Re: [Qemu-devel] [PATCH 6/6] vnc: track & limit connections

[Gerd Hoffmann]

On Di, 2014-10-21 at 14:06 +0800, Gonglei wrote:
> On 2014/10/20 15:02, Gerd Hoffmann wrote:
> 
> > 
> >   Hi,
> > 
> >> If we set the max trying times, and then
> >> There are some concepts:
> >>  - INTERVAL_TIME: a time window that user can connnet vnc server
> >>  - REJECT_TIME: the time of reject any connection
> >>  - MAX_TRY_TIMES: the times that user can connect vnc server in 
> >> INTERVAL_TIME,
> >>    if attach the MAX_TRY_TIMES, the server will lock, any user can not 
> >> connect again
> >>    before REJECT_TIME attached. The old connected client will not be 
> >> influenced.
> > 
> > i.e. effectively rate-limit login attempts.  Makes sense to have an
> > option for that, although I'm not sure it is worth the trouble doing
> > something beyond a simple "one attempt per second allowed" (i.e. stop
> > polling the listening socket for a second after each accept).
> > 
> 
> Hi,
> 
> "one attempt per second allowed" is just reduce the frequency for attack,

Yes.  Which is common practice, to slow down dictionary attacks.

> but I don't think the effect is very well. It can limit the login attempts for
> attack problem from a flood of attack to "one attempt per second" (not
> the same magnitude with my approach for security).

Problem with rejecting is any login attempts for REJECT_TIME is that you
also lock out the good guys.

cheers,
  Gerd