Greylisting (WAS: Re: MailScanner ANNOUNCE: 4.57 released)

[Nerijus Baliunas]

Glenn Steen <glenn.steen <at> gmail.com> writes:

> Currently this only seem to affect milters, and only milters that
> would add recipients and/or message headers.

First, thank you very much for looking at this problem!
I commented out all lines with smfi_addheader() and changed xxfi_flags field
from SMFIF_ADDHDRS to 0 in milter-greylist, which means it does not modify
headers or body. But I still get "              0" after the end of body and " 
            0" too after the last header (instead of "           1389" earlier).
Does it mean Postfix changes queue files when milters are enabled even when
milter does not announce the capability of changing the message?

> Now, I see at least three somewhat different solutions:
> 1) Simply enhance the ReadQf function so that it understands and
> handles p records (meaning we will copy over the actual data added by
> milters, not the p records themselves).
> 2) recalculate the offsets and make sure the precords ar correct, as
> well as the "after end" data being where it is supposed to be.
> 3) Rewrite MailScanner to use the same p record method of adding
> recipients and headers, which of course implies, in a way, that we
> would reimplement the Postfix.pm file from scratch... more or less.

It would be quite nice, meaning MS is changing queue files in official way(?),
but it would also mean MS will not support postfix versions below 2.3, when
milter support was added.

> I'm hugely in favour of doing number 1), since this will be
> a) simplest to implement
> b) least amount of code touched
> c) probably safest... We'll have to look at doing pretty much the same
> sanity checks that Wietse does, but that shouldn't be a huge problem.

Yes, it's probably the best approach.

> If I get a little teensy bit of time, I'll make a stab at some code
> for handling p records as suggested in #1.

Thanks!

BTW, I've got an idea about how to temporary overcome the problem with
corrupting headers. Is Postfix able to add some headers to the message? If yes,
I would configure it to add some header, then pass message to a milter, milter
adds "              0" after this header corrupting it, but it means all the
other important headers are left intact (like Content-Transfer-Encoding:
base64). So is this possible?

Regards,
Nerijus