Re: [websec] Strict-Transport-Security syntax redux

Julian Reschke <julian.reschke@gmx.de> Sat, 29 October 2011 08:07 UTC

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Date: Sat, 29 Oct 2011 10:07:28 +0200
From: Julian Reschke <julian.reschke@gmx.de>
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To: Adam Barth <ietf@adambarth.com>
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Subject: Re: [websec] Strict-Transport-Security syntax redux
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On 2011-10-29 05:08, Adam Barth wrote:
> ...
>> Except for RFC6265, which in the algorithm for parsing "Max-Age=", it
>> algorithmically provides for ignoring a value that doesn't match the
>> effective value ABNF of..
>>
>>   ["-"]*DIGIT
>>
>> ..which would catch the max-age="1" case, but doesn't seem to explicitly
>> address..
>>
>>   max-age=
>
> That's handled by some more general processing rules in the spec.  The
> net result is that it's ignored.
>
>> But in any case, perhaps (additional) browser implementor folk could chime
>> in here -- do we really need to address such detail-level issues (both of
>> the examples above and below) in the syntax/grammar we specify in specs such
>> as these? Or is the new ABNF proposed in the original message in this thread
>> sufficient?
>
> Generally, we prefer to be instructed exactly how to behave for every
> possible input (even illegal ones).  There's a long history of
> quoted-string not being implemented correctly by browsers.  I spec
> this as just splitting the string on ; and then processing each
> substring separately, ignoring bogus/future ones.  I know Julian has a
> dream that all HTTP headers will be parsed the same, but quoted-string
> is sufficiently ill-defined w.r.t. error handling that I prefer to
> avoid it.
> ...

- when discussing generic parsing, we need to distinguish between legacy 
cases like cookies, and new headers, where we can do better

- standardizing handling of broken headers is one thing (and in general 
I prefer not to), but that doesn't mean that when defining a new header 
field we shouldn't minimize the things a sender can get wrong; if we 
know that some recipients will accept both token and quoted-string 
anyway, then it seems like a good thing to simply allow them both, 
reducing the number of special-cases in parsing

- not sure what you mean by "ill-defined w.r.t. error handling"; it's 
defined just like most other syntax elements in HTTP -- is there 
something *specific* to quoted-string you have in mind?

Best regards, Julian