[tor-bugs] #28655 [Obfuscation/BridgeDB]: If a bridge supports obfs4, don't give out its other flavors

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#28655: If a bridge supports obfs4, don't give out its other flavors
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 Reporter:  arma                  |          Owner:  sysrqb
     Type:  defect                |         Status:  new
 Priority:  Medium                |      Milestone:
Component:  Obfuscation/BridgeDB  |        Version:
 Severity:  Normal                |     Resolution:
 Keywords:                        |  Actual Points:
Parent ID:                        |         Points:
 Reviewer:                        |        Sponsor:  Sponsor19
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Comment (by dcf):

 Replying to [ticket:28655 arma]:
 > There's a FOCI 2018 paper looking at blocking of bridges inside China,
 and one of their conclusions is that China has moved from "block by
 IP:port" to "block to IP":
 >
 > Second, it assumes that the FOCI paper is actually correct in its
 conclusions about how China has changed its blocking. I recall in the Q&A
 at the end of the presentation that some folks questioned the analysis,
 but I didn't follow it enough to form a solid opinion. But even if China
 isn't doing its censorship in this new way yet, now is a great time for
 bridgedb to become able to handle it.)

 My, Lynn Tsai's, and Qi Zhong's monitoring of default Tor Browser bridges
 also reached this conclusion, that the GFW changed from single-port
 blocking to all-port blocking (at least for these special bridges). The
 change happened in October 2016.

 https://www.bamsoftware.com/papers/thesis/#sec:china-perport
 https://www.bamsoftware.com/papers/thesis/#sec:china-allports
 > The blocking event of October 20, 2016 was noteworthy not only because
 it occurred before a release, but also because it affected more than one
 port on some bridges. See point ⓗ in
 [https://www.bamsoftware.com/papers/thesis/#fig:proxy-probe-timelines-
 china1 Figure 5.2]. When GreenBelt:7013 was blocked, so were
 GreenBelt:5881 (which had escaped blocking in the previous batch) and
 GreenBelt:12166 (which was awaiting deployment in the next batch).
 Similarly, when MaBishomarim:7920 and JonbesheSabz:4148 were blocked, so
 were the Orbot-reserved MaBishomarim:1984 and JonbesheSabz:1984 (point ⓚ),
 ending an eight-month unblocked streak.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28655#comment:1>
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