mehr als nur ein Notizblock

Wie im OpenVPN-Server-Beitrag geschrie­ben, möchte ich, wenn ich unter­wegs bin, eine gesi­cherte Ver­bin­dung von mei­nem Mac­book zum Ser­ver her­stel­len. Das mache ich mit der Soft­ware Tun­nel­blick.

Nach dem Down­load, dem Moun­ten des Images und dem obli­ga­to­ri­schen Drag and Drop des Pro­gramms in den Application-Ordner kann man das Tool schon star­ten. Nach dem Start kommt eine Warnung

Es exis­tie­ren keine Kon­fi­gu­ra­ti­ons­da­teien im Pfad ~/Library/openvpn. Wenn man das Ange­bot von Tun­nel­blick annimmt (was man tun sollte), dann öffnet sich auto­ma­tisch Text­edit mit einer Beispielkonfigurationsdatei

Die edi­tierte Datei sollte fol­gen­den Inhalt haben

##############################################
# Sample client-side OpenVPN 2.0 config file #
# for connecting to multi-client server.     #
#                                            #
# This configuration can be used by multiple #
# clients, however each client should have   #
# its own cert and key files.                #
#                                            #
# On Windows, you might want to rename this  #
# file so it has a .ovpn extension           #
##############################################
	
# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
client
	
# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun
	
# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one.  On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
;dev-node MyTap
	
# Are we connecting to a TCP or
# UDP server?  Use the same setting as
# on the server.
;proto tcp
proto udp
	
# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote vpn.domain.de 1194
;remote my-server-2 1194
	
# Choose a random host from the remote
# list for load-balancing.  Otherwise
# try hosts in the order specified.
;remote-random
	
# Keep trying indefinitely to resolve the
# host name of the OpenVPN server.  Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
resolv-retry infinite
	
# Most clients don't need to bind to
# a specific local port number.
nobind
	
# Downgrade privileges after initialization (non-Windows only)
;user nobody
;group nobody
	
# Try to preserve some state across restarts.
persist-key
persist-tun
	
# If you are connecting through an
# HTTP proxy to reach the actual OpenVPN
# server, put the proxy server/IP and
# port number here.  See the man page
# if your proxy server requires
# authentication.
;http-proxy-retry # retry on connection failures
;http-proxy [proxy server] [proxy port #]
	
# Wireless networks often produce a lot
# of duplicate packets.  Set this flag
# to silence duplicate packet warnings.
;mute-replay-warnings
	
# SSL/TLS parms.
# See the server config file for more
# description.  It's best to use
# a separate .crt/.key file pair
# for each client.  A single ca
# file can be used for all clients.
ca vpn.domain.de/cacert.pem
cert vpn.domain.de/client1-cert.pem
key vpn.domain.de/client1-key.pem
	
# Verify server certificate by checking
# that the certicate has the nsCertType
# field set to \"server\".  This is an
# important precaution to protect against
# a potential attack discussed here:
#  http://openvpn.net/howto.html#mitm
#
# To use this feature, you will need to generate
# your server certificates with the nsCertType
# field set to \"server\".  The build-key-server
# script in the easy-rsa folder will do this.
;ns-cert-type server
	
# If a tls-auth key is used on the server
# then every client must also have the key.
;tls-auth ta.key 1
	
# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
;cipher x
	
# Enable compression on the VPN link.
# Don't enable this unless it is also
# enabled in the server config file.
comp-lzo
	
# Set log file verbosity.
verb 3
	
# Silence repeating messages
;mute 20

Anschlie­ßend legt man unter ~/Library/openvpn einen Unter­ord­ner für die Zer­ti­fi­kat­da­teien an — ich habe ihn vpn.domain.de genannt. Dahin­ein kopiert man das öffent­li­che Zer­ti­fi­kat der CA und das pri­vate und öffent­li­che Schlüs­sel­paar des Cli­ents, wel­ches vor­her auf dem Ser­ver gene­riert wurde — als Kopier­pro­gramm vom Ser­ver auf das Mac­book bie­tet sich Cyber­duck an.

Anschlie­ßend kann man die Ver­bin­dung starten.

Möchte man mehr über das zusätz­li­che pri­vate Netz­werk wis­sen, so kann man das Ter­mi­nal benutzen:

Nach einem Auf­bau des Tun­nels kann man mit

netstat -nr

sich die aktu­elle Routing-Tabelle anzei­gen lassen.

$ netstat -nr
Routing tables
	
Internet:
Destination        Gateway            Flags    Refs      Use  Netif Expire
default            192.168.1.1        UGSc       14       39    en0
10.8.0.1/32        10.8.0.5           UGSc        0        0   tun0
10.8.0.5           10.8.0.6           UH          1        0   tun0
127                127.0.0.1          UCS         0        0    lo0
127.0.0.1          127.0.0.1          UH          7        0    lo0
169.254            link#4             UCS         0        0    en0
192.168.1          link#4             UCS         4        0    en0
192.168.1.1        0:10:10:10:10:10   UHLW       35        0    en0   1165
192.168.1.2        127.0.0.1          UHS         0        0    lo0
192.168.1.255      link#4             UHLWb       3        0    en0

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