[tor-dev] Configuring Single Onion Services

David Goulet dgoulet at ev0ke.net
Mon Apr 11 18:22:25 UTC 2016

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.


> 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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