Make SSH apps, just like that! 💫
SSH is an excellent platform to build remotely accessible applications on. It offers:
- secure communication without the hassle of HTTPS certificates
- user identification with SSH keys
- accessiblity from anywhere with a terminal
Powerful protocols like Git work over SSH and you can even render TUIs directly over an SSH connection.
Wish is an SSH server with sensible defaults and a collection of middlewares that makes building SSH apps easy. Wish is built on gliderlabs/ssh and should be easy to integrate into any existing projects.
Usually, when we think about SSH, we think about remote shell access into servers,
most commonly through openssh-server.
That's a perfectly valid and probably the most common use of SSH, but it can do so much more than that. Just like HTTP, SMTP, FTP and others, SSH is a protocol! It is a cryptographic network protocol for operating network services securely over an unsecured network. 1
That means, among other things, that we can write custom SSH servers without touching openssh-server,
so we can securely do more things than just providing a shell.
Wish is a library that helps writing these kind of apps using Go.
Wish middlewares are analogous to those in several HTTP frameworks. They are essentially SSH handlers that you can use to do specific tasks, and then call the next middleware.
Notice that middlewares are composed from first to last, which means the last one is executed first.
The bubbletea middleware makes it easy to serve any
Bubble Tea application over SSH. Each SSH session will get their own
tea.Program with the SSH pty input and output connected. Client window
dimension and resize messages are also natively handled by the tea.Program.
You can see a demo of the Wish middleware in action at: ssh git.charm.sh
The git middleware adds git server functionality to any ssh server.
It supports repo creation on initial push and custom public key based auth.
This middleware requires that git is installed on the server.
The logging middleware provides basic connection logging. Connects
are logged with the remote address, invoked command, TERM setting, window
dimensions and if the auth was public key based. Disconnect will log the remote
address and connection duration.
Not all applications will support general SSH connections. To restrict access
to supported methods, you can use the activeterm middleware to
only allow connections with active terminals connected and the
accesscontrol middleware that lets you specify allowed
commands.
Wish includes the ability to easily create an always authenticating default SSH server with automatic server key generation.
There are examples for a standalone Bubble Tea application and Git server in the examples folder.
When building various Wish applications locally you can add the following to
your ~/.ssh/config to avoid having to clear out localhost entries in your
~/.ssh/known_hosts file:
Host localhost
UserKnownHostsFile /dev/null
Wish uses gliderlabs/ssh to implement its SSH server, and OpenSSH is never used nor needed — you can even uninstall it if you want to.
Incidentally, there's no risk of accidentally sharing a shell because there's no default behavior that does that on Wish.
If you want to run a Wish app with systemd, you can create an unit like so:
/etc/systemd/system/myapp.service:
[Unit]
Description=My App
After=network.target
[Service]
Type=simple
User=myapp
Group=myapp
WorkingDirectory=/home/myapp/
ExecStart=/usr/bin/myapp
Restart=on-failure
[Install]
WantedBy=multi-user.targetYou can tune the values below, and once you're happy with them, you can run:
# need to run this every time you change the unit file
sudo systemctl daemon-reload
# start/restart/stop/etc:
sudo systemctl start myappIf you use a new user for each app (which is good), you'll need to create them first:
useradd --system --user-group --create-home myappThat should do it.
We’d love to hear your thoughts on this project. Feel free to drop us a note!
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