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--- info:hosting:basics:firewalls [2018/01/09 10:35]
Thibmo
+++ info:hosting:basics:firewalls [2018/01/09 13:34]
Thibmo
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 {{page>:disclaimer_widget&noheader&nofooter&noeditbtn}}
 This topic will contain some information about firewalls and how to set them up.\\
+The trick with firewalls is to block everything by default, and only allow the traffic that you wish to handle.
+On this page we will provide samples based on Linux's IPTables, as this is what's commonly used for Linux webservers.
+<WRAP center round important>
+To follow this example you are required to login as user root.\\
+If you don't have the password of the root user you can use __//sudo//__ instead.
+</WRAP>
+===== Creating A Persistent Rule File =====
+**Debian/Ubuntu:**
+  - Create a new empty file: <code bash>touch /etc/iptables.up.rules</code>
+  - Edit your interface configuration file: <code bash>nano /etc/network/interfaces</code>
+  - Append your main interface with the following rule: <code bash>        post-up iptables-restore < /etc/iptables.up.rules</code>
+===== Default Set Of Rules =====
+**Debian/Ubuntu:**
+  - Edit your firewall configuration file: <code bash>nano /etc/iptables.up.rules</code>
+  - Set the file's contents to: <code bash>*filter
+:OUTPUT ACCEPT [0:0]
+:INPUT DROP [0:0]
+:FORWARD ACCEPT [0:0]
+# Accept ACK
+-A INPUT -p tcp -m tcp --tcp-flags ACK ACK -j ACCEPT
+# Accept Established
+-A INPUT -m state --state ESTABLISHED -j ACCEPT
+# Accept Related
+-A INPUT -m state --state RELATED -j ACCEPT
+# Accept DNS return
+-A INPUT -p udp -m udp --dport 1024:65535 --sport 53 -j ACCEPT
+# Accept ICMP 0
+-A INPUT -p icmp -m icmp --icmp-type 0 -j ACCEPT
+# Accept ICMP 3
+-A INPUT -p icmp -m icmp --icmp-type 3 -j ACCEPT
+# Accept ICMP 4
+-A INPUT -p icmp -m icmp --icmp-type 4 -j ACCEPT
+# Accept ICMP 8
+-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
+# Accept ICMP 11
+-A INPUT -p icmp -m icmp --icmp-type 11 -j ACCEPT
+# Accept ICMP 12
+-A INPUT -p icmp -m icmp --icmp-type 12 -j ACCEPT
+# Accept SSH To Host
+-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
+# Accept IDENT
+-A INPUT -p tcp -m tcp --dport 113 -j ACCEPT
+# Drop sensitive ports
+-A INPUT -p tcp -m tcp --dport 2049:2050 -j DROP
+# Drop sensitive ports
+-A INPUT -p tcp -m tcp --dport 6000:6063 -j DROP
+# Drop sensitive ports
+-A INPUT -p tcp -m tcp --dport 7000:7010 -j DROP
+COMMIT
+*nat
+:OUTPUT ACCEPT [0:0]
+:POSTROUTING ACCEPT [0:0]
+:PREROUTING ACCEPT [0:0]
+:INPUT ACCEPT [0:0]
+COMMIT
+*mangle
+:POSTROUTING ACCEPT [0:0]
+:PREROUTING ACCEPT [0:0]
+:FORWARD ACCEPT [0:0]
+:OUTPUT ACCEPT [0:0]
+:INPUT ACCEPT [0:0]
+COMMIT
+</code>
+===== Adding more rules =====
+There are plenty of tutorials out there.\\
+Here a few examples:\\
+[[https://www.thegeekstuff.com/2011/06/iptables-rules-examples|thegeekstuff.com]]\\
+[[https://www.digitalocean.com/community/tutorials/iptables-essentials-common-firewall-rules-and-commands|digitalocean.com]]
+For this configuration file you need to truncate both __//sudo//__ and __//iptables//__ from the start of the command.\\
+To apply these new rules you need to perform one of the following tasks:
+  * Reload your network stack: <code bash>iptables -F; service networking restart</code>
+  * Restore the config directly: <code bash>iptables -F; iptables-restore < /etc/iptables.up.rules</code>