From fbde929fce7405f018fc66bb5796bf0a16292913 Mon Sep 17 00:00:00 2001 From: Guilhem Moulin Date: Wed, 30 Oct 2013 21:06:51 +0100 Subject: Configure v4 and v6 iptable rulesets. --- .../common/files/etc/network/if-pre-up.d/iptables | 38 ++++ .../common/files/usr/local/sbin/update-firewall.sh | 245 +++++++++++++++++++++ 2 files changed, 283 insertions(+) create mode 100755 roles/common/files/etc/network/if-pre-up.d/iptables create mode 100755 roles/common/files/usr/local/sbin/update-firewall.sh (limited to 'roles/common/files') diff --git a/roles/common/files/etc/network/if-pre-up.d/iptables b/roles/common/files/etc/network/if-pre-up.d/iptables new file mode 100755 index 0000000..6a50948 --- /dev/null +++ b/roles/common/files/etc/network/if-pre-up.d/iptables @@ -0,0 +1,38 @@ +#!/bin/bash +# +# A pre-up hook to auto-(re)load the iptables rulesets whenever the +# network is brought up. If the action fails, an alert message is passed +# to syslogd. +# +# Copyright 2013 Guilhem Moulin +# +# Licensed under the GNU GPL version 3 or higher. +# + +set -uo pipefail +PATH=/usr/sbin:/usr/bin:/sbin:/bin + +# NOTE: syslog starts after networking during the boot process, messages +# won't be logged at boot time. +log="/usr/bin/logger -st firewall" + +# Ignore the loopback interface; run the strip for ifup only. +[ "$IFACE" != lo -a "$MODE" = start ] || exit 0 + +# We support only IPv4 and IPv6. +[ "$ADDRFAM" = inet -o "$ADDRFAM" = inet6 ] || exit 0 + +$log -p syslog.info -- "Loading $ADDRFAM firewall on interface $IFACE." + +case "$ADDRFAM" in + inet) iptr=/sbin/iptables-restore; rules=rules.v4;; + inet6)iptr=/sbin/ip6tables-restore; rules=rules.v6;; +esac +rules="/etc/iptables/$rules" + +$iptr < $rules 2>&1 | $log -p syslog.err +rv=$? + +[ $rv -gt 0 ] && $log -p syslog.alert \ + "WARN: Failed to load iptables rulesets; the machine may be unprotected!" +exit $rv diff --git a/roles/common/files/usr/local/sbin/update-firewall.sh b/roles/common/files/usr/local/sbin/update-firewall.sh new file mode 100755 index 0000000..cefeea5 --- /dev/null +++ b/roles/common/files/usr/local/sbin/update-firewall.sh @@ -0,0 +1,245 @@ +#!/bin/bash +# +# Create iptables (v4 and v6) rules. Unless [-f] is given, a +# confirmation is asked after loading the new rulesets; if the user +# answers No or doesn't answer, the old ruleset is restored. If the user +# answer Yes (or if the flag [-f] is given), the new ruleset is made +# persistent using iptables-persistent. +# +# This firewall is only targeted towards end-servers, not gateways. In +# particular, there is no NAT'ing at the moment. +# +# Dependencies: netmask(1) +# +# Copyright 2013 Guilhem Moulin +# +# Licensed under the GNU GPL version 3 or higher. +# + +set -ue +PATH=/usr/sbin:/usr/bin:/sbin:/bin + +timeout=10 +force=0 + +[ "${1:-}" = -f ] && force=1 +if ! /usr/bin/tty -s && [ $force -eq 0 ]; then + echo "Error: Not a TTY. Try with -f (at your own risks)!" >&2 + exit 1 +fi + +getInteface() { + /sbin/ip -f "$1" route | sed -nr 's/^default via .*dev (\S+).*/\1/p' | head -1 +} + +WAN=$( getInteface inet ) +WAN6=$(getInteface inet6) + +oldv4table=$(mktemp) +newv4table=$(mktemp) + +oldv6table=$(mktemp) +newv6table=$(mktemp) + +iptables() { + [ -z "$WAN" ] || { echo "$@" >> "$newv4table"; } +} +ip6tables() { + [ -z "$WAN6" ] || { echo "$@" >> "$newv6table"; } +} +tgrep() { + [ -z "$WAN" ] || { /bin/grep -E -- "$@" "$oldv4table" >> "$newv4table" || true; } + [ -z "$WAN6" ] || { /bin/grep -E -- "$@" "$oldv6table" >> "$newv6table" || true; } +} +log() { + /usr/bin/logger -st firewall -p syslog.info -- "$@" +} +fatal() { + /usr/bin/logger -st firewall -p syslog.err -- "$@" + exit 1 +} + +[ -n "$WAN" -o -n "$WAN6" ] || fatal "Error: couldn't find a network interface" + +# Store the existing table +/sbin/iptables-save -t filter > "$oldv4table" +/sbin/ip6tables-save -t filter > "$oldv6table" + +# The usual chains in filter, along with the desired default policies. +cat > "$newv4table" <<- EOF + *filter + :INPUT DROP [0:0] + :FORWARD DROP [0:0] + :OUTPUT DROP [0:0] +EOF +cp -f "$newv4table" "$newv6table" + +# Also, keep fail2ban chains +tgrep ':fail2ban-' + + +# (Host-to-host) IPSec tunnels come first. TODO: test IPSec on IPv6. +tgrep ' -m policy --dir (in|out) --pol ipsec .* --proto esp -j ACCEPT$' + + +# Allow any IPsec ESP protocol packets to be sent and received. +iptables -A INPUT -i $WAN -p esp -j ACCEPT +iptables -A OUTPUT -o $WAN -p esp -j ACCEPT + +ip6tables -A INPUT -i $WAN6 -p esp -j ACCEPT +ip6tables -A OUTPUT -o $WAN6 -p esp -j ACCEPT + + +# Then we have the fail2ban traps +tgrep ' -j fail2ban-\S+$' + + +################################################################################## +# DROP all RFC1918 addresses, martian networks, multicasts, ... +# Credits to http://newartisans.com/2007/09/neat-tricks-with-iptables/ +# http://baldric.net/loose-iptables-firewall-for-servers/ + +if [ -n "$WAN" ]; then + # Private-use networks (RFC 1918) and link local (RFC 3927) + MyNetwork=$( /bin/ip addr show "$WAN" \ + | sed -nr "s/^\s+inet\s(\S+).*\bscope global ($WAN)?$/\1/p") + [ -n "$MyNetwork" ] && \ + for ip in 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16; do + [ "$ip" = "$(/usr/bin/netmask -nc $ip $MyNetwork | sed 's/ //g')" ] \ + || iptables -A INPUT -i $WAN -s "$ip" -j DROP + done + + # Other martian packets: "This" network, multicast, broadcast (RFCs + # 1122, 3171 and 919). + for ip in 0.0.0.0/8 224.0.0.0/4 240.0.0.0/4 255.255.255.255/32; do + iptables -A INPUT -i $WAN -s "$ip" -j DROP + iptables -A INPUT -i $WAN -d "$ip" -j DROP + done +fi + +# Martian IPv6 packets: ULA (RFC 4193) and site local addresses (RFC +# 3879). +for ip6 in fc00::/7 fec0::/10 +do + ip6tables -A INPUT -i $WAN6 -s "$ip6" -j DROP + ip6tables -A INPUT -i $WAN6 -d "$ip6" -j DROP +done + + +# DROP INVALID packets immediately. +for chain in INPUT OUTPUT; do + iptables -A $chain -m state --state INVALID -j DROP + ip6tables -A $chain -m state --state INVALID -j DROP +done + + +# DROP bogus TCP packets. +iptables -A INPUT -p tcp -m tcp --tcp-flags SYN,FIN SYN,FIN -j DROP +iptables -A INPUT -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP + +ip6tables -A INPUT -p tcp -m tcp --tcp-flags SYN,FIN SYN,FIN -j DROP +ip6tables -A INPUT -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP + + +# Allow all input/output to/from the loopback interface. +iptables -A INPUT -i lo -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT +iptables -A OUTPUT -o lo -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT + +ip6tables -A INPUT -i lo -s ::1 -d ::1 -j ACCEPT +ip6tables -A OUTPUT -o lo -s ::1 -d ::1 -j ACCEPT + + +# Allow only ICMP of type 0, 3 and 8. The rate-limiting is done directly +# by the kernel (net.ipv4.icmp_ratelimit and net.ipv4.icmp_ratemask +# runtime options). See icmp(7). +for type in echo-reply destination-unreachable echo-request; do + iptables -A INPUT -i $WAN -p icmp -m icmp --icmp-type $type -j ACCEPT + iptables -A OUTPUT -o $WAN -p icmp -m icmp --icmp-type $type -j ACCEPT +done +ip6tables -A INPUT -i $WAN6 -p icmpv6 -j ACCEPT + + +################################################################################## +# ACCEPT new connections to the services we provide, or to those we want +# to connect to. + +sed -re 's/#.*//; /^\s*$/d' -e 's/^(in|out|inout)\b(.*)/\14\2\n\16\2/' \ + /etc/iptables/services | \ +while read dir proto dport sport; do + # We add two entries per config line: we need to accept the new + # connection, and latter the reply. + stNew=NEW,ESTABLISHED + stEst=ESTABLISHED + + # In-Out means full-duplex + [[ "$dir" =~ inout ]] && stEst="$stNew" + + optsNew= + optsEst= + case "$dport" in + *,*|*:*) optsNew="--match multiport --dports $dport" + optsEst="--match multiport --sports $dport";; + ?*) optsNew="--dport $dport" + optsEst="--sport $dport";; + esac + case "$sport" in + *,*|*:*) optsNew+=" --match multiport --sports $sport" + optsEst+=" --match multiport --dports $sport";; + ?*) optsNew+=" --sport $sport" + optsEst+=" --dport $sport";; + esac + + case "$dir" in + in[46]|inout[46]) iptNew="-A INPUT -i"; iptEst="-A OUTPUT -o";; + out[46]) iptNew="-A OUTPUT -o"; iptEst="-A INPUT -i";; + *) fatal "Error: Unknown direction: '$dir'." + esac + case "$dir" in + *4) ipt="iptables"; if=$WAN;; + *6) ipt="ip6tables"; if=$WAN6;; + esac + + $ipt $iptNew $if -p $proto $optsNew -m state --state $stNew -j ACCEPT + $ipt $iptEst $if -p $proto $optsEst -m state --state $stEst -j ACCEPT +done + + +################################################################################## +# And last come the fail2ban rules. +tgrep '^-[AI] fail2ban-\S+ ' + +echo COMMIT >> "$newv4table" +echo COMMIT >> "$newv6table" + +/usr/bin/uniq "$newv4table" | /sbin/iptables-restore +/usr/bin/uniq "$newv6table" | /sbin/ip6tables-restore + +save() { + mkdir -p /etc/iptables + /sbin/iptables-save > /etc/iptables/rules.v4 + /sbin/ip6tables-save > /etc/iptables/rules.v6 +} + +rv=0 +if [ $force -eq 1 ]; then + # At the user's own risks... + save +else + echo "Try now to establish NEW connections to the machine." + + read -n1 -t$timeout \ + -p "Are you sure you want to use the new ruleset? (y/N) " \ + ret 2>&1 || { [ $? -gt 128 ] && echo -n "Timeout..."; } + case "${ret:-N}" in + [yY]*) echo; save + ;; + *) log "Reverting to old ruleset... "; echo + /sbin/iptables-restore -c < "$oldv4table" + /sbin/ip6tables-restore -c < "$oldv6table" + rv=1 + ;; + esac +fi + +rm -f "$oldv4table" "$newv4table" "$oldv6table" "$newv6table" +exit $rv -- cgit v1.2.3