I was trying to connect from VSCode Windows into a remote Linux server, and got this error

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @        
 WARNING: UNPROTECTED PRIVATE KEY FILE!          @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Permissions for 'C:\\Users\\hanxuel\\OneDrive\\Private\\hanxuel' are too open.

It is required that your private key files are NOT accessible by others.

This private key will be ignored.

Load key "C:\\Users\\hanxuel\\OneDrive\\Private\\hanxuel": bad permissions

Seems the that private SSH key that I am using has too open permissions.

SSH Key Permissions

On Linux, I am pretty clear about the permissions I need to set.

File	Octal Permissions	File Listing Permissions
~/.ssh	700	drwx------
~/.ssh/id_rsa (or other private keys)	600	-rw-------
~/.ssh/id_rsa.pub (or other public keys)	644	-rw-r--r--

So the ~/.ssh directory and SSH private key should be only viewable by myself, although the public key can be more open. The public key is sometimes distributed to other users or used by remote services and it should be public anyway.

Windows SSH Key Permission

Windows file permissions works a bit differently than UNIX. There is filesystem ACL, objects and inheritance. But basically the goal is the same: remove anyone else from reading the private key, except yourself.

Here's a script I found on Superuser.com that does that

:: # Set Variable ::
Set Key="C:\Path\to\key"

:: # Remove Inheritance ::
Cmd /c Icacls %Key% /c /t /Inheritance:d

:: # Set Ownership to Owner ::
Cmd /c Icacls %Key% /c /t /Grant %UserName%:F

:: # Remove All Users, except for Owner ::
Cmd /c Icacls %Key% /c /t /Remove Administrator "Authenticated Users" BUILTIN\Administrators BUILTIN Everyone System Users

:: # Verify ::
Cmd /c Icacls %Key%

Remember to run this script as Administrator.

This is what the output looks like

λ C:\Apps\private_key.cmd 
 
Set Key="C:\Users\hanxuel\OneDrive\Private\hanxuel" 
 
Cmd /c Icacls "C:\Users\hanxuel\OneDrive\Private\hanxuel" /c /t /Inheritance:d 
processed file: C:\Users\hanxuel\OneDrive\Private\hanxuel 
Successfully processed 1 files; Failed processing 0 files 
 
Cmd /c Icacls "C:\Users\hanxuel\OneDrive\Private\hanxuel" /c /t /Grant hanxuel:F 
processed file: C:\Users\hanxuel\OneDrive\Private\hanxuel 
Successfully processed 1 files; Failed processing 0 files 
 
Cmd /c Icacls "C:\Users\hanxuel\OneDrive\Private\hanxuel" /c /t /Remove Administrator "Authenticated Users" BUILTIN\Administrators BUILTIN Everyone System Users 
processed file: C:\Users\hanxuel\OneDrive\Private\hanxuel 
Successfully processed 1 files; Failed processing 0 files 
 
Cmd /c Icacls "C:\Users\hanxuel\OneDrive\Private\hanxuel" 
C:\Users\hanxuel\OneDrive\Private\hanxuel ACME\hanxuel:(F) 
                                                        ACME\xilongj:(F)

Successfully processed 1 files; Failed processing 0 files