cis-gke-v180-4-1-10

name	cis-gke-v180-4.1.10
description	Avoid non-default bindings to system:authenticated (Automated)
category	cis-gke
version	1.8.0
author	cyberstrike-official
tags	["cis","gke","kubernetes","gcp","rbac","service-accounts","cluster-roles"]
cis_id	4.1.10
cis_benchmark	CIS Google Kubernetes Engine (GKE) Benchmark v1.8.0
tech_stack	["kubernetes","gcp","gke"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

4.1.10 Avoid non-default bindings to system:authenticated (Automated)

Profile Applicability

• Level 1

Description

Avoid non-default ClusterRoleBindings and RoleBindings with the group system:authenticated, except the ClusterRoleBindings system:basic-user, system:discovery, and system:public-info-viewer.

Google's approach to authentication is to make authenticating to Google Cloud and GKE as simple and secure as possible without adding complex configuration steps. The group system:authenticated includes all users with a Google account, which includes all Gmail accounts. Consider your authorization controls with this extended group scope when granting permissions. Thus, group system:authenticated is not recommended for non-default use.

Rationale

GKE assigns the group system:authenticated to API server requests made by any user who is signed in with a Google Account, including all Gmail accounts. In practice, this isn't meaningfully different from system:unauthenticated because anyone can create a Google Account.

Binding a role to the group system:authenticated gives any user with a Google Account, including all Gmail accounts, the permissions granted by that role and is strongly discouraged.

Impact

Authenticated users in group system:authenticated should be treated similarly to users in system:unauthenticated, having privileges and permissions associated with roles associated with the configured bindings.

Care should be taken before removing any non-default clusterrolebindings or rolebindings from the environment to ensure they were not required for operation of the cluster. Leverage a more specific and authenticated user for cluster operations.

Audit

Use the following command to confirm there are no non-default ClusterRoleBindings to system:authenticated:

$ kubectl get clusterrolebindings -o json  | jq -r '["Name"], ["-----"], (.items[] | select((.subjects | length) > 0) | select(any(.subjects[]; .name == "system:unauthenticated")) | [.metadata.namespace, .metadata.name]) | @tsv'

Only the following default ClusterRoleBindings should be displayed:

Name
-----
        system:basic-user
        system:discovery
        system:public-info-viewer