Fix SSH key permission on Windows

Set-SshKeyPermissions.ps1

# usage:
# save this function to Set-SshKeyPermissions.ps1
# then run in PowerShell as the desired user (non-elevated):
#
#   .\Set-SshKeyPermissions.ps1
#
#   Set-SshKeyPermissions "$Env:USERPROFILE\.ssh"
#
# Ref: https://scivision.dev/ssh-agent-config/

function Set-SshKeyPermissions {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true, Position = 0)]
        [string]$KeyPath
    )

    Write-Host "Setting permissions for $KeyPath"

    # Define the owner and the key file/directory
    #$Owner = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
    $UserName = $env:UserName
    # This is for your specific user account

    # Disable inheritance and remove all existing permissions
    Write-Host "Disabling inheritance and removing all existing permissions for $KeyPath..."
    icacls "$KeyPath" /c /t /inheritance:d /remove:g Administrator "Authenticated Users" "BUILTIN\Administrators" BUILTIN\Everyone Users System
    # Note: We remove 'System' here to reset it, then grant it back explicitly.

    # Take ownership if not already owned by the current user
    Write-Host "Taking ownership of $KeyPath..."
    Takeown /F "$KeyPath"

    # Grant Full Control to the current user
    Write-Host "Granting Full Control to $UserName for $KeyPath..."
    icacls "$KeyPath" /c /t /grant "${UserName}:F"

    # Grant Full Control to SYSTEM (important for ssh-agent)
    Write-Host "Granting Full Control to SYSTEM for $KeyPath..."
    icacls "$KeyPath" /c /t /grant "SYSTEM:F"

    # Verify permissions
    Write-Host "Verifying permissions for $KeyPath..."
    icacls "$KeyPath"
}