21 comment

1. I know the title specifies using IPtables to allow NFS connections, but I prefer a simpler method. I prefer to use the hosts.allow and hosts.deny files, as the configuration is *much* simpler.

   Within the hosts.allow simply set:
   portmap:192.168.1.0.

   That’s all you need. Because portmap is the lead process, spawning and defining ports for the other services, if you simple limit access to portmap you’ve effectively set the same access restrictions.

2. Christer.

   host.allows simply protects only the portmap service itself. It is still possible for attackers to guess the port numbers of NFS services and attack those services directly, even if they are denied access to the portmapper. Combining both iptables and host.allows should provide the better security.

   Appreciate your post!

3. How do you restart nlockmgr before reloading the iptables firewall? Preferably without breaking the NFS clients that are active….

   Regards,
   Adam

4. Thanks very much for this, very useful!

5. btw (sorry to post twice in quick succession), I noticed that LOCKD_TCPPORT (32803) isn’t included in your IPTABLES rules.. it is necessary to uncomment this line in /etc/sysconfig/iptables?

6. @ cmg,

   Sorry, it was a typo on my part, I’ve updated the faq.

   HTH

7. BTW, Vivek:

   Admin’s will also have to restart the nfslock service in order for rpc.statd and lockd to re-read their configurations.

   # service portmap restart
   # service nfs restart
   # service nfslock restart

   [root@vm2 ~]# for x in MOUNTD_ STATD_ LOCKD_ RQUOTAD_ ; do echo "Scripts that containt \"$x...\"" ; grep $x /etc/init.d/* | cut -d':' -f 1 | uniq ; echo ; done
Scripts that containt "MOUNTD_..."
/etc/init.d/nfs

   Scripts that containt "STATD_..."
   /etc/init.d/nfslock

   Scripts that containt "LOCKD_..."
   /etc/init.d/nfs
   /etc/init.d/nfslock

   Scripts that containt "RQUOTAD_..."
   /etc/init.d/nfs

8. TCP Wrapper (a.k.a. , libwrap, hosts_access(), and/or hosts.allow & hosts.deny) can be used to restrict access to portmap and to nfs: From the Red Hat Enterprise Linux 5 mountd man page…

   rpc.mountd(8) rpc.mountd(8)

   NAME
   rpc.mountd – NFS mount daemon

   TCP_WRAPPERS SUPPORT
   This rpc.mountd version is protected by the tcp_wrapper library. You have to give the clients access to rpc.mountd if they should be allowed to use it. To allow connects from clients of the .bar.com domain you could use the following line in /etc/hosts.allow:

   mountd: .bar.com

   You have to use the daemon name mountd for the daemon name (even if the binary has a different name).

   …and according to The Linux NFS-HOWTO all five services can be protected using TCP Wrapper…

   The first step in doing this is to add the followng entry to /etc/hosts.deny:

   portmap:ALL

   Starting with nfs-utils 0.2.0, you can be a bit more careful by controlling access to individual daemons. It’s a good precaution since an intruder will often be able to weasel around the portmapper. If you have a newer version of nfs-utils, add entries for each of the NFS daemons (see the next section to find out what these daemons are; for now just put entries for them in hosts.deny):

   lockd:ALL
   mountd:ALL
   rquotad:ALL
   statd:ALL

9. It seemed the udp port 2049 should also be enabled for NFSD, right?

   “-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state –state NEW -p udp –dport 2049 -j ACCEPT”

   1. Roc,

      In the case of having full control over your clients, who *should* connect over TCP your added firewall rule is not needed.
      But, if you perform a remote install – of CentOS / RedHat 5.5 in my case – over NFS, it is absolutely needed.
      Message on the client after a noticeable delay “That directory could not be mounted from the server.”

      I personally believe it’s a bug caused by migration of scripts/config files from RH3 via RH4 to RH5 or maybe earlier already.

      For me your post came too late, but nevertheless thanks and a confirm of its need in certain circumstances.

      Gtz,
      Han Coumans

   2. Confirmed!

      I wanted to boot knoppix via PXE. Knoppix is mounted via nfs and needed udp (this line in /etc/sysconfig/iptables) to work

      Thanks!

10. Vivek,

    I just used this fix on Centos 5.5 and it works fine. (I tried Christer Edwards simple solution first and that didn’t). So many thanks.

    But – isn’t it horrible to have to do all this just to get NFS working? There is a graphical tool for NFS in Server Settings. I see now this allows fixed NFS ports to be set, if you knew this to be necessary. But I don’t think it fixes iptables. I did use system-config-securitylevel to add the ports – which worked. At the least, there should be a step by step guide on the Centos Wiki. If you don’t mind, I might have a go at that. Thanks again.

11. Do you also need:

    -A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state –state NEW -p udp –dport 2049 -j ACCEPT

    >

12. Excellent article

13. Great Article Step by Step.

14. Indeed very useful.
    The only thing is really to *write* the /etc/sysconfig/nfs file with the lines /xxPORT=/ uncommented! even if the commented values matches the wanted ones …

15. On CentOS (and probably RedHat and Fedora), a “newbie” method is to use the graphical tool : “system-config-firewall”

    1. OK my bad, should have tested before saying, it doesn’t work so well… :-D

       1. It works ! (if you don’t forget to start services at boot… do not do system being tired…)

16. Hi,

    I’m using CentOS 6.2 now, and everything worked, I did add the extra udp 2049 rule which was missed by the author.

    But…

    the term “RH-Firewall-1-INPUT” did not work, I got this error (line 13 was the first line from this FAQ)

    iptables: Applying firewall rules: iptables-restore: line 13 failed

    I changed it to “INPUT” and that fixed it.

    now my /etc/sysconfig/iptables looks like this:
    http://pastebin.com/FLRT8jQK

    I guess this changed between centOS 5 and CentOS 6?

17. Great, thanks for sharing this article post.Much thanks again. Really Great.

    Still, have a question? Get help on our forum!