On Tue, Oct 23, 2007 at 02:55:41PM -0700, Rob wrote:

quoted text
> On 10/23/07, david l goodrich  wrote:

> > Nobody?  Sad, it's still doing it.

> >

> >

> > On Sun, Oct 21, 2007 at 02:22:43PM -0500, david l goodrich wrote:

> > > I've set up a max-src-conn-rate rule on my gateway router to

> > > mitigate brute-force ssh attacks.  This router protects a /28

> > > subnet, 25.108.82.80/28.

> > >

> > > The relevant rules:

> > >

> > > # pfctl -sr | grep attack

> > > block drop in log quick proto tcp from  to any

> > > pass in log proto tcp from any to any port = ssh keep state

> > > (source-track rule, max-src-conn-rate 3/30, overload

> > >  flush global, src.track 30)

> > > #

> > >

> > > What the three columns of output in the below tcpdump output are:

> > > timestamp, rule action, and target host.  As you can tell from

> > > the tcpdump command, the sending host is the same in all cases,

> > > 208.53.147.204

>

> I'm not a pf newbie by any means, but I'm not really qualified to

> answer questions about it either. That said, I don't usually use an

> '=' sign in my pf rules, and the pf faq doesn't list that as one of

> the accepted operators for the port range

> (http://www.openbsd.org/faq/pf/filter.html). If the rule wasn't being

> parsed correctly, it would cause the behavior you're seeing. Try,

I don't have an = sign in my rule, either, i have it in pf.conf as:
pass in log proto tcp from any to any port ssh \

        keep state (max-src-conn-rate 3/30, \

                        overload  flush global)
but when i look at my rules with pfctl -sr it shows the =.
>

quoted text
> block in log quick proto tcp port ssh keep state \

>    (source-track rule, max-src-conn-rate 3 / 30 overload

> , src.track 30)

I want to pass ssh traffic by default, so a block rule won't be

terribly helpful.
>

quoted text
> Note that I wouldn't use a flush global directive for a rule like

> this, because it can lead to a neat DoS where somebody can spoof one

> of your own IP addresses and shut down any ssh sessions you have

> active.

>

> Here's a working sample from my own currently active pf file:

>

> pass in on $ext proto tcp to  port smtp keep state \

>    (max-src-conn 15 max-src-conn-rate 10 / 45 overload ) \

>    queue 6smtp

Mine's pretty similar, if a bit more verbose.  And I don't use

max-src-conn or queueing.

  --david
>

quoted text
> (FYI, the smtp-overload table moves traffic to a queue that simply

> throttles the connections a little.)

>

> - R.