[tor-bugs] #11648 [Tor]: Problem parsing .z-compressed descriptors fetched via DirPort

Tor Bug Tracker & Wiki blackhole at torproject.org
Thu May 1 15:27:22 UTC 2014


#11648: Problem parsing .z-compressed descriptors fetched via DirPort
-------------------------+-----------------------
     Reporter:  karsten  |      Owner:
         Type:  defect   |     Status:  new
     Priority:  normal   |  Milestone:
    Component:  Tor      |    Version:
   Resolution:           |   Keywords:  tor-relay
Actual Points:           |  Parent ID:
       Points:           |
-------------------------+-----------------------

Comment (by wfn):

 Replying to [comment:4 karsten]:
 > Replying to [comment:2 wfn]:
 > > Last mystery comment for now:
 > >
 > >  1. It seems that zlib header should include the length of the zlib
 image. When sending in multiple chunks, tor is of course unable to provide
 the right length in the header.
 >
 > Well, tor could go through chunks twice, once to sum up their lengths
 and write that to the header, and another time to actually send chunks.

 I suppose. The overall logic would have to be changed, as it's currently
 "make a chunk and send it out right now."

 > But I don't know the code enough to say if this would solve the problem.

 Yeah, maybe this is not a very productive angle anyway.

 > [...]
 > But here's some more information from `curl -vv`: it seems that tor uses
 "deflate" to compress descriptors.  AFAIK, there's also "zlib" and "gzip",
 which tor doesn't seem to use.  Though Python's zlib should support all of
 them.  Hmm.

 I'm reeeally not sure of those terms myself, but I *think* that zlib
 encapsulates DEFLATE either way; it adds (zlib or gzip) header to the
 DEFLATE-compressed data (DEFLATE is a compression algorithm.) So it
 *should* be "the data is DEFLATEd, the only question is if the header is
 in zlib or gzip format." But, I'm not sure.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11648#comment:6>
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