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Re: Cookie crumbling in -09

From: Willy Tarreau <w@1wt.eu>
Date: Sat, 16 Nov 2013 09:22:26 +0100
To: Martin Thomson <martin.thomson@gmail.com>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
Message-ID: <20131116082226.GH11858@1wt.eu>
On Sat, Nov 16, 2013 at 09:02:13AM +0100, Willy Tarreau wrote:
> Hi Martin,
> 
> On Fri, Nov 15, 2013 at 11:52:02AM -0800, Martin Thomson wrote:
> > I've just added some text to the editor's draft [1] around special
> > handling of the cookie header field.  This will allow clients to
> > squeeze out a little more compression efficiency.
> > 
> > After the gaffe earlier this week with -08, I wanted to publicize this
> > a little.  This is the only substantial change between -07 and the
> > imminent -09 in the main specification.
> > 
> > There are, of course, other compression-related changes coming in HPACK.
> > 
> > [1] https://github.com/http2/http2-spec/commit/b9a62379e29174bada803fb27e2a6d36b69513f0
> 
> This part looks strange to me :
> 
>   If there are multiple Cookie header fields after decompression,
>   these MUST be concatenated into a single octet string using the
>   two octet delimiter of 0x3B, 0x20 (the ASCII string "; ").
> 
> Indeed, right now applications correctly handle cookie as a list
> of values which can be aggregated using commas like any other header
> field. Thus, why make a special case of this cookie header and force
> implementations to parse requests to see if there are multiple
> occurrences and merge them differently than what is done for other
> header fields ? I'd rather suggest that if there are multiple Cookie
> header fields after decompression, they MAY be concatenated into a
> single octet string using commas just like any other header field
> (0x2C 0x20).

Or maybe even better, we could probably say that the headers MAY
preferentially be concatenated using 0x3B 0x20, though the default
header field folding using 0x2C 0x20 is fine as well. At least we
allow implementations to restore what they found on the input in
the case the cookies were all on a single line emitted by a browser
using semi-colons.

Willy
Received on Saturday, 16 November 2013 08:22:48 UTC

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