Samba: Linux Iptables Firewall Configuration

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How do I configure iptables firewall under CentOS / Fedora / RHEL / Redhat Linux to allow access to the Samba server? How do I open TCP ports # 137, 138, 139 and 445 under Linux so that all Microsoft Windows machine can access files and printer on a Linux host?

The Samba server can be configured to allow access to certain hosts. However, iptables prevent the access over the Internet. You must allow only the systems on your network as clients of the Samba Linux server.

Iptables Open Port 137, 138, 139 and 445

Edit /etc/sysconfig/iptables file, enter:
# vi /etc/sysconfig/iptables
To allow access to 192.168.1.0/24 network only add the following before the final LOG & DROP statements. The syntax for RHEL/CentOS 5.x/4.x and older is as follows:

-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 137 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 138 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 139 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 445 -j ACCEPT

For CentOS/RHEL 6.x syntax is as follows:

-A INPUT -s 192.168.1.0/24 -m state –state NEW -p udp –dport 137 -j ACCEPT
-A INPUT -s 192.168.1.0/24 -m state –state NEW -p udp –dport 138 -j ACCEPT
-A INPUT -s 192.168.1.0/24 -m state –state NEW -p tcp –dport 139 -j ACCEPT
-A INPUT -s 192.168.1.0/24 -m state –state NEW -p tcp –dport 445 -j ACCEPT

Save and close the file.

Restart Firewall

Type the following command:
service iptables restart

A note about CentOS/RHEL 7 users for opening up Samba ports

You need to use the following commands:
# firewall-cmd --permanent --zone=public --add-service=samba
# firewall-cmd --reload
OR
# firewall-cmd --permanent --add-port=137/tcp
# firewall-cmd --permanent --add-port=138/tcp
# firewall-cmd --permanent --add-port=139/tcp
# firewall-cmd --permanent --add-port=445/tcp

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

10 comment

  1. Great writeup! I think this may put me on the right track to figuring out my system at home.

    I am running Ubuntu 9.04 and recently enabled connection sharing for my 3G USB modem. My problem is that when I enabled ICS I was no long able to access my shared folders from my Windows machines. At first I thought it had to do with my routing tables but after I read this I figured it was my iptables.

    Is there a similar article for this on Ubuntu? I’m sure I can work through it and get it running but it would be nice if there were something to walk me through it (I’m very new).

  5. Jim –

    The original post is over two years old. Here are the correct firewall commands. Change 192.168.1.0/24 to your internal LAN subnet if different. After executing, use the command ‘service iptables save’, or edit /etc/sysconfig/iptables directly.

    -A INPUT -s 192.168.1.0/24 -m state –state NEW -p udp –dport 137 -j ACCEPT
    -A INPUT -s 192.168.1.0/24 -m state –state NEW -p udp –dport 138 -j ACCEPT
    -A INPUT -s 192.168.1.0/24 -m state –state NEW -p tcp –dport 139 -j ACCEPT
    -A INPUT -s 192.168.1.0/24 -m state –state NEW -p tcp –dport 445 -j ACCEPT

    Additionally, firewall rules should not affect the functionality of the samba service… recheck your configuration and logs (/var/log/samba/*.log) for relevant error messages and repost any errors you see here.

  6. Depending on how your browser renders fonts, the firewall rules shown above may not work. In my browser (Firefox 3.6.24 on CentOS 6.2) the characters before ‘state NEW’ and ‘dport nnn” parameters render as a single long dash (somtimes called an ’em’ dash). In order to work correctly the long dash must be changed to 2 consecutive short dashes, then everything is fine. I discovered this doing a copy & paste of the above to modify /etc/sysconfig/iptables.

    Hope this helps!

    Oldan

  7. You can put it all in one line:
    iptables -I INPUT 1 -p tcp -m conntrack –ctstate=NEW -m multiport –dports 137,138,139,445 -j ACCEPT

  9. Today,this configuration is incorrect nowadays,the grammer is wrong,I use following config,you should replace “RH-Firewall-1-INPUT” with “INPUT”:

    
-A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 137 -j ACCEPT
-A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 138 -j ACCEPT
-A INPUT  -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 139 -j ACCEPT
-A INPUT  -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 445 -j ACCEPT

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