StrongSwan vici python usage snippet

readme.md

StrongSwan VPN install and usage

Reliable VPN connection between a companion computer on an air vehicle and a ground control station

These settings are for a hub and spoke model. Rover connections are rw-1 and rw-2 while base is a server with a static ip.

Usage model

• rw-1 is a ground control station running with a dynamic and possibly changing ip (3G, LTE, SATCOM, etc...)
• rw-2 is a companion computer on an air vehicle with a dynamic and possibly changing ip (3G, LTE, SATCOM, etc...)
• base is a server with a known static ip

After installing StrongSwan and setting up the connections, rw-1 and rw-2 can connect to the base. Once connected, rw-1 can communicate directly with rw-2 using the IP addresses which are assigned to them via the base.

Setting it up

1. Download and install strongswan as per StrongSwan_build_notes.txt

2. edit /etc/strongswan.conf

3. edit /etc/ipsec.conf NOTE: Change the IP and select the correct config file (rover or base)

4. edit /etc/ipsec.secrets

5. BASE ONLY: Setup ipv4 port forwarding on server with static ip. Edit /etc/sysctl.conf to include the following:

   #VPN
   net.ipv4.ip_forward = 1
   net.ipv4.conf.all.accept_redirects = 0
   net.ipv4.conf.all.send_redirects = 0
   

6. OPTIONAL: Use the included python scripts to monitor and auto re-connect the tunnel(s) in case of failure. The python script is not required to setup and run a tunnel, rather it shows how an external python script can bring a tunnel up / down and monitor its status.

Some ipsec commands

sudo ipsec start sudo ipsec statusall sudo ipsec up <connection name> sudo ipsec down <connection name> sudo ipsec stop Have fun! :)

ipsec.conf (base)

# /etc/ipsec.conf - strongSwan IPsec configuration file

config setup

conn %default
	ike=aes128-sha256-ecp256,aes256-sha384-ecp384,aes128-sha256-modp2048,aes128-sha1-modp2048,aes256-sha384-modp4096,aes256-sha256-modp4096,aes256-sha1-modp4096,aes128-sha256-modp1536,aes128-sha1-modp1536,aes256-sha384-modp2048,aes256-sha256-modp2048,aes256-sha1-modp2048,aes128-sha256-modp1024,aes128-sha1-modp1024,aes256-sha384-modp1536,aes256-sha256-modp1536,aes256-sha1-modp1536,aes256-sha384-modp1024,aes256-sha256-modp1024,aes256-sha1-modp1024!
	esp=aes128gcm16-ecp256,aes256gcm16-ecp384,aes128-sha256-ecp256,aes256-sha384-ecp384,aes128-sha256-modp2048,aes128-sha1-modp2048,aes256-sha384-modp4096,aes256-sha256-modp4096,aes256-sha1-modp4096,aes128-sha256-modp1536,aes128-sha1-modp1536,aes256-sha384-modp2048,aes256-sha256-modp2048,aes256-sha1-modp2048,aes128-sha256-modp1024,aes128-sha1-modp1024,aes256-sha384-modp1536,aes256-sha256-modp1536,aes256-sha1-modp1536,aes256-sha384-modp1024,aes256-sha256-modp1024,aes256-sha1-modp1024,aes128gcm16,aes256gcm16,aes128-sha256,aes128-sha1,aes256-sha384,aes256-sha256,aes256-sha1!
	ikelifetime=3h
	keylife=20m
	reauth=no
	rekey=no
	rekeymargin=3m
	keyingtries=%forever
	keyexchange=ikev2
	authby=secret
	left=X.X.X.X #<-- Replace with internet facing static IP of base
	leftfirewall=yes
	lefthostaccess=yes
	leftid=@server.strongswan.org
	leftsubnet=10.7.7.0/24

conn rw-1
	right=%any
	rightid=@client1.strongswan.org
	rightsourceip=10.7.7.1
	auto=route

conn rw-2
	right=%any
	rightid=@client2.strongswan.org
	rightsourceip=10.7.7.2
	auto=route

ipsec.conf (rover 1)

# ipsec.conf - strongSwan IPsec configuration file

# basic configuration

config setup
	# strictcrlpolicy=yes
	# uniqueids = no

# Add connections here.

conn %default
	ikelifetime=30m
	keylife=20m
	rekeymargin=3m
	keyingtries=%forever
	keyexchange=ikev2
	authby=secret
	reauth=no

conn rw-1
	left=%defaultroute
	leftsourceip=%config
	leftfirewall=yes
	leftid=@client1.strongswan.org
	right=X.X.X.X #<-- Replace with internet facing static IP of base
	rightsubnet=10.7.7.0/24
	rightid=@server.strongswan.org
	auto=start

ipsec.conf (rover 2)

# ipsec.conf - strongSwan IPsec configuration file

# basic configuration

config setup
	# strictcrlpolicy=yes
	# uniqueids = no

# Add connections here.

conn %default
	ikelifetime=30m
	keylife=20m
	rekeymargin=3m
	keyingtries=%forever
	keyexchange=ikev2
	authby=secret
	reauth=no

conn rw-2
	left=%defaultroute
	leftsourceip=%config
	leftfirewall=yes
	leftid=@client2.strongswan.org
	right=X.X.X.X #<-- Replace with internet facing static IP of base
	rightsubnet=10.7.7.0/24
	rightid=@server.strongswan.org
	auto=start

ipsec.secrets

: PSK 1sFpZAZqEN6Ti9sqt4ZP5EW

strongswan.conf

# strongswan.conf - strongSwan configuration file
#
# Refer to the strongswan.conf(5) manpage for details
#
# Configuration changes should be made in the included files

charon {
	load_modular = no
	make_before_break = yes
	plugins {
		include strongswan.d/charon/*.conf
	}
}

include strongswan.d/*.conf

StrongSwan_build_notes.txt

# install notes for ubuntu 14.04 / odroid xu4
sudo apt-get install libgmp3-dev
# dont apt-get StrongSwan! (its really old)
wget https://download.strongswan.org/strongswan-5.5.1.tar.bz2
tar xvfj strongswan-5.5.1.tar.bz2
cd strongswan-5.5.1
sudo ./configure --prefix=/usr --sysconfdir=/etc --enable-python-eggs --enable-python-eggs-install  --enable-vici
sudo make
sudo make install

vpn_control.py

# This python script is *not* required to setup and run a tunnel,
# rather it shows how an external python script can bring a tunnel up / down and monitor its status.

import vici
import multiprocessing
import collections
import time
# NOTE: unless you are root you will need to do the following: sudo chmod 777 /var/run/charon.vici

# Edit target_connections in the VState to include the VPN connections you would like to keep alive
# if this connection is dropped for some reason it will be re-started automatically by the python script

class VState(object):
    """holds the VPN state"""
    def __init__(self):
        self.alive = True
        self.session = vici.Session()
        self.possible_connections = []
        self.target_connections = ['rw-2']
        self.active_connections = []
    
class StrongSwan(object):
    def __init__(self,  queue = None):
        self.state = VState()
        self.get_possible_connections()
    
    def process_control_connection_in(self):
        '''handle incoming mavlink packets'''
        pass
    
    def check_interfaces(self):
        state = self.state
        for vpn_conn in state.session.list_sas():
            for key in state.active_connections:
		try:
                   print 'key', key
                   print vpn_conn[key]
                   print vpn_conn[key]['established']
                   print vpn_conn[key]['state']
                   print vpn_conn[key]['local-host']
                   print vpn_conn[key]['remote-host']
		except:
		   pass
                
                try:
                    child = vpn_conn[key]['child-sas']
                    if child == {}:
                        child = None
                except:
                    print 'tunnel not connected at child level!'
                    child = None
                
                if child is not None:
                    for child_key in child:
                        
                        print 'time: ', time.time(), 'child key', child_key, child[child_key]['bytes-in'], child[child_key]['bytes-out']
                     
                        #print 'packets'
                        #print 'in: ', child[child_key]['packets-in']
                        #print 'out: ', child[child_key]['packets-out']
                         
                        #print 'bytes'
                        #print 'in: ', child[child_key]['bytes-in']
                        #print 'out: ', child[child_key]['bytes-out']
                     
                        #print child[child_key]['mode']
                        #print 'ip: ', child[child_key]['local-ts']
                        #print child[child_key]['remote-ts']
                        #print 'key: ', child[child_key]['rekey-time']
                        #print 'life: ', child[child_key]['life-time']
                    
                
                if key in state.target_connections and child is None:
                    self.connection_down(key)
                    self.connection_up(key)
        
        for key in state.target_connections:
            if key not in state.active_connections:
                #the connection is inactive
                self.connection_up(key)
                
        
    def connection_up(self, key):
        state = self.state
        print 'up: ', key
	sa = collections.OrderedDict()
	sa['child'] = key
	sa['timeout'] = '2000'
	sa['loglevel'] = '0'
	rep =state.session.initiate(sa)
	rep.next()
	rep.close()
	
        #TODO: handle errors, log?
        
    def connection_down(self, key):
        state = self.state
        print 'down: ', key
	sa = collections.OrderedDict()
	sa['ike'] = key
	sa['timeout'] = '2000'
	sa['loglevel'] = '0'
	rep =state.session.terminate(sa)
	rep.next()
	rep.close()
    
	#TODO: handle errors, log?

    def get_possible_connections(self):
        '''reset and repopulate possible connections based on /etc/ipsec.conf'''
        state = self.state
        state.possible_connections = []
        for conn in state.session.list_conns():
            for key in conn:
                state.possible_connections.append(key)
        
        print 'p',state.possible_connections
                
    def get_active_connections(self):
        state = self.state
        state.active_connections = []
        
        for conn in state.session.list_sas():
            for key in conn:
                state.active_connections.append(key)
        
        print 'a', state.active_connections
                
    def is_alive(self):
        return self.state.alive

def main_loop():
    '''main processing loop'''
    #make a strongSwan control object
    VPN = StrongSwan()
    while VPN.is_alive():
        VPN.process_control_connection_in()
        VPN.get_possible_connections()
        VPN.get_active_connections()
        VPN.check_interfaces()
        time.sleep(1.0)
    


if __name__ == '__main__':
    #run main loop as a process
    main = multiprocessing.Process(target=main_loop)
    main.start()
    main.join() 

@SamuelDudley, seems like your python script gets terminated with the exception when:

• The remote server gets rebooted/stays unavailable
• The VPN cannot be established >2000msec

I took your script as the basis and trying to adopt it in order to be able to restart the VPN connections on our remote peers,