Re: RFC 9113 and :authority header field

2022年7月4日(月) 10:06 Kazuho Oku <kazuhooku@gmail.com>:

> Thanks to Tatsuhiro and to all others for bringing the discussion.
>
> 2022年6月29日(水) 9:37 Martin Thomson <mt@lowentropy.net>:
>
>> On Wed, Jun 29, 2022, at 09:58, Tatsuhiro Tsujikawa wrote:
>> > I think 2) is valid in terms of RFC 7540, but it suddenly becomes
>> > invalid in terms of RFC 9113?
>> > Is this correct?  https://www.fastly.com and https://www.google.com
>> now
>> > reject 2).
>>
>> My understanding is that both are valid alternatives.  As would a third
>> option that contained the same value in both host and :authority.  The 4xx
>> responses you are getting are (probably) compliance bugs.
>>
>
> Are you suggesting that RFC 9113 has an error, or am I missing something?
> I ask this because RFC 9113 section 8.3.1 states:
> "Clients that generate HTTP/2 requests directly MUST use the ":authority"
> pseudo-header field to convey authority information, unless there is no
> authority information to convey (in which case it MUST NOT generate "
> :authority")."
>

Regarding this MUST, it seems that we (maybe unintentionally?) tightened
the language in https://github.com/httpwg/http2-spec/pull/961.

It changed a generic "SHOULD" to a "MUST unless."


> and
> "An intermediary that forwards a request over HTTP/2 MUST construct an "
> :authority" pseudo-header field using the authority information from the
> control data of the original request, unless the original request's target
> URI does not contain authority information (in which case it MUST NOT
> generate ":authority")."
>

This MUST seems to come from
https://github.com/httpwg/http2-spec/pull/845/files.

As of #845, we mandate intermediaries forward origin-form requests (e.g., a
"GET / HTTP/1.1" + Host) using an `:authority` request header field.

Maybe these changes have been unintentional.

Regarding H2O, we did not intend to enforce the use of `:authority` pseudo
header field, so I have no problem in reverting the behavior. But
nevertheless, I think it's worth discussing the state of the specification.


>
> My interpretation of these MUSTs is that a client is forbidden to create a
> HTTP/2 request that omits an `:authority` header field (unless the method
> or the URI permits it to).
>
>
>>
>> Thankfully we know people who might be closer to someone who is able to
>> fix or defend those bugs.  (On CC).
>>
>> This whole host and :authority thing was an original mistake in HTTP/2.
>> It was grounded in the view that HTTP/2 had to faithfully capture every
>> weird thing HTTP/1.1 could express, even when it didn't make sense.  At the
>> time, that was pragmatic and it might have aided deployment into systems
>> that were, on some levels, broken.  In time, we should seek to remove those
>> exceptions.  In the revision, we did some of that by disallowing different
>> values.
>>
>
>
> --
> Kazuho Oku
>


-- 
Kazuho Oku