[tor-bugs] #7590 [Core Tor/Tor]: [PATCH] New option LocalOutboundBindAddress

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#7590: [PATCH] New option LocalOutboundBindAddress
-------------------------------------------------+-------------------------
 Reporter:  ac                                   |          Owner:  (none)
     Type:  enhancement                          |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.4.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-client tor-hs hs-integration     |  Actual Points:
  hs-app-support                                 |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by ac):

 The workarounds are insufficient because:

 1. `iptables`, while fully-functional, requires kernel access that is not
 always available.  (It is not available to me in an actual VM that I rent
 where I do, in fact, run `tor`.)

   I wouldn't be surprised if (e.g.) Windows didn't even have this
 capability exposed to users.

 2. Reconfiguring every single daemon to each individually work around the
 lack of functionality is inadequate and would require patching the code of
 some of those daemons.

   For example, I currently have hidden services `postfix`, `ssh`, and
 `apache`.  Apache runs several CGI type programs, for example the
 configuration interface for `cups`.

   `cups` and `postfix`, by default, grant privileged access to connections
 from IP `localhost`.  So you cannot expose them to tor connections through
 that address, without messing around with them.  `cups` is a reverse proxy
 to a `lighttpd` daemon so you can mess around with the `lighttpd`
 configuratoin file in addition to the `apache` one.  But what about
 `postfix`?  You can probably make it listen on random additional ports or
 addresses, but can you configure it so that it overrides the trust default
 based on its own *listening* address?  Such capability cannot be assumed
 to be present in most software, even if it is possible to do with
 `apache`.

   `ssh` does not grant privileged access to local connections by default,
 but I personally do not want anonymous connections from all-and-sundry
 showing up in output from `w` or in logs as `localhost` when they are
 fundamentally the polar opposite of that.  Again, you cannot hope to
 configure `ssh` to do this based on its own *listening* address or port.
 Even though ssh will listen on any number of addresses or ports, it does
 not let you change how it logs the remote IP conditional on its local
 address (why would it?).

   Even if all those daemons supported the necessary workarounds -- which
 they don't -- I would have to mess with 4 different configuration file
 formats (`lighttpd`, `postfix`, `apache`, `ssh`) trying to get them to
 behave the way I want conditional on something (the listening port) that
 normally isn't a condition of behavior, so it's a giant complicated mess.
 Better to use `iptables`, or patch `tor`.

   Certainly I wouldn't be trying to get the necessary patch into `postfix`
 or `ssh` to work around this, because such a patch would make no sense.
 Unlike this patch, which makes perfect sense and does a completely
 straightforward and sensible thing: sets the bind address on an outgoing
 connection to whatever the user specifies.

 It just makes sense.  You are making a connection, you have an opportunity
 to set the bind address, you give it to the user as a configuration
 option.  Simple, straightforward, sensible, standard practice, no reason
 to think twice.

 There's no reason this can't be done in 2 weeks, or 2 days, or 2 hours.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7590#comment:20>
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