How it works

The secret ingredient to all our services is how we enable users publish content without needing to install anything. We accomplish this with the SSH tools you already have installed on your system. All a user needs is an SSH client to manage their content.

By using the SSH protocol and Go's implementation of SSH, we can create Go binaries that interface with SSH in unique ways. Further, we are inside the context of a Go binary, not a traditional SSH session where the user could figure out how to execute arbitrary commands.

charm.sh wish is the underlying library we use to enable all our SSH apps to work seamlessly with SSH clients. Wish lets end-developers construct an SSH server with a middleware stack. This makes it easy to programmatically compose and extend a traditional SSH server. So we have built middleware to serve our needs:

• Authentication and authorization with keypairs and a database
• Uploading files with scp, sftp, rsync, and sshfs
• Piping into an SSH server
• Rendering a TUI
• Remote CLI

All of these are just middleware. After understanding the features and limitations of the SSH protocol and implementing middleware with wish, all that's left is a traditional Go app.

Whenever a user uploads a file to our SSH app, we don't actually store anything in our VM from the user. Instead we transfer the file, in-memory, to a database or object store. This makes our SSH apps stateless.

We support a few clients for file uploads:

• scp
• sftp
• rsync
• sshfs

All of these are implemented using wish and our own Go library.