[tor-dev] "old style" hidden services after Prop224

Razvan Dragomirescu razvan.dragomirescu at veri.fi
Tue Sep 13 15:13:58 UTC 2016

I disagree with your approach, for comparison's sake, let's say v2 is IPv4
and v3 is IPv6. When IPV6 was introduced, IPv4 was kept around (and still
is to this day, although IPv6 is arguably a much better solution in a lot
of areas). Expecting _everyone_ to just switch to IPv6 or get cut off is a
bit of a pipe dream.

Tor hidden services are a bit "special" because it's hard to poll their
owners on their intentions. Some hidden service operators have gone to
great lengths to advertise their .onion URLs (v2-style), some have even
generated vanity addresses (like Facebook). Forcing a switch to v3 at some
point presents a very interesting opportunity for phishing because suddenly
a service known and trusted at some address (as opaque as it is) would need
to move to an even more opaque address, with no way to determine if the two
are really related, run by the same operator, etc. If I were a LE agency, I
would immediately grab v3 hidden services, proxy content to existing v2
services and advertise my v3 URL everywhere, then happily monitor traffic.

All I'm saying is don't remove the v2 services, even if you choose to no
longer support them. Some operators (like my company) may choose to
continue to patch the v2 areas if required and release the patches to the
community at large. Forcing us out altogether would make us drop Tor and
start using an alternative network or expending the additional effort to
make our services network-agnostic (so no more good PR for Tor).

Ivan was right, moving to v3 would be, at least for my project, extremely
complex and unwieldy. Ed25519 is not supported by any smartcards I know
(but can be "hacked" by manually defining Curve25519 params and converting
back and forth). But then we'd have to modify the service re-registration
(or wait for OnionBalance to do it), then add another layer for
OnionCat-like lookups, etc. It would be far easier to just drop the Tor
dependency at that point or centralize it a bit more.

Just my 2 cents, if any hidden service operators wish to chime in, feel
free to do so. After all, it's us (them? :) ) that will have to make the
changes to their services.


On Tue, Sep 13, 2016 at 5:40 PM, s7r <s7r at sky-ip.org> wrote:

> On 9/13/2016 3:27 PM, David Goulet wrote:
> [SNIP]
> > Hello!
> >
> > So I 100% share Ivan's concerns. The Hidden Service subsytem of Tor is
> quite
> > complex, lots of pieces need to be glued together and prop224 will add a
> lot
> > of new code (in the 10 of thousand+).
> >
> > We decided a while back to have the two protocols living side by side at
> first
> > that is current system (v2) and next gen (v3). Relays will need to
> support v2
> > for a while after v3 is release because well not everybody updates their
> tor
> > to the latest. Lots of people have current .onion for which they need a
> > transition to the new generation which includes telling their users
> about the
> > new 52 character one and SSL certs and so on...
> >
> > The question arise now. Someone running a .onion upgrades her tor that
> > supports v3, should we allow v2 to continue running or transition it to
> v3 or
> > make them both happy together...? We haven't discuss this in depth and
> thus we
> > need to come to a decision before we end up implementating this (which is
> > _soon_). I personally could think that we probably want to offer a
> transition
> > path and thus have maybe a torrc option that controls that behavior
> meaning
> > allowing v2 for which we enable by default at first and then a
> subsequent Tor
> > release will disable it so the user would have to explicitely set it to
> > continue running v2 .onion and then finally rip off v2 entirely in an
> other
> > release thus offering a deprecation path.
> >
> > However, we are clear that every _new_ service will be v3 and never
> again v2
> > unless it already exists that is we can find a RSA private key
> (considering we
> > do the above of course). And considering both will be supported for a
> while,
> > we'll have to maintain v2 security wise but all new features will go in
> v3.
> >
> > Let's discuss it and together we can come up with a good plan! :)
> >
> > Thanks!
> > David
> >
> v2= old-style (RSA1024) hidden services
> v3= prop 224 (ed25519) hidden services
> I agree with David - it will be problematic to maintain support for both
> v2 and v3, unlimited in the future. It's clear that we need to offer a
> reasonable transition period, so everyone can upgrade and move their
> customers/user bases to the new hidden services, but this doesn't mean
> v2 should work forever.
> v2 hidden services already provide questionable security (from crypto
> point of view) and in the future things will only get worse for v2. I
> agree that there are a lot of third party tools working with v2 hidden
> services (OnionCat, OnionBalance) -  these all need to be improved to
> support prop 224 hidden services.
> Considerable resources are spent on v3 hidden services. They are better
> vs v2 from all points of view, I don't think keeping the v2 code and
> therefor allowing additional attack surface + creating the task to
> maintain this old code (v2) in future releases is worth it. This is how
> things work in software, if something gets upgraded everything upper
> layer should upgrade as well. Keeping parallel older versions to allow a
> feature of non-mandatory upgrades is not solid reason for us to do it.
> Also, we need to move with Prop 245 (deprecate TAP handshake entirely)
> and the v2 hidden service code is the blocker for this.
> So, my opinion is to deprecate v2 entirely after a sane and reasonable
> transition period.  Apologies to whom this will create headaches -
> technologically everything can be adjusted to v3 hidden services, it's
> just some work required -- it's not going to be fun but it's the clean
> way for the longer term future.
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