https://issues.apache.org/SpamAssassin/show_bug.cgi?id=6668

--- Comment #15 from Darxus <[email protected]> 2011-10-04 21:13:11 UTC ---
(In reply to comment #14)
> > I don't understand why you say that.  It's just another way of handing a
> > 127.0.0.255 within spamassassin.  So as far as RBLs and WLs are concerned 
> > it's
> > still just an implementation of providing a .255 response for users who are
> > over limit.
> 
> Because to me 255 is a legitimate bit mask for a valid response. 

I was providing an example (127.0.0.255), not suggesting that value always be
treated this way.  I think it would be necessary to create another eval thing
to define a regex for each RBL.

> > As an example, say an email provider is using spamassassin to filter 
> > millions
> > of emails a day.  Some of the rules (RCVD_IN_XBL, RCVD_IN_PBL, RCVD_IN_SBL)
> > cause queries is to zen.spamhaus.org.  That being over their free use
> > threshold, they start returning (only) 127.0.0.255 for all queries, to 
> > indicate
> > the over limit condition.  SpamAssassin notices the 127.0.0.255 value, and
> > stops running all rules that hit zen.spamhaus.org.
> 
> Zen, according to their docs, does not issue a .255. See
> http://www.spamhaus.org/faq/answers.lasso?section=DNSBL%20Usage#200

Right, just providing an example.

> In short, an error bitmask will have YEARS of lag in getting an error code in
> place for RBLs.

For all of them, yes.

> > How is that a DoS ready to happen?  Are we having another misunderstanding
> > here?
> 
> I just see that as an avenue to figure out how to trick your system into
> getting a DNS response that changes SA not to query an RBL in order to get all
> my Spam through.  With the number of DNS servers that change responses, this
> doesn't sound that hard.

Sounds hard to me (to use this to cause a DoS).

> If DNSWL needs another public mirror, have them email me.  

I'll let them know.


If I don't get any positive responses within a couple days, I'll close this (or
someone else can feel free).

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