#!/usr/bin/env bash

#   COPYRIGHT NOTICE STARTS HERE
#
#   Copyright 2019 Samsung Electronics Co., Ltd.
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.
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#   COPYRIGHT NOTICE ENDS HERE

# Check all ports exposed by pods to internal network and look for
# open JDWP ports
#
# Dependencies:
#     kubectl + config
#     netcat
#
# Return value: Number of discovered JDWP ports
# Output: List of pods and exposing JDWP interface
#

if [ "$#" -lt 1 ]; then
    echo "Usage: $0 <k8s-namespace>"
    exit 1
fi

K8S_NAMESPACE=$1
LOCAL_PORT=12543

list_pods() {
	kubectl get po --namespace=$K8S_NAMESPACE | grep Running | awk '{print $1}' | grep -v NAME
}

do_jdwp_handshake() {
	local ip="127.0.0.1"
	local port=$1
	local jdwp_challenge="JDWP-Handshake\n"
	local jdwp_response="JDWP-Handshake"

	# 10s timeout to avoid hangs when service doesn't answer at all
	local response=`nc -w 10 $ip $port <<<$jdwp_challenge | tr '\0' '\n'`
	if [[ $response == *"$jdwp_response"* ]]; then
		return 0
	fi

	return 1
}
# get open ports from procfs as netstat is not always available
get_open_ports_on_pod() {
	local pod=$1
	local open_ports_hex=`kubectl exec --namespace=$K8S_NAMESPACE $pod cat /proc/net/tcp 2>/dev/null| grep -v "local_address" | awk '{ print $2" "$4 }' | grep '0A$' | tr ":" " " | awk '{ print $2 }' | sort | uniq`
	for hex_port in $open_ports_hex; do
		echo $((16#$hex_port))
	done
}

N_PORTS=0

# go through all pods
for pod in `list_pods`; do
	open_ports=`get_open_ports_on_pod $pod`
	# if there is no open ports just go to next pod
	if [ -z "$open_ports" ]; then
		continue
	fi

	# let's setup a proxy and check every open port
	for port in $open_ports; do
		# run proxy
		kubectl port-forward --namespace=$K8S_NAMESPACE $pod $LOCAL_PORT:$port &>/dev/null &
		sleep 1
		proxy_pid=$!

		do_jdwp_handshake $LOCAL_PORT
		if [ $? -eq 0 ]; then
			echo $pod $port
			((++N_PORTS))
		fi
		kill $proxy_pid 2>/dev/null
		wait $proxy_pid 2>/dev/null
	done
done

exit $N_PORTS