ssh

authors:

benharri


table of contents

or, how to tell other computers to do cool things

all users are required to use an ssh keypair for login, or will be required to proceed with manual account recovery. you can also set up two-factor authentication to log in without your keypair.

geosparkies.com details §

for example, to connect to geosparkies.com, you can do:

ssh user@geosparkies.com
mosh user@geosparkies.com

ssh is also available on port 443 using the address ssh.geosparkies.com:

ssh -p 443 user@ssh.geosparkies.com

this is useful if you’re on a limited public network that blocks non-http ports.

if you are prompted for a verification code, it’s for 2fa. it will not work if you haven’t set it up. be sure you’re using the right ssh keypair.

intro §

** if you just want to get right to a tutorial you can skip over this background info**

while geosparkies.com is accessible on the web and features lovely web pages written by its users, most interaction with geosparkies.com takes place inside the machine that runs geosparkies.com as opposed to via web forms that have an effect from outside geosparkies.com’s computer.

this is what sets geosparkies.com apart from most other online communities. you connect directly to another computer from yours alongside other people and then write your web pages, chat, and play games all via text-based interfaces right on geosparkies.com’s computer.

prior to the web (which debuted in 1995) this is how pretty much all computer stuff got done. you connected directly to a machine (usually over a direct, physical phone line) and did your work there.

for a long time, people used a tool called telnet to connect to other computers. these days we use a tool called ssh.

ssh is a text-based tool that provides a direct connection from your computer to another. ssh is an acronym that stands for secure shell. the shell part refers to the fact that it’s a text-based tool; we use the word shell to refer to a text-based interface that you give commands to. the secure part refers to the fact that, when you’re using ssh, no one can spy on your connection to another computer (unlike the old telnet command).

why bother with all of this? passwords are really insecure and hard to manage. using keys makes life easier for you, fair user (your account is less likely to be hacked) and for me, your humble sysadmin (less administration than passwords).

how to make an ssh key §

SSH supports a handful of types of cryptographic keys. The most used are RSA and the more modern Ed25519.

RSA is the de-facto standard and is supported everywhere (just choose a big enough key like 4096 bits to be secure). Ed25519 is designed to be faster and smaller withouth sacrificing security, so is best suited for embedded devices or machines with low resources. It’s supported on tilde (and really on any modern system) but you may find older systems which do not support it.

Below you’ll find instructions to generate either type (or both if you want).

Keep in mind that these instructions leave your private keys unencrypted in your local hard disk. So keep them private; never share them. A good solution is to provide a password for them at creation time, but this implies entering a password any time you used them (impractical) or use something like ssh-agent (a bit more complex)

pick your fighter: [mac] | [windows] | [linux]

mac §

generating your keypair §

  1. open terminal (it’s in /Applications/Utilities)

  2. create your .ssh directory:

mkdir -m 700 ~/.ssh
  1. create your keypair:
ssh-keygen -t ed25519 -a 100
  1. if you press enter to accept the defaults, your public and private key will be located at ~/.ssh/id_ed25519.pub and ~/.ssh/id_ed25519

cat ~/.ssh/id_ed25519.pub

  1. copy the output of the last command and paste it in the sshkey field on the signup form (or email it to ~root if you already have an account)

using your keypair §

once an admin approves your signup, you can join the geosparkies.com

  1. open terminal (it’s in /Applications/Utilities)

  2. ssh to geosparkies.com:

ssh username@geosparkies.com

where username is your username (~benharri would use ssh benharri@geosparkies.com)

  1. profit???

windows §

Ensure OpenSSH is installed §

1. Open Settings, select Apps, then select Optional Features
1. Scan the list to see if the OpenSSH is already installed. If not, at the top of the page, select Add a feature, then...
1. Find OpenSSH Client, then select Install

generating your keypair §

  1. open your command prompt (Start -> Search -> type “cmd”)

  2. create your keypair:

ssh-keygen -t ed25519 -a 100
  1. If you press enter to accept the defaults, your public and private key will be located at %USERPROFILE%.ssh_ed25519.pub and %USERPROFILE%.ssh_ed25519 respectively.

Note: %USERPROFILE% is a short code that the computer expands to mean c:_name, or whatever the relevant path is to your user’s main folder.

Next we will open up the public key so we can copy its contents.

notepad %USERPROFILE%\.ssh\id_ed25519.pub
  1. Copy the text of the pubkey that opens in Notepad and paste it in the sshkey field on the signup form or email it to the relevant sign-up address for the tilde you are joining.

using your keypair §

once an admin approves your signup, you can join the geosparkies.com

  1. open command prompt (Start -> Search -> type “cmd”)

  2. ssh to geosparkies.com:

ssh username@geosparkies.com

where username is your username (~benharri would use ssh benharri@geosparkies.com)

  1. profit???

linux §

there are a lot of linux distros, but ssh and ssh-keygen should be available in almost all cases. if they’re not, look up how to install ssh for your distro.

generating your keypair §

  1. make sure you have a ~/.ssh directory
mkdir -m 700 ~/.ssh
  1. create your keypair
ssh-keygen -t ed25519 -a 100
  1. if you press enter to accept the defaults, your public and private key will be located at ~/.ssh/id_ed25519.pub and ~/.ssh/id_ed25519
cat ~/.ssh/id_ed25519.pub
  1. copy the output of the last command and paste it in the sshkey field on the signup form (or email it to root@geosparkies.com if you already have an account)

using your keypair §

once an admin approves your signup, you can join the geosparkies.com

  1. open a terminal (this depends on your distro)

  2. ssh to geosparkies.com:

where username is your username (~benharri would use ssh benharri@geosparkies.com)

ssh username@geosparkies.com

Note: If you generated your key to the location above (%USERPROFILE%...) then you will be able to SSH to your tilde server without having to specify the location of the key. That folder is the default used by SSH and it will be found automatically. If you generated your keys in a different location or moved them, you will need to specify the full path to the private key.

ssh -i c:\path\to\my\private\key username@your.tilde
  1. profit???

this tutorial is based on and uses parts of the geosparkies.com ssh primer and the tilde.town ssh guide.