Ok I have a problem about NFS, but I warn you, it's pretty complex :P

So... My architecture look like the following :
NFSD
|
|
Router
|
|
Clients

1-Please note that NFSD and Clients are on different Class C IP so I need a Linux Router in the middle to do NAT. Everything works fine 'bout it.

2-NFSD is a box who is running an NFS Server. This Server is for Log, because Router is also acting as a syslog server. Every client send their log to Router.

3-Router is mounting NFS partition RW because it has to put his logs on it. Clients should only be able to mount it RO for security reason.


TROUBLE : NFS is too stupid to support NAT, so when a client mount NFS partition (trough NAT Router) the NFSD authentify the connection as it is coming from the router. Becuz Router has full RW access to NFS partition, every clients got the RW access too.
So I'm trying to built some crazy iptables rules to ensure that all trafic going to NFSD from client will not be Nated. I'm not sure I'm right but I'm trying to use some -j DNAT and -j SNAT to change source/destination of packet.

So far it's not working, but I suspect the NFS protocol the be guilty since it doesn't respect standard (not always using Syn before tcp communication, sometime use port not identified for NFS/Portmap to talk).

Ok so here is these iptables line. It is commented, I know.

#echo " NFS/Portmap Forwarding"
# This is because NFS Protocol is stupid and doesn't suport NAT
# So I have to force forwarding to ensure my NFSD Safety

#$IPTABLES -t nat -A PREROUTING -p tcp -s 192.168.1.2 -d 192.168.0.2 --sport 111 -j DNAT --to-destination 192.168.0.2
#$IPTABLES -t nat -A POSTROUTING -p tcp -s 192.168.1.2 -d 192.168.0.2 --sport 111 -j SNAT --to-source 192.168.1.2
#$IPTABLES -t nat -A PREROUTING -p udp -s 192.168.1.2 -d 192.168.0.2 --sport 111 -j DNAT --to-destination 192.168.0.2
#$IPTABLES -t nat -A POSTROUTING -p udp -s 192.168.1.2 -d 192.168.0.2 --dport 111 -j SNAT --to-source 192.168.1.2


#$IPTABLES -t nat -A PREROUTING -p tcp -s 192.168.1.2 -d 192.168.0.2 --sport 2049 -j DNAT --to-destination 192.168.0.2
#$IPTABLES -t nat -A POSTROUTING -p tcp -s 192.168.1.2 -d 192.168.0.2 --dport 2049 -j SNAT --to-source 192.168.1.2
#$IPTABLES -t nat -A PREROUTING -p udp -s 192.168.1.2 -d 192.168.0.2 --sport 2049 -j DNAT --to-destination 192.168.0.2
#$IPTABLES -t nat -A POSTROUTING -p udp -s 192.168.1.2 -d 192.168.0.2 --dport 2049 -j SNAT --to-source 192.168.1.2


#$IPTABLES -t nat -A PREROUTING -p tcp -s 192.168.0.2 -d 192.168.1.2 --sport 111 -j DNAT --to-destination 192.168.1.2
#$IPTABLES -t nat -A POSTROUTING -p tcp -s 192.168.0.2 -d 192.168.1.2 --dport 111 -j SNAT --to-source 192.168.0.2
#$IPTABLES -t nat -A PREROUTING -p udp -s 192.168.0.2 -d 192.168.1.2 --sport 111 -j DNAT --to-destination 192.168.1.2
#$IPTABLES -t nat -A POSTROUTING -p udp -s 192.168.0.2 -d 192.168.1.2 --dport 111 -j SNAT --to-source 192.168.0.2

#$IPTABLES -t nat -A PREROUTING -p tcp -s 192.168.0.2 -d 192.168.1.2 --sport 2049 -j DNAT --to-destination 192.168.1.2
#$IPTABLES -t nat -A POSTROUTING -p tcp -s 192.168.0.2 -d 192.168.1.2 --dport 2049 -j SNAT --to-source 192.168.0.2
#$IPTABLES -t nat -A PREROUTING -p udp -s 192.168.0.2 -d 192.168.1.2 --sport 2049 -j DNAT --to-destination 192.168.1.2
#$IPTABLES -t nat -A POSTROUTING -p udp -s 192.168.0.2 -d 192.168.1.2 --dport 2049 -j SNAT --to-source 192.168.0.2

With these lines, everything works, BUT NFSD (192.168.0.2) still authentificate connection from clients (192.168.1.2) as it is coming from router (192.168.1.1/192.168.0.1).


It is a real problem and a real security hole.
Any (freak) idea how I can fix it?


NB: Please don't tell me "use something else", I HAVE to use NFS... just one word : University.

I have similar problem using NFS, albeit on my small office network. Did you find a workaround to the problem? My NFS server keeps refusing a connection because it looks like everything is coming from the router.

Thanks