[tor-dev] Is it time to drop support for the v1/v2 protos?

[Nick Mathewson]

On Sat, Dec 27, 2014 at 9:38 AM, Tom van der Woerdt <info at tvdw.eu> wrote:
> Hi all,
>
> After reading the Tor spec [1] I did some digging and realized that the old
> handshakes and link protocols (v1 (certs up-front) and v2 (renegotiation))
> are not used anymore as of 0.2.3.6-alpha which introduced link proto v3.
>
> Supporting v1 and v2 requires (among other things) supporting SSLv3 which
> (imho) should be deprecated everywhere.
>
> This makes me wonder why Tor still supports these: is it for compatibility
> with even older versions (consensus health says no) or are there other
> reasons? If someone were to invest a couple of hours and remove all support
> for them from the Tor code and the Tor spec, would this hurt the network or
> would it be a welcome patch?

There are already a couple of tickets for removing these, and I would
like to see them go.  The master ticket is
    https://trac.torproject.org/projects/tor/ticket/9476

(The fact that this ticket is in the 0.2.6 milestone does *not* mean
it will automatically get finished in 0.2.6!  If somebody writes good
patches, then the odds would go up a lot.)

One thing that we would need to think about here is the behavior of
any zombie 0.2.2 clients and servers that are still lying around.  If
they just stop connecting to Tor, great.  But if they do something
obnoxious like fail to connect and then retry repeatedly, we would
need to design our code here so as not to inadvertently turn all these
non-functional clients and servers into a DDoS botnet against Tor.  :)

In any case, removing client-side support for these protocol versions
is a definite "yes, let's do that".  Removing server-side support
would need a little safety testing, but I'd take a patch for that too.

yrs,
-- 
Nick