Re: Quoted pairs in the test suite

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Stuart D. Gathman wrote:
> On Mon, 14 Apr 2008, Frank Ellermann wrote:
> > Hi, does the SPF test suite cover oddities like
> > MAIL FROM:<"\b\a\c\k\s\l\a\s\h"@test.example"> ?
> >
> > In the SPF I18N entry of the FAQ I claim that
> > implementations will evaluate a %{l} local part
> > macro as "backslash" (without the quotes), but
> > actually I'm far from sure that implementations
> > get <quoted-pair> within <quoted-string> right.
>
> Good question.  So what is the right expansion for %{l}:
>
> 1) backslash
> 2) \b\a\c\k\s\l\a\s\h
> 3) "\b\a\c\k\s\l\a\s\h"
> 4) any of the above
>
> You could argue that %{l}@%{d} (in an exp, for example) should be a
> syntactically valid email.  And leaving the quotes intact would be the
> easiest way to ensure that.

You cannot expect SPF implementations to safely generate valid RFC 2821/ 
2822 local-parts.  You could say "%{l}"@%{d} (with the quotes) in an 
explanation string, but if the local-part's _value_ was "foo (with the 
quote), the SPF implementation would generate ""foo"@<domain>, whereas 
the proper RFC 2821/2822 representation would be "\"foo"@<domain>.

It cannot be done reliably.  SPF wasn't designed to do it.

(Also note that RFC 2821, section 4.1.2, sort of states quoted-string 
local-parts as being bad practice.)

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