Qubes-os port forwarding to allow external connections

qvm-portfwd-iptables

#!/bin/bash

# Frédéric Pierret <frederic.pierret@qubes-os.org>

# Adapted from previous work:
# - https://gist.github.com/daktak/f887352d564b54f9e529404cc0eb60d5
# - https://gist.github.com/jpouellet/d8cd0eb8589a5b9bf0c53a28fc530369
# - https://gist.github.com/Joeviocoe/6c4dc0c283f6d6c5b1a3f5af8793292b

[ "$DEBUG" = 1 ] && set -x

ip() {
	qvm-prefs -g -- "$1" ip
}

netvm() {
	qvm-prefs -g -- "$1" netvm
}

forward() {
	local action="$1"
	local from_qube="$2"
	local to_qube="$3"
	local port="$4"
	local proto="$5"
	local persistent="$6"

	local iface
	local from_ip
	local to_ip
	local nft_cmd
	local nft_handle

	# TODO: Handle multiple interfaces in sys-net. It currently catches only the first physical interface.
	iface=$(qvm-run -p -u root "$from_qube" "ifconfig | grep cast -B 1 --no-group-separator | grep -vE '^(vif|lo)' | grep -oE '^[^: ]+' | head -1")
	from_ip=$(qvm-run -p -u root "$from_qube" "hostname -I | cut -d ' ' -f 1")
	to_ip=$(ip "$to_qube")

	if [ "x$from_ip" = "xNone" ]; then
		local from_ip=
	fi

	if [[ "$action" = "clear" ]]; then
		echo "$from_qube: Clearing Port Forwarding from $from_qube iptables" >&2
		qvm-run -p -u root "$from_qube" "iptables-save | grep -v 'PortFwd $from_qube' | iptables-restore"

		nft_cmd="nft list table ip qubes-firewall -a | tr -d '\"' | grep 'iifname $iface accept # handle' | awk '{print \$NF}'"
		nft_handle=$(qvm-run -p -u root "$from_qube" "$nft_cmd")

		if [[ $nft_handle =~ ^[0-9]+$ ]]; then
			qvm-run -p -u root "$from_qube" "nft delete rule ip qubes-firewall forward handle $nft_handle"
		fi
		qvm-run -p -u root "$from_qube" "sed -i '/PortFwd $from_qube>$to_qube:$proto$port/d' /rw/config/rc.local"
		qvm-run -p -u root "$from_qube" "sed -i '/PortFwd $from_qube>$to_qube:$proto$port/d' /rw/config/rc.local"
		if ! qvm-run -p -u root "$from_qube" "grep -q 'PortFwd' /rw/config/rc.local"; then
			qvm-run -p -u root "$from_qube" "sed -i '/nft add rule ip qubes-firewall forward meta iifname $iface accept/d' /rw/config/rc.local"
		fi
	else
		echo "$from_qube: Forwarding on $iface port $port to $to_qube ($from_ip -> $to_ip)" >&2
		forward_rule1="iptables -t nat -A PREROUTING -i $iface -p $proto ${from_ip:+-d} $from_ip --dport $port -j DNAT --to-destination $to_ip -m comment --comment \"'PortFwd $from_qube>$to_qube:$proto$port'\""
		forward_rule2="iptables -I FORWARD 2 -i $iface -p $proto ${to_ip:+-d} $to_ip --dport $port -m conntrack --ctstate NEW -j ACCEPT -m comment --comment \"'PortFwd $from_qube>$to_qube:$proto$port'\""
		forward_rule3="nft add rule ip qubes-firewall forward meta iifname $iface accept"

		qvm-run -p -u root "$from_qube" "iptables-save | grep -v 'PortFwd $from_qube>$to_qube:$proto$port' | iptables-restore"
		qvm-run -p -u root "$from_qube" "$forward_rule1"
		qvm-run -p -u root "$from_qube" "$forward_rule2"
		qvm-run -p -u root "$from_qube" "$forward_rule3"
		if [ "$persistent" = 1 ]; then
			qvm-run -p -u root "$from_qube" "echo $forward_rule1 >> /rw/config/rc.local"
			qvm-run -p -u root "$from_qube" "echo $forward_rule2 >> /rw/config/rc.local"
			if ! qvm-run -p -u root "$from_qube" "grep -q 'nft add rule ip qubes-firewall forward meta iifname $iface accept' /rw/config/rc.local"; then
				qvm-run -p -u root "$from_qube" "echo $forward_rule3 >> /rw/config/rc.local"
				# Ensure rc.local is executable
				qvm-run -p -u root "$from_qube" "chmod +x /rw/config/rc.local"
			fi
		fi 
	fi
}

input() {
	local action="$1"
	local qube="$2"
	local port="$3"
	local proto="$4"
	local persistent="$5"

	if [[ "$action" = "clear" ]]; then
		echo "$qube: Clearing Port Forwarding from $qube iptables" >&2
		qvm-run -p -u root "$qube" "iptables-save | grep -v 'PortFwd $qube' | iptables-restore"
		qvm-run -p -u root "$qube" "sed -i '/PortFwd $qube:$proto$port/d' /rw/config/rc.local"
	else
		echo "$qube: Allowing input to port $port" >&2
		qvm-run -p -u root "$qube" "iptables-save | grep -v 'PortFwd $qube:$proto$port' | iptables-restore"
	
		input_rule="iptables -I INPUT 5 -p $proto --dport $port -m conntrack --ctstate NEW -j ACCEPT -m comment --comment \"'PortFwd $qube:$proto$port'\""
		qvm-run -p -u root "$qube" "$input_rule"
		if [ "$persistent" = 1 ]; then
			qvm-run -p -u root "$qube" "echo $input_rule >> /rw/config/rc.local"
			# Ensure rc.local is executable
			qvm-run -p -u root "$qube" "chmod +x /rw/config/rc.local"
		fi
	fi
}

recurse_netvms() {
	local action="$1"
	local this_qube="$2"
	local port="$3"
	local proto="$4"
	local persistent="$5"

	local outer_dom

	outer_dom=$(netvm "$this_qube")
	if [[ -n "$outer_dom" && "$outer_dom" != "None" ]]; then
		forward "$action" "$outer_dom" "$this_qube" "$port" "$proto" "$persistent"
		recurse_netvms "$action" "$outer_dom" "$port" "$proto" "$persistent"
	fi
}

usage() {
	echo "Usage: ${0##*/} --action ACTION --qube QUBE --port PORT --proto PROTO --persistent" >&2
	echo "" >&2
	echo "Exemple: " >&2
	echo " -> ${0##*/} --action create --qube work --port 22" >&2
	echo " -> ${0##*/} --action create --qube work --port 444 --proto udp --persistent" >&2
	echo " -> ${0##*/} --action clear --qube work --port 22" >&2
	echo " -> ${0##*/} --action clear --qube work --port 444 --proto udp" >&2
	echo "" >&2
	echo "Default value for PROTO is 'tcp' and iptables are not persistent"
	exit 1
}

if ! OPTS=$(getopt -o a:q:p:n:s --long action:,qube:,port:,proto:,persistent -n "$0" -- "$@"); then
    echo "An error occurred while parsing options." >&2
    exit 1
fi

eval set -- "$OPTS"

while [[ $# -gt 0 ]]; do
    case "$1" in
        -a | --action ) ACTION="$2"; shift ;;
        -q | --qube ) QUBE="$2"; shift ;;
        -p | --port ) PORT="$2"; shift ;;
        -n | --proto ) PROTO="$2"; shift ;;
        -s | --persistent ) PERSISTENT=1; shift ;;
    esac
    shift
done

if [ -z "$PROTO" ]; then
	PROTO="tcp"
fi

if { [ "$ACTION" != "create" ] || [ "$ACTION" == "clear" ]; } && { [ -z "$QUBE" ] || [ -z "$PORT" ]; }; then
	usage
fi

if ! qvm-check "$QUBE" > /dev/null 2>&1; then
	echo "Qube '$QUBE' not found." >&2
	exit 1
fi

input "$ACTION" "$QUBE" "$PORT" "$PROTO" "$PERSISTENT"
recurse_netvms "$ACTION" "$QUBE" "$PORT" "$PROTO" "$PERSISTENT"

#jfyi in https://forum.qubes-os.org/t/port-forwarding-to-allow-external-connections-qvm-portfwd-iptables/18870 ,
i have attempted to grasp the "essentials" of what this script does (minus the undo). But also:

• replaced all short form options
• renamed iface to incomingInterface
• renamed from_ip to incomingPacketRecipient
• renamed to_ip to outgoingPacketRecipient

What seems to be the essence is this:

iptables -I INPUT 5 -p $proto --dport $port -m conntrack --ctstate NEW -j ACCEPT -m comment --comment "'PortFwd $qube:$proto$port'"

And then traversing the net vms:

iptables -t nat -A PREROUTING -i $iface -p $proto ${from_ip:+-d} $from_ip --dport $port -j DNAT --to-destination $to_ip -m comment --comment "'PortFwd $from_qube>$to_qube:$proto$port'"
iptables -I FORWARD 2 -i $iface -p $proto ${to_ip:+-d} $to_ip --dport $port -m conntrack --ctstate NEW -j ACCEPT -m comment --comment "'PortFwd $from_qube>$to_qube:$proto$port'"
nft add rule ip qubes-firewall forward meta iifname $iface accept