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  Secure Boot CDs for VPN HOWTO
  Jeffery Douglas Waddell  jefferydouglaswaddell (at) gmail
  (dot) com
  V1.0        2007-05-15      Initial release

  This document describes the creation of live boot CDs used to make
  secure VPN connections from anywhere (over the Internet) to internal
  networks that have firewall exposure to the Internet.

  Table of Contents

  1. Introduction
     1.1 Copyright
     1.2 Disclaimer
     1.3 News
     1.4 Credits
     1.5 Translations

  2. Theory
  3. Technologies
  4. Implementation
     4.1 Getting and modifying a DSL-based .ISO file.
     4.2 Comments on modifying the software on the CD.
     4.3 Setting up multi user OpenVPN server.
     4.4 References:

  5. Maintenance
  6. Advanced Issues
  7. Features
  8. Troubleshooting
  9. Further Information
  10. Getting Help
  11. Concluding Remarks
  12. Questions and Answers
  13. Bits and Pieces
     13.1 Making a Windows autorun CD.

  14. Examples


  1.  Introduction

  For several years now, users at the Institution where I currently work
  part-time have expressed a need for a robust and secure connection to
  the internal network. The internal network actually has some clients
  that are on private networks and some clients that are Internet-

  Being mostly a Microsoft shop, the options that have been available
  were not deemed appropriate for various reasons, usually due to
  security concerns.  After being introduced to the problem a few months
  ago and listening to the concerns surrounding it, I suggested using a
  boot CD, which would alleviate all of their security concerns. They
  gave me the go ahead to give it a try. I now have a working prototype
  and this document describes the process used to create it.

  1.1.  Copyright

  Copyright � 2006-11-13 by Jeffery Douglas Waddell.  You are free:

  �  to copy, distribute, display, and perform the work

  �  to make derivative works

  �  to make commercial use of the work Under the following conditions:
     Attribution. You must give the original author credit.  Share
     Alike. If you alter, transform, or build upon this work, you may
     distribute the resulting work only under a license identical to
     this one.

  �  For any reuse or distribution, you must make clear to others the
     license terms of this work.

  �  Any of these conditions can be waived if you get permission from
     the author.

  1.2.  Disclaimer

  Use the information in this document at your own risk. I disavow any
  potential liability for the contents of this document. Use of the
  concepts, examples, and/or other content of this document is entirely
  at your own risk.

  All copyrights are owned by their owners, unless specifically noted
  otherwise. Use of a term in this document should not be regarded as
  affecting the validity of any trademark or service mark.

  Naming of particular products or brands should not be seen as

  You are strongly recommended to take a backup of your system before
  major installation and backups at regular intervals.

  1.3.  News

  �  V0.06  2007-02-09       (pre-release)

  �  V0.05  2007-02-05       (pre-release)

  �  V0.04  2007-02-05       (pre-release)

  �  V0.03  2006-12-12       (pre-release)

  �  V0.02  2006.12.11       First Draft (pre-release)

  �  V0.01  2006.11.13       webgenerated sgml form (pre-release)

  1.4.  Credits

  I used many resources to do what I did.  A big thank you to all those
  that have contributed to these projects.  They include but are not
  limited to:





  1.5.  Translations

  Currently there are no translations.  If you would you like to
  translate this, Please contact me at jefferydouglaswaddell (at) gmail
  (dot) com .

  2.  Theory

  To begin, I will attempt to lay out the problem a little more
  thoroughly and give the theory behind the prototype.

  In the case of the Institution, there is a set of machines that are
  behind a very robust firewall.  This firewall allows VERY little to go
  through.  As far as connecting out to the Internet, many things,
  including access to HTTP, FTP, secure shell, etc., are allowed.  As
  far as connecting in, none of those are allowed.

  You can imagine the firewall as a set of machines on the edge of our
  internal network.  There is a lot of unsecured traffic within our
  internal network, which has both private networks and internet
  addressed clients within it.  To be allowed to do any of the things
  that require a connection INTO the network from the Internet, a server
  allowing the connection must be on the periphery of the network (i.e.
  part of the firewall).

  The desire has been to be able to access the internal network
  sufficiently to do work from home (on par with doing work in the
  office), but without opening up the firewall such that our unsecured
  traffic would be exposed to the Internet. There is also sensitive,
  internal data within the internal network that can be accessed, that
  should neither be copied to the home machine (laptop, etc.) nor
  printed at the home machine.

  So the question becomes: how do you allow enough access to give
  certain people the ability to do their jobs from home and still
  protect the sensitive information and the network as a whole?  Other
  security considerations that came up were:

  �  The potential for a laptop with sensitive information on it to be

  �  A home machine to being used in a way that breaks policy and yet
     can't be traced or effectively enforced due to it's off-site

  The answer that came to my mind was to give the users a boot CD that
  they could place in a machine (whether at Uncle Joe's, their own
  house, or the internet cafe at the airport) and use to boot into their
  internal work desktop.  The theory is that connecting to a server on
  the periphery of the network, which then gives them access to their
  desktop, is at least as secure as if they had accessed the network
  from their internal desktop, and that a great deal of control can be
  exercised over when and how that access is granted.  Being a boot CD,
  no on-site OS configuration will be required, nor will extra
  precautions concerning malware, spy-ware, or viruses need to be taken.
  In the next section, Technologies, I will examine some of the ways
  this can be implemented, and in the Implementation section I will
  explain how we actually did it.

  3.  Technologies

  Since many people are already familiar with openVPN, this seemed like
  a good idea.  However, in and of itself openVPN is not sufficient.
  The most convenient way for people to be able to work is for them to
  be able to directly connect to their already existing desktop.  All of
  the users here run either Windows XP (tm) or Windows 2000 (tm), which
  suggests rdesktop as a solution.  But rdesktop can't get through the
  firewall and we won't open our firewall for that traffic as it would
  be too hard to secure.  Adding openVPN allows for more security, but
  it runs into the following problems within the scope of our

  1. We would have to set up openVPN server on EACH internal desktop and
     each external client machine (at home, at the Internet cafe, or
     wherever) and it would therefore be highly subject to IT time and
     in general be a pain to get set up and working for each separate
     user's setup.

  2. If you allow a direct remote session (even over openVPN) you run
     into several potential security risks.

     a. key loggers on the external client box

     b. attacks directly on the internal Windows(tm) box through the VPN
        ports that are now open and exposed on the Internet.

     c. viruses, spy ware and other malware on the client box infecting
        the internal workplace desktop (and any others that it has
        connection with) through the established VPN connection.

     d. having the private key stored on multiple desktops around the
        organization on unsecured desktops. Someone with access to that
        key (which would need to be on the internal machine in order to
        establish the the VPN connection) could allow unauthorized key-

  3. Only the specific external machine that is setup by IT services
     personnel would be able to connect and use the resources, when what
     is actually desired is that the authorized user can get access from

  In order to eliminate the security issues above and to make it less of
  a difficult system to maintain into the future, I suggested creating a
  Linux live CD that boots, logs into an openVPN server that connects
  the external and internal networks, and then automatically opens the
  individuals internal desktop using rdesktop.

  4.  Implementation

  Many decisions had to be made as to which direction to go. The
  following subsections detail some of the paths I took to get to a
  working prototype.  Please modify to suit your environment.  Where
  appropriate I will make clarifying comments.

  I looked at several live CD distributions and concluded that DSL would
  work best for the purposes at hand.  I considered the following:

  1. Ubuntu.  This live CD expects a relatively high-end machine and has
     way more applications than would be useful to this project.
     Instead of trying to remove tons of applications and whittle it
     down I opted not to use this one.  It could be a good choice though
     if you are trying to give people a full desktop PLUS access to an
     internal network.

  2. PuppyLinux.  This live CD looked really good, however I had trouble
     figuring out the SFS file system it uses for its root, and was able
     to get to instructions and tools on how to deal with the Knoppix
     compressed file system much more easily.

  3. Knoppix.  This live CD, like Ubuntu, was too top heavy for the
     specific purposes of this project.

  4. Damn Small Linux.  This live CD has a 50 MB footprint, will work on
     almost anything hardware-wise, and is what I chose to implement.

  4.1.  Getting and modifying a DSL-based .ISO file.

  The choice of DSL means that we are relying on DSL's built in ability
  to automatically find, configure and attach to a network via DHCP.
  DSL's wireless support is very minimal and thus we do not support
  wireless at this time.  The end user will need a machine that normally
  attachs to the Internet through DHCP from their provider and uses a
  normal wired network card to do so.

  1. Fresh install of Ubuntu (, EdUbuntu
     (, xUbuntu (, or
     kUbuntu (

  2. Use Synaptic to add repositories (all available)

  3. Install qemu, open-vpn and cloop-utils

  4. Get an ISO (I recommend the dsl-3.0 ISO); hopefully I'll soon have
     one of my prototype CD images (sans VPN keys) available on the
     Internet for your downloading pleasure.  Refer the Examples section
     - this ISO might be a good place for you to start.

  5. Mount the ISO somewhere.


          mkdir /tmp/workingiso


          mount -t iso9660 -o loop dsl-3.0.iso /tmp/working.iso

  6. Unpack the compressed file system of the ISO


          extract_compressed_fs /tmp/workingiso/KNOPPIX/KNOPPIX > /var/tmp/KNOPPIX-cloop

     b. Mount it somewhere


             mkdir /tmp/workingiso.cloop


             mount -o loop /var/tmp/KNOPPIX-cloop /tmp/workingiso.cloop

  7. Now that you have access to the inner workings of the CD, copy that
     to a place where you can work with it.

     a. Make a directory to work in (i.e. /home/jeff/Desktop/vpn-tree)


          tar -C /tmp/workingiso.cloop -cf - . | tar -C /home/jeff/Desktop/vpn-tree -xvpf -

  8. Also copy the outer part of the CD, where you can work with it.

     a. Make a directory to work in (e.g. /home/jeff/Desktop/vpn-cd-


          tar -C /tmp/workingiso -cf - . | tar -C /home/jeff/Desktop/vpn-cd-tree -xvpf -

  9. Make a CD image with what you have now to confirm you've made it
     this far without error.


          mkisofs -pad -l -r -J -V "YOURVPN v0.1" -no-emul-boot -boot-load-size 4 -boot-info-table -b boot/isolinux/isolinux.bin -c boot/isolinux/ -hide-rr-moved  -o yourvpn.iso /home/jeff/Desktop/vpn-cd-tree/

     Assuming the above worked you can now test it with


          qemu -boot d -cdrom yourvpn.iso

     Now you can start making changes.

     a. Mount your proc using

          mount -t proc none /home/jeff/Desktop/vpn-tree/proc


          chroot /home/jeff/Desktop/vpn-tree

     c. Make any changes you would like to the file system.

     After messing around, it's time to write out your new compressed
     file image and make a CD.

     a. Exit from chroot

     b. Unmount the image's proc (don't forget this step or you will not
        have a working image when you build it later)

     c. Make the compressed file image

          mkisofs -L -R -l -V "YOURVPN ISO9660" -v -allow-multidot /home/jeff/Desktop/vpn-tree/ | create_compressed_fs - 65536 > /home/jeff/Desktop/vpn-cd-tree/KNOPPIX/KNOPPIX

     d. Make the cd image

          mkisofs -pad -l -r -J -V "YOURVPN v0.2" -no-emul-boot -boot-load-size 4 -boot-info-table -b boot/isolinux/isolinux.bin -c boot/isolinux/ -hide-rr-moved -o yourvpn.iso /home/jeff/Desktop/vpn-cd-tree/

     e. Test it in an emulator (I tend to enjoy qemu...use whatever you
        like: vmware, xen, ?)

          qemu -boot d -cdrom yourvpn.iso

     Repeat as necessary to get the desired ISO image.

     Burn image and enjoy.

  4.2.  Comments on modifying the software on the CD.

  1. Unpack openvpn*.deb to the root file system after chroot.

  2. Make sure all the proper libraries were copied to the proper place.

     a. chroot

     b. ldd /usr/sbin/openvpn

     c. Go to the other root terminal on the main system and copy any
        libraries from the main system to the vpn-tree

     d. Make the tun node: mknod /dev/net/tun c 10 200

  3. Remove the loading of the DSL business card graphic by editing the
     vpn-cd-tree/boot/isolinux/boot.msg file and removing "^Xlogo.16"

  4. Cause it not to wait for boot options by editing vpn-cd-
     tree/boot/isolinux/isolinux.cfg and changing the line that says
     "PROMPT 1" to "PROMPT 0"

  5. Edit the file vpn-tree/etc/skel/.xinitrc to reflect what we wish to
     happen on the desktop. Remove code to load icons onto desktop;
     remove code to make the windows see through; add code to establish
     VPN connection; add code to load rdesktop and make connection to
     correct machine.

  6. Edit the display screen for boot.

     a. copy vpn-cd-tree/boot/isolinux/minirt24.gz to /tmp

     b. gunzip minirt24.gz

     c. mount -o loop minirt24 /mnt

     d. edit /etc/linuxrc to display text indicating Institution's name
        (you would put whatever is appropriate for your institution
        here) instead of "DSL"

     e. umount /mnt

     f. gzip minirt24

     g. copy minirt24.gz over to vpn-cd-tree/boot/isolinux/minirt24.gz

  4.3.  Setting up multi user OpenVPN server.

  1. Follow instructions on making cert and keys for the server.

  2. You will need to enter several pieces of information that are
     covered in the openVPN HOWTO.

  3. Remember to create a password-protected key for the client.

  4. Set all the configuration as desired.

  5. For each client you will need to

     a. make a password-protected key using the certificate

     b. place the certificate, and client key (only) in the vpn-
        tree/etc/openvpn/keys directory

     c. adjust the vpn-tree/etc/openvpn/openvpn.cfg file to have the
        proper key files indicated (see the server configuration file in
        the Samples section)

     d. adjust the added routes in the vpn-tree/opt/

     e. adjust the vpn-tree/etc/skel/.xinitrc to point to the correct
        rdesktop IP.

  6. Rebuild the CD.

  7. Test in the emulator.

  8. Once it works correctly, either burn the ISO or make a qemu Windows
     emulator version by placing the .ISO in the win-qemu-yourvpn-cd
     directory and building that .ISO (don't forget to burn it

  4.4.  References:





  5.  Maintenance

  Once built there is NO maintenance to the CDs.  If you need to change
  the private key password for the the individual user, burn them a new
  CD.  If they lose a CD, give them a fresh burn.  If the CD gets
  destroyed, give them a new copy.

  The openVPN server requires little maintenance.  It is recommended
  that you periodically check the openVPN logs on the server to
  determine the likelihood of nefarious activity and act accordingly.
  Usage-tracking is beyond the scope of this document.

  6.  Advanced Issues

  I believe that the majority of security and ease of use issues are
  dealt with by the technologies I have described here.  Certainly there
  are many issues that this technology could expose (mostly internal
  political or policy issues within your own institution).

  If you discover any flaws in the technology.  Please contact me about
  Also, if you can explain the proper pf rules to get *bsd to properly
  forward (masquerade the 10. network) packets to Internet-routed
  network segments on the internal side of the VPN, I would definitely
  like to hear from you.  I could not get it to work, whereas the Linux
  masquerading rule I found just works.

  7.  Features

  1. Ease of use for the end user:

     a. Put in CD

     b. Boot machine

     c. Type in private key password

     d. Log into work desktop and work as usual

  2. Ease of use for the administrator(s):

     a. Key generation is separate from use.

     b. A user's access can be specifically revoked (without affecting
        their work desktop) using a single command.

     c. All new users can be denied by shutting down the openVPN server
        process on the server.

     d. All connections can be broken by shutting down the entire
        server; this will also deny future access until the server is
        brought back up and the end user reboots.

  3. The CD build process can be automated for ease of creation.

  4. The openVPN logs can be used to determine (or trace) nefarious or
     out-of-policy computer use.

  8.  Troubleshooting

  There are several troubleshooting techniques that I used in the course
  of this project.  I would expect people attempting this to be familiar
  with most or all of them.  Here are a few:

  1. tcpdump is your friend when attempting to prove that your traffic
     really is going over the VPN.

  2. ldd is very helpful in finding out what libraries are missing when
     you have to install a package by hand.

  3. qemu or another emulator is priceless when you don't wish to waste
     a bunch of physical CDs or the time it takes to burn and boot them.

  9.  Further Information

  As mentioned elsewhere, please see for more
  information on openVPN...the HOWTO is especially good.

  Please see for more info on DSL.

  For live CD information, Google may be your best bet, although there
  is now a live CD book that seems fairly good.

  10.  Getting Help

  Obviously the above mentioned communities can help you with varying
  aspects of the respective pieces of this puzzle.

  If you need help understanding how to put it all together, feel free
  to contact me after you've thoroughly read (and maybe tried) this

  11.  Concluding Remarks

  There you have it.  May it be of use.

  12.  Questions and Answers

  When I receive questions generated from this document I will compile
  them and insert them here.

  13.  Bits and Pieces

  13.1.  Making a Windows autorun CD.

  Due to a policy decision, we will not be deploying this, although it
  does work.  The security concerns over this method include the

  1. Key logger on the host Windows (tm) machine.  This could
     conceivably be used to capture the private key password and
     potentially grant unauthorized access.

  2. Malware on the host Windows (tm) machine.  Might be able to send
     through the VPN...seems unlikely.

  3. A virus on the host Windows (tm) machine.  Might be able to
     propagate itself through to the internal network...again this seems

  This is what you do to create one.  This method is likely useful for
  other projects.


       mkdir win-qemu-yourvpn-cd

  2. Download from

  3. Unzip into the win-qemu-yourvpn-cd

  4. Move all the qemu-0.8.2-windows files up one directory. Remove the
     qemu-0.8.2 directory.

  5. Make an icon file.  I used a stock one and resized with GIMP.

  6. Create an autorun.inf file in win-qemu-yourvpn-cd directory
     containing the following:


  7. Copy qemu-win.bat to yourvpn.bat.

  8. Edit yourvpn.bat replacing the last line in the file with: qemu.exe
     -L . -m 64 -soundhw all -localtime -cdrom yourvpn.iso

  9. Copy the fully made bootable .ISO image yourvpn.iso from where it
     is currently to win-qemu-yourvpn-cd

     Make an ISO of this directory: mkisofs -pad -l -r -J -V "WQYOURVPN
     v0.1"  -hide-rr-moved  -o wqyourvpn.iso /home/jeff/Desktop/win-

     Burn the ISO and try it on a Windows (tm) box.

  14.  Examples

  Here is the config file (with IP address and key names removed for the
  CD).  Text in upper case is used to indicate that you need to change
  whatever is there to your setup.


  # 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.

  # 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 my-server-2 1194

  # Choose a random host from the remote
  # list for load-balancing.  Otherwise
  # try hosts in the order specified.

  # 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.

  # Downgrade privileges after initialization (non-Windows only)
  user nobody
  group nogroup

  # Try to preserve some state across restarts.

  # 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.

  # 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 /etc/openvpn/keys/ca.crt
  cert /etc/openvpn/keys/THECDUSERSCRTFILE.crt

  # 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:
  # 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.

  # Set log file verbosity.
  verb 3

  # Silence repeating messages
  mute 20

  #added in hopes of removing a command line option
  auth-retry interact


  Here is the openVPN configuration file for the server.


  # Sample OpenVPN 2.0 config file for            #
  # multi-client server.                          #
  #                                               #
  # Edited on 9/12/2006 by Jeff Waddell           #
  #                                               #
  # 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 tap0" if you are ethernet bridging
  # and have precreated a tap0 virtual interface
  # and bridged it with your ethernet interface.
  # 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 /etc/openvpn/keys/ca.crt
  cert /etc/openvpn/keys/server.crt
  key /etc/openvpn/keys/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 /etc/openvpn/keys/dh1024.pem

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

  # 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  Finally we
  # must set aside an IP range in this subnet
  # (start= end= to allocate
  # to connecting clients.  Leave this line commented
  # out unless you are ethernet bridging.

  # 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 (
  # back to the OpenVPN server.
  ;push "route"
  ;push "route"

  # 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
  # First, uncomment out these lines:
  ;client-config-dir ccd
  # Then create a file ccd/Thelonious with this line:
  #   iroute
  # 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
  # First uncomment out these lines:
  ;client-config-dir ccd
  # Then add this line to ccd/Thelonious:
  #   ifconfig-push

  # 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
  ;push "redirect-gateway"

  # Certain Windows-specific network settings
  # can be pushed to clients, such as DNS
  # or WINS server addresses.  CAVEAT:
  ;push "dhcp-option DNS"
  ;push "dhcp-option WINS"

  # 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.

  # 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.

  # 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 60

  # 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.

  # 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.

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


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