Bonjour à tous,
je vous expose mon soucis concernant mon server DHCP & FW (avec iptables/ufw).
J’ai deux réseaux, un qui accède à internet en 192.168.1.1 (le DNS) et un interne à mon serveur DHCP en 10.10.10.0/24.
J’ai bien configuré mon DHCP qui alloue dynamiquement les adresses sur mon réseau interne sans problème avec pour DNS 192.168.1.1.
Sur cette même machine j’ai monté mon accès NAT via ufw pour avoir internet sur mon réseau privé.
Pour cela voici ce que j’ai effectué:
/etc/default/ufw
/etc/ufw/sysctl.conf
net/ipv4/ip_forward=1
net/ipv6/conf/default/forwarding=1
net/ipv6/conf/all/forwarding=1
/etc/ufw/before.rules
#
# rules.before
#
# Rules that should be run before the ufw command line added rules. Custom
# rules should be added to one of these chains:
# ufw-before-input
# ufw-before-output
# ufw-before-forward
#
# règles pour la table NAT
*nat
:POSTROUTING ACCEPT [0:0]
# transmission du trafic provenant de enp0s3 vers enp0s8
-A POSTROUTING -s 10.10.10.0/24 -o enp0s8 -j MASQUERADE
COMMIT
# Don't delete these required lines, otherwise there will be errors
*filter
:ufw-before-input - [0:0]
:ufw-before-output - [0:0]
:ufw-before-forward - [0:0]
:ufw-not-local - [0:0]
# End required lines
# allow all on loopback
-A ufw-before-input -i lo -j ACCEPT
-A ufw-before-output -o lo -j ACCEPT
# quickly process packets for which we already have a connection
-A ufw-before-input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
# drop INVALID packets (logs these in loglevel medium and higher)
-A ufw-before-input -m conntrack --ctstate INVALID -j ufw-logging-deny
-A ufw-before-input -m conntrack --ctstate INVALID -j DROP
# ok icmp codes for INPUT
-A ufw-before-input -p icmp --icmp-type destination-unreachable -j ACCEPT
-A ufw-before-input -p icmp --icmp-type source-quench -j ACCEPT
-A ufw-before-input -p icmp --icmp-type time-exceeded -j ACCEPT
-A ufw-before-input -p icmp --icmp-type parameter-problem -j ACCEPT
-A ufw-before-input -p icmp --icmp-type echo-request -j ACCEPT
# ok icmp code for FORWARD
-A ufw-before-forward -p icmp --icmp-type destination-unreachable -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type source-quench -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type time-exceeded -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type parameter-problem -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type echo-request -j ACCEPT
# allow dhcp client to work
-A ufw-before-input -p udp --sport 67 --dport 68 -j ACCEPT
#
# ufw-not-local
#
-A ufw-before-input -j ufw-not-local
# if LOCAL, RETURN
-A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN
# if MULTICAST, RETURN
-A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN
# if BROADCAST, RETURN
-A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN
# all other non-local packets are dropped
-A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny
-A ufw-not-local -j DROP
# allow MULTICAST mDNS for service discovery (be sure the MULTICAST line above
# is uncommented)
-A ufw-before-input -p udp -d 224.0.0.251 --dport 5353 -j ACCEPT
# allow MULTICAST UPnP for service discovery (be sure the MULTICAST line above
# is uncommented)
-A ufw-before-input -p udp -d 239.255.255.250 --dport 1900 -j ACCEPT
-A ufw-before-input -p udp --sport 67 --dport 68 -j ACCEPT
#
# ufw-not-local
#
-A ufw-before-input -j ufw-not-local
# if LOCAL, RETURN
-A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN
# if MULTICAST, RETURN
-A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN
# if BROADCAST, RETURN
-A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN
# all other non-local packets are dropped
-A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny
-A ufw-not-local -j DROP
# allow MULTICAST mDNS for service discovery (be sure the MULTICAST line above
# is uncommented)
-A ufw-before-input -p udp -d 224.0.0.251 --dport 5353 -j ACCEPT
# allow MULTICAST UPnP for service discovery (be sure the MULTICAST line above
# is uncommented)
-A ufw-before-input -p udp -d 239.255.255.250 --dport 1900 -j ACCEPT
# don't delete the 'COMMIT' line or these rules won't be processed
COMMITensuite j’active mes règles:
Ok, parfait ! Mon host n’accède plus à rien sur internet à par le SSH. Cependant… le NAT fonctionne très, même trop vu qu’aucune règle n’est respecté ! C’est à dire que mes clients interne accède à tout sans passer par le filtre de ufw. Là par exemple l’host n’a pas internet alors que les clients oui… si je coupe mon ufw et je reboote, mes clients n’accèdent plus à rien (normal ufw est éteint) et l’host accède bien à internet.
Je relance ufw, l’host coupé d’internet et mes clients accède à internet…
Pourquoi et où est ce que je me suis planté pour que les règles de UFW ne s’appliquent pas au NAT ?!
Un petit sudo iptables -L pour aider:
[code]administrateur@DHCP:~$ sudo iptables -L
[sudo] password for administrateur:
Chain INPUT (policy DROP)
target prot opt source destination
ufw-before-logging-input all – anywhere anywhere
ufw-before-input all – anywhere anywhere
ufw-after-input all – anywhere anywhere
ufw-after-logging-input all – anywhere anywhere
ufw-reject-input all – anywhere anywhere
ufw-track-input all – anywhere anywhere
Chain FORWARD (policy ACCEPT)
target prot opt source destination
ufw-before-logging-forward all – anywhere anywhere
ufw-before-forward all – anywhere anywhere
ufw-after-forward all – anywhere anywhere
ufw-after-logging-forward all – anywhere anywhere
ufw-reject-forward all – anywhere anywhere
ufw-track-forward all – anywhere anywhere
Chain OUTPUT (policy DROP)
target prot opt source destination
ufw-before-logging-output all – anywhere anywhere
ufw-before-output all – anywhere anywhere
ufw-after-output all – anywhere anywhere
ufw-after-logging-output all – anywhere anywhere
ufw-reject-output all – anywhere anywhere
ufw-track-output all – anywhere anywhere
Chain ufw-after-forward (1 references)
target prot opt source destination
Chain ufw-after-input (1 references)
target prot opt source destination
ufw-skip-to-policy-input udp – anywhere anywhere udp dpt:netbios-ns
ufw-skip-to-policy-input udp – anywhere anywhere udp dpt:netbios-dgm
ufw-skip-to-policy-input tcp – anywhere anywhere tcp dpt:netbios-ssn
ufw-skip-to-policy-input tcp – anywhere anywhere tcp dpt:microsoft-ds
ufw-skip-to-policy-input udp – anywhere anywhere udp dpt:bootps
ufw-skip-to-policy-input udp – anywhere anywhere udp dpt:bootpc
ufw-skip-to-policy-input all – anywhere anywhere ADDRTYPE match dst-type BROADCAST
Chain ufw-after-logging-forward (1 references)
target prot opt source destination
Chain ufw-after-logging-input (1 references)
target prot opt source destination
LOG all – anywhere anywhere limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "
Chain ufw-after-logging-output (1 references)
target prot opt source destination
LOG all – anywhere anywhere limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "
Chain ufw-after-output (1 references)
target prot opt source destination
Chain ufw-before-forward (1 references)
target prot opt source destination
ACCEPT all – anywhere anywhere ctstate RELATED,ESTABLISHED
ACCEPT icmp – anywhere anywhere icmp destination-unreachable
ACCEPT icmp – anywhere anywhere icmp source-quench
ACCEPT icmp – anywhere anywhere icmp time-exceeded
ACCEPT icmp – anywhere anywhere icmp parameter-problem
ACCEPT icmp – anywhere anywhere icmp echo-request
ufw-user-forward all – anywhere anywhere
Chain ufw-before-input (1 references)
target prot opt source destination
ACCEPT all – anywhere anywhere
ACCEPT all – anywhere anywhere ctstate RELATED,ESTABLISHED
ufw-logging-deny all – anywhere anywhere ctstate INVALID
DROP all – anywhere anywhere ctstate INVALID
ACCEPT icmp – anywhere anywhere icmp destination-unreachable
ACCEPT icmp – anywhere anywhere icmp source-quench
ACCEPT icmp – anywhere anywhere icmp time-exceeded
ACCEPT icmp – anywhere anywhere icmp parameter-problem
ACCEPT icmp – anywhere anywhere icmp echo-request
ACCEPT udp – anywhere anywhere udp spt:bootps dpt:bootpc
ufw-not-local all – anywhere anywhere
ACCEPT udp – anywhere 224.0.0.251 udp dpt:mdns
ACCEPT udp – anywhere 239.255.255.250 udp dpt:1900
ufw-user-input all – anywhere anywhere
Chain ufw-before-logging-forward (1 references)
target prot opt source destination
Chain ufw-before-logging-input (1 references)
target prot opt source destination
Chain ufw-before-logging-output (1 references)
target prot opt source destination
Chain ufw-before-output (1 references)
target prot opt source destination
ACCEPT all – anywhere anywhere
ACCEPT all – anywhere anywhere ctstate RELATED,ESTABLISHED
ufw-user-output all – anywhere anywhere
Chain ufw-logging-allow (0 references)
target prot opt source destination
LOG all – anywhere anywhere limit: avg 3/min burst 10 LOG level warning prefix "[UFW ALLOW] "
Chain ufw-logging-deny (2 references)
target prot opt source destination
RETURN all – anywhere anywhere ctstate INVALID limit: avg 3/min burst 10
LOG all – anywhere anywhere limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "
Chain ufw-not-local (1 references)
target prot opt source destination
RETURN all – anywhere anywhere ADDRTYPE match dst-type LOCAL
RETURN all – anywhere anywhere ADDRTYPE match dst-type MULTICAST
RETURN all – anywhere anywhere ADDRTYPE match dst-type BROADCAST
ufw-logging-deny all – anywhere anywhere limit: avg 3/min burst 10
DROP all – anywhere anywhere
Chain ufw-reject-forward (1 references)
target prot opt source destination
Chain ufw-reject-input (1 references)
target prot opt source destination
Chain ufw-reject-output (1 references)
target prot opt source destination
Chain ufw-skip-to-policy-forward (0 references)
target prot opt source destination
ACCEPT all – anywhere anywhere
Chain ufw-skip-to-policy-input (7 references)
target prot opt source destination
DROP all – anywhere anywhere
Chain ufw-skip-to-policy-output (0 references)
target prot opt source destination
DROP all – anywhere anywhere
Chain ufw-track-forward (1 references)
target prot opt source destination
ACCEPT tcp – anywhere anywhere ctstate NEW
ACCEPT udp – anywhere anywhere ctstate NEW
Chain ufw-track-input (1 references)
target prot opt source destination
Chain ufw-track-output (1 references)
target prot opt source destination
Chain ufw-user-forward (1 references)
target prot opt source destination
Chain ufw-user-input (1 references)
target prot opt source destination
ACCEPT tcp – anywhere anywhere tcp dpt:ssh
ACCEPT udp – anywhere anywhere udp dpt:ssh
Chain ufw-user-limit (0 references)
target prot opt source destination
LOG all – anywhere anywhere limit: avg 3/min burst 5 LOG level warning prefix "[UFW LIMIT BLOCK] "
REJECT all – anywhere anywhere reject-with icmp-port-unreachable
Chain ufw-user-limit-accept (0 references)
target prot opt source destination
ACCEPT all – anywhere anywhere
Chain ufw-user-logging-forward (0 references)
target prot opt source destination
Chain ufw-user-logging-input (0 references)
target prot opt source destination
Chain ufw-user-logging-output (0 references)
target prot opt source destination
Chain ufw-user-output (1 references)
target prot opt source destination[/code]
Un grand merci à tous d’avance !!!
Jean-Baptiste