[tor-dev] Configuring Single Onion Services

Tue Apr 12 01:06:12 UTC 2016

On 12 Apr (10:48:37), Tim Wilson-Brown - teor wrote:
> 
> > On 12 Apr 2016, at 04:22, David Goulet <dgoulet at ev0ke.net> wrote:
> > 
> > On 08 Apr (10:15:19), Tim Wilson-Brown - teor wrote:
> >> Hi All,
> >> 
> >> I'm working on proposal 260's Rendezvous Single Onion Services in #17178.
> >> 
> >> They are faster, because they have one hop between the service and the introduction and rendezvous points.
> >> But this means that their location is easy to discover (non-anonymous).
> >> So we want to come up with a design that makes it hard to configure a non-anonymous service by accident.
> >> 
> >> Here's a cut-down version of an email I sent to tor-onions for feedback, for those who are on both lists:
> >> 
> >> Nick's concern was that users could configure Single Onion Services without realising that it provides no server location anonymity.
> >> I initially thought we could change the torrc option name to make this clear. ...
> >> I now believe that trying to overload the name of a feature with warnings about its downsides was a mistake. …
> >> 
> >> This would mean that Single Onion Service operators would include in their torrc:
> >> 
> >> SingleOnionMode 1
> >> HiddenServiceDir …
> >> ...
> >> 
> >> As a separate issue, I think there are two alternative designs that can prevent users from configuring the feature and then exposing their location unintentionally:
> >> 
> >> Tor2WebMode requires users to add a compilation option: --enable-tor2web-mode
> >> We could do this with Single Onion Services as well: --enable-single-onion-mode
> >> If SingleOnionMode is configured without the compilation option, tor warns the user and refuses to start.
> >> When it is configured, tor warns the user they're non-anonymous, then starts.
> >> However, using a compilation option makes the feature harder to test.
> >> And Tor2Web operators already don't like having to compile separate binaries.
> >> It's likely Single Onion operators would feel similarly.
> >> 
> >> Alternately, we could add a torrc option: NonAnonymousMode
> >> If SingleOnionMode is configured without NonAnonymousMode, tor warns the user and refuses to start.
> >> When it is configured, tor warns the user they're non-anonymous, then starts.
> > 
> > Just to be clear, the user would have to enable _both_ options to make the
> > single onion mode work? Like so:
> > 
> >    SingleOnionMode 1
> >    NonAnonymousMode 1
> >    HiddenServiceDir ...
> > 
> > Basically asking the user to *explicitely" set an option that says "Ok you are
> > aware that you will loose anonymity".
> > 
> > It's a bit weird to have to enable two options for one feature (single onion)
> > BUT I like the double torrc option forcing the users to understand what's
> > going on (also adding semantic to the config file).
> > 
> > Bikesheding: the name though could be a bit misleading. What if that tor
> > process is also used as a client to "wget" stuff on the server for instance.
> > Won't I be confused if NonAnonymousMode is _set_ not knowing it applies to
> > what? Idea: "HiddenServiceNonAnonymousMode 1". Pretty explicit that it's for
> > the service.
> 
> Actually, NonAnonymousMode applies to the whole tor instance.
> 
> This was an issue we encountered a few months ago, and we decided that it's
> safer to prevent users from opening a SOCKSPort when SingleOnionMode is set.
> 
> Otherwise, the tor instance could be de-anonymised through the
> Single Onion Service, and that has implications for client anonymity as well.

Makes sense actually!

Great, then NonAnonymousMode sounds good to me in this case.

Thanks!
David

> 
> So the permitted combinations are:
> 
> Anonymous Client and Hidden Service
> Anonymous Client
> Hidden Service
> 
> Tor2WebMode and --enable-tor2web-mode and SingleOnionMode and NonAnonymousMode (I can not imagine a use case for this)
> SingleOnionMode and NonAnonymousMode
> Tor2WebMode and --enable-tor2web-mode
> 
> Tim
> 
> > 
> > Cheers!
> > David
> > 
> >> 
> >> I spoke with Nick on IRC and he's happy with either of these options.
> >> 
> >> I'd like to proceed with the NonAnonymousMode torrc option, unless there are compelling reasons against that design.
> >> I hope that this will allow us to get SingleOnionMode merged early in tor 0.2.9.
> >> 
> >> Tim
> >> 
> >> Tim Wilson-Brown (teor)
> >> 
> >> teor2345 at gmail dot com
> >> PGP 968F094B
> >> ricochet:ekmygaiu4rzgsk6n
> >> 
> >> 
> >> 
> > 
> > 
> > 
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> > 
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> 
> Tim Wilson-Brown (teor)
> 
> teor2345 at gmail dot com
> PGP 968F094B
> ricochet:ekmygaiu4rzgsk6n
> 
> 
> 

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