Add-PoShEndpointAccess.ps1

#========================================================================
# Created By: Anders Wahlqvist
# Website: DollarUnderscore (http://dollarunderscore.azurewebsites.net)
#========================================================================

function Add-PoShEndpointAccess
{
    <#
    .Synopsis
       Adds a group or user to a PowerShell (WinRM) endpoint to allow remote management.

    .DESCRIPTION
       This function will edit the SDDL of a PowerShell (WinRM) endpoint to 
       allow remote management for the specified account/group.

       If you run this against a remote computer, CredSSP needs to be enabled and you need
       to restart the WinRM-service manually afterwards (this function uses WinRM to connect
       to the remote machine, which is why it will not restart the service itself).

    .PARAMETER SamAccountName
       The SamAccount name of the user or group that you want to give access to. Could also be in the form
       domain\SamAccountName, for example contoso\Administrator.

    .PARAMETER ComputerName
       Specifies the computer on which the command runs. The default is the local computer.

    .PARAMETER EndpointName
       Specifies then name of the WinRM endpoint you want to configure, the default is Microsoft.PowerShell.

    .EXAMPLE
       Add-PoShEndpointAccess -SamAccountName "contoso\PoShUsers" -ComputerName MyPoShEndpoint.contoso.com

    #>

    [CmdletBinding()]
    Param
    (
        [Parameter(Mandatory=$true,
                   ValueFromPipelineByPropertyName=$true)]
        $SamAccountName,

        [Parameter(Mandatory=$false)]
        $ComputerName = '.',

        [Parameter(Mandatory=$false)]
        $EndpointName = 'Microsoft.PowerShell'
    )

    Begin { }

    Process {
        if ($ComputerName -eq '.' -OR $ComputerName -eq "$($env:COMPUTERNAME)") {
                $IdentityObject = New-Object Security.Principal.NTAccount $SamAccountName
                try {
                    $sid = $IdentityObject.Translate([Security.Principal.SecurityIdentifier]).Value
                }
                catch {
                    throw "Failed to translate $SamAccountName to a valid SID."
                }

                try {
                    $PSSConfig = Get-PSSessionConfiguration -Name $EndpointName -ErrorAction Stop
                }
                catch {
                    if ($_.Tostring() -like '*access is denied*') {
                        throw 'You need to have Admin-access to run this command!'
                    }
                }

                $existingSDDL = $PSSConfig.SecurityDescriptorSDDL
                $isContainer = $false
                $isDS = $false

                $SecurityDescriptor = New-Object -TypeName Security.AccessControl.CommonSecurityDescriptor -ArgumentList $isContainer,$isDS, $existingSDDL
                $accessType = 'Allow'
                $accessMask = 268435456
                $inheritanceFlags = 'none'
                $propagationFlags = 'none'
                $SecurityDescriptor.DiscretionaryAcl.AddAccess($accessType,$sid,$accessMask,$inheritanceFlags,$propagationFlags)

                $null = Set-PSSessionConfiguration -Name $EndpointName -SecurityDescriptorSddl ($SecurityDescriptor.GetSddlForm('All')) -Confirm:$false -Force

        }
        else {
            Invoke-Command -ArgumentList $SamAccountName,$EndpointName -ScriptBlock {
                $IdentityObject = New-Object Security.Principal.NTAccount $args[0]
                $EndpointName = $args[1]

                try {
                    $sid = $IdentityObject.Translate([Security.Principal.SecurityIdentifier]).Value
                }
                catch {
                    throw "Failed to translate $($args[0]) to a valid SID."
                }

                try {
                    $PSSConfig = Get-PSSessionConfiguration -Name $EndpointName -ErrorAction Stop
                }
                catch {
                    if ($_.Tostring() -like '*access is denied*') {
                        throw 'You need to have Admin-access and enable CredSSP to run this command remotely!'
                    }
                }

                $existingSDDL = $PSSConfig.SecurityDescriptorSDDL
                $isContainer = $false
                $isDS = $false

                $SecurityDescriptor = New-Object -TypeName Security.AccessControl.CommonSecurityDescriptor -ArgumentList $isContainer,$isDS, $existingSDDL
                $accessType = 'Allow'
                $accessMask = 268435456
                $inheritanceFlags = 'none'
                $propagationFlags = 'none'
                $SecurityDescriptor.DiscretionaryAcl.AddAccess($accessType,$sid,$accessMask,$inheritanceFlags,$propagationFlags)

                $null = Set-PSSessionConfiguration -Name $EndpointName -SecurityDescriptorSddl ($SecurityDescriptor.GetSddlForm('All')) -Confirm:$false -Force -NoServiceRestart

            } -ComputerName $ComputerName
        }
    }

    End { }
}