# Cis GCP Cos 5.5

> Ensure access to the su command is restricted

- Skill: `cyberstrikeus/cis-gcp-cos-5-5` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-gcp-cos-5-5`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-gcp-cos-5-5/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-gcp-cos-5-5

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# 5.5 Ensure access to the su command is restricted (Automated)

## Description

The `su` command allows a user to run a command or shell as another user. The program has been superseded by `sudo`, which allows for more granular control over privileged access. Normally, the `su` command can be executed by any user. By uncommenting the `pam_wheel.so` statement in `/etc/pam.d/su`, the `su` command will only allow users in the wheel group to execute `su`.

## Rationale

Restricting the use of `su`, and using `sudo` in its place, provides system administrators better control of the escalation of user privileges to execute privileged commands. The sudo utility also provides a better logging and audit mechanism, as it can log each command executed via `sudo`, whereas `su` can only record that a user executed the `su` program.

## Audit Procedure

Run the following command and verify output includes matching line:

```bash
# grep pam_wheel.so /etc/pam.d/su
auth required pam_wheel.so use_uid
```

Run the following command and verify users in `wheel` group match site policy:

```bash
# grep wheel /etc/group
wheel:!:10:root,<user list>
```

## Expected Result

The `/etc/pam.d/su` file should contain `auth required pam_wheel.so use_uid` and the wheel group in `/etc/group` should only contain authorized users.

## Remediation

Add the following line to the `/etc/pam.d/su` file:

```
auth required pam_wheel.so use_uid
```

Create a comma separated list of users in the wheel statement in the `/etc/group` file:

```
wheel:!:10:root,<user list>
```

`/etc` is stateless on Container-Optimized OS. Therefore, `/etc` cannot be used to make these changes persistent across reboots. The steps mentioned above needs to be performed after every boot.

## Profile

- Level 1 - Server