[Mimedefang] Validate users before scanning?

[Joseph Brennan]

--On Thursday, May 19, 2005 9:49 -0400 Joseph Brennan 
<brennan at columbia.edu> wrote:

>
>
>> Sendmail has two macros available: ${nbadrcpts} and ${nrcpts}, that
>> contain the values you are looking for. However, mimedefang currently
>> has no way to extract these macro's before calling filter_begin.
>
> New in sendmail 8.13!  I missed this addition.  I suppose this could
> be used in local_check_rcpt too.  I have to look at this.  Thanks!


This works, but with qualifications:

SLocal_check_rcpt
R$*             $: $1 $| $&{nbadrcpts}
R$* $| 2        $#error $@ 5.7.1 $: "550 Too many bad recipients"


The catch is that the count is necessarily one behind.

Send to 1st bad recipient:   nbadrcpts = 0 so far, so OK
Send to 2nd bad recipient:   nbadrcpts = 1 so far, so OK
Send to any 3rd recipient:   nbadrcpts = 2 so far, so reject

So the reject could happen on a valid recipient.  Still this might
be useful in stopping dictionary attacks.

The number 2 seems too small.

In a milter, we could more easily write conditions around this rule.


Joseph Brennan
Academic Technologies Group, Academic Information Systems (AcIS)
Columbia University in the City of New York