[asterisk-dev] Rate limiting traffic to address potential DoS issues?

[Jason Parker]

----- Kevin P. Fleming <kpfleming at digium.com> wrote:
> A community member has communicated to me a couple of issues where if
> he sends large volumes of correctly-formatted (but otherwise invalid)
> packets at Asterisk channel drivers, Asterisk behaves quite poorly. In
> general it does not crash, but it will lose calls, respond very
> slowly, etc.
> 
> I have been loath to start trying to build remediation for this into
> Asterisk itself, since that's a very slippery slope and we could end
> up spending the next six months trying to come up with new attack
> vectors and then coding to deal with them. In addition, at least in my
> opinion, there are good, free tools already to do this sort of thing
> (rate limiting of incoming traffic), as well as solid commercial
> products.
> 
> However, I'd like to get the opinions of our developer community... do
> you think this is something we should attempt to address within
> Asterisk itself, or we are better off to post some 'best practices'
> documents that demonstrate ways that existing tools can be used to
> combat these attacks?
> 

Let's look at other apps (say, apache) for an example of something similar.  What happens if you throw thousands of requests at apache per second?  It's going to die.  And why shouldn't it?  Stuff like this, in my opinion, is best handled at the firewall level, or perhaps with a load balancer of sorts.  Sure, we can (and definitely should) continue to improve, so that we can *PROPERLY* handle higher call volumes, but in this case, what happens if they just resort to a good old packet flood?

-- 
Jason Parker
Digium