Unconditional punycode conversion
vint at google.com
Wed Mar 9 17:50:47 CET 2011
no, anything with "--" is reserved. See Definitions RFC.
On Wed, Mar 9, 2011 at 11:36 AM, Simon Josefsson <simon at josefsson.org>wrote:
> Andrew Sullivan <ajs at shinkuro.com> writes:
> > On Tue, Mar 08, 2011 at 01:02:14AM +0100, Simon Josefsson wrote:
> >> The next-to-last part of IDNA2008-lookup is section 5.5 of RFC 5891:
> >> The string that has now been validated for lookup is converted to ACE
> >> form by applying the Punycode algorithm to the string and then adding
> >> the ACE prefix ("xn--").
> >> Consider an IDNA2008-lookup input label of "foo". The above appear to
> >> say that this string should be punycode encoded, which seems wrong.
> > Sections 5.2 and 5.3 suggest that the label should be "in Unicode" and
> > need to be a putative U-label. It is unfortunate that the text
> > doesn't explicitly here say that the algorithm already doesn't apply
> > to NR-LDH labels, but I think that's correct. So you shouldn't need
> > to run "foo" through punycode because you didn't take that branch: you
> > can tell before you get to the IDNA2008 lookup rules that it's an
> > NR-LDH label, so it won't be processed.
> Thanks -- indeed, making it explicit which sub-sections of section 5
> applies to all labels or just (putative) U-labels would have helped.
> To verify my understanding: the label "ab--cd" is permitted by IDNA2008
> despite it having "--" in the third and fourth characater positions?
> That would be because section 5.4 only applies to non-ascii labels.
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