Set-WmiNamespaceSecurity.ps1

# Copyright (c) Microsoft Corporation.  All rights reserved. 
# For personal use only.  Provided AS IS and WITH ALL FAULTS.

# Set-WmiNamespaceSecurity.ps1
# Example: Set-WmiNamespaceSecurity root/cimv2 add steve Enable,RemoteAccess

# https://blogs.msdn.microsoft.com/wmi/2009/07/27/scripting-wmi-namespace-security-part-3-of-3/

Param (
    [parameter(Mandatory=$true,Position=0)][string] $namespace,
    [parameter(Mandatory=$true,Position=1)][string] $operation,
    [parameter(Mandatory=$true,Position=2)][string] $account,
    [parameter(Position=3)][string[]] $permissions = $null,
    [bool] $allowInherit = $false,
    [bool] $deny = $false,
    [string] $computerName = '.',
    [System.Management.Automation.PSCredential] $credential = $null
)
   
Process {
    $ErrorActionPreference = 'Stop'
 
    Function Get-AccessMaskFromPermission($permissions) {
        $WBEM_ENABLE = 1
        $WBEM_METHOD_EXECUTE = 2
        $WBEM_FULL_WRITE_REP = 4
        $WBEM_PARTIAL_WRITE_REP = 8
        $WBEM_WRITE_PROVIDER = 0x10
        $WBEM_REMOTE_ACCESS = 0x20
        $WBEM_RIGHT_SUBSCRIBE = 0x40
        $WBEM_RIGHT_PUBLISH = 0x80
        $READ_CONTROL = 0x20000
        $WRITE_DAC = 0x40000

        $WBEM_RIGHTS_FLAGS = $WBEM_ENABLE,$WBEM_METHOD_EXECUTE,$WBEM_FULL_WRITE_REP,$WBEM_PARTIAL_WRITE_REP,$WBEM_WRITE_PROVIDER,$WBEM_REMOTE_ACCESS,$READ_CONTROL,$WRITE_DAC
        $WBEM_RIGHTS_STRINGS = 'Enable','MethodExecute','FullWrite','PartialWrite','ProviderWrite','RemoteAccess','ReadSecurity','WriteSecurity'
 
        $permissionTable = @{}
 
        for ($i = 0; $i -lt $WBEM_RIGHTS_FLAGS.Length; $i++) {

            $permissionTable.Add($WBEM_RIGHTS_STRINGS[$i].ToLower(),$WBEM_RIGHTS_FLAGS[$i])
        }

        $accessMask = 0

        foreach ($permission in $permissions) {
            if (-not $permissionTable.ContainsKey($permission.ToLower())) {
                throw "Unknown permission: $permission`nValid permissions: $($permissionTable.Keys)"
            }
            $accessMask += $permissionTable[$permission.ToLower()]
        }
       
        $accessMask
    }
 
    if ($PSBoundParameters.ContainsKey('Credential')) {
        $remoteparams = @{ComputerName=$computer;Credential=$credential}
    } else {
        $remoteparams = @{}
    }
       
    $invokeparams = @{Namespace=$namespace;Path='__systemsecurity=@'} + $remoteParams
 
    $output = Invoke-WmiMethod @invokeparams -Name GetSecurityDescriptor
    if ($output.ReturnValue -ne 0) {
        throw "GetSecurityDescriptor failed: $($output.ReturnValue)"
    }

    $acl = $output.Descriptor

    $computerName = (Get-WmiObject @remoteparams Win32_ComputerSystem).Name
   
    if ($account.Contains(‘\’)) {
        $domainaccount = $account.Split(‘\’)
        $domain = $domainaccount[0]
        if (($domain -eq '.') -or ($domain -eq 'BUILTIN')) {
            $domain = $computerName
        }
        $accountname = $domainaccount[1]
    } elseif ($account.Contains('@')) {
        $domainaccount = $account.Split('@')
        $domain = $domainaccount[1].Split('.')[0]
        $accountname = $domainaccount[0]
    } else {
        $domain = $computerName
        $accountname = $account
    }

    $getparams = @{Class='Win32_Account';Filter="Domain='$domain' and Name='$accountname'"} + $remoteParams
    $win32account = Get-WmiObject @getparams
 
    if ($win32account -eq $null) {
        throw "Account was not found: $account"
    }

    switch ($operation) {
        'add' {
            if ($permissions -eq $null) {
                throw '-Permissions must be specified for an add operation'
            }
            $accessMask = Get-AccessMaskFromPermission($permissions)
   
            $ace = (New-Object System.Management.ManagementClass('win32_Ace')).CreateInstance()
            $ace.AccessMask = $accessMask

            $CONTAINER_INHERIT_ACE_FLAG = 0x2

            if ($allowInherit) {
                $ace.AceFlags = $CONTAINER_INHERIT_ACE_FLAG
            } else {
                $ace.AceFlags = 0
            }
                       
            $trustee = (New-Object System.Management.ManagementClass('win32_Trustee')).CreateInstance()
            $trustee.SidString = $win32account.Sid
            $ace.Trustee = $trustee
           
            $ACCESS_ALLOWED_ACE_TYPE = 0x0
            $ACCESS_DENIED_ACE_TYPE = 0x1
 
            if ($deny) {
                $ace.AceType = $ACCESS_DENIED_ACE_TYPE
            } else {
                $ace.AceType = $ACCESS_ALLOWED_ACE_TYPE
            }
 
            $acl.DACL += $ace.psobject.immediateBaseObject
        }
       
        'delete' {
            if ($permissions -ne $null) {
                throw 'Permissions cannot be specified for a delete operation'
            }

            [System.Management.ManagementBaseObject[]]$newDACL = @()
            foreach ($ace in $acl.DACL) {
                if ($ace.Trustee.SidString -ne $win32account.Sid) {
                    $newDACL += $ace.psobject.immediateBaseObject
                }
            }
 
            $acl.DACL = $newDACL.psobject.immediateBaseObject
        }
       
        default {
            throw "Unknown operation: $operation`nAllowed operations: add delete"
        }
    }
 
    $setparams = @{Name='SetSecurityDescriptor';ArgumentList=$acl.psobject.immediateBaseObject} + $invokeParams
 
    $output = Invoke-WmiMethod @setparams
    if ($output.ReturnValue -ne 0) {
        throw "SetSecurityDescriptor failed: $($output.ReturnValue)"
    }
}