Virtual disk shrinking must be disabled on the virtual machine (VM).

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-256453	VMCH-70-000004	SV-256453r886402_rule		Medium

Description
Shrinking a virtual disk reclaims unused space in it. If there is empty space in the disk, this process reduces the amount of space the virtual disk occupies on the host drive. Normal users and processes (those without root or administrator privileges) within virtual machines have the capability to invoke this procedure. However, if this is done repeatedly, the virtual disk can become unavailable while this shrinking is being performed, effectively causing a denial of service. In most datacenter environments, disk shrinking is not done, so this feature must be disabled. Repeated disk shrinking can make a virtual disk unavailable. The capability to shrink is available to nonadministrative users operating within the VM's guest operating system.

Description

Shrinking a virtual disk reclaims unused space in it. If there is empty space in the disk, this process reduces the amount of space the virtual disk occupies on the host drive. Normal users and processes (those without root or administrator privileges) within virtual machines have the capability to invoke this procedure. However, if this is done repeatedly, the virtual disk can become unavailable while this shrinking is being performed, effectively causing a denial of service. In most datacenter environments, disk shrinking is not done, so this feature must be disabled. Repeated disk shrinking can make a virtual disk unavailable. The capability to shrink is available to nonadministrative users operating within the VM's guest operating system.

STIG	Date
VMware vSphere 7.0 Virtual Machine Security Technical Implementation Guide	2023-02-27

Details

Check Text ( C-60128r886400_chk )
From the vSphere Client, right-click the Virtual Machine and go to Edit Settings >> VM Options >> Advanced >> Configuration Parameters >> Edit Configuration. Verify the "isolation.tools.diskShrink.disable" value is set to "true". or From a PowerCLI command prompt while connected to the ESXi host or vCenter server, run the following command: Get-VM "VM Name" \| Get-AdvancedSetting -Name isolation.tools.diskShrink.disable If the virtual machine advanced setting "isolation.tools.diskShrink.disable" does not exist or is not set to "true", this is a finding.

Check Text ( C-60128r886400_chk )

From the vSphere Client, right-click the Virtual Machine and go to Edit Settings >> VM Options >> Advanced >> Configuration Parameters >> Edit Configuration.

Verify the "isolation.tools.diskShrink.disable" value is set to "true".

or

From a PowerCLI command prompt while connected to the ESXi host or vCenter server, run the following command:

Get-VM "VM Name" | Get-AdvancedSetting -Name isolation.tools.diskShrink.disable

If the virtual machine advanced setting "isolation.tools.diskShrink.disable" does not exist or is not set to "true", this is a finding.

Fix Text (F-60071r886401_fix)
From the vSphere Client, right-click the Virtual Machine and go to Edit Settings >> VM Options >> Advanced >> Configuration Parameters >> Edit Configuration. Find the "isolation.tools.diskShrink.disable" value and set it to "true". If the setting does not exist, add the Name and Value setting at the bottom of screen. Note: The VM must be powered off to configure the advanced settings through the vSphere Client. Therefore, it is recommended to configure these settings with PowerCLI as this can be done while the VM is powered on. Settings do not take effect via either method until the virtual machine is cold started, not rebooted. or From a PowerCLI command prompt while connected to the ESXi host or vCenter server, run the provided commands as shown below. If the setting does not exist, run: Get-VM "VM Name" \| New-AdvancedSetting -Name isolation.tools.diskShrink.disable -Value true If the setting exists, run: Get-VM "VM Name" \| Get-AdvancedSetting -Name isolation.tools.diskShrink.disable \| Set-AdvancedSetting -Value true

Fix Text (F-60071r886401_fix)

From the vSphere Client, right-click the Virtual Machine and go to Edit Settings >> VM Options >> Advanced >> Configuration Parameters >> Edit Configuration.

Find the "isolation.tools.diskShrink.disable" value and set it to "true".

If the setting does not exist, add the Name and Value setting at the bottom of screen.

Note: The VM must be powered off to configure the advanced settings through the vSphere Client. Therefore, it is recommended to configure these settings with PowerCLI as this can be done while the VM is powered on. Settings do not take effect via either method until the virtual machine is cold started, not rebooted.

or

From a PowerCLI command prompt while connected to the ESXi host or vCenter server, run the provided commands as shown below.

If the setting does not exist, run:

Get-VM "VM Name" | New-AdvancedSetting -Name isolation.tools.diskShrink.disable -Value true

If the setting exists, run:

Get-VM "VM Name" | Get-AdvancedSetting -Name isolation.tools.diskShrink.disable | Set-AdvancedSetting -Value true