Using SSH Keys

Page Contents

Hint

If you do not know what ssh is we recommend that you read up on it . However, the simple material presented here will help you getting started quickly.

To access remote resources this is often achieved via SSH. You need to provide a public ssh key to FutureSystem. We explain how to generate a ssh key, upload it to the FutureSystem portal and log onto the resources. This manual covers UNIX, Mac OS X. For Windows we will prepare an add on to this document.

Using SSH from Windows

Hint

For Linux users, please skip to the section Generate a SSH key

Hint

For Mac users, please skip to the section Using SSH on Mac OS X

Warning

For this class we recommend that you use a virtual machine via virtual box and use the Linux ssh instructions. The information here is just provided for completness and no support will be offered for native windows support.

Windows users need to have some special software to be able to use the SSH commands. If you have one that you are comfortable with and know how to setup key pairs and access the contents of your public key, please feel free to use it.

The most popular software making ssh clients available to Windows users include

We will be discussing here how to use it in Powershell with the help of chopolatey.

Chocolatey is a software management tool that mimics the install experience that you have on Linux and OSX. It has a repository with many packages. Before using and installing a package be aware of the consequences when installing software on your computer. Please be aware that there could be malicious code offered in the chocolatey repository although the distributors try to remove them.

The installation is sufficently explained at

Once installed you have a command choco and you should make sure you have the newest version with

choco upgrade chocolatey

Now you can browse packages at

Search for openssh and see the results. You may find different versions. Select the one that most suits you and satisfies your security requirements as well as your architecture. Lets assume you chose the Microsoft port, than you can install it with:

choco install win32-openssh

Other packages of interest include

  • LaTeX:: choco install miktex
  • jabref: choco install jabref
  • pycharm: choco install pycharm-community
  • python 2.7.11: choco install python2
  • pip: choco install pip
  • virtual box: choco install virtualbox
  • emacs: choco install emacs
  • lyx: choco install lyx
  • vagrant: choco install vagrant

Before installing any of them evaluate if you need them.

Using SSH on Mac OS X

Mac OS X comes with an ssh client. In order to use it you need to open the Terminal.app application. Go to Finder, then click Go in the menu bar at the top of the screen. Now click Utilities and then open the Terminal application.

Generate a SSH key

|info-image| Hint

In case you do not want to type in your password everytime, please learn about ssh-agent and ssh-add.

First we must generate a ssh key with the tool ssh-keygen. This program is commonly available on most UNIX systems (this includes Cygwin if you installed the ssh module or use our pre-generated cygwin executable). It will ask you for the location and name of the new key. It will also ask you for a passphrase, which you MUST provide. Some teachers and teaching assistants advice you to not use passphrases. This is WRONG as it allows someone that gains access to your computer to also gain access to all resources that have the public key. Also, please use a strong passphrase to protect it appropriately.

In case you already have a ssh key in your machine, you can reuse it and skip this whole section.

To generate the key, please type:

Example:

ssh-keygen -t rsa -C localname@indiana.edu

This command requires the interaction of the user. The first question is:

Enter file in which to save the key (/home/localname/.ssh/id_rsa):

We recommend using the default location ~/.ssh/ and the default name id_rsa. To do so, just press the enter key.

Note

Your localname is the username on your computer.

The second and third question is to protect your ssh key with a passphrase. This passphrase will protect your key because you need to type it when you want to use it. Thus, you can either type a passphrase or press enter to leave it without passphrase. To avoid security problems, you MUST chose a passphrase. Make sure to not just type return for an empty passphrase:

Enter passphrase (empty for no passphrase):

and:

Enter same passphrase again:

If executed correctly, you will see some output similar to:

Generating public/private rsa key pair.
Enter file in which to save the key (/home/localname/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/localname/.ssh/id_rsa.
Your public key has been saved in /home/localname/.ssh/id_rsa.pub.
The key fingerprint is:
34:87:67:ea:c2:49:ee:c2:81:d2:10:84:b1:3e:05:59 localname@indiana.edu
The key's random art image is::

+--[ RSA 2048]----+
|.+...Eo= .       |
| ..=.o + o +o    |
|O.  o o +.o      |
| = .   . .       |
+-----------------+

Once, you have generated your key, you should have them in the .ssh directory. You can check it by

$ cat ~/.ssh/id_rsa.pub

If everything is normal, you will see something like:

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCXJH2iG2FMHqC6T/U7uB8kt6KlRh4kUOjgw9sc4Uu+Uwe/EwD0wk6CBQMB+HKb9upvCRW/851UyRUagtlhgythkoamyi0VvhTVZhj61pTdhyl1t8hlkoL19JVnVBPP5kIN3wVyNAJjYBrAUNW4dXKXtmfkXp98T3OW4mxAtTH434MaT+QcPTcxims/hwsUeDAVKZY7UgZhEbiExxkejtnRBHTipi0W03W05TOUGRW7EuKf/4ftNVPilCO4DpfY44NFG1xPwHeimUk+t9h48pBQj16FrUCp0rS02Pj+4/9dNeS1kmNJu5ZYS8HVRhvuoTXuAY/UVcynEPUegkp+qYnR user@myemail.edu

Add or Replace Passphrase for an Already Generated Key

In case you need to change your change passphrase, you can simply run “ssh-keygen -p” command. Then specify the location of your current key, and input (old and) new passphrases. There is no need to re-generate keys:

ssh-keygen -p

You will see the following output once you have completed that step:

Enter file in which the key is (/home/localname/.ssh/id_rsa):
Enter old passphrase:
Key has comment '/home/localname/.ssh/id_rsa'
Enter new passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved with the new passphrase.