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Setting up SSH keys

787 words·4 mins

Brief explanation about SSH #

Here is what Wikipedia has to say about SSH:

“Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line login and remote command execution, but any network service can be secured with SSH.”

In simple terms, Secure Shell or SSH is a network protocol that allows users to control and modify remote servers over the internet

Setting up SSH keys #

Since SSH is encrypted, we are required to use a password or set up key pairs in order to use it. Although using passwords can seem convinient at first, they are no where as secure as key pairs when it comes to security. It is highly recommended that you use key pairs to login to your SSH server or in this case your remote repository server.

I’m assuming you are on a unix machine like all sane developers.

  • First, check if you already have an existing ssh key pair:

    ls -l ~/.ssh/

    If a message appears in the console containing the text “No such file or directory”, then you do not yet have an SSH key, and you will need to create one. If no message has appeared in the console output, you already have a key and can skip this section.

  • Generate an ssh key pair if you don’t have one already, and follow with the rest of the process:

    ssh-keygen -C <email address>

    The C flag is just to add a comment (in this case your email address or hostname for that matter) so that you get to add a comment to help you remember the key. Although you can add anything as a comment, it is generally a convention to add either your your email address or hostname as your comment.

    You may additionally get prompted for a location to save your generated keypair. Default is fine. So just press Enter.

    It will also ask for a password. Enter one if you wish, but it’s not required.

Adding them to your remote repository of choice #

Go to your remote repository of choice, and add the SSH keypair. For instance, I will be showing how to add one on GitHub.

On GitHub #

Login to your github account and go to settings in the top right corner. Next on the left hand side, click SSH and GPG keys. Then, click the green button in the top right corner that says New SSH Key. Name your key something that is descriptive enough for you to remember where it came from. Leave this window open while you do the next steps.

Now you need to copy your public SSH key. To do this, we’re going to use a command called cat to read the file to the console. (Note that the .pub file extension is important in this case.)

cat ~/.ssh/id_*.pub

Highlight and copy the output, which starts with ssh- and ends with your saved comment from earlier, which in this case should be your email address.

Now, go back to GitHub in your browser window and paste the key you copied into the key field. Then, click Add SSH key. You’re done! You’ve successfully added your SSH key!

Testing your ssh keys #

When you test your connection, you’ll need to authenticate this action using your password, which is the SSH key passphrase you created earlier. For more information on working with SSH key passphrases, see “ Working with SSH key passphrases”.

  • Enter the following on a terminal:

        ssh -T
        # attempts to ssh onto github

    You may see a warning like this:

        > The authenticity of host ' (IP ADDRESS)' can't be established.
        > RSA key fingerprint is SHA256:nThbg6kXUpJWGl7E1IGOCspRomTxdCARLviKw6E5SY8.
        > Are you sure you want to continue connecting (yes/no)?
  • Verify the fingerprint in the message you see matches GitHub’s RSA public key fingerprint. If it does, then type yes:

        > Hi username! You've successfully authenticated, but GitHub does not
        > provide shell access.

    You might see this error message:

        Agent admitted failure to sign using the key.
        debug1: No more authentication methods to try.
        Permission denied (publickey).

    This is a known problem with certain Linux distributions. For more information, see “ Error: Agent admitted failure to sign”.

  • Verify that the resulting message contains your username. If you receive a “permission denied” message, see “ Error: Permission denied (publickey)”.

Conclusion #

So there you have it. You just generated an SSH key pair and added it to a remote repository (like GitHub in this case) of your choice. Now every time you push or pull code to your remote repository make sure you are doing so over the SSH protocol and not the HTTPS protocol.