Setting up a Share Using Windows ACLs

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Introduction

Extended access control lists (ACL) enable you to set permissions on shares, files, and directories using Windows ACLs and applications. Samba supports shares using extended ACLs on:

  • Domain members
  • Active Directory (AD) domain controllers (DC)
  • NT4 primary domain controller (PDC)
  • NT4 backup domain controllers (BDC)
  • Standalone hosts

As an alternative to extended ACLs, you can set up shares using POSIX ACLs. For details, see Setting up a Share Using POSIX ACLs.



Preparing the Host

You need to set up Samba before you are able to create a share. Depending on what type of Samba server you require, see:


File System Support

The file system, the share will be created on, must support:

  • user and system xattr name spaces.
  • extended access control lists (ACL).

For further details, see File system support.


Samba Extended ACL Support

To create a share with extended access control list (ACL) support, the smbd service must have been built with ACL support enabled. A Samba host working as an Active Directory (AD) domain controller (DC), is always enabled with extended ACL support.

To verify if Samba has been built with ACL support, enter:

# smbd -b | grep HAVE_LIBACL
   HAVE_LIBACL

If no output is displayed:



Enable Extended ACL Support in the smb.conf File

To configure shares using extended access control lists (ACL), you must enable the support in the smb.conf file. To enable extended ACL support globally, add the following settings to the [global] section of your smb.conf file:

vfs objects = acl_xattr
map acl inherit = yes
store dos attributes = yes

Alternatively, to enable extended ACL support only for a specific share, add the parameters to the share's section.

For further details about the parameters, see the smb.conf(5) man page.


Granting the SeDiskOperatorPrivilege Privilege

Only users and groups having the SeDiskOperatorPrivilege privilege granted can configure share permissions.

To grant the privilege to the Domain Admins group, enter:

# net rpc rights grant "SAMDOM\Domain Admins" SeDiskOperatorPrivilege -U "SAMDOM\administrator"
Enter SAMDOM\administrator's password:
Successfully granted rights.

To list all users and groups having the SeDiskOperatorPrivilege privilege granted, enter:

# net rpc rights list privileges SeDiskOperatorPrivilege -U "SAMDOM\administrator"
Enter administrator's password:
SeDiskOperatorPrivilege:
  BUILTIN\Administrators
  SAMDOM\Domain Admins



Adding a Share

To share the /srv/samba/Demo/ directory using the Demo share name:

  • As the root user, create the directory:
# mkdir -p /srv/samba/Demo/
  • Add the [Demo] share definition to your smb.conf file:
[Demo]
       path = /srv/samba/Demo/
       read only = no
Further share-specific settings and file system permissions are set using the Windows utilities.
  • Reload the Samba configuration:
# smbcontrol all reload-config



Setting Share Permissions and ACLs

When you configure a share with extended access control lists (ACL) support, you set the share permissions using Windows utilities instead of adding parameters to the share section in the smb.conf file.

To set permissions and ACLs on the Demo share:

  • Log on to a Windows host using an account that has the SeDiskOperatorPrivilege privilege granted.
  • Click Start, enter Computer Management, and start the application.
  • Select Action / Connect to another computer.
  • Enter the name of the Samba host and click OK to connect the console to the host.
  • Open the System Tools / Shared Folders / Shares menu entry.
Computer Management Shares.png
  • Right-click to the share and select Properties.
  • Select the Share Permissions tab and set the share permissions. For example:
Demo Share Permissions.png
Samba stores share permissions in the /usr/local/samba/var/locks/share_info.tdb database.
  • Select the Security tab.
  • Click the Edit button and set the file system ACLs on the share's root directory. For example:
Demo Share Security.png
For details where the ACLs are stored, see File System ACLs in the Back End.
  • Click OK to close the Permissions for Demo window.
  • Click OK to store the updated settings.

For further details about configuring share permissions and ACLs, see the Windows documentation.



Setting ACLs on a Folder

To set file system permissions on a folder located on a share that uses extended access control lists (ACL):

  • Log on to a Windows host using an account that has Full control on the folder you want to modify the file system ACLs.
  • Navigate to the folder.
  • Right-click to the folder and select Properties.
  • Select the Security tab and click the Edit button.
  • Set the permission. For example:
Folder Permissions.png
For details where the ACLs are stored, see File System ACLs in the Back End.
  • Click OK to close the Permissions for Folder window.
  • Click OK to store the updated settings.

For further details about setting ACLs, see the Windows documentation.



File System ACLs in the Back End

Samba stores the file system permissions in extended file system access control lists (ACL) and in an extended attribute. For example:

  • To list the extended ACLs of the /srv/samba/Demo/ directory, enter:
# getfacl /srv/samba/Demo/
# file: srv/samba/Demo/
# owner: root
# group: root
user::rwx
user:root:rwx
group::---
group:root:---
group:domain\040users:rwx
group:domain\040admins:rwx
mask::rwx
other::---
default:user::rwx
default:user:root:rwx
default:group::---
default:group:root:---
default:group:domain\040users:rwx
default:group:domain\040admins:rwx
default:mask::rwx
default:other::---
  • To list the user.SAMBA_PAI extended attribute of the /srv/samba/Demo/ directory, enter:
# getfattr -d /srv/samba/Demo/
# file: srv/samba/Demo/
user.SAMBA_PAI=0sAgScBwAHAAABAAAAAAAAAAAAAAAC/////wABAAAAAAAAAAAAAAABEScAAAABECcAAAABAAAAAAAAAAAAAAAC/////wABAAAAAAAAAAAAAAMBEScAAAMBECcAAA==

The previous example of file system ACLs and the extended attribute is mapped to the following Windows ACLs:

Principal Permissions Applies to
Domain Users (SAMDOM\Domain Users) Modify, Read & execute, List folder contents, Read, Write (This folder, subfolders and files)
Domain Admins (SAMDOM\Domain Admins) Full control (This folder, subfolders and files)



Troubleshooting

For troubleshooting, see: