[tor-bugs] #30708 [Circumvention/Obfs4]: Create a docker image for obfs4proxy

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#30708: Create a docker image for obfs4proxy
------------------------------------------------+--------------------------
 Reporter:  phw                                 |          Owner:  phw
     Type:  task                                |         Status:
                                                |  needs_review
 Priority:  Medium                              |      Milestone:
Component:  Circumvention/Obfs4                 |        Version:
 Severity:  Normal                              |     Resolution:
 Keywords:  anti-censorship-roadmap, sponsor28  |  Actual Points:
Parent ID:  #30777                              |         Points:  3
 Reviewer:                                      |        Sponsor:
                                                |  Sponsor28-must
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Changes (by phw):

 * status:  assigned => needs_review


Comment:

 I created a docker image for an obfs4 Tor bridge:
 https://dip.torproject.org/anti-censorship/docker-obfs4-bridge. You can
 test it by cloning the repository and, after entering the directory,
 running:
 {{{
 docker build -t phwinter/obfs4-bridge:0.1 .
 }}}
 Then, you can start the docker image by running:
 {{{
 ./deploy-container.sh
 }}}

 I had to work around a docker design issue: we cannot use a static OR port
 or obfs4 port in the image because that would make it possible to scan the
 IPv4 address space for these ports and block all bridges you find that
 way. We therefore need random ports. Docker's `build` command has a `-P`
 switch that picks a random, external port and forwards it to an internal,
 static port but the issue is that the image has no easy way of learning
 what external port docker picked. Tor however needs to know because it has
 to advertise these ports in its descriptor.

 My workaround is a shell script that automatically determines a random
 port and passes it to the image via environment variables. It's not pretty
 but it works.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30708#comment:2>
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