If you enable dev mode you get access to a full linux environment, including ssh.

You can even use ssh without dev mode, but it is crippled.

There's a built-in SSH as part of crosh[0] and a more usable version paired with a HTML-based terminal emulator as an app[1]

[0] basic troubleshooting shell in CrOS

[1] https://chrome.google.com/webstore/detail/pnhechapfaindjhomp...