Now back to SSH: When we connect to a server using SSH it will use the samemethod to establish the identity of the server. So when you connect for thefirst time SSH will ask you if you know this computer. So if you type
This means the host presented a different key than it used to. This cansometimes happen if the server you want to connect to was reinstalled. So ifyou know that the server was reinstalled or upgraded you can tell ssh toforget the previous host key. For example to forget the host key forbastion.desy.de just use
The line containing ProxyJump tells ssh to not directly connect to the hostbut first connect to the gateway host and then connect from there. We could makethis more complicated if needed by also adding a ProxyJump to the gateway serverconfiguration if we need to perform even more jumps. You should now be able tologin to KEKCC by just typing ssh kekcc and also copy files directly withscp. But you will have to enter your password two times, once whenconnecting to the gateway server and then when connecting to the KEKCC machine.
As you have seen there is a lot of entering your password, especially whenjumping between hosts. Time to take care of that. Remember when we explainedasymmetric encryption? SSH can use it to authenticate you to a server. This isusually safer and more convenient than using the password directly.
First, we need to create a private/public key pair to be used for SSH, called anidentity. We want to do this on your local machine. There is an easy way todo this by just calling ssh-keygen. Without any options this will justcreate a private/public key pair we can use but you might at least give it acomment string so that you can identify the key easier.
Now sometimes you might want to have a connection other than ssh to a machinelike the KEKCC login node that is not reachable. For example to reach aweb server like that is only reachable inside the keknetwork we need to connect to port 80 on the machine bweb3.cc.kek.jp
Very often one might want to synchronize a folder from a server with a localmachine. You already downloaded most of it but now you created a few new plotsand running scp -r would copy everything again unless you really specifyjust the new files.
which will efficiently copy everything in folder on server and put it inthe directory localfolder (beware, it matters whether or not you put a slashat the end of the target)/ The most common options are
This also allows to add port forwards to an existing connection: once you areconnected to a server you can run ssh -fNL localport:remotehost:remoteportserver locally in a different terminal to add a port forwarding.
to connect to the other node. Alternatively, youcan directly connect to a specific host instead of the login node, but forthat you might need to extend your ssh config to also use agateway server for the specific nodes in the cluster, e.g. for the KEKCC:
For inbound SMTP from the internet, mail will come from the Exchange 2010 Edge server in the DMZ. However if you want to take advantage of the load-balanced address for sending email internally then another DNS entry is preferred:
Want to access the Internet safely and securely from your smartphone or laptop when connected to an untrusted network such as the WiFi of a hotel or coffee shop? A Virtual Private Network (VPN) allows you to traverse untrusted networks securely as if you were on a private network. The traffic emerges from the VPN server and continues its journey to the destination.
OpenVPN is a full-featured, open-source Secure Socket Layer (SSL) VPN solution that accommodates a wide range of configurations. In this tutorial, you will set up an OpenVPN server on an Ubuntu 18.04 server and then configure access to it from Windows, macOS, iOS and/or Android. This tutorial will keep the installation and configuration steps as simple as possible for each of these setups.
Note: If you plan to set up an OpenVPN server on a DigitalOcean Droplet, be aware that we, like many hosting providers, charge for bandwidth overages. For this reason, please be mindful of how much traffic your server is handling.
To complete this tutorial, you will need access to an Ubuntu 18.04 server to host your OpenVPN service. You will need to configure a non-root user with sudo privileges before you start this guide. You can follow our Ubuntu 18.04 initial server setup guide to set up a user with appropriate permissions. The linked tutorial will also set up a firewall, which is assumed to be in place throughout this guide.
To begin building the CA and PKI infrastructure, use wget to download the latest version of EasyRSA on both your CA machine and your OpenVPN server. To get the latest version, go to the Releases page on the official EasyRSA GitHub project, copy the download link for the file ending in .tgz, and then paste it into the following command:
You have successfully installed all the required software on your server and CA machine. Continue on to configure the variables used by EasyRSA and to set up a CA directory, from which you will generate the keys and certificates needed for your server and clients to access the VPN.
Within the EasyRSA directory is a script called easyrsa which is called to perform a variety of tasks involved with building and managing the CA. Run this script with the init-pki option to initiate the public key infrastructure on the CA server:
Although you can generate a private key and certificate request on your client machine and then send it to the CA to be signed, this guide outlines a process for generating the certificate request on the server. The benefit of this is that we can create a script which will automatically generate client configuration files that contain all of the required keys and certificates. This lets you avoid having to transfer keys, certificates, and configuration files to clients and streamlines the process of joining the VPN.
Next, find the line containing a dh directive which defines the Diffie-Hellman parameters. Because of some recent changes made to EasyRSA, the filename for the Diffie-Hellman key may be different than what is listed in the example server configuration file. If necessary, change the file name listed here by removing the 2048 so it aligns with the key you generated in the previous step:
By default, the OpenVPN server uses port 1194 and the UDP protocol to accept client connections. If you need to use a different port because of restrictive network environments that your clients might be in, you can change the port option. If you are not hosting web content on your OpenVPN server, port 443 is a popular choice since it is usually allowed through firewall rules.
If you followed the Ubuntu 18.04 initial server setup guide listed in the prerequisites, you should have a UFW firewall in place. Regardless of whether you use the firewall to block unwanted traffic (which you almost always should do), for this guide you need a firewall to manipulate some of the traffic coming into the server. Some of the firewall rules must be modified to enable masquerading, an iptables concept that provides on-the-fly dynamic network address translation (NAT) to correctly route client connections.
Next, adjust the firewall itself to allow traffic to OpenVPN. If you did not change the port and protocol in the /etc/openvpn/server.conf file, you will need to open up UDP traffic to port 1194. If you modified the port and/or protocol, substitute the values you selected here.
Start the OpenVPN server by specifying your configuration file name as an instance variable after the systemd unit file name. The configuration file for your server is called /etc/openvpn/server.conf, so add @server to end of your unit file when calling it:
If your system is configured to use systemd-resolved for DNS resolution, the IP address after the nameserver option will be 127.0.0.53. There should also be comments in the file like the output that is shown that explain how systemd-resolved is managing the file. If you have a different IP address than 127.0.0.53 then chances are your system is not using systemd-resolved and you can go to the next section on configuring Linux clients that have an update-resolv-conf script instead.
The site will return the IP address assigned by your internet service provider and as you appear to the rest of the world. To check your DNS settings through the same website, click on Extended Test and it will tell you which DNS servers you are using.
Thank you for writing this tutorial. I could connect to the server from a remote computer running on windows but i cant seem to reroute the traffic correctly since i cannot browse the web i get a lot of timeouts(ERR_CONNECTION_TIMED_OUT).
After googling and reading about it, I can understand the need for security and having two different servers for certificates and the vpn, but I do not think that the average user will ever have the need to go that far.
Connecting two server running different type of SSH can be nightmare if you does not know how to convert the key. In this tutorial, I will try to explain on how to convert the public key from OpenSSH to SSH2 and SSH2 to OpenSSH. To convert the key, it must be done in OpenSSH server.
$ ssh-keygen -t dsa -f newkeyGenerating public/private dsa key pair.Enter passphrase (empty for no passphrase):Enter same passphrase again:Your identification has been saved in newkey.Your public key has been saved in newkey.pub.The key fingerprint is:c6:db:3a:ff:4c:79:a7:d8:cb:be:82:e8:9d:db:8c:e9 brad@eta