Re: Headers folding

Julien ÉLIE wrote:
>
> Hi,
>
> As you are speaking about headers and compliance of USEFOR with
> RFC 3977 and RFC 5322, I wonder what happens to folding.
>
> In RFC 3977, we have:
>
>
> 9.7.  Articles
>
>     header = header-name ":" [CRLF] SP header-content CRLF
>     header-content = *(S-CHAR / [CRLF] WS)
>     S-CHAR   = %x21-FF
>     WS = 1*(SP / TAB)
>     SP  = %x20
>     TAB = %x09
>
> A.1.  Header Folding
>
>   NNTP allows a header line to be folded (by inserting a CRLF pair)
>   before any space or TAB character.
>
>   Both email and Netnews articles are required to have at least one
>   octet other than space or TAB on each header line.  Thus, folding can
>   only happen at one point in each sequence of consecutive spaces or
>   TABs.  Netnews articles are further required to have the header name,
>   colon, and following space all on the first line; folding may only
>   happen beyond that space.  Finally, some non-conforming software will
>   remove trailing spaces and TABs from a line.  Therefore, it might be
>   inadvisable to fold a header after a space or TAB.
>
>   For maximum safety, header lines SHOULD conform to the following
>   syntax rather than to that in Section 9.7.
>
>
>     header = header-name ":" SP [header-content] CRLF
>     header-content = [WS] token *( [CRLF] WS token )
>
>     token     = 1*P-CHAR
>     P-CHAR    = A-CHAR / UTF8-non-ascii
>     A-CHAR    = %x21-7E
>     UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4
>     UTF8-2    = %xC2-DF UTF8-tail
>     UTF8-3    = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2UTF8-tail /
>                 %xED %x80-9F UTF8-tail / %xEE-EF 2UTF8-tail
>     UTF8-4    = %xF0 %x90-BF 2UTF8-tail / %xF1-F3 3UTF8-tail /
>                 %xF4 %x80-8F 2UTF8-tail
>     UTF8-tail = %x80-BF
>
>
>
>
> Well, my question is for 9.7:
>
>    header = header-name ":" [CRLF] SP header-content CRLF
>
> Is it a valid header for USEFOR?  and for RFC 5322?
I'm sure it is possible to construct a header that conforms to this 
syntax but isn't valid in USEFOR (the header "Date: nonsense" is illegal 
both in USEFOR and in RFC 5322, but conforms to the syntax above).

The syntax above also (and perhaps more importantly) allows UTF-8 in 
headers, something that is illegal in RFC 5322 and USEFOR. You should 
check for conformance with the EAI spec.
>
>
> In A.1, it looks strange to have written the syntax this way:
>
>     header-content = [WS] token *( [CRLF] WS token )
>
> Hopefully it works!  (token does not contain WS but it comes
> afterwards with "WS token"!)
>