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Re: Weak validators in conditional requests

Mark Nottingham <mnot@mnot.net> Wed, 03 October 2018 07:17 UTC

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From: Mark Nottingham <mnot@mnot.net>
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Date: Wed, 03 Oct 2018 17:14:40 +1000
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References: <bf5a9b56-c416-d4ab-2fbe-ac9b0482dcaa@measurement-factory.com> <0ACB722F-BC39-49BE-9401-F01193E45DAD@mnot.net> <59f34446-46d1-7988-dae8-81bb799f68f9@measurement-factory.com>
To: Eduard Bagdasaryan <eduard.bagdasaryan@measurement-factory.com>
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Subject: Re: Weak validators in conditional requests
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Eduard,

> On 4 Sep 2018, at 9:09 pm, Eduard Bagdasaryan <eduard.bagdasaryan@measurement-factory.com> wrote:
> 
> Yes, it is stated there, but only about If-Match and If-None-Match
> headers. What about If-Modified-Since, If-Unmodified-Since
> and If-Range?

In 723x, the strong vs. weak comparison function distinction is only defined for ETags, not for Last-Modified. The requirements on comparison for LM are defined here:
  https://httpwg.org/specs/rfc7232.html#lastmod.comparison

For If-Range, 7233 says:

"""
A server that evaluates an If-Range precondition MUST use the strong comparison function when comparing entity-tags (Section 2.3.2 of [RFC7232]) and MUST evaluate the condition as false if an HTTP-date validator is provided that is not a strong validator in the sense defined by Section 2.2.2 of [RFC7232]. 
"""

https://httpwg.org/specs/rfc7233.html#header.if-range

Cheers,

> 
> 
> On 04.09.2018 05:01, Mark Nottingham wrote:
>>> Could you please help with the following two questions:
>>> 
>>> 1. The old RFC 2616 has a MUST requirement:
>>> 
>>> 
>>>> A cache or origin server receiving a conditional request, other than
>>>> a full-body GET request, MUST use the strong comparison function to
>>>> evaluate the condition.
>>>> 
>>> But I have not found this (or equivalent) in HTTPbis. Is it deprecated?
>>> 
>> It's stated in the definition of each conditional header; see:
>>   
>> https://httpwg.org/specs/rfc7232.html#preconditions
> 

--
Mark Nottingham   https://www.mnot.net/

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