[Clug-tech] [clug-talk] VPN Use

Jon me at jonwatson.ca
Thu Nov 30 07:10:35 PST 2006


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Hi Robert,

I enabled IP forwarding as you suggested, but no go. Same dropped packet
pproblem.

Here's my server config. There is a full path to my keys and certs, but
I see no reason to advertise where they are :)

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap" if you are ethernet bridging.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# 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 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ***ca.crt
cert ***server.crt
key ***server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh1024.pem 1024
# Substitute 2048 for 1024 if you are using
# 2048 bit keys.
dh ***dh1024.pem

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 10.8.0.1 255.255.255.255"
;push "route 192.168.20.0 255.255.255.0"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
client-config-dir ccd
route 192.168.0.0 255.255.255.0
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# the TUN/TAP interface to the internet in
# order for this to work properly).
# CAVEAT: May break client's network config if
# client's local DHCP server packets get routed
# through the tunnel.  Solution: make sure
# client's local DHCP server is reachable via
# a more specific route than the default route
# of 0.0.0.0/0.0.0.0.
push "redirect-gateway"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
;push "dhcp-option DNS 10.8.0.1"
;push "dhcp-option WINS 10.8.0.1"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
;tls-auth ta.key 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC        # Blowfish (default)
;cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES

# Enable compression on the VPN link.
# If you enable it here, you must also
# enable it in the client config file.
comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nogroup

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

Thanks for your help!

J

Robert Toole wrote:
> Jon, Please post your OpenVPN server config file...
> 
> Also check that you are enabling IP forwarding in the kernel on your
> server, as OpenVPN runs in userspace, it does not route, you need the
> kernel to do that.
> 
> On red-hat based distros edit /etc/sysctl.conf:
> 
> remove: net.ipv4.ip_forward = 0
> add: net.ipv4.ip_forward = 1
> 
> This only takes effect on reboot, to enable it without rebooting the
> server:
> 
> echo 1 > /proc/sys/net/ipv4/ip_forward
> 
> then we'll take a look at your server config file (edit out the secret
> bits) and see what we see.
> 
> Thanks,
> 
> On Wed, 2006-29-11 at 22:46 -0700, Jon wrote:
> You could be right, but there's nothing in the docs about that. It seems
> like the OpenVPN server is supposed to do it's own routing based on the
> settings I've listed off in clug-tech.
> 
> J
> 
> Jamie Furtner wrote:
>>>> You probably need to set up your server to masquerade the traffic coming 
>>>> through your VPN network. By default, your machine should not know how 
>>>> to deal with these packets as they're from an unknown network.
>>>>
>>>> Something like (from memory)
>>>> iptables -t nat -A POSTROUTING -j MASQUERADE -o eth0 -s 192.168.0.0/24
>>>> should do it - change the eth0 and 192.168.0.0/24 for your 
>>>> internet-facing adapter and your VPN network, respectively.
>>>>
>>>> Jamie
>>>>
>>>>
>>>> Jon wrote:
>>>> Hmm...nope. Can't get it. I've tried everything on the OpenVPN mailing
>>>> list. I'm going to move this to Clug-Tech even though it doesn't appear
>>>> to me that anyone watches that group.
>>>>
>>>> J
>>>>
>>>> Jon wrote:
>>>>   
>>>>>>> Good lord that was easy. Well, kind of - I'm getting  MULTI: bad source
>>>>>>> address from client [192.168.0.103], packet dropped from the server now,
>>>>>>>  but I'll sort that out. At least the traffic is going to the openVPN
>>>>>>> server.
>>>>>>>
>>>>>>> Very cool, thanks.
>>>>>>>
>>>>>>> J
>>>>>>>
>>>>>>> Robert Toole wrote:
>>>>>>>     
>>>>>>>>> You need to uncomment the following line in the OpenVPN server config file:
>>>>>>>>>
>>>>>>>>> push "redirect-gateway"
>>>>>>>>>
>>>>>>>>> see the comments in the sample config file from the OpenVPN package for
>>>>>>>>> detailed explanation.
>>>>>>>>>
>>>>>>>>> Hope that helps.
>>>>>>>>>
>>>>>>>>> Robert Toole
>>>>>>>>> rtoole at tooleweb.ca
>>>>>>>>>
>>>>>>>>> Jon wrote:
>>>>>>>>> Hi All,
>>>>>>>>>
>>>>>>>>> I think I'm about 3 seconds away from understanding how to do this, but
>>>>>>>>> it's a looong three seconds.
>>>>>>>>>
>>>>>>>>> I've set up an OpenVPN server and can successfully connect to it from my
>>>>>>>>> laptop using the OpenVPN in client mode. All is good, but I'm not quite
>>>>>>>>> able to make the leap to what I really want to happen.
>>>>>>>>>
>>>>>>>>> I want to experiment using this VPN in public hotspots to secure my
>>>>>>>>> traffic. In short, I want all my traffic to go from my wifi card to my
>>>>>>>>> OpenVPN server and THEN out into the Internet. At the moment, even when
>>>>>>>>> connected to the VPN, a quick visit to What's my IP shows my home WAN IP
>>>>>>>>> so I know I'm not coming out of my VPN server.
>>>>>>>>>
>>>>>>>>> I'm thinking I need to be looking at routing or tunneling or something.
>>>>>>>>> I'm familiar with using VPNs to access server shares, mail servers, and
>>>>>>>>> the like, but not how to tell my NIC to exclusively send traffic to it
>>>>>>>>> instead out to the Internet at large.
>>>>>>>>>
>>>>>>>>> Does that even make sense? Sheesh...nudges welcome. Oh, and since this
>>>>>>>>> is a Talk list - I'm totally up for hearing about cool things one can do
>>>>>>>>> with a VPN.
>>>>>>>>>
>>>>>>>>> Thanks!
>>>>>>>>>
>>>>>>>>> J
>>>>>>>>>         
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>>>>>>>     
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