- tor-relays - lists.torproject.org

questions about attacks involving single-end measurements of available bandwidth
by Mirimir 10 Oct '14

10 Oct '14

In planning how to configure Tor relays, I've been considering various known attacks. Most involve systemic issues about design and implementation, and so aren't relevant to relay configuration. But there is one that seems relevant, and addressable. I've been reading the work of Sambuddho Chakravarty and coworkers, in particular his thesis and a technical report on LinkWidth.[0],[1] What seems relevant here are deanonymization attacks on clients and hidden services that rely on traffic watermarking in conjunction with single-end measurements of available relay bandwidth. I am somewhat dubious about real-world workability. Fast relays simultaneously handle numerous connections, and so it's arguable that no single connection substantially perturbs available bandwidth. But on the other hand, it takes months for traffic through new relays to ramp up, and perhaps they are easier to scope while relatively idle. Regardless, Tor relays are very specialized. And so it should be trivial to craft iptables rules that prevent responses to LinkWidth and other tools for single-end bandwidth measurement, but don't interfere with anything essential. However, I haven't come across anything that seems relevant. Has this threat been addressed? Or am I missing something that complicates the response? Or conversely, is it not something to worry about? [0] Chakravarty (2014) Traffic Analysis Attacks and Defenses in Low Latency Anonymous Communication (PhD thesis) http://www.cs.columbia.edu/~angelos/Papers/theses/sambuddho_thesis.pdf [1] Chakravarty et al. (2008) LinkWidth: A Method to Measure Link Capacity and Available Bandwidth using Single-End Probes http://academiccommons.columbia.edu/download/fedora_content/download/ac:110…

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Need Routing Info on Relays
by Tor Zilla 09 Oct '14

09 Oct '14

Hi Folks, I am trying to figure out how the packet flows over a Tor network.. There is a mix of information.. Some claim that the ISP is not aware of the payload as the complete data is encrypted whereas some say that your ISP is not used at all when using Tor network. AFAIK my packets go to the outer web via my ISP and there is no way to by pass that. I might be wrong. Can someone give me a detailed packet flow? Thanks, Torzilla11

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Re: [tor-relays] . obfsproxy not working on bridge relay
by Jan Nielsen 09 Oct '14

09 Oct '14

I believe that error means obfsproxy was either not installed correctly or your torrc is not pointing to the correct location. Follow the below link's instructions. Also, a quick google search for that error provided resukts from this mailing list. Follow its instructions as well. https://lists.torproject.org/pipermail/tor-relays/2014-February/003892.html On Oct 8, 2014 6:00 AM, <tor-relays-request(a)lists.torproject.org> wrote: > Send tor-relays mailing list submissions to > tor-relays(a)lists.torproject.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays > or, via email, send a message with subject or body 'help' to > tor-relays-request(a)lists.torproject.org > > You can reach the person managing the list at > tor-relays-owner(a)lists.torproject.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of tor-relays digest..." > > Today's Topics: > > 1. obfsproxy not working on bridge relay (jchase) > 2. Re: obfsproxy not working on bridge relay (George Kadianakis) > > > ---------- Forwarded message ---------- > From: jchase <jchase(a)riseup.net> > To: tor-relays(a)lists.torproject.org > Cc: > Date: Wed, 08 Oct 2014 10:36:39 +0000 > Subject: [tor-relays] obfsproxy not working on bridge relay > Hi, > Due to m limited bandwidth I've decided to turn my relay into a bridge. > I seem to have everything right except if I restart tor I get a warning > that "managed proxy obfsproxy is 'closed'". I'm sure this has come up in > the past but I can find it in the archives. > In torrc I have: > SocksPort 0 > ORPort 9001 > Exitpolicy reject *:* > Log notice file /var/log/tor/notices.log > Contact info [] > Nickname rasptorholland > BridgeRelay 1 > ServerTransportPlugin obfs3 exec /usr/bin/obfsproxy managed > ServerTransportListenAddr obfs3 0.0.0.0:9030 > DisableDebuggerAttachment 0 > > Both ports are forwarded, though I can't find proof that tor is actually > using port 9030. > > Any suggestions? > -J. Chase > > > > > ---------- Forwarded message ---------- > From: George Kadianakis <desnacked(a)riseup.net> > To: tor-relays(a)lists.torproject.org > Cc: > Date: Wed, 08 Oct 2014 11:41:22 +0100 > Subject: Re: [tor-relays] obfsproxy not working on bridge relay > jchase <jchase(a)riseup.net> writes: > > > Hi, > > Due to m limited bandwidth I've decided to turn my relay into a bridge. > > I seem to have everything right except if I restart tor I get a warning > > that "managed proxy obfsproxy is 'closed'". I'm sure this has come up in > > the past but I can find it in the archives. > > In torrc I have: > > SocksPort 0 > > ORPort 9001 > > Exitpolicy reject *:* > > Log notice file /var/log/tor/notices.log > > Contact info [] > > Nickname rasptorholland > > BridgeRelay 1 > > ServerTransportPlugin obfs3 exec /usr/bin/obfsproxy managed > > ServerTransportListenAddr obfs3 0.0.0.0:9030 > > DisableDebuggerAttachment 0 > > > > Hello, > > how did you install obfsproxy? Which installation instructions did you > follow? Seems like you didn't follow: > https://www.torproject.org/projects/obfsproxy-instructions.html.en > > What happens if you run '/usr/bin/obfsproxy managed' in a terminal? > > > _______________________________________________ > tor-relays mailing list > tor-relays(a)lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays > >

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Bridges and advertised bandwidth
by Jan Nielsen 09 Oct '14

09 Oct '14

Hi everyone. I am currently operating 4 bridges on VPSs. They all appear to working correctly. However, 2 of the 4 bridges have 0kb/s as their advertised bandwidth while the other two are advertising around 100KB/s. Is there a reason for the 0kb/s? Does this indicate an error in my bridges or simply a gitch? See this for reference. https://globe.torproject.org/#/search/query=acrossthebridge Thank you.

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How many exits can we run?
by Eric Hocking 09 Oct '14

09 Oct '14

Hi everyone, Is there a limit to how many exit nodes we can run?

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Re: [tor-relays] obfsproxy not working on bridge relay - solved?
by jchase 08 Oct '14

08 Oct '14

> From: George Kadianakis <desnacked(a)riseup.net> > To: tor-relays(a)lists.torproject.org > Subject: Re: [tor-relays] obfsproxy not working on bridge relay > Message-ID: <874mve973h.fsf(a)riseup.net> > Content-Type: text/plain > > jchase <jchase(a)riseup.net> writes: > >> Hi, >> Due to m limited bandwidth I've decided to turn my relay into a bridge. >> I seem to have everything right except if I restart tor I get a warning >> that "managed proxy obfsproxy is 'closed'". I'm sure this has come up in >> the past but I can find it in the archives. >> In torrc I have: >> SocksPort 0 >> ORPort 9001 >> Exitpolicy reject *:* >> Log notice file /var/log/tor/notices.log >> Contact info [] >> Nickname rasptorholland >> BridgeRelay 1 >> ServerTransportPlugin obfs3 exec /usr/bin/obfsproxy managed >> ServerTransportListenAddr obfs3 0.0.0.0:9030 >> DisableDebuggerAttachment 0 >> > > Hello, > > how did you install obfsproxy? Which installation instructions did you > follow? Seems like you didn't follow: > https://www.torproject.org/projects/obfsproxy-instructions.html.en > > What happens if you run '/usr/bin/obfsproxy managed' in a terminal? Hello, Thanks for your advice! I had installed obfsproxy with apt-get on a Pi. I removed that and tried pip. It took me a while to find out that pip was actually python-pip. (Maybe the Tor website could be more specific about that.) That install went well. You asked me to see what happened after the command '/usr/bin/obfsproxy managed'. It took me a while to find that obfsproxy was installed in /usr/local/ , not in /usr/bin/ . And now, until further notice from tor, things seem to work fine. Thanks, J. Chase

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obfsproxy not working on bridge relay
by jchase 08 Oct '14

08 Oct '14

Hi, Due to m limited bandwidth I've decided to turn my relay into a bridge. I seem to have everything right except if I restart tor I get a warning that "managed proxy obfsproxy is 'closed'". I'm sure this has come up in the past but I can find it in the archives. In torrc I have: SocksPort 0 ORPort 9001 Exitpolicy reject *:* Log notice file /var/log/tor/notices.log Contact info [] Nickname rasptorholland BridgeRelay 1 ServerTransportPlugin obfs3 exec /usr/bin/obfsproxy managed ServerTransportListenAddr obfs3 0.0.0.0:9030 DisableDebuggerAttachment 0 Both ports are forwarded, though I can't find proof that tor is actually using port 9030. Any suggestions? -J. Chase

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Trying Trusted Tor Traceroutes
by Sebastian Urbach 08 Oct '14

08 Oct '14

Dear list members, We are happy to present the preleminary analysis results from TTTT: http://arxiv.org/pdf/1410.1823v1.pdf The conclusions are: 1. We have found that AS-path prediction techniques significantly overestimate ASes and IXes traversed by Tor traffic, calling into question the results of previous evaluations of the network-level adversary threat. 2. Our simulations show that Tor may currently be less vulnerable to an AS or IXP adversary than has been previously found. We also find that proposed path-selection algorithms to avoid a network adversary still leave a significant chance for users to be deanonymized over time due to the errors in path prediction, and these algorithms lead to significant rates of connection failures, even though in the large majority of cases the failures could be avoided with better measurement. 3. Thus our results suggest the importance of accurate measurement both for understanding Tor security and for improving it. -- Mit freundlichen Grüssen / Sincerely yours Sebastian Urbach ----------------------------------------- Definition of TOR: 10% luck, 20% skill, 15% concentrated power of will, 5% pleasure, 50% pain and 100% reason to remember the name! -----------------------------------------

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Less Traffic on my relay
by Tor Zilla 07 Oct '14

07 Oct '14

Hi All, I am a noob to the Tor community and its fun serving Tor as one of the relays. I am planning to setup multiple relays however before i jump into anything further i setup one machine as a non exit relay to test how much traffic i can route.. Not to forget i also read the article on torproject.org which mentions the life cycle of a relay.. Now its the 4th day of my relay and the traffic is almost nothing but as per the article i must see an increase in traffic on day 4.. The machine is ON for almost an hour now and the traffic is too less. Received : 3.62MB Sent : 1.6MB My dedicated bandwidth to Tor is 60 KB/s.. Do i need to keep the machine on 24/7 because as of now its just ON for 3 to 4 hours.. Assuming that the traffic is low on the entire Tor network is this kind of traffic normal or something is wrong on my side..? Your help will me much appreciated.. Thanks and Regards, Torzilla11

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Tor metrics regarding bridges running transports
by Jan Nielsen 07 Oct '14

07 Oct '14

Hi all. I was wondering if these metrics exist? I couldn't find anything on tor metrics. They list the amount of users using transports but there is no information regarding the number of bridges running particular pluggable transports.

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