cli/insert: do not lose the SMTP envelope

[J Farkas]

On 2016-01-02 at 13:28:02, Tomi Ollila wrote:
> On Fri, Jan 01 2016, J Farkas <jf.hyqohaczlksw4tx6ae at l2015aftruuq.dns007.net> wrote:
> > Make sure we store the envelope sender/recipient if provided by
> > qmail-command(8) in $RPLINE and $DTLINE.
> > ---
> 
> Probably good feature, but like
> http://www.qmail.org/man/man8/qmail-command.html 
> says:
> 
>           qmail-local supplies several useful environment variables to
>           command.  WARNING: These environment variables are not
>           quoted.  They may contain special characters.  They are
>           under the control of a possibly malicious remote user.
> 
> Should we check that the contents of RPLINE and DTLINE are well-formed
> before writing these to the mail files ?

Thank you for reviewing and being so careful!

That warning is not applicable for the *LINE variables which are
supposed to end up in the message without further munging (they even
have the LF appended already).

The extra carefulness is only relevant for anyone trying to *parse*
those strings, like $EXT via unsafe languages, when EXT becomes the
part following the dash after the username (considering 
bgates-(){:;};shutdown at example.org for example)

It still should be what the envelope sender was, and what was considered
valid at the time.

I actually checked if there's any relevance for this warning: most
maildir delivering program does it already in one form or the other; in
fact, there is a command in the qmail distribution:
http://www.qmail.org/man/man1/preline.html which does the exact same
getenv and copy to the output.

If you'd liek to confirm, there's one repo for what seems to be the
original qmail source for this file shows even DJB does it the same way:

https://github.com/c-rack/qmail/blob/master/preline.c

I would think it's not worth the extra fork and pipe for this.  I don't
see how anyone could do without these headers saved, to be honest :)

Janos