Introduction

The article Remote Access will show you possible solutions to remotely access a managed client or your data inside the D-ITET networks from the selfmanaged client network or from devices outside the ETH network. It will cover the following topics:

• mailbox access
• remote terminal session
• remote desktop session
• file transfer
• network file system access

Remote access and network restrictions

Remote access possibilities depend on firewall restrictions between the remote client and the target network. The networks are segmented into virtual private zones (VPZ). Each of these zones corresponds to a certain network security level profile and contains one or more subnets being protected by the appropriate zone firewall. Traffic between subnets belonging to the same VPZ does not pass the zone firewall and thus there are no traffic flow restrictions (no subnets or service ports blocked). The relevant VPZ's for D-ITET are:

• itet-isg (ISG D-ITET managed servers and clients)

• itet-staff (Selfmanaged clients; most often these are selfmanaged laptops)

• itet-iot (Internet of things; small unmanaged devices, often lacking a possibility to configure them in a secure way)

• VPN zones (Public VPN zones like "guest", "student-net", "staff-net"; you will be assigned to this zone by default when you connect to the ETH network using the VPN client. An exception would be if a realm to enter a specific private VPZ zone is configured in the VPN client. The latter is only enabled in exceptional cases; contact ISG D-ITET for details.)

• Internet (this is not a real VPZ, but it describes all networks outside of the ETHZ intranet)

Enabled remote access protocols

The following table shows protocols which are relevant for remote access:

Remote access map of allowed traffic

The following table shows the allowed traffic flows for remote access related services:

• ¹ NFS access from unmanaged clients is not allowed for security reasons.
• ² These protocols are only enabled for the servers involved in the D-ITET mail system.

From the zones itet-isg and itet-staff to the internet the ip transport protocols TCP/ UDP are generally enabled. Every machine inside can initiate a connection to an arbitrary server port in the internet.

Mailbox Access

Web Access (Roundcube)

You can access your inbox and your mail folders with a web browser on any client with internet connectivity. Our web server with the Roundcube software can be reached under https://email.ee.ethz.ch.

IMAP/ SMTP Access

You can also access your mail with any IMAP/ SMTP based mail client software ( Thunderbird, Outlook, Smartphone Mail Programs, Windows 10 Mail, ......) over the internet. IMAP/ SMTP access to our mail servers is enabled for the internet. Detailed information is available in the Email overview page.

SSH - remote terminal session

In the Linux world remote terminals are widely used. The secure shell ssh allows secure (i.e. encrypted connection) remote terminal sessions. To establish such sessions, you will need an SSH client application. Under Linux and Mac OSX, the program is called ssh and is usually provided by the basic installation of the operating system. Under MS Windows, a 3rd party manufacturer application like PuTTY (http://www.chiark.greenend.org.uk/~sgtatham/putty), X-Win32, or the Cygwin SSH client must be installed separately.

Establishing a remote terminal session

From ETH internal

• On an ETH-internal client you can simply enter

  ssh <Your ETH username>@<targethostname>.ee.ethz.ch
  

After a successful login, a remote terminal session is established on the selected target host. If you omit <Your ETH username>@ in the ssh commandline, your shell's current session login username is used.

From ETH external

There are two possibilities:

• To connect to an ssh service from an ETH-external client, one must install and activate the VPN client software on that computer and then proceed in a way as if the client were an ETH-internal computer (see above). Using fully qualified hostnames (e.g. ssh hostname.ee.ethz.ch instead of just ssh hostname) allows you to access the target ETH server from anywhere (using the VPN client or the method described in the next paragraph), especially from selfmanaged/ private computers that are not in the ee.ethz.ch subdomain.

• Alternatively¹, for ETH-external clients, one may establish a "direct" connection (without VPN client) to the target host via our login server login.ee.ethz.ch. For the latter, use the following commandline (example for the Linux built-in ssh application):

  ssh -o ProxyJump=<Your ETH username>@login.ee.ethz.ch <Your ETH username>@<targethostname>.ee.ethz.ch
  

For a transparent access you can configure your client SSH configuration with something similar as

Host login.ee.ethz.ch
    User <Your ETH username>
    PreferredAuthentications publickey

Host *.ee.ethz.ch !login.ee.ethz.ch
    User <Your ETH username>
    ProxyJump login.ee.ethz.ch
    PreferredAuthentications publickey

• If you want to establish a "direct" connection (without VPN client) to the target host via our login server login.ee.ethz.ch from an ETH-external Windows client using PuTTY, read this article.

• For a key-based ssh login see https://computing.ee.ethz.ch/FAQ/SSHkeys .

SSH details

The ssh protocol has some integrated features like

• X11 forwarding (run a Linux GUI application remotely and display it's window on the local computer)
• encrypted file transfer, encrypted remote shell sessions
• ssh tunnelling (purpose is most often to bypass firewall restrictions)

With these features ssh also offers solutions to additional tasks which are covered in the following chapters.

The host login.ee.ethz.ch might be used to log in to the D-ITET network from anywhere (all D-ITET users are allowed to log in there). Use this host only as a starting point (i.e. to establish further connections to other D-ITET-internal computers from there), but do not execute processes that will consume a lot of CPU resources (e.g. do not run Matlab/ compute jobs on this machine!).

For advanced users: If you want to make sure a managed ISG D-ITET Linux computer you intend to access with ssh is in fact the machine you are expecting (and not a modified/ hacked one; e.g. with man-in-the-middle-attack), you can verify its hostkey. How that works is described on this website: https://computing.ee.ethz.ch/SshFingerprints

Remote Desktop Session

Windows Remote Desktop

To access your Windows computer remotely, please read Windows Remote Desktop Services.

X11VNC

x11vnc can be used to connect to a desktop session running on the physical display of a host. Please see the X11VNC HOWTO for further details. In case you have no running session on the physical display and need to login graphically, please contact support and provide the name of the host you need to access.

VNC

VNC is the preferred solution for remote desktop sessions on Linux machines. Please read the VNC article for more details.

File Transfer

HTTP download

The HTTP download is a simple solution to transfer a data file to an external user. On the client side no additional software is needed, a web browser is sufficient.

Here are the sample commands to provide a data file for download with a required authorization in your personal web page:

mkdir /home/<Your ETH username>/public_html/transfer
cp /scratch/<Your ETH username>/datafile /home/<Your ETH username>/public_html/transfer/
htpasswd -s -c /home/<Your ETH username>/public_html/.htpasswd download

Create a file .htaccess in the download folder /home/<Your ETH username>/public_html/transfer with content:

AuthUserFile "/home/<Your ETH username>/public_html/.htpasswd"
AuthName "Downloads"
AuthType Basic
Require user download

Under the address http://people.ee.ethz.ch/~<Your ETH username>/transfer the file can now be downloaded with user download and the password set with the htpasswd command.

Linux scp

Between two Linux machines you can transfer a file with the ssh-integrated secure file copy (scp). The command is:

<Your private username>@home> scp <path-to-datafile> <Your ETH username>@<hostname>:<path-to-target directory>

With the command

<Your private username>@home> scp document.pdf <Your ETH username>@login.ee.ethz.ch:/home/<Your ETH username>/Documents/

the file document.pdf on your linux machine is copied in the Documents subdirectory in your home at D-ITET.

Windows WinSCP/ FileZilla

Windows has no SSH integrated, so you must use an additional software. The popular programs WinSCP (https://winscp.net) and FileZilla (https://filezilla-project.org) are the preferred choice. FileZilla is also available for the linux platform and is already installed on our managed linux clients.

ID polybox - Own Cloud Storage

ID provides 50 GB storage to every ETH member https://www.ethz.ch/services/en/it-services/catalogue/storage/polybox.html. The polybox client software is available for different plattforms and synchronizes a local storage on the client with the owncloud server storage. If the client software is installed on two machines you can therefore transfer data between the two machines with the polybox/ownclound client.

SWITCHfilesender

SWITCH offers a service for the exchange of big sized data which can not be send by mail called Filesender (https://www.switch.ch/services/filesender). It's a good solution for sporadic transfers of big sized data (up to 300GB) to a site where no ETH account can be used. The uploaded data will be cleaned automatically after a pre-defined time.

Network File System Access

NFS access

Because NFS is not enabled between the internal networks nor to the internet it has no significance in remote access solutions. NFS is only used by ISG D-ITET managed linux clients to access user and project homes on servers and dedicated storage systems of ID and ITET by Linux automount tables.

SMB/ CIFS access

This Microsoft network file sharing protocol has a user based authentication and therefore has a great significance for accessing data resources not only on windows file servers. Linux servers are also providing SMB/ CIFS access with use of the samba software suite, an emulation of the windows file sharing protocol for Linux file servers.

More information how to access your data you find under:

• Workstations/FindYourData

• Services/FileAccess

SSHFS

SSHFS is a FUSE-based filesystem client for mounting remote directories over a Secure Shell connection. FUSE (Filesystem in Userspace) is a simple interface for userspace programs to export a virtual filesystem to the Linux kernel. FUSE provides a secure method for non privileged users to create and mount their own filesystems. It is a solution to access storage locations on the remote side which are not accessible over SMB/CIFS.

Usage on Linux

Mounting a remote directory:

mkdir scratch 
sshfs -o follow_symlinks <Your ETH username>@<host>.ee.ethz.ch:/scratch scratch
ls scratch
fusermount -u scratch

Usage on Windows

Please install the Windows WSL 2 subsystem on your Windows 10/11 machine according to https://docs.microsoft.com/en-us/windows/wsl/install.

Install the sshfs software package:

sudo apt-get install sshfs

You must now edit the file /etc/fuse.conf to uncomment the default entry #user_allow_other:

...
# Allow non-root users to specify the allow_other or allow_root mount options.
user_allow_other
#
....

Now you should be able to perform a sshfs mount to your linux machine in the ETH network:

mkdir scratch                                                                                  # create a mountpoint in your WSL 2 home directory
sshfs -o allow_other,follow_symlinks <Your ETH username>@<host>.ee.ethz.ch:/scratch  scratch   # sshfs fuse mount
cd scratch
explorer.exe .                                                                                 # starts a windows explorer in /scratch of the target machine

To umount the remote directory terminate the windows explorer and enter the command:

cd ..
fusermount -u scratch