# CIS-Inspired RHEL 9 Hardening Role

This role provides a practical, production-style hardening baseline for RHEL 9 and Oracle Linux 9 systems. It is inspired by CIS Benchmark controls for Red Hat Enterprise Linux 9 version 2.0.0, but it is intentionally scoped to common operational controls that infrastructure and security operations teams frequently automate.

This is not a full CIS certification implementation.

## Supported Platforms

- Red Hat Enterprise Linux 9
- Oracle Linux 9

The role fails safely on unsupported operating systems or unsupported major versions.

## Implemented Controls

- SSH daemon hardening for root login, empty passwords, password authentication, retry limits, login grace time, and client keepalive behavior.
- Removal of selected legacy network packages such as telnet, rsh-server, and ypbind.
- Optional installation and enablement of chrony, auditd, and rsyslog.
- CIS-inspired IPv4 network sysctl settings.
- Service enablement for chronyd, auditd, and rsyslog.
- Safe disabling of known legacy services when they are present.
- Basic audit backlog and audit rule examples.
- Sudo defaults for `use_pty` and a configurable sudo logfile.
- Rsyslog service validation and journald configuration presence checks.
- Optional filesystem mount option persistence for selected paths.

## Safety Philosophy

The defaults are conservative. The role supports Ansible check mode and avoids destructive production behavior by default. Filesystem mount option management is disabled unless `cis_manage_mount_options` is explicitly enabled, and even then the role persists configured options without remounting live filesystems.

Review variables before using this role in production.

## Common Variables

```yaml
cis_disable_root_login: true
cis_disable_password_auth: false
cis_install_auditd: true
cis_enable_chrony: true
cis_enable_rsyslog: true
cis_remove_legacy_packages: true
cis_enable_sysctl_hardening: true
cis_manage_mount_options: false
```

## Check Mode

Run a full safety preview:

```bash
ansible-playbook playbooks/cis-rhel9-hardening.yml --check --diff
```

Run only SSH controls in check mode:

```bash
ansible-playbook playbooks/cis-rhel9-hardening.yml --check --diff --tags ssh
```

## Tags

Useful tags include:

- `precheck`
- `packages`
- `ssh`
- `sysctl`
- `services`
- `audit`
- `sudo`
- `logging`
- `filesystem`
- `postcheck`

Example:

```bash
ansible-playbook playbooks/cis-rhel9-hardening.yml --tags precheck,ssh,postcheck
```

## Production Rollout Notes

This role is a hardening starting point for internal infrastructure teams. It should be reviewed against local access patterns, break-glass procedures, compliance requirements, monitoring expectations, and host build standards before rollout.