cis-bind-v100-10-4

name	cis-bind-v100-10-4
description	Ensure Only the Necessary SELinux Booleans are Enabled (Automated)
category	cis-bind
version	1.0
author	cyberstrike-official
tags	["cis","bind","dns","isc-bind","bind9","selinux"]
cis_id	10.4
cis_benchmark	CIS ISC BIND DNS Server 9.11 Benchmark v1.0.0
tech_stack	["bind","isc-bind","dns","linux","selinux"]
cwe_ids	["CWE-732"]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS 10.4 — Ensure Only the Necessary SELinux Booleans are Enabled

Profile Applicability

• Caching Only Name Server Level 2
• Authoritative Name Server Level 2

Description

SELinux booleans allow or disallow specific behaviors. There are two boolean variables specific to the ISC BIND DNS server:

• named_tcp_bind_http_port - Allow named to tcp bind http port
• named_write_master_zones - Allow named to write master zones

The named_tcp_bind_http_port would allow enabling the BIND statistics http channel which is not recommended. The named_write_master_zones allows BIND to update the master files, which is necessary when dynamic updates are performed, or the server is automatically maintaining DNSSEC digital signatures.

Rationale

Enabling only the necessary named related booleans provides a defense in depth approach, that will deny actions that are not in use or expected.

Impact

Not specified.

Audit Procedure

Perform the following steps to determine if the recommended state is implemented:

Use getsebool to verify the named_tcp_bind_http_port boolean has a value of off.

# getsebool named_tcp_bind_http_port
named_tcp_bind_http_port --> off

The named_write_master_zones boolean is not audited as many BIND servers will require the boolean to be enabled.

Remediation

Perform the following to implement the recommended state:

Disable the SELinux boolean using the setsebool command as shown below with the -P option to make the change persistent.

# setsebool -P named_tcp_bind_http_port off

Default Value

The default value for named_tcp_bind_http_port is off.

References

None listed in benchmark.

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v7	9.2 Ensure Only Approved Ports, Protocols and Services Are Running	N	Y	Y

MITRE ATT&CK Mappings