AzSession: Connecting to Azure AD-joined VM’s

Microsoft has introduced a pretty cool feature where you can use Azure Active Directory credentials for AAA against a Linux virtual machine (see Microsoft Docs for more information). Getting signed in the first time is a bit cumbersome, but in my opinion worth it for the convenience and security.

There is, however, a massive caveat: you can no longer (trivially) SSH to the machine in an external client, as the AZAD sign-in flow generates an ephemeral key pair on the VM for you, and requires interop with AZAD to do so. The Azure CLI PowerShell module does offer a means to export a key, but due to its ephemeral nature, you can only use it for around an hour:

This works fine with OpenSSH and anything that can either read its default configuration (~./ssh/config or %USERPROFILE%\.ssh\config) or take a configuration file as an argument.

However, exporting the config file to the default location won’t work if you already have a configuration file (presumably to prevent clobbering the user’s settings). Inconveniently, my best friend New-PSSession doesn’t take a configuration file from the command line, so I had to find a work-around.

Now, when it creates a session over SSH, New-PSSession uses OpenSSH under the hood, so it follows that it would respect the default user configuration. Thus, I created the AzSession PowerShell module to: