Traffic from and to 127.0.0.0/8 must only appear on the loopback interface, never on any other interface. This ensures offending packets are logged, and the loopback interface cannot be abused for processing traffic from and to any other networks.
Signed-off-by: Peter Müller peter.mueller@ipfire.org --- src/initscripts/system/firewall | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/src/initscripts/system/firewall b/src/initscripts/system/firewall index cc5baa292..1c62c6e2c 100644 --- a/src/initscripts/system/firewall +++ b/src/initscripts/system/firewall @@ -80,6 +80,14 @@ iptables_init() { fi iptables -A NEWNOTSYN -j DROP -m comment --comment "DROP_NEWNOTSYN"
+ # Log and subsequently drop spoofed packets or "martians", arriving from sources + # on interfaces where we don't expect them + iptables -N SPOOFED_MARTIAN + if [ "$DROPSPOOFEDMARTIAN" == "on" ]; then + iptables -A SPOOFED_MARTIAN -m limit --limit 10/second -j LOG --log-prefix "DROP_SPOOFED_MARTIAN " + fi + iptables -A SPOOFED_MARTIAN -j DROP -m comment --comment "DROP_SPOOFED_MARTIAN" + # Chain to contain all the rules relating to bad TCP flags iptables -N BADTCP
@@ -177,14 +185,18 @@ iptables_init() { iptables -A INPUT -j ICMPINPUT iptables -A ICMPINPUT -p icmp --icmp-type 8 -j ACCEPT
- # Accept everything on loopback + # Accept everything on loopback if source/destination is loopback space... iptables -N LOOPBACK - iptables -A LOOPBACK -i lo -j ACCEPT - iptables -A LOOPBACK -o lo -j ACCEPT + iptables -A LOOPBACK -i lo -s 127.0.0.0/8 -j ACCEPT + iptables -A LOOPBACK -o lo -d 127.0.0.0/8 -j ACCEPT + + # ... and drop everything else on the loopback interface, since no other traffic should appear there + iptables -A LOOPBACK -i lo -j SPOOFED_MARTIAN + iptables -A LOOPBACK -o lo -j SPOOFED_MARTIAN
- # Filter all packets with loopback addresses on non-loopback interfaces. - iptables -A LOOPBACK -s 127.0.0.0/8 -j DROP - iptables -A LOOPBACK -d 127.0.0.0/8 -j DROP + # Filter all packets with loopback addresses on non-loopback interfaces (spoofed) + iptables -A LOOPBACK -s 127.0.0.0/8 -j SPOOFED_MARTIAN + iptables -A LOOPBACK -d 127.0.0.0/8 -j SPOOFED_MARTIAN
for i in INPUT FORWARD OUTPUT; do iptables -A ${i} -j LOOPBACK