spf-discuss
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[spf-discuss] Re: SPF Internationalization

2008-04-14 02:19:09
Alessandro Vesely wrote:
 
Actually, an example with uppercase macros would be most welcome
in the specs. If you feel like writing one on the FAQ meanwhile,
it may clarify its meaning.

We can discuss it here until we arrive at a less Greek version ;-)

 domain.example. IN TXT "v=spf1 a -all exp=mumble.example"
 mumble.example. IN TXT "http://domain.example/why?user=%{l}";

For a local part "test" in test(_at_)domain(_dot_)example this results in
an explanation http://domain.example/why?user=test as it should. 

For a local part "oo/ps" in "oo/ps"@domain.example it should
also work, http://domain.example/why?user=oo/ps

For a local part "Q&A" in "Q&A"@domain.example it could break:
http://domain.example/why?user=Q&A   Worse for "S P" (space):
http://domain.example/why?user=S P  

The issue depends on the position of the macro in the URL, and
of course on the expansion of the macro.  The same examples
with %{L} instead of &{l} yield:

http://domain.example/why?user=test      - as before 
http://domain.example/why?user=oo%2Fps   - %2F for /
http://domain.example/why?user=Q%26A     - %26 for &
http://domain.example/why?user=S%20P     - %20 for SP  

It's not limited to %{L} vs. %{l}, e.g., HELO %{H} can also be
odd if it's used in the URL of an explanation.

 [ISP hints]
I have two servers at 194.243.254.162/31, CIDR is a useful 
abbreviation here too.

Yeah, I wanted a /24 example, where I can later say 11.22.33.nn
without going into details, ISPs are supposed to know what CIDR
is - just in case the word "CIDR" links to RFC 4632 :-)

Many use "_spf" rather than "dummy". Does it make sense to
follow that trend?

Sure, here I didn't want to go into details about underscores
in DNS names, there's a separate FAQ entry for this:
http://www.openspf.org/FAQ/Underscore_in_DNS

If readers think that _spf is required it won't cause havoc, 
but implementors should not get odd ideas, any <target-name>
is okay.

 Frank

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