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From Dirk-Willem van Gulik <Dirk-Willem.van.Gu...@bbc.co.uk>
Subject Re: DoS with mod_deflate & range requests
Date Wed, 24 Aug 2011 15:46:24 GMT

On 24 Aug 2011, at 16:35, Tim Bannister wrote:

> On Tue, Aug 23, 2011, Roy T. Fielding wrote:
>> And the spec says ...
>> 
>>   When a client requests multiple ranges in one request, the
>>   server SHOULD return them in the order that they appeared in the
>>   request.
>> 
>> My suggestion is to reject any request with overlapping ranges or more
>> than five ranges with a 416, and to send 200 for any request with 4-5
>> ranges.  There is simply no need to support random access in HTTP.
> 
> Deshpande & Zeng in http://dx.doi.org/10.1145/500141.500197 describe a
> method for "streaming" JPEG 2000 documents over HTTP, using many more than
> 5 ranges in a single request.
> A client that knows about any server-side limit could make multiple
> requests each with a small number of ranges, but discovering that limit
> will add latency and take more code.

Agreed - I've seen many 10's of ranges in a single request for things like clever PDF pagination
(or tiny TIFF quicklooks for the pages), clever http fake streaming and clever use of jumping
to i-Frames.

I think we just need to sit this out - and accept up to RequestFieldSize limit bytes on that
line - and then do a sort & merge overlaps as needed. 

And then it is fine.

Dw
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