PR Summary

This PR fixes the remoting key exchange hang in OutOfProc transport connections, when transferring SecureString objects.
Fixes issue: #259

PR Context

When a SecureString object is transferred over the remoting layer, a key exchange algorithm is lazily run so that the contents of the SecureString can be encrypted. This is not strictly necessary since both WinRM and SSH remoting channels already encrypt data on the wire by default. But the key exchange must remain for compatibility reasons.

The hang occurs when the target sends an encrypted SecureString object to the client for the first time. The client begins a key exchange handshake with the target so that it can handle the object. This works fine for WinRM based remote connections because the client processes session and command protocol messages on different threads. But the OutOfProc based transport implementations process client protocol messages on a single thread, and the lazily initiated key exchange results in a deadlock.

The fix is to update the OutOfProc transport manager base class to detect and process command and session client protocol messages on separate threads.

This is not a low risk change since it affects four remote implementations that are based on the OutOfProc transport: background jobs, PowerShellDirect, named pipes, SSH.

Repro Steps:

$session = New-PSSession -Host localhost
Invoke-Command $session { $ss = ConvertTo-SecureString "Hello" -AsPlainText -Force }
Invoke-Command $session { $ss }

#Result
Hang

#Expected
SecureString object to be returned.

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    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode (which runs in a different PS Host).
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).