Windows – Permissions to create files and folders but only modify owned files

ownershippermissionswindowswindows-server

I want to set permissions on a folder in which every local user should be able to:

Create new files or folders
But only a file's owner should be able to modify it or delete it

Since we need the Create Files/ Write Data, Create Folders/ Append Data and Write Attributes permissions in order to create files, how do I prevent users from modifying the file of another owner? Further, with Write Attributes allowed, every modification (except deletion) is permitted. But if I disable this permission, I can not create files.

What permissions should I be using?

Best Answer

The keys you're missing are the CREATOR OWNER identity and the "Apply To" setting.

Apply the following permissions to your shared folder to allow the Everyone identity to create files & folders, but only a file or folder's* owner (CREATOR OWNER identity) to edit/rename/delete it:

+---------------+--------------------------------+----------------------+
| Identity      | Permissions                    | Apply To             |
+---------------+--------------------------------+----------------------+
| Everyone      | Read & Execute                 | This folder,         |
|               |                                | subfolders and files |
+---------------+--------------------------------+----------------------+
| Everyone      | - Create files / write data    | This folder and      |
|               | - Create folders / append data | subfolders           |
+---------------+--------------------------------+----------------------+
| CREATOR OWNER | Full control                   | Files only           |
+---------------+--------------------------------+----------------------+
| CREATOR OWNER | Delete                         | Subfolders           |
|               |                                | only                 |
+---------------+--------------------------------+----------------------+

What we're doing here is granting Everyone enough permissions to Read everything in the folder and create files & folders, but that's it. Then the CREATOR OWNER permissions take over. When an object is created, Windows applies any permissions granted to the CREATOR OWNER identity to the object's creator.

So Full Control on Files only allows the creator of a file to do anything with it he wishes. The Delete on "Subfolders only" is a bit more obscure; this is necessary to allow the creator of a folder to 1) Rename, and 2) Delete it. However, if a folder owner attempts to delete a folder that contains files or folders he does not own, then the delete operation will fail.

*These permissions allow modifying folders owned by a user, which you did not specifically request. However, if you don't allow this, then users can create a folder but not rename it. This is problematic, for example, if a user creates a folder via the Windows context menu. In this case Windows first creates a folder named New Folder then prompts the user to rename it, but once it's first created the user would in fact not be able to rename it.

Related Solutions

Windows – NTFS Permissions – Create Files and Folder but prevent Deletion and Modification

Through a process of trial and error, I have found that by NOT granting 'Write Attributes', this has the effect of preventing a user from modifying/deleting existing files (which is what I want). However, I would really like an explanation as to precisely why this works.

This is a function of precisely how a file modification occurs. When you modify a file, the operating system doesn't actually modify the file you're editing. It replaces the file you're editing with the copy you changed. So, essentially, a file modification takes a copy of the original file, loads it into memory (where you modify it), deletes the original file, and creates a new file with the same name in the same place. This is why NTFS Delete permissions are required to modify files - in fact, if you check the Advanced permissions on an NTFS object, there is no Modify permission - a modification is really just a delete and a write.

So, in order to create that new copy of a file, it has to write the file attributes of this new file... and, of course, writing attributes requires the Write attributes NTFS permission. So that is why you can't modify a file without having the Write attributes NTFS permission.

Specifically, thanks to a chat with Fitzroy, the NTFS file attribute that needs to be written under the user's security context (that can't be, without the Write Attributes permission), when modifying a file, but not when creating a completely new one, would be the file's LastModificationTime. This is a part of the Standard Information attribute, according to one of the Microsoft Core Team developers.

Windows – How to prevent users from deleting one folder, while still giving them modify permissions to other files and folders

I am trying to prevent users from accidentally deleting a certain folder in a parent folder, while still giving them modify permission on all other files and folders in the parent folder. But they should be also able to modify files and folders in this certain folder

Prevent Folder Deletion or inadvertent Drag and Drop with NTFS security

If you want to prevent a specific folder from being deleted or dragged and dropped elsewhere, even if it has elevated implicit permissions, you can set an explicit DENY to the FOLDER ONLY for the user account or security group which you want to prevent this action from being performed.

You can complete this folder security lock down using ICACLS with a local path (e.g C:\Path\FolderA\FolderE) or a UNC path (e.g \\server\share\FolderA\FolderE).

Example ICACLS syntax to run from an elevated command prompt

ICACLS "\\server\share\FolderA\FolderE" /deny "<UserOrGroupNameToDeny>":(DE)

Permissions Used

/deny user:permission
   Explicitly deny the specified user access rights.
   This will also remove any explicit grant of the 
   same permissions to the same user.

perm is a permission mask and can be specified in one of two forms:
   a comma-separated list in parentheses of specific rights:
         DE - delete

What this does

Running the above with those options in that syntax will set an explicit DENY to the NTFS DELETE permission on that FOLDER ONLY to that specific user account of security group.

You can confirm the deny permissions to the folder for the user account or security group by:

right-click the folder you've used in the command,
Select the Security tab,
In the Group or user name: area scroll to or select and highlight the account or group you've used in the command,
In the Permissions for Administrators area you will see the NTFS permission attributes for Allow and Deny
You'll see a check mark in the DENY column of the special permissions row for the account or group you've used in the command

Select Advanced and go to the Permissions tab
Check for the Name (or Principal) value that you used in command, for DENY in the Type field
The Permissions (or Access) field should show Delete and the Apply to (or Applies to) will show this folder only

NOTES

Please note that unchecking an ALLOW DELETE attribute is not the same as leaving that in place as-is and then creating a separate NTFS ACL rule for this same security group or user account saying to explicitly DENY the DELETE security.

This solution does NOT disallow DELETE this way

(WRONG)