It’s been a while since my last blog entry, and I’ve decided to catch you up on some of the projects that I’ve been working on in my home lab. This next series of posts is going to revolve around the do-it-yourself home VPN.
What is a VPN, or virtual private network?
“A VPN is a communications environment in which access is controlled to permit peer connections only within a defined community of interest, and is constructed though some form of partitioning of a common underlying communications medium, where this underlying communications medium provides services to the network on a nonexclusive basis [1].”
In essence, a VPN is private and controlled network communication over a non-private medium – the Internet.
We love Linux and we love it for its open source nature, security, and powerful tools. There are a lot of free as well as commercial VPN solutions available for Ubuntu. We are not going to list or rank all the top VPN providers. We don’t necessarily want to rank them simply because users choose their VPN provider based on their personal requirements. If you want an US VPN service, you should look for the best US VPN service that supports OpenVPN. The intent of the article is to help newbies configure and use their favorite VPN service without going back and forth in Ubuntu community forum and embarrass oneself before the rather patronizing users.
VPN-ing into your server will allow you to connect to every possible service running on it, as if you were sitting next to it on the same network, without individually forwarding every port combination for every service you would like to access remotely.
Using a VPN connection also has the upshot of, if desired, granting access to other computers on the network as if you where in it locally from anywhere across the internet.
While not the most secure of the VPN solutions out there, PPTP is by far the simplest to install, configure and connect to from any modern system and from windows specifically as the client is a part of the OS since the XP days and you don’t need to mess with certificates (like with L2TP+IPsec or SSL VPNs) on both sides of the connection.
[notice]This software may not be legal to use in some countries or localities, or for certain uses. We are not lawyers, so we cannot advise you on this.[/notice]
From the README.md file:
PURPOSE
If you’re using a VPN service today, you may have found the following limitations:
1) All or nothing. Either ALL traffic goes down the VPN or none – unable to be selective.
2) Only one VPN at a time. Cannot selectively route certain sites down one VPN, and others down another VPN.
3) Unless you’ve configured your VPN at the router level, it’s likely that only a single device can use your VPN at one time.
This project serves to address each of the above – see the FEATURES section.
If for some reason you don’t want to run this on a Raspberry Pi, but would instead prefer to do something similar using a DD-WRT based router, the same author covered that topic a couple of years ago: StrongVPN PPTP on DD-WRT – Source based routing (improved) (Darran Boyd)
This is an edited version of a post that originally appeared on a blog called The Michigan Telephone Blog, which was written by a friend before he decided to stop blogging. It is reposted with his permission. Comments dated before the year 2013 were originally posted to his blog. In order to comply with Federal Trade Commission regulations, I am disclosing that he received a free product sample of the item under review prior to writing the review, and that any links to Amazon.com in this article are affiliate links, and if you make a purchase through one of those links I will receive a small commission on the sale.
Here’s what the publisher wants you to know about the book (my comments will follow):
In Detail
OpenVPN is a powerful, open source SSL VPN application. It can secure site-to-site connections, WiFi, and enterprise-scale remote connections. While being a full-featured VPN solution, OpenVPN is easy to use and does not suffer from the complexity that characterizes other IPsec VPN implementations. It uses the secure and stable TLS/SSL mechanisms for authentication and encryption. This book is an easy introduction to this popular VPN application. After introducing the basics of security and VPN, it moves on to cover using OpenVPN, from installing it on various platforms, through configuring basic tunnels, to more advanced features, such as using the application with firewalls, routers, proxy servers, and OpenVPN scripting.
This is a practical guide to using OpenVPN for building both basic and complex Virtual Private Networks. It will save you a lot of time and help you build better VPNs that suit your requirements. While providing only necessary theoretical background, the book takes a practical approach, presenting plenty of examples. It starts with an introduction into the theory of VPNs and OpenVPN, followed by a simple installation example on almost every available platform. After a concise and ordered list of OpenVPN’s parameters, we dive into connecting several machines in a safe way. The last third of the book deals with professional and high-end scenarios, and also mobile integration. After having read the whole book and followed and understood all the examples, you will be an expert in VPN, Security, and especially in OpenVPN Technology. This book was written for version 2.0.9 of OpenVPN, but all examples have been tested and run smoothly on version 2.1 too. Read the full Table of Contents for Beginning OpenVPN 2.0.9
What you will learn from this book
Install OpenVPN on Windows Server, Vista, and Mac OS X and also on different Linux versions and FreeBSD
Learn basic security concepts necessary to understand VPNs and OpenVPN in particular
Take a look at encryption matters, symmetric and asymmetric keying, and certificates
Connect Windows and Linux systems and safely transfer the necessary encryption keys using WinSCP
Learn about OpenVPN, its development, features, resources, advantages, and disadvantages compared to other VPN solutions, especially IPsec
Discuss non-standard and advanced methods of installing OpenVPN by compiling the source code provided by the OpenVPN project
Create an encryption key for OpenVPN and use it to set up an OpenVPN tunnel between two Windows systems in the same network
Create X.509 server and client certificates for use with OpenVPN and learn how to use tools to debug and monitor VPN tunnels
Create and administer certificates that have to be transferred to the machines that are supposed to take part in the VPN
Configure two different firewall networks that connect to each other through the secure OpenVPN tunnel
Install and use XCA and TinyCA2 to generate certificate revocation lists that are used to block unwanted connections by formerly authorized clients
Install OpenVPN on Windows Mobile and Smartphones running embedded Linux, like Nokia’s Maemo platform
Analyze the flow of datagrams between the VPN servers and the connected networks with tools like ifconfig, ping, traceroute, and mtr
Approach
This book is an easy introduction to OpenVPN. While providing only necessary theoretical background, it takes a practical approach, presenting plenty of examples. It is written in a friendly style making this complex topic easy and a joy to read. It first covers basic VPN concepts, then moves to introduce basic OpenVPN configurations, before covering advanced uses of OpenVPN.
Who this book is written for
This book is for both experienced and new OpenVPN users. If you are interested in security and privacy in the internet, or want to have your notebook or mobile phone connected safely to the internet, the server in your company, or at home, you will find this book useful. It presumes basic knowledge of Linux, but no knowledge of VPNs is required.
Now back to my mini-review. If you read my original review (which explains why I think a VPN can be an important part of securing private VoIP networks, among other uses), you know that I found Mr. Feilner’s original book quite helpful in giving me a grasp on VPNs, a subject I’d known very little about prior to that point. There were a few things I thought could have been covered better, though, so I was interested to see if those things had been addressed in this updated edition.
As I had more or less noted, the author seemed to slightly prefer SuSE Linux over other versions of Linux, and the Shorewall firewall over other Linux firewall solutions, and (in my opinion) the new book still uses more pages than are really necessary talking about how to set up and configure Shorewall, but at least now the authors do provide some minimal information about the far more popular iptables firewall tool (a little over three pages). It would have been nice to see a more in-depth treatment of this subject, because sometimes setting up iptables correctly is one key to getting your VPN to work as you want it to, particularly if you need or want to do anything more complicated than a simple VPN tunnel. It’s a minor nit, to be sure, because there’s plenty of information on the web about how to set up and configure iptables, but I personally would have given that topic more than three pages.
Then I discovered they’d made one addition that I really wanted to see: A totally new chapter on OpenVPN GUI tools, and in particular, a section on Webmin’s OpenVPN plugin. My disappointment again was that this was not a more exhaustive treatment of the subject. Actually, it’s little more than a mention that the plugin exists, and a few screenshots. Granted that this was more than appeared in the original volume, and just informing readers of the existence of that plugin is no small thing, but when I did my series on Setting up an OpenVPN tunnel using a CentOS-based system as the server and a router flashed with Tomato firmware as the client, it took me twoparts to explain how to configure the Webmin plugin. That same chapter also talks about some client GUI’s for Linux, but doesn’t spend more than a page or two on any of them.
I’m not really faulting the authors here — it’s very apparent that they write about what they know, and they definitely know their stuff when it comes to OpenVPN, whereas they may not be quite as familiar with Webmin or iptables. That said, Windows users should find all the information they need to set up an OpenVPN tunnel and then some, and Linux newbies get enough information to at least point them in the right direction. As for Mac users, the coverage there is about the same as in the previous edition, which is to say that there’s about three pages on how to install Tunnelblick. However, much of the information in the book is not OS specific, and those with some experience with Linux or OS X should have no trouble at all following along.
On a positive note, there are many examples and screenshots in the book, and in this one the screenshots are actually readable (well, I did need my reading glasses for a few of them, but then I’m getting to the point where I need my reading glasses to read the cooking directions on a frozen dinner!). And, the authors’ writing style is clear and easy to understand. Also, there’s a totally new (albeit relatively short) chapter on Mobile Security, which may be of interest to some of the “road warriors” out there.
So, my recommendation is this: If you read Markus Feilner’s previous book on OpenVPN and liked it, you’re almost certainly going to want to read this one, just to get up to date. If you didn’t read the previous edition but just want to get up to speed on OpenVPN, this really is one of the better books on the subject, provided that you understand that at times you may have to supplement the book with a bit of additional research on the Web, particularly if you are running OS X or Linux as your operating system (but at least you’ll have a much better handle on topics for additional research).
The reason this is a mini-review and not a full review is because due to personal/family issues I haven’t had time to do much more than skim through the new book, rather than give it a complete read as I normally prefer to do. But since Packt Publishing kindly sent me the book over a month ago, I feel as though it’s a disservice to both them and to the readers of this blog to delay mentioning it any longer. Despite my comments about the paucity of additional pages on the particular topics I’d hoped to read more about, this is still a great book for those who need to set up and secure an OpenVPN tunnel, particularly if you’re just starting out and know next to nothing about VPNs and/or OpenVPN.
This is an edited version of a post that originally appeared on a blog called The Michigan Telephone Blog, which was written by a friend before he decided to stop blogging. It is reposted with his permission. Comments dated before the year 2013 were originally posted to his blog. The link to Amazon.com in this article is an affiliate link, and if you make a purchase through that link I will receive a small commission on the sale.
If you have set up an OpenVPN server on your system and are using it regularly, eventually you are going to want to trim the log file. Webmin actually makes that easy. Simply click on System, then Log File Rotation. You should see a bunch of existing log file rotation rules. Up near the top of the page there’s a line that reads:
Select all. | Invert selection. | Add a new log file to rotate.
Click on Add a new log file to rotate. You should get a page that looks like this:
Webmin Log File Rotation - Add New File page
The main thing here is to get the correct log file path into the topmost text area. The path will be something like:
/etc/openvpn/servers/servername/logs/openvpn.log
I generally keep all the default settings except for these two:
Rotate even if log file is empty? (I set to No) Ignore log file if missing? (I set to Yes)
But you can do as you wish. The important thing is to make sure that the log isn’t simply allowed to grow forever Set it up as you like, click Create, and you’re through.
And now a note for FreePBX and Asterisk users. When setting up an extension, if you use the permit and deny fields to enhance security, the correct way to fill these out may not be intuitive. For example, if you do sip show peers from the CLI, an extension at the client end of the tunnel may show up with an address in the range of addresses assigned by the client router (such as 192.168.5.x) and yet when you fill out the permit field, using that address may not work. Asterisk’s log file will generally tell you the address it wants to see, and in our case that was 10.8.0.10! No, I don’t know why, but just wanted to give you a “heads up” on that one.
Deny and Permit fields from FreePBX extension page
I had mentioned in Part 3 some of the things that needed to be done if, from machines on the server side of the VPN tunnel, you wanted to be able to access machines at the client network (where the router with the Tomato firmware is located) that are on the WAN port side of the router. Bear in mind that anything connected to one of the LAN ports on the router is considered to be part of your VPN, but sometimes you might wish to access a machine or device (such as an “upstream” router) on the WAN side of the router with the Tomato firmware. To do this, you need to add the route to the WAN side network in the server configuration (in the “up” and “down-pre” script sections at the bottom of the Webmin server’s configuration page, using an additional “route add” and an additional “route delete” statement), and then on the client configuration page you must add an additional iroute statement – all of those take the same format as the lines you added to access the network on the LAN side of your client. At that point, you can access machines on the WAN port side of the Tomato router, but it’s not reciprocal – they can’t access machines on the server side.
Now, I need to make an important distinction here – I’m talking about machines connected to the WAN side of the Tomato-firmware router. Anything connected to one of that router’s LAN ports should already have full access to your network (on the server side). But the thing to remember is that ANY traffic sent out by a client connected to the LAN side will go through the tunnel. In some cases that may not be the desired behavior – you might have a few devices that should use the local Internet connection for all outgoing traffic (that is, as a rule they DON’T send their traffic through the tunnel), BUT you’d like to make an exception so that they can access only the local network on the server side of the tunnel, so that “local” traffic CAN be routed through the tunnel. So, you’d have such devices on the WAN port side of the Tomato-firmware router (that is, connected to the same “upstream” router or switch as the Tomato-firmware router) so they don’t use your tunnel for the bulk of their traffic.
So the question then becomes, is it possible to allow those devices to use your tunnel ONLY for traffic to the local network on the server side of your tunnel? Well, it is, but it’s a bit tricky to set up. Note that you MUST first have it working in the opposite direction (that is, at a machine connected to the server side of the network, you can reach machines on the WAN port side of your Tomato-firmware router – that’s what I was talking about a couple of paragraphs up). If you can’t do that, you’re not going to get it working in the opposite direction. If you CAN do that, then here are the additional steps:
In the Tomato-firmware router, click on “Advanced” (in the left-hand menu), then “Firewall”, then check the box next to “Respond to ICMP ping.” You should now be able to ping the Tomato-firmware router from another device on the WAN side of the network (which may be important for testing and troubleshooting).
Next, click on “Administration”, then “Scripts”, then click the “Firewall” tab. You should see a big text entry box with (probably) nothing in it. Enter lines similar to the following:
In this example, addresses on the WAN port side of the Tomato-firmware router are in the 192.168.10.x range, while addresses on the server-side LAN are in the 192.168.0.x range. If either is different on your system, be sure to change all three instances of the appropriate base address.
Then click the Save button at the bottom of the page. After that it should look like this:
Administration | Scripts page | Firewall tab
Reboot the router (or you can ssh in and manually enter each of the lines from a command prompt, if you want to avoid the reboot). Now any traffic for the server-side LAN that reaches the Tomato-firmware router will get passed through the tunnel, but you still need to instruct the individual machines or devices to route that traffic correctly (which may be easier said than done for some machines). I don’t know how you do it from a Windows box, but I can tell you how it’s done on a temporary basis (that is, it survives until the next reboot) on a Linux-based or Mac OS X based machine. For the sake of these examples, assume the Tomato router is at (and can be pinged at) 192.168.10.50:
From a Linux box: sudo route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.10.50 eth0
(eth0 is the name of the interface used to connect to your local network)
From a Mac OS X box:
At a terminal prompt enter: sudo route add -net 192.168.0.0 -netmask 255.255.255.0 192.168.10.50
Then, if there are shares on server side of the network that you want to connect to, and you know the host machine’s IP address, open a Finder window, click on “Go” in the top menu bar, and enter this as the destination (substituting the correct IP address for the target machine): smb://192.168.0.xx:139
Note that in at least some cases, the connect attempt will fail if you don’t explicitly specify the port (:139) – this is apparently some kind of bug in recent versions of OS X.
If anyone knows how this is done on a Windows box, or how to make these route statements persist after a reboot (remember, they must be run by the root user or a user with root-level privileges, which is why the sudo statement is used — and you can’t put sudo in a script because it prompts for a password), please leave a comment and share your knowledge!
If you have followed this series thus far, I should point out that these articles are not static – if I find a mistake, or a better way to do things, they may get changed. On the other hand, since this particular router probably won’t be in my possession much longer, it may be something that I don’t do much more work on.
One thing I had said I would do in this last article is to give you a list of links that I found useful, or at least interesting, while working on this project. I didn’t actually utilize the information in all of these, and some are even a bit off-topic for the subject at hand, but this is just a small fraction of the pages I went through while trying to get this to work:
thor2002ro’s SDHC | SNMP | VPN | USB Mod (includes features from both of the above versions plus some additional features, but note that latest versions won’t run on routers with insufficient memory).
Optware installation instructions (supposed to also work with Tomato firmware, potentially allows use of numerous software packages originally written or converted for Linksys NSLU2)
“A set of disk utilities that will execute on a Tomato router. With these utilities you can now create ext2 partitions on a USB drive on the router itself, so you don’t have to use a Linux desktop machine to do it anymore.”
And there’s probably plenty of other great links that I’ve missed.
Finally, one more word about the TAP/TUN issue. I would sort have liked to have gotten this working in TAP mode. However when I tried to set it up, OpenVPN (on the server) complained about a missing brctl file. Well, it turned out that the way to get that file was to do yum install bridge-utils – sounds easy, right? I assure you, absolutely nothing about this project was easy, at least not for me.
The problem was that after I had installed the software and switched both sides from TUN to TAP, and then restarted the OpenVPN server, it brought down the entire local network! I mean to tell you, I couldn’t connect to any web pages or do anything else until I physically killed the power to the server box! When I brought it back up and disabled OpenVPN, everything connected to the LAN worked fine again. When I uninstalled bridge-utils and went back to using TUN, the tunnel started working again. I had been up all night, it was coming up on 7:00 AM, and I was just so doggone frustrated by that point that I never even tried to get TAP working again. Besides, I just don’t like doing things that can bring down the entire network. I suspect it was doing some kind of packet flood thing, sort of a denial-of-service attack on my local network – pardon me if I’m not thrilled about the prospect of trying that again!
After some additional online research, I suspect that part of the problem is that after installing bridge-utils, you need to create and/or modify certain files, such as /etc/sysconfig/network-scripts/ifcfg-br0, /etc/sysconfig/network-scripts/ifcfg-eth0, and possibly /etc/sysconfig/network-scripts/ifcfg-eth1 (though I’m not at all sure about that last one). For example, one site I went to (which, for some reason, I could only read by using Google’s cached copy, which is why I’m not giving a link) said, “Configure this server’s network configuration to use a bridge as its primary interface. You do this by bridging the physical ethX and virtual tapX interfaces into one logical br0 interface. The br0 interface will be assigned an IP address, and not the physical or virtual interfaces.” That site also suggests that those files should read as follows (note that I do not recommend following this advice verbatim, see my comments below):
/etc/sysconfig/network-scripts/ifcfg-br0 DEVICE=br0
TYPE=Bridge
IPADDR=192.168.0.50 <— local IP of the server
NETMASK=255.255.255.0
ONBOOT=yes
Please note the above is totally untested at this point, and I’m afraid that the advice to modify the existing files (particularly /etc/sysconfig/network-scripts/ifcfg-eth0) may (or may not) be ill-advised. What concerns me is that the /etc/sysconfig/network-scripts/ifcfg-eth0 file seems to contain a lot of essential information that is in effect being thrown out – for example, on our system, it reads as follows:
I’m just not sure what is the proper thing to do here — maybe just add the BRIDGE=br0 line to the existing file? But, if you do decide to try a full replacement of any file, be sure to copy the existing file to a safe location so that if things go badly you can recover your original file!
Some of the comments I have read suggest that TAP mode is not as efficient in transferring data, and/or not as secure (unless you add even more configuration options), so I’m thinking maybe we should leave well enough alone. But, if you have a truly burning desire to get it going, I suggest using the following Google search string for additional information – it may be strange, but it actually produced the most relevant results of all the searches I’ve tried over the last few days:
Hopefully this page won’t show up as the first result! 🙂
If you have any ideas about what went wrong, or in particular, if you manage to get this working in TAP mode, I’d be most interested to hear about it (and how you did it, if you got it working) – the comments are open.
EDIT (November 30, 2011): While I’m not really wanting to reopen this project at this late date (this still remains about the hardest thing I’ve ever tried to do with a computer, and I have a distinct aversion to revisiting it), I did receive an e-mail today from James R, which I will post verbatim here. NOTE THAT THIS IS NOT TESTED BY ME, SO USE AT YOUR OWN RISK:
From: James R (address redacted)
Subject: OpenVPN in bridged mode
Date: November 30, 2011 11:32:40 AM EST
The following is a script to fix the problems with getting bridged mode OpenVPN working with PBX in a Flash (CentOS 5.7 with Webmin). First you install the third party Webmin OpenVPN module, then use the script below. I haven’t tested it yet, but I believe it should work if not explain what actions needed to be done to repair it. Be kind, as my scripting skills are quite poor.
cat /usr/libexec/webmin/openvpn/br_scripts/bridge_start | sed
'2iPATH=$PATH:/sbin:/usr/sbin' >
/usr/libexec/webmin/openvpn/br_scripts/bridge_start
cat /usr/libexec/webmin/openvpn/br_scripts/bridge_end | sed
'2iPATH=$PATH:/sbin:/usr/sbin' >
/usr/libexec/webmin/openvpn/br_scripts/bridge_end
(End of James R’s e-mail. I fixed some punctuation and capitalization in the first paragraph, but otherwise it’s the way he sent it. I was NOT sure if the final couple of sections were really supposed to be three lines each, or one line each that got broken up by the e-mail software. I suspect the latter, but I’m leaving them as is in case I’m wrong about that. Again, please remember that the above is UNTESTED by me.)
Here’s another bit of information that may be useful for those of you that don’t know much about Linux — here is a very small list of Linux commands that may be useful in diagnosing any problems with your VPN tunnel:
ifconfig – shows the current list of network interfaces. On both ends of your tunnel you should see a tunx interface when the tunnel is operational. On Windows-based systems a similar command is ipconfig.
ip route show – shows current routing information for the system (see also route). ip route list gives a slightly different view.
iptables -L – lists the current iptables rules. Add the -v option to get a more verbose display.
netstat -r – similar to route but with a slightly different view.
ping address – tries to get a response from another connected machine or device. Note that not all systems or devices will respond to pings.
route – shows the current routing tables on the system (see also ip route show).
tcpdump -n – this shows a running display of all activity on the network interfaces. Be careful because this can produce a LOT of output very quickly. Use Control-C to interrupt, then be prepared to wait until the buffer empties (may take a few seconds).
tracerouteaddress – If you run a traceroute to a network address (either on the LAN or on the Internet) it will attempt to show each system the packets pass through on the way to their destination. This can be useful for determining if traffic to a particular destination is actually going through your tunnel. On Windows-based systems use tracert (a holdover from MS-DOS days when filenames were limited to eight characters!).
whichprogram-name – not a network command per se, but if you get an error message about a missing program, you can use whichprogram-name to try to determine if the program exists on your system, and the correct path to that program.
Note that there are additional options for most or all of the above commands – read the man page for that command (e.g. man tcpdump) if you are interested, or use a search engine to find more information (yeah, I think most man pages are painful, too). man is short for manual, by the way, not a reference to gender.
Anyway, I’m still trying to catch up on lost sleep, but if I think of anything else pertinent I’ll probably add it to this article, rather than making this series any longer. I hope if you attempt this, it’s not nearly as painful for you as it was for me!
This is an edited version of a post that originally appeared on a blog called The Michigan Telephone Blog, which was written by a friend before he decided to stop blogging. It is reposted with his permission. Comments dated before the year 2013 were originally posted to his blog. The link to Amazon.com in this article is an affiliate link, and if you make a purchase through that link I will receive a small commission on the sale.
Okay, time for the hard part… well, at least it was for me. Please understand, the instructions at The ‘Point and Click’ Home VPN HowTo Guide, combined with the knowledge I acquired from the book OpenVPN: Building and Integrating Virtual Private Networks (Amazon affiliate link) by Markus Feilner, enabled me to get a tunnel going using a software client with no sweat. But getting it to work with the Tomato VPN client, and in particular, to get it to work the way we needed it to, was a whole other thing. It turned out, as so often happens that some simple configuration changes were all that was needed – but finding the correct configuration changes to make were pure grief.
I want to digress just a moment to speak about those elitists that seem to frequent certain forums and IRC channels, and just love to tell newbies (often in not so polite terms) that all the answers can be found by using Google. I’ve pretty much figured out that most of the time, the person saying that doesn’t know the answer either, but they are like the schoolyard bully that gets their kicks by picking on others. In this case, Google may have had the answers somewhere, but they sure weren’t showing up in the first few pages of results. Instead, what was showing up was many others who were having the same problems and asking the same questions, but not getting answers! And usually after the first four or five pages of results, the results became even less relevant, if that were possible. Finally, after taking a more or less scattershot approach to seeking help, I came up with a “recipe” that works in this situation. Of course I cannot guarantee it will work for you… heck, I can’t guarantee it will work for me next week… but at least it’s working as I write this. But the next time someone suggests that you should just Google it (or something like that), I suggest you ask them what search terms they would suggest using that will bring you the answer to your question. When whatever they suggest doesn’t work, let them know and ask for more suggestions, and just keep repeating until you find the answer or they get sick of talking to you. If we all did that, I suspect some of the online bullies would discover that maybe they should keep quiet if they don’t know the answer.
Okay, so to begin, let’s make sure we are all on the same page. I assume you’ve installed the Webmin OpenVPN + CA module (again, following the instructions at The ‘Point and Click’ Home VPN HowTo Guide) but if you had difficulty locating the module, try here — as I write this, it appears that the newest version of the module is the OpenVPNadmin WebMin pre-release 2.5 version. And when you try to download it, if you get “Unauthorized access to downloads!”, try a different browser, or make sure JavaScript and cookies are enabled. You will probably need to download it to your computer first, then upload it to Webmin, if your experience is anything like mine was.
When you go into the module, you’ll initially see a page like this:
OpenVPN administration page
This is “home base” for this module, so when I say “return to the admin page”, this is the page I mean. It’s also the page you use to create a new Certification Authority (normally you only need to do that once, but if you really want to you can make more). In the upper left corner there is a link labeled “Module Config” – click on it and make sure all the paths are correct:
OpenVPN + CA configuration page
A couple notes on this page: First, although it indicates that “Server Hint for Clients” is a required field, there is no indication of what actually goes there, nor any default value. Second, the information under “If you use bridge device” is only applicable if you use TAP mode (remember, we’re using TUN), but I do know the defaults are not correct. Just in case you ever want to try to get TAP mode working, here is what these paths should be (at least on our installation):
Command to start Bridge: /usr/libexec/webmin/openvpn/br_scripts/bridge_start
Command to stop Bridge: /usr/libexec/webmin/openvpn/br_scripts/bridge_end
Path to DOWN-ROOT-PLUGIN: /usr/share/openvpn/plugin/lib/openvpn-down-root.so
Do check the paths on this page, because the defaults aren’t totally correct. Now let’s return to the admin page. I probably should have mentioned that you don’t really need to change any of the defaults for making a certificate for just your own use – those values are probably only important if you are creating a certificate that will be used by the public. Once you have made a certificate, you can click on the Certification Authority List, where you’ll see this page:
OpenVPN Certification Authority page
I really don’t know why you can create a new Certification Authority on both this page and the main admin page, but oh well… once you have created one it will show up in the list at the top of the page. You can click on it to view what you created, but there’s nothing you can change there. The main thing of importance is the “Keys List” link, where you can actually create new keys and view existing ones:
OpenVPN key list and key creation page
Okay, now here’s the important thing to remember about key creation: You need one key for your server, and one key for each client. You will note we have a server key, and client key for the software client (used for testing) and one more for the OpenVPN client on the Asus router.
As you may have surmised, except for the key name field, you can leave everything else at the defaults. However, there is one thing on this page that will lead you astray. It says, “Server key doesn’t need password!“, which might lead you to think that a client key does need one, but that’s not true. And if you use a password with your Tomato-based client key, you will never make a successful connection. The keys are far stronger protection than passwords anyway, so the only reason you might even consider using one is for a software client where you want to keep anyone other than an authorized user from connecting to the VPN tunnel. Anyway, don’t use a password for your server key or your Tomato OpenVPN client key!!!
Okay, now it’s time to navigate back to the admin page, then click on “VPN list”. Once you have created a server key, you can create your actual server. So click on the New VPN Server button and a page will come up that permits you to create a server configuration. This is where things get really tricky. Here is how ours is filled out:
OpenVPN Server page
Now the above is actually the edit page you get once the server is created and you have returned to edit it. Note that some values cannot be changed after the initial entry, so be sure you get them right the first time. In particular, make sure to select tun and not tap. If you do make a mistake, you can always delete the entire server configuration and start over, but that’s a bit of a pain. There are some differences in our configuration and the one at The ‘Point and Click’ Home VPN HowTo Guide, and generally speaking there are good reasons for the differences. But that said, nobody is claiming our configuration is perfect, just that it works! If you see something here you think should be changed, feel free to leave a comment.
Note in particular the text fields at the bottom of the page. Getting those right is the key to making this thing work! So, here’s what’s in each of those:
Of course, in the Additional Configurations section you want the line push “dhcp-option WINS 192.168.0.50” to point to a WINS server on your network, if you have one (if you don’t, just leave that line out).
In the up and down-pre scripts, if you want to be able to reach the local network behind the WAN port of the router on the client side, you should add additional route add and route delete lines in a format similar to those above, but substituting that network’s address range.
Now, once again, I’m NOT saying this is a perfect configuration, just that it works for us. However, if you notice something that just doesn’t look right, feel free to leave a comment. Much of the added configuration was put in so that traffic from the primary LAN to addresses in the 192.168.5.x address space would actually go through the tunnel – that was the hardest part. It was (relatively) easy to create a tunnel in the first place, but getting packets to and from their intended destinations was another matter entirely.
When you have configured your server and clicked “Save”, it should show up in your server list:
OpenVPN Server List page
Now click on “Clients List” – there will be a button labeled “New VPN Client” (no screenshot, it’s just a button to click at this point). Click that button and you will be presented with a client configuration page. Here’s the one we created for our Tomato OpenVPN client running on the Asus router (again, this is actually the edit page, since the client is already created on our system):
OpenVPN Client Configuration page
Most of the settings here will be the defaults but there are two things to pay particular attention to: First, the “Remote IP” must be the external address of your server – remember that this is the configuration that goes to the client. And second, notice the ccd file content box at the bottom – it is crucial that this be filled in correctly. In our case, we used this line:
iroute 192.168.5.0 255.255.255.0
If you miss this – and I speak from experience on this one – the packets from the Internet or your local LAN just aren’t going to get back to the client end of the tunnel! And remember to add an additional, similar line if you also want to be able to reach the network connected to the WAN port at the client router, substituting the base address of that network for the 192.168.5.0.
Once you have saved this, it should appear in the VPN client list:
OpenVPN Client List page
Once you have configured a client, the next step is to export its configuration, particularly the certificate and key files, to your computer using the “Export” link – all the necessary files will be packed up in a ZIP file. The instructions at The ‘Point and Click’ Home VPN HowTo Guide tell you how to use this file with a software client, but with your Tomato firmware you will have to unzip the file and then open each of the three files (ca.crt, plus the client certificate and key files), in a text editor or viewer. Only those three files are used with the Tomato OpenVPN client; the others in the ZIP archive are not. Then you will need to cut and paste the contents of those files into the three fields that appear under VPN Tunneling | Client | Keys tab in the Tomato firmware (see the screenshot of that page in Part 1 if you’re not sure what file’s contents goes where). With regard to the Client Certificate, there is some extra information at the top of the file that does not need to be pasted into the text field – you only need the two lines —–BEGIN CERTIFICATE—– and —–END CERTIFICATE—– plus all the lines in between those two tags. On an Asus WL-520GU router it doesn’t matter much, but there have been cases with some other makes of router where leaving that excess information in was just enough excess data to “brick” the router! So if in doubt, leave the data above the —–BEGIN CERTIFICATE—– line out.
Once you have everything ready, you can go to the OpenVPN admin page in Webmin and start the server, then in your Tomato firmware start the client. HOPEFULLY the client and server will connect and start communicating. You can check from the server’s admin page by clicking on “Active Connection” – hopefully you will see something like this:
OpenVPN Active Connections page
If you do, congratulations! If not, you have some troubleshooting to do. On the server, take a look at the log file: /etc/openvpn/servers/servername/logs/openvpn.log. On the client, click on Logs (under Status in the left-hand menu) and look at the last several lines. OpenVPN usually doesn’t suffer in silence — when something isn’t working, chances are one or both logs will be filled with messages that may or may not be helpful. You can always try going to Google and using OpenVPN plus the actual error message text (enclosed in quotation marks); once in a while that will actually bring up something useful.
Still stuck? My plan is to add a Part 4 to this series, that will provide links to some of the most useful resources I’ve collected along this journey. But you can certainly help — if I’ve made any errors in these instructions (not at all unlikely given the sleep I’ve missed during this project), and you find them and can figure out what was incorrect, PLEASE leave a comment. I will warn you that writing to me with your error message will probably get you nowhere – I can definitely play the part of the blind leading the blind, so to speak, but first I have to heal from all the bruises encountered on this journey! 🙂
I sincerely hope these posts have been useful to you! In Part 4 I’ll wrap this up with brief instructions for rotating the log file so it doesn’t grow forever, provide the aforementioned list of links, and give you a bit more insight into why I set this up using TUN mode even though I’d probably have preferred to use TAP.
This is an edited version of a post that originally appeared on a blog called The Michigan Telephone Blog, which was written by a friend before he decided to stop blogging. It is reposted with his permission. Comments dated before the year 2013 were originally posted to his blog.
EDIT (Jaunary 2011): Since I originally wrote this article in 2009, a new project has appeared called Easy OpenVPN, which is described as “a collection of bash scripts which will install and configure the Open VPN software on your PBXIAF server. Also includes scripts for creating client certificate files.” The project’s page further notes that these scripts are compatible with the security models used in, and have been tested with PBX In A Flash and Elastix, and that they may be compatible with other PBX distributions, but have not been formally tested. It also notes that the scripts do not interact directly with Asterisk or FreePBX. I have NOT tested these scripts, but it sounds as if it they might work on just about any CentOS-based OS. Certainly, if you are using one of those distributions, it’s worth looking into — it might be a faster and easier way to set up OpenVPN on your server than the procedure I outline here. Some instructions can be found in this thread. Even if you go that route, you might still want to read the rest of this series, since it gives some explanations and usage tips that may come in handy if the scripts don’t configure OpenVPN the way you’d like. FURTHER EDIT: If you want a dedicated OpenVPN server, check this out: Create a VPN with the Raspberry Pi (from Linux User & Developer).
Before you can begin to set up the OpenVPN server, there is some preparation work that needs to be done. But first, let’s talk about the prerequisites and assumptions we are making here. In the case of the tunnel I was helping to set up, the OpenVPN server was located on a box that runs the Elastix PBX distribution, which includes the CentOS operating system, plus FreePBX and Asterisk and a few other things. It doesn’t really matter whether the box has other servers on it (of course, if it’s a really old/slow box there may be performance issues), but for the purposes of our instructions here, the most important thing is that you have Webmin installed. Let me repeat that loud and clear:
You MUST have Webmin installed to use these instructions!
You don’t have Webmin installed and you don’t want to install it? Fine, shoo, away with you then. There are hundreds of other installation guides on the Internet, go find one you like. You have to keep in mind that with me, whenever there’s a choice between using the Linux command line or manually editing a configuration file, and using a nice GUI, I’ll pick the GUI every time. Some people (usually long time Linux users) seem to have some philosophical objection to using Webmin – if that’s you then you’re obviously much too smart to need these instructions, so what are you doing here?
I’m going to assume you already have Webmin installed, but if you don’t, try doing yum install webmin — it might already be in a CentOS repository. If that doesn’t work, you should be able to do this:
Once you get Webmin installed (or if you are using a Debian-based distribution such as Ubuntu) go to The ‘Point and Click’ Home VPN HowTo Guide — we’re going to refer to that document several times, so you may want to keep it open in another browser tab. But for now, just follow the instructions related to installing Webmin, starting (for CentOS users) with the subheading “Access Webmin”. For now, just follow the instructions in the two paragraphs in that section. On a Debian-based system, I’d try following the entire document, but I can tell you there are parts missing for a CentOS-based system, so stick with us for a bit.
Another assumption we are making is that your primary network (the one the server in on) has addresses in the 192.168.0.1 through 192.168.0.255 range. It’s okay if the “0” in the third octet is some other number (hopefully it’s not 5, because that what we used at the client end) but the main point is that we’re assuming it’s a small network. If you’re using more than 255 addresses on the primary network it’s not an insurmountable problem, as long as the client end has its own unique address space.
Open the file /etc/hosts.allow at the server – you should see something like this:
ALL : 192.168.0.0/255.255.255.0
If you do, you could change it to the following two lines (note the change in the netmask in the first line):
ALL : 192.168.0.0/255.255.0.0
ALL : 10.8.0.0/255.255.255.0
However, if there are any addresses in the range 192.168.0.0 through 192.168.255.255 that are normally reachable but not in your LAN — a primary example is a cable modem status page on 192.168.100.1 — you may not want to extend the scope of your local network quite that much. You could use a more restrictive netmask — for example, you could use these two lines, which is what I’d recommend for this project:
ALL : 192.168.0.0/255.255.240.0
ALL : 10.8.0.0/255.255.255.0
That would specify that anything in the range 192.168.0.0 through 192.168.15.255 is on your local network (including subnets on the other side of your tunnel). Alternately, if you wish to be a bit more precise and/or secure, you could specify the network(s) at the distant ends of the tunnel individually (using a more restrictive netmask), e.g.:
ALL : 192.168.0.0/255.255.255.0
ALL : 192.168.5.0/255.255.255.0
ALL : 10.8.0.0/255.255.255.0
(If you do the latter, you may also want to add a line for the network on the WAN side of the client router, e.g. ALL : 192.168.1.0/255.255.255.0 to be able to reach devices in that subnet from the server side of the tunnel — assuming that won’t conflict with any addresses on your own local network).
You also need to go into your router (the one between the OpenVPN server and the Internet, that controls the LAN at the server end – not the client router running the Tomato firmware) and expand the scope of your local network. I can’t give you specific instructions for your router, but generally the principle is the same as in the hosts.allow file – in most cases you need to expand the scope of the local netmask to 255.255.something.0, where something is less restrictive than 255 and includes all local nets on both sides of the tunnel, but not your cable or DSL modem’s status page (don’t worry about the 10.8.0.x addresses, your router won’t see those). I suggest using 255.255.240.0 and then making sure that your local networks on both ends of the tunnel fall within the range 192.168.0.x through 192.168.15.x. The reason you need to change the netmask is so that when something on your primary LAN tries to connect to an address in the 192.168.5.x range (on the other side of the tunnel), your router will send out an ARP probe to find out which device on the network has that address (getting the OpenVPN server to respond is another issue that we’ll cover later). But if you are trying to get to something on the backside of your router (the modem status page being the prime example), you don’t want your router thinking it’s on your LAN – hence the need for care when changing the netmask.
If for some reason you can’t follow my suggestions about local network range, you’ll still need to figure out an appropriate netmask, both for the etc/hosts.allow file and your server-side router configuration. Fortunately, there are many pages on the Web that will help you – Google the phrase “netmask calculator” (include the quotes) and you’ll find several sites that will help you calculate an appropriate netmask. Of course, there are limits on this – you’re going to have a much harder time making this all work if all the local networks on both sides of the tunnel aren’t in the 192.168.x.x range (or, more specifically, don’t have at least the first two octets of the LAN IP address in common).
While you are in the router on the server side of your connection, you need to open UDP port 1194 for incoming traffic and point it at your OpenVPN server – otherwise outside connection attempts will never be received by the server. Don’t open the corresponding TCP port – it’s really not a good idea to use TCP for OpenVPN unless you are forced to do so (by an overly restrictive ISP, for example).
You also need to open up the file /etc/sysctl.conf and make sure that the following line is NOT commented out (add it if it doesn’t already exist):
net.ipv4.ip_forward=1
Also, at a terminal prompt, execute the following:
echo 1 > /proc/sys/net/ipv4/ip_forward
While in the terminal, you SHOULD upgrade OpenVPN to the most current version (or install it if it’s not already installed). Older versions of OpenVPN will not work with these instructions. Just type openvpn from a command prompt and at the top of the resulting output it should show you what version you have, if it is installed. It will look something like this:
OpenVPN 2.2.0 i686-redhat-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [eurephia] built on Jun 6 2011
2.2.0 is the version in this example. But on a recent CentOS install, just doing yum install openvpn only offered to install version 2.0.9, which is too old to work with these instructions! Here is how I installed a newer version (edited July 27, 2011 to reflect a better way):
Add the dag repository if you haven’t done so already. In the /etc/yum.repos.d directory, create a new file called dag.repo:
touch /etc/yum.repos.d/dag.repo
Edit the file using any text editor (for example, nano /etc/yum.repos.d/dag.repo) and add the following lines exactly as shown:
[dag] name=Dag RPM Repository for Red Hat Enterprise Linux baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag gpgcheck=1 enabled=1
Save the edited file and then from a command prompt import the repository’s key:
rpm –import http://apt.sw.be/RPM-GPG-KEY.dag.txt
Now if you do
yum install openvpn
You should get the latest version plus any dependencies (it should offer to upgrade your current version if it is older). Note that you must use compatible versions of OpenVPN at both the client and server ends, so once you have an OpenVPN tunnel working, it might not be a good idea to just go upgrading the software at one end or the other unless you know the newer version is still compatible with what you’re using on the other end (minor version upgrades are probably okay, but I am not guaranteeing that!).
Now return to The ‘Point and Click’ Home VPN HowTo Guide — you want to find the section headed “Setting Firewall rule(s) to allow VPN web traffic to redirect out eth0” — now I will just say that you need to follow those instructions, but when setting up the actual rules, I found that only two were really important. So if I were rewriting their instructions, here is how I’d say it:
First we’ll assume that the firewall is not set up yet so click Reset Firewall. Now we need to add some rules. From the Showing IPTable: dropdown select Packet filtering (filter) where we’ll create the following rule:
Forwarded Packets (FORWARD)
Accept If input interface is tun0
Incoming interface
Equals
tun0
Then, from the Showing IPTable: dropdown select Network address translation (nat) where we’ll create the following rule — this is the rule that goes along with the VPN “push redirect-gateway”. This allows the VPN web traffic to be routed out through your connection:
Packets after routing (POSTROUTING)
Masquerade If source is 10.8.0.0/24 and output interface is eth0
Source address or network
Equals
10.8.0.0/24
Outgoing interface
Equals
eth0
Why not add the rest of the rules? Well, if you Reset Firewall as instructed, you don’t need them, because they are specifying default conditions. But if you didn’t want to reset the firewall because you already have some preexisting rules, or if you ever actually decide to go in and configure some more restrictive firewall rules, then you may need some of the other rules listed. There’s certainly no harm in adding the other rules, but I’d rather emphasize the two that are absolutely necessary to get this working, assuming you started with a clean slate.
When you are finished, the two rules pages should look like this:
Firewall rule: Accept If input interface is tun0Firewall rule: Masquerade If source is 10.8.0.0/24 and output interface is eth0
(I know that at this point, some Elastix and FreePBX users may be wondering if the above would interfere with the operation of fail2ban, in the event they have installed it. As far as I can tell, the answer is no… fail2ban communicates with the firewall in a different way, and unless you add rules that explicitly contradict what fail2ban does, I don’t think there will be any issues. However, I do recommend that you temporarily disable fail2ban, possibly from Webmin’s System | Bootup and Shutdown page, prior to connecting a new VoIP adapter or similar device on the client end of a tunnel for the first time. The reason is that if the device fails to register for any reason, such as a mis-typed password, fail2ban might refuse connections even after you fix the issue, and it might even clamp down on other connections from the client end of your tunnel. So get your devices registered and working, then restart fail2ban. Alternately, if turning off fail2ban makes you nervous, you could open /etc/fail2ban/jail.conf in a text editor, then edit the ignoreip option under the [DEFAULT] section to include the IP addresses or network on the client side of your tunnel — for example, you could add 10.8.0.0/24 and 192.168.5.0/24 as address ranges you don’t ever want to ban.)
Once again, return to The ‘Point and Click’ Home VPN HowTo Guide — now you want to start at the section, “Install OpenVPN-admin module” and continue through to the part entitled “Testing the VPN Server using the OpenVPN client GUI from Windows.” If their suggested download method doesn’t work, use the download link on this page to download it to your local machine, then in Webmin install the module “From uploaded file” rather than “From ftp or http URL” as the article suggests. What I suggest you do here is setup TWO clients, one for a soft client you can use for testing purposes, and one that you will use with the OpenVPN client in the Tomato firmware. While you might be able to get a Windows-based client to work using the instructions shown, I can assure you that the Tomato client isn’t going to work until you add a few additional tweaks, which we’ll cover in Part 3. But you can certainly set up and test the Windows-based client if you like, just to assure yourself that the server is actually working.
Just so you don’t spend a couple hours beating yourself up wondering why the server won’t start, I will point out that there’s a glitch in the Webmin OpenVPN module. When you click on the VPN server list and then click on Start to start a server, the server name is supposed to turn from red to black, and the word Start is supposed to turn to Stop. For whatever reason, that doesn’t happen on our server… you can click Start until the cows come home and it still won’t turn black. It probably has something to do with the module configuration itself – for example there’s a setting for PID file path of running OpenVPN processes (*) which by default is set to /var/run, which may not be correct — however, when I changed it to /var/run/openvpn, which does seem to be correct, it made no difference. I just start and stop the server using the buttons at the bottom of the main “OpenVPN Administration” page, which seem to work fine. EDIT: See Leon Baker’s comment in the comments section below for a fix for this problem. Thanks, Leon!
Next up, in Part 3: Configuring the OpenVPN server using Webmin (or more specifically, the changes and additions you need to make to actually get it working as expected). More screenshots!!!
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