cis-nginx-v300-2-3-1

DevOps & Security

Ensure NGINX directories and files are owned by root (Manual)

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CIS 2.3.1 — Ensure NGINX directories and files are owned by root

Profile Applicability

Level 1 - Webserver
Level 1 - Proxy
Level 1 - Loadbalancer

Description

The NGINX configuration directory and all contained files must be owned by the root user and group to prevent unauthorized modification.

Rationale

The NGINX configuration controls the security posture of the web server. If a non-privileged user (including the nginx worker user) can modify these files, they can trivially escalate privileges (e.g., by loading a malicious module or changing the user directive to root). Ensuring that only root owns these files guarantees that configuration changes require administrative privileges.

Impact

None. The NGINX master process runs as root and can read these files. The worker processes (running as nginx) do not need write access to the configuration.

Audit Procedure

1. Identify Configuration Directory:

Run nginx -V and look for --conf-path to find the main configuration file location (e.g., /etc/nginx/nginx.conf). The directory containing this file is the target.

2. Verify Ownership:

Run the following command to audit the ownership of the configuration directory and its contents:

find /etc/nginx -name "*" \( -not -user root -o -not -group root \) -exec ls -ld {} \;

(Replace /etc/nginx with the actual configuration path in case it is different)

Evaluation:

PASS: The command produces no output. All files are owned by root:root.
FAIL: The command lists files owned by other users (e.g., nginx or a developer account).

Remediation

Set the ownership of the NGINX configuration directory and files to root:

chown -R root:root /etc/nginx

(Replace /etc/nginx with the actual configuration path in case it is different)

Note: Ensure that this does not break access to specific files if you have a custom setup where external processes need write access.

Default Value

The default ownership and group for nginx is root.

References

https://nginx.org/en/docs/ngx_core_module.html

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.3 Configure Data Access Control Lists	Y	Y	Y
v7	14.6 Protect Information through Access Control Lists	Y	Y	Y

MITRE ATT&CK Mappings

Tactic	Technique
Persistence	T1222 - File and Directory Permissions Modification

Profile

Level 1 - Webserver
Level 1 - Proxy
Level 1 - Loadbalancer