The system must limit VM logging records.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-39495	ESXI5-VM-000041	SV-51353r1_rule		Medium

Description
Use these settings to limit the total size and number of log files. Normally a new log file is created only when a host is rebooted, so the file can grow to be quite large. Ensure new log files are created more frequently by limiting the maximum size of the log files. If restricting the total size of logging data is wanted, VMware recommends saving 10 log files, each one limited to 1,000KB. Datastores are likely to be formatted with a block size of 2MB or 4MB, so a size limit too far below this size would result in unnecessary storage utilization. Each time an entry is written to the log, the size of the log is checked; if it is over the limit, the next entry is written to a new log. If the maximum number of log files already exists, when a new one is created, the oldest log file is deleted. A denial-of-service attack that avoids these limits might be attempted by writing an enormous log entry. But each log entry is limited to 4KB, so no log files are ever more than 4KB larger than the configured limit. A second option is to disable logging for the virtual machine. Disabling logging for a virtual machine makes troubleshooting challenging and support difficult. Do not consider disabling logging unless the log file rotation approach proves insufficient. Uncontrolled logging can lead to denial-of-service due to the datastore becoming filled.

Description

Use these settings to limit the total size and number of log files. Normally a new log file is created only when a host is rebooted, so the file can grow to be quite large. Ensure new log files are created more frequently by limiting the maximum size of the log files. If restricting the total size of logging data is wanted, VMware recommends saving 10 log files, each one limited to 1,000KB. Datastores are likely to be formatted with a block size of 2MB or 4MB, so a size limit too far below this size would result in unnecessary storage utilization. Each time an entry is written to the log, the size of the log is checked; if it is over the limit, the next entry is written to a new log. If the maximum number of log files already exists, when a new one is created, the oldest log file is deleted. A denial-of-service attack that avoids these limits might be attempted by writing an enormous log entry. But each log entry is limited to 4KB, so no log files are ever more than 4KB larger than the configured limit. A second option is to disable logging for the virtual machine. Disabling logging for a virtual machine makes troubleshooting challenging and support difficult. Do not consider disabling logging unless the log file rotation approach proves insufficient. Uncontrolled logging can lead to denial-of-service due to the datastore becoming filled.

STIG	Date
VMware ESXi Version 5 Virtual Machine Security Technical Implementation Guide	2015-12-03

Details

Check Text ( C-46755r2_chk )
Temporarily disable Lockdown Mode and enable the ESXi Shell via the vSphere Client. Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials. If connecting to vCenter Server, click on the desired host. Click the Configuration tab. Click Software, Security Profile, Services, Properties, ESXi Shell, and Options, respectively. Start the ESXi Shell service, where/as required. As root, log in to the ESXi Shell and locate the VM's vmx file. # find / \| grep vmx Check the VM's ".vmx" file for the correct " = " pair. keyword = log.keepOld keyval = 10 # grep "^" If the above command return is either empty or does not reflect the above keyword and keyval value(s), this is a finding. NOTE: This setting has no effect on VMs that already have logging disabled. This setting, however, will enforce the limiting of VM logging records should there be a "temporary" need to enable VM logging to troubleshoot a VM performance issue. Re-enable Lockdown Mode on the host.

Check Text ( C-46755r2_chk )

Temporarily disable Lockdown Mode and enable the ESXi Shell via the vSphere Client.

Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials.
If connecting to vCenter Server, click on the desired host.
Click the Configuration tab.
Click Software, Security Profile, Services, Properties, ESXi Shell, and Options, respectively.
Start the ESXi Shell service, where/as required.

As root, log in to the ESXi Shell and locate the VM's vmx file.
# find / | grep vmx

Check the VM's ".vmx" file for the correct " = " pair.
keyword = log.keepOld
keyval = 10
# grep "^"

If the above command return is either empty or does not reflect the above keyword and keyval value(s), this is a finding. NOTE: This setting has no effect on VMs that already have logging disabled. This setting, however, will enforce the limiting of VM logging records should there be a "temporary" need to enable VM logging to troubleshoot a VM performance issue.

Re-enable Lockdown Mode on the host.

Fix Text (F-44507r2_fix)
Configure the VM with the correct " = " pair. To edit a powered-down virtual machine's .vmx file, first remove it from vCenter Server's inventory. Manual additions to the .vmx file from ESXi will be overwritten by any registered entries stored in the vCenter Server database. Make a backup copy of the .vmx file. If the edit breaks the virtual machine, it can be rolled back to the original version of the file. Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials. If connecting to vCenter Server, click on the desired host. Click the Configuration tab. Click Storage. Right-click on the appropriate datastore and click Browse Datastore. Navigate to the folder named after the virtual machine, and locate the .vmx file. Right-click the .vmx file and click Remove from inventory. Temporarily disable Lockdown Mode and enable the ESXi Shell via the vSphere Client. Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials. If connecting to vCenter Server, click on the desired host. Click the Configuration tab. Click Software, Security Profile, Services, Properties, ESXi Shell, and Options, respectively. Start the ESXi Shell service, where/as required. As root, log in to the ESXi host and locate the VM's vmx file. # find / \| grep vmx Add the following to the VM's vmx file. keyword = "keyval" Where: keyword = log.keepOld keyval = 10 Re-enable Lockdown Mode on the host. Re-register the VM with the vCenter Server: Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials. If connecting to vCenter Server, click on the desired host. Click the Configuration tab. Click Storage. Right-click on the appropriate datastore and click Browse Datastore. Navigate to the folder named after the virtual machine, and locate the .vmx file. Right-click the .vmx file and click Add to inventory. The Add to Inventory wizard opens. Continue to follow the wizard to add the virtual machine.

Fix Text (F-44507r2_fix)

Configure the VM with the correct " = " pair.

To edit a powered-down virtual machine's .vmx file, first remove it from vCenter Server's inventory. Manual additions to the .vmx file from ESXi will be overwritten by any registered entries stored in the vCenter Server database. Make a backup copy of the .vmx file. If the edit breaks the virtual machine, it can be rolled back to the original version of the file.

Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials.
If connecting to vCenter Server, click on the desired host.
Click the Configuration tab.
Click Storage.
Right-click on the appropriate datastore and click Browse Datastore.
Navigate to the folder named after the virtual machine, and locate the .vmx file.
Right-click the .vmx file and click Remove from inventory.

Temporarily disable Lockdown Mode and enable the ESXi Shell via the vSphere Client.

Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials.
If connecting to vCenter Server, click on the desired host.
Click the Configuration tab.
Click Software, Security Profile, Services, Properties, ESXi Shell, and Options, respectively.
Start the ESXi Shell service, where/as required.

As root, log in to the ESXi host and locate the VM's vmx file.
# find / | grep vmx

Add the following to the VM's vmx file.
keyword = "keyval"

Where:
keyword = log.keepOld
keyval = 10

Re-enable Lockdown Mode on the host.

Re-register the VM with the vCenter Server:
Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials.
If connecting to vCenter Server, click on the desired host.
Click the Configuration tab.
Click Storage.
Right-click on the appropriate datastore and click Browse Datastore.
Navigate to the folder named after the virtual machine, and locate the .vmx file.
Right-click the .vmx file and click Add to inventory. The Add to Inventory wizard opens.
Continue to follow the wizard to add the virtual machine.