W3C home > Mailing lists > Public > public-webappsec@w3.org > March 2014

Re: [integrity] What should we hash?

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Sat, 15 Mar 2014 00:04:57 -0400
Message-ID: <5323D169.4090203@mit.edu>
To: Devdatta Akhawe <dev.akhawe@gmail.com>
CC: Mark Nottingham <mnot@mnot.net>, "public-webappsec@w3.org" <public-webappsec@w3.org>
On 3/14/14 10:50 PM, Devdatta Akhawe wrote:
>> So the browser needs to both be streaming the compressed data to disk and
>> teeing it off to a decompression stream which computes the hash as it goes,
>> right?  Or alternately decompressing and then recompressing?
> Well, we aren't supporting progressive hashes right now.

I'd like to understand what that means.  Does that mean the hash can't 
be computed in a streaming fashion, but actually needs the entire 
decompressed data in a single chunk (in memory?) to compute the hash?

I'm really hoping I'm just misunderstanding this point....

> How about a hybrid with Mark's idea only for only the downloads case?
> We default to undoing content-encodings and the developer can opt-in
> to computing the hash on the gzip'ed file. In most cases, the
> programmer won't need to specify anything extra but for .tar.gz file,
> the programmer will need to add a "encoding=gzip" to the anchor link.
> The spec can allow browsers to just delete the download if they don't
> want to do unzip the document and the programmer forgot to give the
> hash with encoding=gzip.

This seems reasonable, with one caveat: I would prefer there be no 
optional behavior here.  What the non-optional behavior should be 
depends on the above question about streaming vs not.

Received on Saturday, 15 March 2014 04:05:29 UTC

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