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Iptables

Voir les règles définies. Documentation OVH

Voir les règles
sudo iptables -L
Création d'un fichier de test iptables
sudo editor /etc/iptables.test.rules
Ajout de règles
*filter


  # Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
  -A INPUT -i lo -j ACCEPT
  -A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT


  # Accepts all established inbound connections
  -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


  # Allows all outbound traffic
  # You could modify this to only allow certain traffic
  -A OUTPUT -j ACCEPT


  # Allows HTTP and HTTPS connections from anywhere (the normal ports for websites)
  -A INPUT -p tcp --dport 80 -j ACCEPT
  -A INPUT -p tcp --dport 443 -j ACCEPT


  # Allows SSH connections
  # The --dport number is the same as in /etc/ssh/sshd_config
  -A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT
  # Add an authorised IP
  # -A INPUT -p tcp -m state --state NEW --dport 22 -s IP_ADRESS -j ACCEPT


  # Now you should read up on iptables rules and consider whether ssh access
  # for everyone is really desired. Most likely you will only allow access from certain IPs.


  # Allow ping
  #  note that blocking other types of icmp packets is considered a bad idea by some
  #  remove -m icmp --icmp-type 8 from this line to allow all kinds of icmp:
  #  https://security.stackexchange.com/questions/22711
  -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT


  # log iptables denied calls (access via 'dmesg' command)
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7


  # Reject all other inbound - default deny unless explicitly allowed policy:
  -A INPUT -j REJECT
  -A FORWARD -j REJECT


  COMMIT
Activer les règles
sudo iptables-restore < /etc/iptables.test.rules

Autoriser le trafic sur des ports spécifiques

Autoriser le trafic du système (le localhost)
sudo iptables -A INPUT -i lo -j ACCEPT
Autoriser le trafic Web HTTP
sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT
Autoriser le trafic Internet HTTPS
sudo iptables -A INPUT -p tcp --dport 443 -j ACCEPT
Autoriser le trafic SSH
sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT

Rendre les changements permanents

Installer le paquet
sudo apt install iptables-persistent

Les fichiers /etc/iptables/rules.v4 et /etc/iptables/rules.v6 seront créés.

Sauvegarder la configuration iptables
sudo sh -c 'iptables-save > /etc/iptables/rules.v4'
Restaurer les règles
sudo iptables-restore < /etc/iptables/rules.v4
Ajouter les nouvelles règles en gardant les actuelles
sudo iptables-restore -n < /etc/iptables/rules.v4