[tor-bugs] #22794 [Applications/Tor Browser]: Don't open AF_INET/AF_INET6 sockets when AF_LOCAL is configured.

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#22794: Don't open AF_INET/AF_INET6 sockets when AF_LOCAL is configured.
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 Reporter:  yawning                              |          Owner:
                                                 |  pospeselr
     Type:  defect                               |         Status:
                                                 |  assigned
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-security, tbb-sandboxing,        |  Actual Points:
  TorBrowserTeam201801                           |
Parent ID:  #20775                               |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by yawning):

 Really though, just look at `nsSOCKSIOLayer`.

  1. All outgoing SOCKS connections made by firefox start out their lives
 as `AF_INET` sockets. (Assumption, firefox code gives me a headache, but
 it matches the trace output).
  2. When firefox actually goes to connect to the proxy (`ConnectToProxy`),
 the `FixupAddressFamily` routine is called.
  3. `FixupAddressFamily` checks to see if the proxy actually is reachable
 via an `AF_INET` socket, and if not, opens a new file descriptor with the
 correct domain.

 What appears to have happened judging for a cursory inspection of the file
 history was:

   1. Back in the day, this was only expected to handle `AF_INET`, because
 "this IPng thing will never happen".
   2. When `AF_INET6` support was required, it was kludged on this way.
   3. When `AF_UNIX` (and Windows pipes or whatever that's also in the
 code) support was required, the kludge was enhanced.

 Which is great if the only reason you want something like `AF_UNIX` is to
 use `AF_UNIX` socket for the hell of it, and not so great if you want use
 something like seccomp to prohibit `AF_INET`.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22794#comment:18>
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