[tor-bugs] #28655 [Circumvention/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:  phw
     Type:  defect                  |         Status:  needs_revision
 Priority:  High                    |      Milestone:
Component:  Circumvention/BridgeDB  |        Version:
 Severity:  Normal                  |     Resolution:
 Keywords:  bridgedb                |  Actual Points:
Parent ID:                          |         Points:  2
 Reviewer:                          |        Sponsor:  Sponsor19
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Changes (by sysrqb):

 * status:  needs_review => needs_revision


Comment:

 Sorry this took so long to review. It looks good! I only have a few small
 nitpicks.

 -
 [https://gitweb.torproject.org/user/phw/bridgedb.git/tree/bridgedb/test/test_https_distributor.py?h=bug28655&id=ad034c358a38dcea98948d4b2c50e0758f15ce13#n197
 Reusing]  `bridges` is a little confusing (used first as a method
 parameter), can you use a different variable name?
 - Ugh,
 [https://gitweb.torproject.org/user/phw/bridgedb.git/tree/bridgedb/filters.py?h=bug28655&id=ad034c358a38dcea98948d4b2c50e0758f15ce13#n157
 python]. Sure, I guess that's correct. (no changes needed)
 - I agree extending `SUPPORTED_TRANSPORTS` or creating a new `list` config
 option like `PROBING_RESISTANT_TRANSPORTS` is a good idea. Hard-coding the
 list of probing resistant PTs in one place is not great, but hard-coding
 them in two places is asking for bugs :)

 Overall, I think the bridgedb patch is good. I worry about making
 `SUPPORTED_TRANSPORTS` more complex. I think a simple `str` -> `boolean`
 mapping is easy to understand. The two ways I see doing this are not as
 obvious:

 `dict` -> `tuple` as `str` -> (`boolean`, `boolean`)
 `dict` -> `dict` -> `boolean` as `str` -> `str` ({supported, probing
 resistant}) -> `boolean`)

 Maybe you had another idea for this, as well :) but with these options, I
 think adding a new config variable would be more readable.

 For the leekspin patch, I think it looks good. My only concern is in the
 [https://gitweb.torproject.org/user/phw/leekspin.git/tree/leekspin/util.py?id=3bc9c660e8df80fe89693c8e4fad38955011bf20#n65
 description] of the new argument. It says `m` out of `n`, but it's not
 immediately obvious what `m` is here. `n` is an actual argument (`-n`,
 `--descriptors`), but `m` is not a valid argument. Replacing `<m>` with
 `<xp>` would make it more readable, or somehow note `m` **is** `xp`: "make
 `<m>` (`xp`) out of all `<n>`".

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28655#comment:17>
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