lacework-global-268
Ensure 'Enable Connecting to Serial Ports' Is Not Enabled for VM Instance (Automated)
Profile Applicability
• Level 1
Description
Interacting with a serial port is often referred to as the serial console, which is similar to using a terminal window, in that input and output is entirely in text mode and there is no graphical interface or mouse support.
If you enable the interactive serial console on an instance, clients can attempt to connect to that instance from any IP address. Therefore, you should disable interactive serial console support.
Rationale
A virtual machine instance has four virtual serial ports. Interacting with a serial port is similar to using a terminal window, in that input and output is entirely in text mode and there is no graphical interface or mouse support. The instance's operating system, BIOS, and other system-level entities often write output to the serial ports, and can accept input such as commands or answers to prompts. Typically, these system-level entities use the first serial port (port 1) and serial port 1 is often referred to as the serial console.
The interactive serial console does not support IP-based access restrictions such as IP whitelists. If you enable the interactive serial console on an instance, clients can attempt to connect to that instance from any IP address. This allows anybody to connect to that instance if they know the correct SSH key, username, project ID, zone, and instance name.
Therefore interactive serial console support should be disabled.
Audit
From Console:
- Login to Google Cloud console
- Go to Computer Engine
- Go to VM instances
- Click on the Specific VM
- Ensure
Enable connecting to serial ports
belowRemote access
block is unselected.
From Command Line:
Ensure the below command's output shows null
:
gcloud compute instances describe <instance_name> --zone=<region> --format="json(metadata.items[].key,metadata.items[].value)"
or key
and value
properties from below command's json response are equal to serial-port-enable
and 0
or false
respectively.
{
"metadata": {
"items": [
{
"key": "serial-port-enable",
"value": "0"
}
]
}
}
Remediation
From Console:
- Login to Google Cloud console.
- Go to Computer Engine.
- Go to VM instances.
- Click the Specific VM.
- Click
Edit
. - Unselect
Enable connecting to serial ports
belowRemote access block
. - Click
Save
.
From Command Line:
Use the below command to disable
gcloud compute instances add-metadata <instance_name> --zone=<zone> --metadata=serial-port-enable=false
or
gcloud compute instances add-metadata <instance_name> --zone=<zone> --metadata=serial-port-enable=0
Prevention:
You can prevent VMs from having serial port access enable by Disable VM serial port access
organization policy:
https://console.cloud.google.com/iam-admin/orgpolicies/compute-disableSerialPortAccess.
References
https://cloud.google.com/compute/docs/instances/interacting-with-serial-console