Re: JSON headers

[Carsten Bormann <[e-mail]>]

> It is allowed by the structure of the *wire format*.

The syntax indeed cannot prevent it.
It's still not *allowed* in JSON.

> The *specification* has a "SHOULD have unique names", but then, that's
> only a SHOULD (exactly because we know we can't rely on it, otherwise we
> wouldn't have the prose about what recipients can do with it).

It is a SHOULD because people were chickening out because of a possible
political conflict with ECMA 404.  Note well that no reason is given to
ever violate that SHOULD.

Now, for performance reasons, there is no requirement on a receiver to
check for this constraint.  Protocol design 101 tells us that a lack of
checking will cause implementations to emit invalid JSON just because
they can (the "soup" effect).  Hence the description in RFC 7159 what
goes wrong when you do that.  (However, the security considerations fail
to mention the check-vs-use vulnerabilities that inevitably come from
the variety in implementation strategies; the last paragraph of Section
8 of RFC 7049 does apply.)

This discussion may be a bit off-topic for the HTTP WG, but I think it
is important to understand JSON when using it in HTTP.

Grüße, Carsten