[tor-bugs] #2732 [Tor Hidden Services]: Simplify hid_serv_responsible_for_desc_id (was: Audit hid_serv_responsible_for_desc_id)

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#2732: Simplify hid_serv_responsible_for_desc_id
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 Reporter:  rransom              |          Owner:  rransom           
     Type:  defect               |         Status:  assigned          
 Priority:  major                |      Milestone:  Tor: 0.2.1.x-final
Component:  Tor Hidden Services  |        Version:                    
 Keywords:                       |         Parent:                    
   Points:                       |   Actualpoints:                    
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Changes (by rransom):

  * status:  new => assigned
  * priority:  critical => major


Comment:

 Currently, `hid_serv_responsible_for_desc_id`:

 1. calls `hid_serv_acting_as_directory` to check that the relay is
 configured as a hidden service directory, and that the relay is listed in
 the consensus with the HSDir flag (and returns 0 otherwise);
 2. calls `hid_serv_get_responsible_directories` to get a list of up to
 `REND_NUMBER_OF_CONSECUTIVE_REPLICAS` (currently 3) HSDir nodes whose
 ‘identity digest’s follow the hidden service descriptor's ‘descriptor ID’;
 3. uses `rend_id_is_in_interval` to verify that the relay's ‘identity
 digest’ is in the circular interval after the HS ‘descriptor ID’ and
 before or equal to the ‘identity digest’ of the last relay in the list
 returned by `hid_serv_get_responsible_directories` (and returns 0
 otherwise).  (Note that this relies on the undocumented fact that
 `hid_serv_get_responsible_directories` adds relays to the list in the
 order in which it encounters them.)

 This is equivalent to the following (much simpler) behaviour:

 1. Call `hid_serv_get_responsible_directories` to get a list of all relays
 responsible for the ‘descriptor ID’, then
 2. return 1 if this relay is in the resulting list, or 0 if it is not.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/2732#comment:1>
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