Wietse Venema wrote:
Daniel L. Miller:
Henrik K wrote:
On Sun, Jan 17, 2010 at 10:44:48PM -0800, Daniel L. Miller wrote:
Daily scanning of logfiles does not accomplish this. Nor would even an
hourly scan - and constant logfile scanning strikes me as inelegant. If
there is any method currently existing within Postfix to accomplish this
goal please point me at it! If not, I'd like to discuss possible means
and methods for a future implementation.
I've been meaning to make something like this for postfix, your post
refreshed me. Amavisd-new penpals is ok (and you can make other custom
queries to it's database), but it can't make MTA bypass all the ptr/helo/foo
checks. My main problem is all bad SOHO servers etc that get blocked by
those.
It can be achieved with a simple policy daemon that records all outgoing
recipients and/or relays and compares them for incoming messages, possibly
adding a header that you can also reuse in SA for scoring.
I created one - the problem is execution. I took the greylist.pl and
tweaked it - and it now adds recipient addresses to a database very
simply. But I only want that to happen with valid senders/clients.
Placing this policy daemon, which always returns "dunno", in the
smtpd_recipient_restrictions very simply generates a list of recipients
- but without any validation. And duplicating validation within this
daemon strikes me as wasteful.
Ideally, I'd like this daemon called immediately upon successful
delivery, or at what Postfix determines as "successful delivery" based
on the remote server response. Without tailing the logfile I don't see
how else to accomplish it - but I don't LIKE that form of
implementation. Might be the only way to do it at this time - but
perhaps having such status messages available might be considered
sufficiently worthwhile to implement a new feature?
I'm not sure you are solving the right problem. What is the likelihood
that a local user specifies an invalid remote address, and how
problematic is it for your to have a few invalid remote addresses
on your whitelist? If you use a btree or hash database, they won't
slow down the database searches.
Valid addresses don't live forever, either. After some time you
will have to expire unused entries from your database anyway, so
you might just as well live with a minor degree of pollution from
the occasional invalid remote address.
I cheated - I went right past sender validation and started discussing
recipient verification. Because Postfix already does (or can do)
recipient verification, I like the thought of keeping the whitelist
clean. You're of course correct that the whitelist would need
expiration at some point.
But my primary issue is sender validation. I don't see how, currently,
to implement this as a policy daemon without re-writing sender
validation into the policy daemon. I don't see any way, for example, to
call another policy daemon after permit_sasl_authenticated returns "OK".
--
Daniel
