cis-gcp-foundations-3-9

name	cis-gcp-foundations-3.9
description	Ensure No HTTPS or SSL Proxy Load Balancers Permit SSL Policies With Weak Cipher Suites
category	cis-gcp-foundations
version	4.0.0
author	cyberstrike-official
tags	["cis","gcp","networking","ssl","load-balancer"]
cis_id	3.9
cis_benchmark	CIS Google Cloud Platform Foundation Benchmark v4.0.0
tech_stack	["gcp"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

3.9 Ensure No HTTPS or SSL Proxy Load Balancers Permit SSL Policies With Weak Cipher Suites (Manual)

Profile Applicability

• Level 1

Description

Secure Sockets Layer (SSL) policies determine what port Transport Layer Security (TLS) features clients are permitted to use when connecting to load balancers. To prevent usage of insecure features, SSL policies should use (a) at least TLS 1.2 with the MODERN profile; or (b) the RESTRICTED profile, because it effectively requires clients to use TLS 1.2 regardless of the chosen minimum TLS version; or (3) a CUSTOM profile that does not support any of the following features:

TLS_RSA_WITH_AES_128_GCM_SHA256
TLS_RSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_RSA_WITH_AES_256_CBC_SHA
TLS_RSA_WITH_3DES_EDE_CBC_SHA

Rationale

Load balancers are used to efficiently distribute traffic across multiple servers. Both SSL proxy and HTTPS load balancers are external load balancers, meaning they distribute traffic from the Internet to a GCP network. GCP customers can configure load balancer SSL policies with a minimum TLS version (1.0, 1.1, or 1.2) that clients can use to establish a connection, along with a profile (Compatible, Modern, Restricted, or Custom) that specifies permissible cipher suites. To comply with users using outdated protocols, GCP load balancers can be configured to permit insecure cipher suites. In fact, the GCP default SSL policy uses a minimum TLS version of 1.0 and a Compatible profile, which allows the widest range of insecure cipher suites. As a result, it is easy for customers to configure a load balancer without even knowing that they are permitting outdated cipher suites.

Impact

Creating more secure SSL policies can prevent clients using older TLS versions from establishing a connection.

Audit

From Google Cloud Console

1. See all load balancers by visiting https://console.cloud.google.com/net-services/loadbalancing/loadBalancers/list.
2. For each load balancer for SSL (Proxy) or HTTPS, click on its name to go the Load balancer details page.
3. Ensure that each target proxy entry in the Frontend table has an SSL Policy configured.
4. Click on each SSL policy to go to its SSL policy details page.
5. Ensure that the SSL policy satisfies one of the following conditions:
   • has a Min TLS set to TLS 1.2 and Profile set to Modern profile, or