VMware Server 2.0 Security - Access, Roles and Permissions

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Whilst there has been much coverage of the advantages offered by virtualization solutions such as VMware Server, it is only relatively recently that attention has been given to the potential security risks associated with deploying such technology. Whilst the guest operating systems running in virtual machines are, arguably, no less vulnerable than those running on physical hardware (unless the underlying hypervisor itself is in some way compromised), unauthorized access to the virtualization management interface gives an intruder the ability to power off and even permanently delete mission critical systems and data.

The goal of this chapter of VMware Server 2.0 Essentials is to provide an overview of the security access and permissions controls offered by VMware Server 2.0




VMware Server 2.0 Access Controls

The security features of VMware Server are designed to both control access to the VI Web Access management interface, and to restrict the activities that may be performed once a user has successfully logged in.

Access to the VI Web Access interface is controlled by the login screen which is present when a web browser connects to the VMware Server system. Rather than duplicate functionality, VMware Server leverages the login and password mechanism offered by the host operating system. This level of security works in conjunction with VMware Server specific roles and permissions, defined by an administrator, which govern permitted actions once the user is logged in.

As such, a user can only log into the VI Web Access interface if they have a valid login and password on the system hosting VMware Server 2.0. In addition, the user must have been assigned the appropriate login permissions by a VMware Server administrator (by default, all users on the host system are configured to have no access). The first administrator was created during the VMware Server 2.0 installation process, though other users may be assigned administrative privileges through the VI Web Access interface.


Understanding Privileges, Roles and Permissions

Once a user has successfully logged into the VI Web Access interface, the next level of security involves the use of privileges, roles and permissions to control the actions which the user can perform and the information to which access is permitted.

A privilege provides the right to perform a particular task on a specific VMware Server object within an object category. For example, a user may be given the privilege to power off a virtual machine.

Roles are essentially a number of privileges grouped together and given a name which can then be assigned to users and groups on specific objects or categories. For example, a group of privileges may be bundled into a role for trainee administrators which allows them power virtual machines on and off, but not to remove them from the inventory. VMware Server is supplied with a three pre-defined roles:

  • No Access - The default role for users other than the administrator. Denies access to the VI Web Access interface. Attempts to log in will be met with a You do not have permissions to login to the server message.
  • Read Only - Allows the user to login and view, but not change, configuration settings and virtual machine states. Access to virtual machine consoles is also denied.
  • Administrator - Provides full privileges to all aspects of VMware Server 2.0, including the ability to configure roles, permissions and privileges for all users and groups.

Obviously, a role does very little unless it is applied to a user or group of users and one or more VMware Server object. This pairing is referred to a permission. For example, assigning the read-only role to a specific user, and applying that to an inventory object is essentially creating a permission.

Creating, Modifying and Removing Roles

As previously outlined, a role is a collection of privileges brought together in a named group. It addition to the three pre-defined system it is also possible to construct custom roles from a wide range of privileges. To create a custom role, log into the VI Web Access interface as a user with administrative privileges, and select the Administration -> Manage Roles menu option to invoke the Manage Roles dialog which will list any existing roles. To create a new role, click on the Add button to launch the New Authorization Role dialog as illustrated below:


Create a new VMware Server Role


In the New Authorization Role dialog, enter a name for the new role in the field provided and then construct the role by enabling the required privileges. Note that each category may may be selected in its entirety by selecting the category. Alternatively, unfold a category sub-tree and select from individual privileges. When the required privileges have been selected, click on OK to create the new role, which the role will appear in the list under the specified name.

To modify a role, select it from the list in the Manage Roles dialog and click on the Modify button. In the Edit existing roles dialog, make the necessary changes to the privilege selections, rename the role if necessary and click on OK to commit the modifications.

An existing role may removed from the system by selecting it from the Manage Roles dialog and clicking on the Remove button. If the selected role is currently assigned to users or groups a dialog appears provided the choice to remove the role entirely together with any associated permissions, or to re-assign permissions to another pre-existing role.

Creating, Modifying and Removing Permissions