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RE: [Xen-users] Promiscuous mode

To: "Felix Kuperjans" <felix@xxxxxxxxxxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Promiscuous mode
From: "Jonathan Tripathy" <jonnyt@xxxxxxxxxxx>
Date: Mon, 14 Jun 2010 13:12:00 +0100
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Hi Mike and Felix,
 
Felix: Would use those 2 rules below, along with these arptables rule stop ARP spoofing?
 
I havn't forgotton about trying your routing method by the way. I've got a big list of stuff to try out :)
 # Default policy for packets in the FORWARD chain is DROP.
  arptables -P FORWARD DROP

  # Flush all existing rules in the FORWARD chain.
  arptables -F FORWARD
# Accept ARP requests coming from the domU into the bridge.
  arptables -A FORWARD --opcode Request --in-interface vif1.0 -j ACCEPT

  # Accept ARP requests coming out of the bridge into the domU.
  arptables -A FORWARD --opcode Request --out-interface vif1.0 -j ACCEPT

  # Accept ARP replies coming out of the bridge from the physical
  #  network into the domU.
  arptables -A FORWARD --opcode Reply --out-interface vif1.0 \
    --in-interface peth0 -j ACCEPT
 
Mike: The DomUs will be on the same subnet
 
Thanks
 
Jonathan

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx on behalf of Felix Kuperjans
Sent: Mon 14/06/2010 12:56
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Promiscuous mode

Hi Jonathan,

keep in mind that others may still use ARP spoofing attacks, because your rules do not filter ARP packages. This will not allow hosts to receive packages of other hosts in that scenario, but it could still deny the communication of other hosts completely.

You won't have any promiscious interfaces if you use routing, btw.

Regards,
Felix

Am 14.06.2010 13:19, schrieb Mike Viau:
> Mon, 14 Jun 2010 10:41:49 +0100 <jonnyt@xxxxxxxxxxx> wrote:
> Hi Everyone,

> In order to prevent DomU from entering promiscuous mode, is it just a matter of adding these 2 rules when the vif is created?

> # Accept packets leaving the bridge going to the domU only if
>   #  the destination IP for that packet matches an authorized IPv4
>   #  address for that domU.
>   iptables -A FORWARD -m physdev --physdev-out vif1.0 \
    --destination 216.146.46.43 -j ACCEPT

>   # Accept packets coming into the bridge leaving the physical
>   #  network interface peth0 only if the source IP for that packet
>   #  matches an authorized IPv4 address for that domU.  
>   iptables -A FORWARD -m physdev --physdev-in vif1.0 \
>     --physdev-out peth0 --source 216.146.46.43 -j ACCEPT
> I got the above from http://www.standingonthebrink.com/index.php/ipv6-ipv4-and-arp-on-xen-for-vps/
> Does that provide total protection? What about if traffic was going from Dom1 to Dom3, could Dom2 snoop in?
> Thanks


I would think so, provided the rules above filter all traffic expect to/from a specific ip. Therefore if all domU are on separate ip networks the traffic should be on completely different networks too. 


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