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  • Iptables state tracking

    - by complexgeek
    Hi there. I've just taken over administration of a fairly complex firewall ruleset for a firewall box running Fedora Core 12, and there's one thing about it that is puzzling me. When I run nmap on the gateway from outside the network, I see all the expected services, but also sunrpc on port 111. The INPUT chain has DEFAULT DROP set, and there is no rule allowing port 111. As best I can tell (watching the packet counters before/during/after the scan) it's being allowed by the rule: "-m state --state RELATED,ESTABLISHED -j ACCEPT" but I don't understand why a brand new TCP connection would be considered RELATED or ESTABLISHED. Any suggestions would be greatly appreciated. EDIT: Conntrack modules: nf_conntrack_netlink 14925 0 nfnetlink 3479 1 nf_conntrack_netlink nf_conntrack_irc 5206 1 nf_nat_irc nf_conntrack_proto_udplite 3138 0 nf_conntrack_h323 62110 1 nf_nat_h323 nf_conntrack_proto_dccp 6878 0 nf_conntrack_sip 16921 1 nf_nat_sip nf_conntrack_proto_sctp 11131 0 nf_conntrack_pptp 10673 1 nf_nat_pptp nf_conntrack_sane 5458 0 nf_conntrack_proto_gre 6574 1 nf_conntrack_pptp nf_conntrack_amanda 2796 1 nf_nat_amanda nf_conntrack_ftp 11741 1 nf_nat_ftp nf_conntrack_tftp 4665 1 nf_nat_tftp nf_conntrack_netbios_ns 1534 0 nf_conntrack_ipv6 18504 2 ipv6 279399 40 ip6t_REJECT,nf_conntrack_ipv6 INPUT chain on the filter table: -A INPUT -s 192.168.200.10/32 -p tcp -m tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT -A INPUT -s 127.0.0.0/8 -i lo -j ACCEPT -A INPUT -p udp -m udp --sport 67:68 --dport 67:68 -j ACCEPT -A INPUT -d 192.168.200.5/32 -i eth0 -j ACCEPT -A INPUT -d 192.168.1.2/32 -i eth0 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p tcp -m multiport --dports 22,80,443 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p tcp -m multiport --sports 22,25,80,443 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p udp -m udp --dport 1194 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p udp -m udp --sport 1194 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p udp -m multiport --sports 53,123 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p icmp -m icmp --icmp-type 8 -j ACCEPT -A INPUT -i eth0 -m state --state NEW -j ACCEPT -A INPUT -d {public_ip}/32 -m state --state NEW -j ACCEPT -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT eth0 is connected to the internal network, eth3 is connected to an ADSL modem in bridge mode, ppp0 is the WAN connection tunneled over eth3.

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