tilde.club/docs/ssh.md

tilde.club uses ssh public-key authentication.

If you want access to tilde.club, you'll need to create a new SSH key pair and then send the public key to the admins; they will then associate it with your account and let you know when things are ready for you to log in.

Mac

Generating your key pair

1. Open Terminal (in /Applications/Utilities/).
2. In the Terminal window, paste the following:

mkdir -m 700 -p ~/.ssh                          # Create your .ssh directory
ssh-keygen -t rsa -b 2048 -f ~/.ssh/tilde.club  # Create your keys

1. The ssh-keygen program will generate two new keys (private and public), and prompt you for a password. Please set a good password (at least 9 characters, and not just letters or numbers), and make a note of it somewhere safe.
2. Now, in Terminal, type: open ~/.ssh to open a Finder window showing your .ssh directory.
3. Take the tilde.club.pub file and attach it to an email to ford@ (our friendly host). Do not attach the file tilde.club -- that is your private key, which you should never ever ever share with anyone.

Using your key pair

1. Open Terminal.
2. type ssh -i ~/.ssh/tilde.club username@tilde.club (substituting in your own username)

Note that it's possible to save an SSH configuration so that you don't have to type this whole long thing every time; here's a good primer on how to do that.

Linux

Generating your key pair

If you're on Linux you can use the same commands as on the Mac to generate a tilde.club key pair, but attaching tilde.club.pub is left as an exercise for the reader.

Using your key pair

At a command prompt, type ssh -i ~/.ssh/tilde.club username@tilde.club (substituting your own username).

Note that it's possible to save an SSH configuration so that you don't have to type this whole long thing every time; here's a good primer on how to do that.

Windows

Generating your key pair

The easiest method to generate a key pair on Windows is to use PuTTY, a freely-available SSH client which comes with its own key generator.

1. Download PuTTY here. (Specifically, get the Windows Installer version; if you want to download the binaries individually, you want to make sure you get the PuTTYgen binary which is what generates key pairs.)
2. Run PuTTYgen.
3. From the main window, click the Generate button; you'll be asked to move the mouse around to generate randomness, which you should do until PuTTYgen tells you that it's generating the key.
4. Once the key pair is generated, click the Save public key button, choose a directory you want to save it into, and in the "File name" field, type tilde.club.pub. Save the key.
5. Halfway down the main window, type a good password into the "Key passphrase" field (at least 9 characters, and not just letters or numbers), and repeat it in the "Confirm passphrase" field.
6. Click the Save private key button, choose the same directory as you did above, type tilde.club into the "File name" field, and save the private key.
7. Finally, email the tilde.club.pub file to ford@ (our friendly host). Do not attach the file tilde.club -- that is your private key, which you should never ever ever share with anyone.

Using your key pair

1. Run PuTTY.
2. In the first window that comes up, you should be in the main "Session" category (in the left-hand column). On the right, in the "Host Name" field, type tilde.club.
3. In the left-hand column, find the SSH entry underneath the Connection section and then click on the small plus sign next to it to open it up; then find the Auth entry beneath it and click on it.
4. On the right, the last field should be "Private key file for authentication"; click the Browse button and find the tilde.club file you saved above. Select it and click the Open button.
5. Finally, click the Open button at the bottom of the main PuTTY window to open your connection. You'll be asked for your username ("login as:"); type it in and hit Enter. You'll then be asked for your key passphrase; type it in and hit enter, and you're in.

Note that you can save these settings from that first page of the main PuTTY window, so you don't have to do this every time.

Why go through all this?

One of the weakest links in online account security is your password. If someone were to take over the tilde server (specifically the SSH server, sshd), they would be able to capture the passwords of everyone who uses a password to log in. (This isn't theoretical -- it has actually happened.) If users use their SSH keys to log in instead, hackers can't do this anymore; a user's private key never leaves their own computer and can't be captured on the server.

Additionally, if you use an ssh agent, you can login without entering a password every time. On OS X the Apple Keychain provides this functionality. On Linux it's ssh-agent and possibly keychain. On Windows pageant provides this capability for PuTTY.