Re: [DNSOP] Status of "let localhost be localhost"?

Richard Barnes <rlb@ipv.sx> Wed, 02 August 2017 23:27 UTC

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From: Richard Barnes <rlb@ipv.sx>
Date: Wed, 2 Aug 2017 19:27:40 -0400
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To: Ted Lemon <mellon@fugue.com>
Cc: Robert Edmonds <edmonds@mycre.ws>, Mike West <mkwst@google.com>, dnsop <dnsop@ietf.org>, Jacob Hoffman-Andrews <jsha@eff.org>, william manning <chinese.apricot@gmail.com>
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Subject: Re: [DNSOP] Status of "let localhost be localhost"?
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On Wed, Aug 2, 2017 at 4:27 PM, Ted Lemon <mellon@fugue.com> wrote:

> On Aug 2, 2017, at 2:02 PM, Robert Edmonds <edmonds@mycre.ws> wrote:
>
> draft-west-let-localhost-be-localhost-03 upgrades the requirements in
> RFC 6761 §6.3 to make them much stricter, for all applications,
> converting SHOULDs to MUSTs, etc. So we're not arguing about whether
> localhost "should" be treated specially, but whether it MUST be treated
> specially, by all applications. Can the W3C not impose stricter
> requirements on browser developers even if 6761 doesn't impose mandatory
> treatment for "localhost"?
>
>
> It should be MUST in both cases.   But writing that in an RFC doesn't make
> it so.   Bear in mind when you look at the W3C document that it is talking
> about what would be ideal, not what is actually present in browsers.
>
> As an app developer worried about security footprint, I would be wiser to
> be cautious and use ::1 or 127.0.0.1, rather than using localhost and
> relying on the name resolution infrastructure.   But the use case that I
> would be most skeptical about is using localhost in a URL.   I think that
> should be MUST NOT.   Apparently there is not wholehearted agreement on
> this topic, however... :)
>

You have this backwards.  Browser today do take the more cautious, IP-based
approach.  It sucks for developers.  They want to be able to use
"localhost", but in order to do it safely, they will need to hard-wire it
internally (since as you say, writing an RFC doesn't make resolvers
change).  And they don't want to hard-wire unless that's the clear semantic
because standards are what make the web work.

--Richard