Convert firewall to nftables.

Debian Buster uses the nftables framework by default.

2 files changed, 61 insertions, 445 deletions

diff --git a/roles/common/files/usr/local/sbin/update-firewall b/roles/common/files/usr/local/sbin/update-firewall
new file mode 100755
index 0000000..957bdc1
--- /dev/null
+++ b/roles/common/files/usr/local/sbin/update-firewall
@@ -0,0 +1,61 @@
+#!/bin/bash
+
+set -ue
+PATH=/usr/sbin:/usr/bin:/sbin:/bin
+export PATH
+
+NFTABLES="/etc/nftables.conf"
+
+script="$(mktemp --tmpdir=/dev/shm)"
+oldrules="$(mktemp --tmpdir=/dev/shm)"
+newrules="$(mktemp --tmpdir=/dev/shm)"
+netns=
+cleanup(){
+    rm -f -- "$script" "$oldrules" "$newrules"
+    [ -z "$netns" ] || ip netns del "$netns"
+}
+trap cleanup EXIT INT TERM
+
+echo "flush ruleset" >"$script" # should be included already, but...
+cat <"$NFTABLES" >>"$script"
+
+ip netns add "nft-dryrun"
+netns="nft-dryrun"
+
+# clear sets in the old rules before diff'ing with the new ones
+nft list ruleset -sn >"$oldrules"
+ip netns exec "$netns" nft -f - <"$oldrules"
+ip netns exec "$netns" nft flush set inet filter fail2ban
+ip netns exec "$netns" nft flush set inet filter fail2ban6
+ip netns exec "$netns" nft list ruleset -sn >"$oldrules"
+
+declare -a INTERFACES=()
+for iface in /sys/class/net/*; do
+    idx="$(< "$iface/ifindex")"
+    INTERFACES[idx]="${iface#/sys/class/net/}"
+done
+
+# create dummy interfaces so we can use iif/oif in the nft rules
+# (we preserve indices to preserve canonical set representation)
+for idx in "${!INTERFACES[@]}"; do
+    [ "${INTERFACES[idx]}" != "lo" ] || continue
+    ip netns exec "$netns" ip link add "${INTERFACES[idx]}" index "$idx" type dummy
+done
+
+ip netns exec "$netns" nft -f - <"$script"
+ip netns exec "$netns" nft list ruleset -sn >"$newrules"
+ip netns del "$netns"
+netns=
+
+if [ ! -t 0 ] || [ ! -t 1 ]; then
+    diff -q -- "$oldrules" "$newrules" && exit 0 || exit 1
+elif ! diff -u --color=auto --label=a/ruleset --label=b/ruleset \
+                -- "$oldrules" "$newrules" && nft -f - <"$script"; then
+    read -p "Ruleset applied. Revert? [Y/n] " -r -t10 r || r="y"
+    if [ "${r,,[a-z]}" != "n" ]; then 
+        echo "Reverting..."
+        echo "flush ruleset" >"$script"
+        cat <"$oldrules"    >>"$script"
+        nft -f - <"$script"
+    fi
+fi
diff --git a/roles/common/files/usr/local/sbin/update-firewall.sh b/roles/common/files/usr/local/sbin/update-firewall.sh
deleted file mode 100755
index 8ef3ab9..0000000
--- a/roles/common/files/usr/local/sbin/update-firewall.sh
+++ /dev/null
@@ -1,445 +0,0 @@
-#!/bin/bash
-
-# Create iptables (v4 and v6) rules.  Unless one of [-f] or [-c] is
-# given, or if the ruleset is unchanged, 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 (requires a pre-up
-# hook) by moving it to /etc/iptables/rules.v[46].
-#
-# The [-c] flag switch to dry-run (check) mode.  The rulesets are not
-# applied, but merely checked against the existing ones.  The return
-# value is 0 iff. they do not differ.
-#
-# 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 <guilhem@fripost.org>
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-set -ue
-PATH=/usr/sbin:/usr/bin:/sbin:/bin
-timeout=10
-
-force=0
-check=0
-verbose=0
-addrfam=
-
-secproto=esp # must match /etc/ipsec.conf; ESP is the default (vs AH/IPComp)
-if [ -x /usr/sbin/ipsec ] && /usr/sbin/ipsec status >/dev/null; then
-    ipsec=y
-else
-    ipsec=n
-fi
-
-fail2ban_re='^(\[[0-9]+:[0-9]+\]\s+)?-A f2b-\S'
-IPsec_re=" -m policy --dir (in|out) --pol ipsec --reqid [0-9]+ --proto $secproto -j ACCEPT$"
-declare -A rss=() tables=()
-
-usage() {
-    cat >&2 <<- EOF
-		Usage: $0 [OPTIONS]
-
-		Options:
-		    -f force:   no confirmation asked
-		    -c check:   check (dry-run) mode
-		    -v verbose: see the difference between old and new ruleset
-		    -4 IPv4 only
-		    -6 IPv6 only
-	EOF
-    exit 1
-}
-
-log() {
-    logger -st firewall -p user.info -- "$@"
-}
-fatal() {
-    logger -st firewall -p user.err  -- "$@"
-    exit 1
-}
-
-iptables() {
-    # Fake iptables/ip6tables(8); use the more efficient
-    # iptables-restore(8) instead.
-    echo "$@" >>"$new";
-}
-commit() {
-    # End a table
-    echo COMMIT >>"$new"
-}
-inet46() {
-    case "$1" in
-        4) echo "$2";;
-        6) echo "$3";;
-    esac
-}
-ipt-chains() {
-    # Define new (tables and) chains.
-    while [ $# -gt 0 ]; do
-        case "$1" in
-            ?*:*) echo ":${1%:*} ${1##*:} [0:0]";;
-            ?*)   echo "*$1";;
-        esac
-        shift
-    done >>"$new"
-}
-
-ipt-trim() {
-    # Remove dynamic chain/rules from the input stream, as they are
-    # automatically included by third-party servers (such as strongSwan
-    # or fail2ban).  The output is ready to be made persistent.
-    grep -Ev -e '^:f2b-\S' \
-             -e "$IPsec_re" \
-             -e '-j f2b-\S+$' \
-             -e "$fail2ban_re"
-}
-
-ipt-diff() {
-    # Get the difference between two rulesets.
-    if [ $verbose -eq 1 ]; then
-        diff -u -I '^#' --color=auto "$@"
-    else
-        diff -q -I '^#' "$@" >/dev/null
-    fi
-}
-
-ipt-persist() {
-    # Make the current ruleset persistent.  (Requires a pre-up hook
-    # script to load the rules before the network is configured.)
-
-    log "Making ruleset persistent... "
-    [ -d /etc/iptables ] || mkdir /etc/iptables
-
-    local f rs table
-    for f in "${!tables[@]}"; do
-        ipts=$(inet46 $f iptables ip6tables)-save
-        rs=/etc/iptables/rules.v$f
-
-        for table in ${tables[$f]}; do
-            ip netns exec $netns $ipts -t $table
-        done | ipt-trim >"$rs"
-        chmod 0600 "$rs"
-    done
-}
-
-ipt-revert() {
-    [ $check -eq 0 ] || return
-    log "Reverting to old ruleset... "
-
-    local rs
-    for f in "${!rss[@]}"; do
-        $(inet46 $f iptables ip6tables)-restore -c <"${rss[$f]}"
-        rm -f "${rss[$f]}"
-    done
-    exit 1
-}
-
-run() {
-    # Build and apply the firewall for IPv4/6.
-    local f="$1"
-    local ipt=$(inet46 $f iptables ip6tables)
-    tables[$f]=filter
-
-    # The default interface associated with this address.
-    local if=$( /bin/ip -$f -o route show to default scope global \
-              | sed -nr '/^default via \S+ dev (\S+).*/ {s//\1/p;q}' )
-
-    # Store the old (current) ruleset
-    local old=$(mktemp --tmpdir current-rules.v$f.XXXXXX) \
-          new=$(mktemp --tmpdir new-rules.v$f.XXXXXX)
-    for table in ${tables[$f]}; do
-        $ipt-save -ct $table
-    done >"$old"
-    rss[$f]="$old"
-
-    local fail2ban=0
-    # XXX: As of Wheezy, fail2ban is IPv4 only.  See
-    #      https://github.com/fail2ban/fail2ban/issues/39 for the current
-    #      state of the art.
-    if [ "$f" = 4 ] && which fail2ban-server >/dev/null; then
-        fail2ban=1
-    fi
-
-    # The usual chains in filter, along with the desired default policies.
-    ipt-chains filter INPUT:DROP FORWARD:DROP OUTPUT:DROP
-
-    if [ ! "$if" ]; then
-        # If the interface is not configured, we stop here and DROP all
-        # packets by default.  Thanks to the pre-up hook this tight
-        # policy will be activated whenever the interface goes up.
-        commit
-        mv "$new" /etc/iptables/rules.v$f
-        return 0
-    fi
-
-    # Fail2ban-specific chains and traps
-    if [ $fail2ban -eq 1 ]; then
-        echo ":fail2ban - [0:0]"
-        # Don't remove existing rules & traps in the current rulest
-        grep    -- '^:f2b-\S'     "$old" || true
-        grep -E -- ' -j f2b-\S+$' "$old" || true
-        grep -E -- "$fail2ban_re" "$old" || true
-    fi >>"$new"
-
-    if [ "$f" = 4 -o "$f" = 6 ] && [ "$ipsec" = y ]; then
-        # IPsec tunnels come first (IPv4 only).
-        grep -E -- "$IPsec_re" "$old" >>"$new" || true
-
-        # Allow any IPsec $secproto protocol packets to be sent and received.
-        iptables -A INPUT  -i $if -p $secproto -j ACCEPT
-        iptables -A OUTPUT -o $if -p $secproto -j ACCEPT
-    fi
-
-
-    ########################################################################
-    # DROP all RFC1918 addresses, martian networks, multicasts, ...
-    # Credits to http://newartisans.com/2007/09/neat-tricks-with-iptables/
-    #            http://baldric.net/loose-iptables-firewall-for-servers/
-
-    local ip
-    if [ "$f" = 4 ] && [ "$ipsec" = y ]; then
-        # Private-use networks (RFC 1918) and link local (RFC 3927)
-        local MyIPsec="$( ip -4 -o route show table 220 dev $if | sed 's/\s.*//' )"
-        local MyNetwork="$( ip -4 -o address show dev $if scope global \
-                          | sed -nr "s/^[0-9]+:\s+$if\s+inet\s(\S+).*/\1/p" \
-                          | while read ip; do
-                              for ips in $MyIPsec; do
-                                [ "$ips" = "$(netmask -nc "$ip" "$ips" | sed 's/^ *//')" ] || echo "$ip"
-                              done
-                            done
-                          )"
-        [ "$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
-            # Don't lock us out if we are behind a NAT ;-)
-            for myip in $MyNetwork; do
-                [ "$ip" = "$(netmask -nc "$ip" "$myip" | sed 's/^ *//')" ] || echo "$ip"
-            done | uniq | while read ip; do iptables -A INPUT -i $if -s "$ip" -j DROP; done
-        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 $if -s "$ip" -j DROP
-            iptables -A INPUT -i $if -d "$ip" -j DROP
-        done
-
-    elif [ "$f" = 6 ]; then
-        # Martian IPv6 packets: ULA (RFC 4193) and site local addresses
-        # (RFC 3879).
-        for ip in fc00::/7 fec0::/10; do
-            iptables -A INPUT -i $if -s "$ip" -j DROP
-            iptables -A INPUT -i $if -d "$ip" -j DROP
-        done
-    fi
-
-    # DROP INVALID packets immediately.
-    iptables -A INPUT  -m state --state INVALID -j DROP
-    iptables -A OUTPUT -m state --state INVALID -j DROP
-
-    # DROP bogus TCP packets.
-    iptables -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-    iptables -A INPUT -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-    iptables -A INPUT -p tcp \! --syn -m state --state NEW      -j REJECT --reject-with tcp-reset
-
-    # Allow all input/output to/from the loopback interface.
-    local localhost=$(inet46 $f '127.0.0.1/8' '::1/128')
-    iptables -A INPUT  -i lo -s "$localhost" -d "$localhost" -j ACCEPT
-    iptables -A OUTPUT -o lo -s "$localhost" -d "$localhost" -j ACCEPT
-    if [ "$f" = 4 ] && [ "$ipsec" = y ]; then
-        # Allow local access to our virtual IP
-        ip -4 -o route show table 220 dev $if \
-        | sed -nr 's/.*\ssrc\s+([[:digit:].]{7,15})(\s.*)?$/\1/p' \
-        | while read ips; do
-            iptables -A INPUT  -i lo -s "$ips" -d "$ips" -j ACCEPT
-            iptables -A OUTPUT -o lo -s "$ips" -d "$ips" -j ACCEPT
-        done
-    fi
-
-    # Prepare fail2ban.  We make fail2ban insert its rules in a
-    # dedicated chain, so that it doesn't mess up the existing rules.
-    [ $fail2ban -eq 1 ] && iptables -A INPUT -i $if -j fail2ban
-
-    if [ "$f" = 4 ]; then
-        # 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).
-        local t
-        for t in  'echo-reply' 'destination-unreachable' 'echo-request'; do
-            iptables -A INPUT  -p icmp -m icmp --icmp-type $t -j ACCEPT
-            iptables -A OUTPUT -p icmp -m icmp --icmp-type $t -j ACCEPT
-        done
-    elif [ $f = 6 ]; then
-        iptables -A INPUT  -p icmpv6 -j ACCEPT
-        iptables -A OUTPUT -p icmpv6 -j ACCEPT
-    fi
-
-
-    ########################################################################
-    # ACCEPT new connections to the services we provide, or to those we want
-    # to connect to.
-
-    sed -re 's/#.*//; /^\s*$/d' -e "s/^(in|out|inout)$f?(\s.*)/\1\2/" \
-            /etc/iptables/services | \
-    grep -Ev '^(in|out|inout)\S\s' | \
-    while read dir proto dport sport; do
-        # We add two entries per config line: we need to accept the new
-        # connection, and latter the reply.
-        local stNew=NEW,ESTABLISHED,RELATED
-        local stEst=ESTABLISHED,RELATED
-
-        # In-Out means full-duplex
-        [[ "$dir" =~ ^inout ]] && stEst="$stNew"
-
-        local iptNew= iptEst= optsNew= optsEst=
-        case "$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|inout) iptNew="-A INPUT  -i";  iptEst="-A OUTPUT -o";;
-            out)      iptNew="-A OUTPUT -o";  iptEst="-A INPUT  -i";;
-            *) fatal "Error: Unknown direction: '$dir'."
-        esac
-
-        iptables $iptNew $if -p $proto $optsNew -m state --state $stNew -j ACCEPT
-        iptables $iptEst $if -p $proto $optsEst -m state --state $stEst -j ACCEPT
-    done
-
-    iptables -A OUTPUT -o $if -p tcp -j REJECT --reject-with tcp-reset
-    iptables -A OUTPUT -o $if -p udp -j REJECT --reject-with port-unreach
-    if [ "$f" = "4" ]; then
-        iptables -A OUTPUT -o $if -p icmp -j REJECT --reject-with icmp-host-unreachable
-        iptables -A OUTPUT -o $if         -j REJECT --reject-with icmp-host-prohibited
-    else
-        iptables -A OUTPUT -o $if -j REJECT
-    fi
-
-    ########################################################################
-    commit
-
-
-    local rv1=0 rv2=0 persistent=/etc/iptables/rules.v$f
-    local oldz=$(mktemp --tmpdir current-rules.v$f.XXXXXX)
-
-    # Reset the counters.  They are not useful for comparing and/or
-    # storing persistent ruleset.  (We don't use sed -i because we want
-    # to restore the counters when reverting.)
-    sed -r -e '/^:/ s/\[[0-9]+:[0-9]+\]$/[0:0]/' \
-           -e 's/^\[[0-9]+:[0-9]+\]\s+//' \
-           "$old" >"$oldz"
-
-    ip netns exec $netns $ipt-restore <"$new" || ipt-revert
-
-    for table in ${tables[$f]}; do
-       ip netns exec $netns $ipt-save -t $table
-    done >"$new"
-
-    ipt-diff --label="a/$ipt-save" --label="b/$ipt-save" "$oldz" "$new" || rv1=$?
-
-    if ! [ -f "$persistent" ] && [ -x /etc/network/if-pre-up.d/iptables ]; then
-        rv2=1
-    else
-        ipt-trim <"$new" | ipt-diff --label="a/rules.v$f" --label="b/$ipt-save" "$persistent" - || rv2=$?
-    fi
-
-    local update="Please run '${0##*/}'."
-    if [ $check -eq 0 ]; then
-        uniq "$new" | $ipt-restore || ipt-revert
-    else
-        if [ $rv1 -ne 0 ]; then
-            log "WARN: The IPv$f firewall is not up to date! $update"
-        fi
-        if [ $rv2 -ne 0 ]; then
-            log "WARN: The current IPv$f firewall is not persistent! $update"
-        fi
-    fi
-
-    rm -f "$oldz" "$new"
-    return $(( $rv1 | $rv2 ))
-}
-
-
-# Parse options
-while [ $# -gt 0 ]; do
-    case "$1" in
-        -?*) for (( k=1; k<${#1}; k++ )); do
-                o="${1:$k:1}"
-                case "$o" in
-                    4|6) addrfam="$o";;
-                    c) check=1;;
-                    f) force=1;;
-                    v) verbose=1;;
-                    *) usage;;
-                esac
-            done
-        ;;
-        *) usage;;
-    esac
-    shift
-done
-
-# If we are going to apply the ruleset, we should either have a TTY, or
-# use -f.
-if ! tty -s && [ $force -eq 0 ] && [ $check -eq 0 ]; then
-    echo "Error: Not a TTY. Try with -f (at your own risks!)" >&2
-    exit 1
-fi
-
-# Create an alternative net namespace in which we apply the ruleset, so
-# we can easily get a normalized version we can compare latter.  See
-# http://bugzilla.netfilter.org/show_bug.cgi?id=790
-netns="ipt-firewall-test-$$"
-ip netns add $netns
-
-trap 'ip netns del $netns 2>/dev/null || true; ipt-revert' SIGINT
-trap 'ip netns del $netns; rm -f "${rss[@]}"'              EXIT
-
-rv=0
-for f in ${addrfam:=4 6}; do
-    run $f || rv=$(( $rv | $? ))
-done
-
-if [ $force -eq 1 ]; then
-    # At the user's own risks...
-    ipt-persist
-
-elif [ $check -eq 1 ] || [ $rv -eq 0 ]; then
-    # Nothing to do, we're all set.
-    exit $rv
-
-else
-    echo "Try now to establish NEW connections to the machine."
-
-    read -n1 -t$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; ipt-persist
-        ;;
-        *) echo; ipt-revert
-        ;;
-    esac
-fi