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

[Gonglei]

On 2014/10/21 16:57, Gerd Hoffmann wrote:

> 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.
> 

Yes. But I think it is not a big problem, when the REJECT_TIME is over,
the good guys can connect vnc successfully immediately.
Or maybe we just lock those guys with "the same Source IP address" ?

Best regards,
-Gonglei