.6.x 1. Introduction With ticket #27359, we begin encoding microdescriptor families in memory in a reference-counted form, so that if 10 relays all list the same family, their family only needs to be stored once. For large families, this has the potential to save a lot of RAM -- but only if the families are the same across those relays. Right now, family lines are often encoded in different ways, and placed into consensuses and microdescriptor lines in whatever format the relay reported. This proposal describes an algorithm that authorities should use while voting to place families into a canonical format. This algorithm is forward-compatible, so that new family line formats can be supported in the future. 2. The canonicalizing algorithm To make a the family listed in a router descriptor canonical: For all entries of the form $hexid=name or $hexid~name, remove the =name or ~name portion. Remove all entries of the form $hexid, where hexid is not 40 hexadecimal characters long. If an entry is a valid nickname, put it into lower case. If an entry is a valid $hexid, put it into upper case. If there are any entries, add a single $hexid entry for the relay in question, so that it is a member of its own family. Sort all entries in lexical order. Remove duplicate entries. Note that if an entry is not of the form "nickname", "$hexid", "$hexid=nickname" or "$hexid~nickname", then it will be unchanged: this is what makes the algorithm forward-compatible. 3. When to apply this algorithm We allocate a new consensus method number. When building a consensus using this method or later, before encoding a family entry into a microdescriptor, the authorities should apply the algorithm above. Relay MAY apply this algorithm to their own families before publishing them. Unlike authorities, relays SHOULD warn about unrecognized family items.

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Updates and review on "Proposal 254: Padding Negotiation"
by George Kadianakis 30 Oct '18

30 Oct '18

Hey Mike, I took another look at prop#254 and made some changes of my own in my torspec branch circuitpadding-proposal-updates (see commit ab37543). Let me know if they look right to you. Some of those I had to look into the code to understand, and I hope I got them right. Furthermore, I opened a pull request with a few questions and comments for further improvements and clarifications: https://github.com/torproject/torspec/pull/39 Cheers!

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Re: [tor-dev] obfs4, meek, active probing and the timeline of pluggable transports
by Piyush Kumar Sharma 29 Oct '18

29 Oct '18

Hello all, I have a few specific questions related to the pluggable transports. 1.) I believe that obfs4 stops active probing(the latest problem as brought to notice by Ensafi et al, IMC 2015 and Shinying Cho, FOCI 2018), and hence discovering obfs4 Tor bridges using active probing is not possible. Is that true? If so, then we are good to go and hence we don't need any other pluggable transport to work for us as long as obfs4 is working? 2.) What was the motivation to bring in meek as a pluggable transport, given the fact that obfs4 works great to cover all the existing problems with Tor detection. Was the motivation just the fact that, it will be much easier for the users to use meek than obfs4 or something other than this? 3.) I searched a lot but could not find the timeline in which pluggable transports were built. As in what was developed and deployed first, obfs4 or meek? Regards Piyush IIITD

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Add EVENT message to pt-spec.txt and control-spec.txt
by David Goulet 29 Oct '18

29 Oct '18

Greetings tor-dev! We've been working on improving PT reporting towards Tor so for instance Tor Browser can better inform the user or take actions based on the PT state when connecting to the network. The following ticket summarize it: https://trac.torproject.org/projects/tor/ticket/28180 To achieve this, we are submitting these to torspec.git patches to extend both the pt-spec.txt and control-spec.txt to support such mechanism. This is the first draft. Below is the link to the PT spec patch. It adds the EVENT message that for now is only used, as you will see, for reporting connection status message. However, you should see this EVENT message as extendable to whatever the PT would like to report to Tor that we can think of in the future: https://gitweb.torproject.org/user/dgoulet/torspec.git/commit/?h=ticket2818… The second, is simpler, it is how Tor will send it back to the control port: https://gitweb.torproject.org/user/dgoulet/torspec.git/commit/?h=ticket2818… Please, any questions or feedbacks is very welcome! The main idea here is to keep things simple and extendable. Note that since Tor doesn't implement the PT 2.0 spec yet, we haven't done anything for that spec but after skimming the version 2, I think we can easily move this EVENT message concept if we want it. Cheers! David -- t2Mtu4qBote14xSTFee/xnHlXp1eabwHFbehBlktnus=

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(no subject)
by sarpedon montecarlo 26 Oct '18

26 Oct '18

Hi! I am supposed to implement, a python application that runs tor in background. The running tor is under direct control of the python app via control port. This running tor, is the proxy for the Tor Browser; By this I mean, when the Tor Browser starts, it will connect to this process, instead of the bundled tor provided by itself. The controlling features I am into, are as below: A) I want to attach streams coming from each tabs of the Tor Browser, attached to a separate circuit; By this I mean each tab of the browser, use a separate circuit, and do not share circuits with each other.(just like the way ordinary TBB does that) for this I am aware that Tor Button plugin does something with the streams to separate streams of a specific tab from other streams. Then by using IsolateSocksStream option on the tor side, tor will successfully isolate each tabs streams. My problem here, is that I am handling the routing and stream attaching all by myself and I can not use the provided IsolateSocksStream option because I am handling the circuit generation by myself because of the specific policies I am using for generating circuits, and their related paths. So if I am facing a bunch of streams, and I have a bunch of circuits myself, How am I going to detect that Stream A is from tab A of TBB and Stream B is from tab B of TBB, so I attach stream A to circuit A, and attach stream B to circuit B. Thanks in advance.

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tor-dev October 2018