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How can I seize ownership of a directory using Powershell?

Posted on 2009-05-05
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Last Modified: 2012-05-06
I have a script that I utilized to correct errant security permissions on users home directories. The script eroors on folders where I don't have explicit permissions, however. Looking at a sampling of them, the only way I can get permission on them is to seize ownership of them, then modify the permissions appropriately, and set the Owner to the correct one. Is there a way to seize ownership via Powershell? Attached is the script that I have been using.

Thanks in advance for any help!
###
### This script will change the permissions on the immediate subfolders of \\chstor1\home 
### to give the following (By inheriting thge first 3, and explicitly setting the 4th):
### Domain Administrators: Full Control
### IT - - Helpdesk 2 : Full Control
### SVC_DataBackup : Read
### End User: Modify
###
 
$ErrorActionPreference = "Continue"
Set-Location e:\Data\Home
$Mismatches = "e:\data\home\Mismatches.txt"
$Inherit = [System.Security.AccessControl.InheritanceFlags]"ContainerInherit, ObjectInherit"
$propogation = [System.Security.AccessControl.PropagationFlags]"None"
 
if (Test-Path $Mismatches) {
Clear-Content $Mismatches
}
else {
New-Item $Mismatches -Type File
}
 
$Foldername = Get-ChildItem * | Where-Object {$_.attributes -match "Directory"}
 
foreach ($Fullpath in $Foldername) {
$ACLBase = Get-Acl e:\Data\Home\
### Uncomment the following line to verify default permissions during step debugging
#Set-Acl -Path $Fullpath -AclObject $ACLBase
$username = $Fullpath.Name
$AddACL = "advocatesinc\$username", "Modify", $Inherit, $propogation, "Allow"
$AccessRule = New-Object System.Security.AccessControl.FileSystemAccessRule $AddACL
 
### Error Handling for directories that don't have a matching username
Trap [Exception] {
  Write-Host "Error occurred, ignoring it"
  Add-Content $Mismatches "Missing account $username"
  Continue;
}
$ACLBase.SetAccessRule($AccessRule)
$ACLBase | Set-Acl $Fullpath 
}

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Question by:tilbard
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6 Comments
 
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Expert Comment

by:Chris Dent
ID: 24304221

There's a SetOwner Method of the $ACLBase object above. To use that you need to construct an IdentityReference.

Something like the below.

You should be able to happily change between possible owners as listed when you look at  the same option in the GUI.

Chris
# Create an Identity Reference for the Local Administrators Group
$LocalAdminGroup = `
  New-Object System.Security.Principal.NTAccount("BUILTIN", "Administrators")
# Call SetOwner on the current ACL
$ACLBase.SetOwner($LocalAdminGroup)
# Apply the updated ACL
Set-ACL $FullPath -AclObject $ACLBase

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Author Comment

by:tilbard
ID: 24304584
After adding that it still generates the same error regarding an Unauthorized action. After doing a bit of browsing, I found some workarounds though. Specifically by calling takeown.exe (referenced here: http://justanothersysadmin.wordpress.com/2008/03/22/take-ownership-of-files-and-folders-through-script/#more-13). While obviously not the best way to do it (it just rubs me wrong calling an external program for what should work), I'm a bit time constrained, so had to go with that for now. I'll leave the question open for now, and add the exact error it generates after it finishes with the takeown.exe method, as I still want to figure out WHY it wouldn't work (for personal knowledge if nothing else).
0
 
LVL 70

Expert Comment

by:Chris Dent
ID: 24304727

Hmmm sorry I neglected to strip my read permission prior to changing the owner. It's rather disappointing, it seems overriding ownership when you have no access is a bit of a back door, something that PowerShell seems unable to utilise.

I'll keep looking, but it's not looking all that promising.

Chris
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Author Comment

by:tilbard
ID: 24306006
One last question before I assign points (You'll get them either way though, don't worry. ;) ). When running the script, the unauthorized action error isn't being caught by the trap. Is there anyway to trap that so that I don't have to run takeown.exe against directories that don't have any trouble? As you can imagine, it adds quite a bit of time to the script if it runs it against every folder, since it has to recurse through each one. Being able to call it within the trap would speed things up quite a bit, and make the output a bit more readable.
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Accepted Solution

by:
Chris Dent earned 500 total points
ID: 24306135

We'd could trap it like this.

Chris
Set-Variable -Name "Unauthorised" -Value $False -Scope Script
Trap [System.UnauthorizedAccessException] { 
  $Script:Unauthorised = $True; Continue;
}
Get-ACL $Fullpath.FullName
If ($Script:Unauthorised) {
  # Reset Ownership Here 
}
# Otherwise carry on with setting the permissions

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Author Closing Comment

by:tilbard
ID: 31577982
Worked great, thanks!
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