Replace permissions with icacls.exe

Question

We have a lot of folders with the following permissions:

PS C:\> icacls.exe C:\Temp\Test
C:\Temp\Test    BUILTIN\Administrators:(OI)(CI)(F)
                NT AUTHORITY\SYSTEM:(OI)(CI)(F)
                DOMAIN\USER:(OI)(IO)(RX)
                DOMAIN\USER:(CI)(RX) 

We would like to replace the two permissions from DOMAIN\USER to one with (OI)(CI)(RX).
To achive that, we used icacls.exe /grant:r. Unfortunately the :r parameter does not work.

PS C:\> icacls.exe --% C:\Temp\Test /grant:r DOMAIN\USER:(OI)(CI)(RX)
PS C:\> icacls.exe C:\Temp\Test
C:\Temp\Test    BUILTIN\Administrators:(OI)(CI)(F)
                NT AUTHORITY\SYSTEM:(OI)(CI)(F)
                DOMAIN\USER:(OI)(IO)(RX)
                DOMAIN\USER:(CI)(RX)
                DOMAIN\USER:(OI)(CI)(F)

As you can see, the permission was added and not replaced. Is there a way to replace the permissions with icacls.exe?

Answer 1

cacls.exe provides the parameter /P to achieve the replacement (see here).

cacls.exe C:\Temp\Test /E /P DOMAIN\USER:F

This one would work but then I struggled about the special permissions (DOMAIN\USER2:(OI)(CI)(IO)(M))

So I wrote some PowerShell code to achieve the same with icacls.exe.
Before granting the new explicit permission, the old one will be removed with /remove:g.

$FolderPath = 'C:\Temp\Test'
$NewPermission = @('DOMAIN\USER1:(OI)(CI)(F)', 'DOMAIN\USER2:(OI)(CI)(RX,W)', 'DOMAIN\USER2:(OI)(CI)(IO)(M)')

$IcaclsOutput = icacls.exe "$FolderPath"
$InheritedPermission = @()
$InheritedPermission = foreach ($Line in $IcaclsOutput)
{
    #Check if last line
    if ($Line -eq '')
    {
        break
    }

    #Get inherited permissions
    $Permission = ''
    $Permission = $Line.Substring($FolderPath.Length + 1, $Line.Length - ($FolderPath.Length + 1))
    if ($Permission -notlike '*(I)*')
    {
        $Permission.Split(':')[0]
    }
}

$InheritedPermission = $InheritedPermission | Sort-Object -Unique

#Set new permission
if ($InheritedPermission.Count -ne 0)
{
    #Remove granted explicit permissions and add new on 
    icacls.exe "$FolderPath " /remove:g ($InheritedPermission) /grant:r ($NewPermission)
}
else
{
    #Add new one
    icacls.exe "$FolderPath " /grant:r ($NewPermission)
}