Re: Syntax validation of articles by injecting agents

[Russ Allbery <rra@xxxxxxxxxxxx>]

Julien ÉLIE <julien@xxxxxxxxxxxxxxx> writes:

> RFC 5537 mentions that an injecting agent MUST reject any proto-article
> that is not syntactically valid as defined by RFC 5536.

In retrospect, I suspect that should either have been a SHOULD or it
should have singled out the netnews-specific restrictions.  I don't think
anyone pointed out at the time that it would mean rejecting all non-MIME
messages, and I suspect we would have changed it if we'd realized that as
fairly impractical.

The point was more to reject messages with syntactically invalid
Newsgroups headers and whatnot.

> And what if a news reader generates an incorrect User-Agent: header
> field?  or if it always adds a tail-entry which is not a path-nodot
> in Path:?  All its posts will be rejected by a RFC-compliant injecting
> agent...
> It it the intention?

I wonder how many user agents generate invalid Path headers.  Hm.

I have a hard time justifying rejecting articles on the basis of syntactic
problems in purely informational headers like User-Agent.

> I quite understand that it would help to have better compliant
> articles.  For instance, rejecting articles with "all" in their
> distribution list.

That, at least, the user probably has some control over.

> But in some cases, people would need to upgrade their news
> readers...  (and maybe change their news readers if it is
> no longer maintained)
> Or news admins will not be willing to upgrade to a news server
> that is RFC-compliant.  (Unless syntax checks can be deactivated
> but then, news admins will deactivate them, and the duty of
> injecting agents will be useless -- "it bears much of the burden
> of diagnosing broken posting agents or communicating policy
> violations to posters".)

> How can we handle that MUST without hurt?

I'm guessing that server implementations will need to be selective about
what headers that it's applied to, unfortunately.  It would probably be
nice to have a picky mode that fully enforces the syntax, though, if for
no other reason than to serve as a testbed for posting agents.

-- 
Russ Allbery (rra@xxxxxxxxxxxx)             <http://www.eyrie.org/~eagle/>