ietf-nntp Folding

[Russ Allbery]

Clive D W Feather <clive at demon.net> writes:

> I'm unsure where we got to here - my mailbox contains a brief exchange
> between you and Charles.

> Can I please have definitive answers to each of the following:

> (1) Can a header line be folded between the colon and the first space?

We went back and forth on this one, but the conservative answer is no, so
in the interests of moving forward with the draft, let's just take the
conservative answer unless anyone wants to argue strongly for some other
alternative.  I'm pretty sure there are existing implementations that
couldn't handle folding before the first space.

> (2) Can an unfolded header line end with white space?

Yes.

> (3) Can a header line be folded twice between two non-white space
>     characters, so that a post-folding line contains only white space?

The concern here is that if trailing whitespace is stripped somehow, such
a line would then look like the header boundary and result in significant
mangling of the message.  I really think that server software should
handle this properly, but it's probably the case that sending this sort of
message is a bad idea.  (Although I have seen messages like that not
infrequently, and they appear to be handled reasonably correctly.)

> (4) Can folding occur after a white space character, so that a post-folding
>     line ends with white space?

Yes.  The folding has to happen before a whitespace character, but if
there are multiple consecutive whitespace characters, it can happen
between them.

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>