Linux Security Guardian

Autonomous multi-client Linux server security management via SSH MCP. Runs full audit at 1 AM IST nightly via cron. Iterates over all clients and their server fleets. Covers system hardening, CVE scanning (CISA KEV + OSV.dev + NVD API), user auditing, SSH config (incl. weak ciphers/MACs/Kex), firewall rules, running services, file permissions, log analysis, SSL certs, kernel parameters (incl. BPF restrictions), Docker daemon security defaults (userns-remap, no-new-privileges, seccomp), fail2ban auto-install, unattended-upgrades auto-enable, CIS benchmark scoring, systemd sandbox analysis, AppArmor/SELinux audit, and swap encryption check. Non-breaking actions auto-applied. Critical patches and network/firewall changes require owner confirmation. Report sent per-server and per-client via email plugin/skill (not bundled). All owner-specific config lives in core-extra/config/ — no hardcoded names, domains, or emails.

vk@cyber-bye

Install

openclaw skills install @cyber-bye/linux-security-guardian

Linux Security Guardian

⚡ SSH MCP — REQUIRED DEPENDENCY

SSH MCP is a hard dependency. The agent MUST have SSH MCP tools available to operate. No local/legacy fallback. All operations go through SSH MCP.

Prerequisite

yaml

# SSH MCP server must be running and accessible
dependency: ssh_mcp
status: required    # if unavailable → ABORT, alert owner

Server Profile Config

Each target server needs a saved connection in SSH MCP database. Configure in SERVER_PROFILE.md:

yaml

ssh_mcp:
  connection_id: "<id-name-or-alias-from-ssh-conn-list>"   # Saved connection ID, Name, or Alias
  # OR inline config:
  # host: "<server-ip>"
  # port: 22
  # username: "<user>"
  # key_path: "</path/to/key>"

Audit Modules

All 26 modules execute commands via SSH MCP. Each module file lists commands that get wrapped with ssh_exec(op="run", sessionId, command):

text

module command → ssh_exec(op="run", sessionId, command="module command")
              → ssh_exec(op="logs", commandId=cmdId)
              → parse output

CVE Scan

The external CVE scan runs locally (on the guardian host) using curl to CISA KEV, OSV.dev, and NVD API. Usage requires --client and --server to write results to per-server paths:

bash

bash cve/cve-scan.sh --client "client-1" --server "server-01"

# Writes results to:
#   cve/<client>/<server>/scan-results/YYYY-MM-DD.md
#   cve/<client>/<server>/advisories/<CVE-ID>.md

Steps:

bash

# 1. SSH MCP: ssh_exec(op="run", sessionId, command="dpkg-query -W ...") → save locally
# 2. Read from cve/<client>/<server>/scan-results/installed-packages.txt
# 3. curl CISA KEV → filter Linux entries → write advisories
# 4. curl POST OSV.dev batch → match packages → write advisories
# 5. curl NVD API (optional) → cross-check → write advisories

Core-Extra Config System

All owner-specific data lives in core-extra/config/ — never hardcoded in hooks or modules.

Profile

File	Contains	Fields
`core-extra/config/profile.md`	Owner identity + domain + email	`Owner.name`, `Domain.primary`, `Email.noreply`

How Agents Use It

text

At session start → load core-extra/config/profile.md
→ Owner.name  → used in SOUL.md [WORKSPACE OWNER]
→ Email.noreply → used as from: in mail-sender.md
→ Domain.primary → used in config generation

To change: edit core-extra/config/profile.md only.

Rule

NO hardcoded names, domains, or emails in hooks/, modules/, or root files
All personal/owner data comes from core-extra/config/profile.md
The core-extra directory is part of the skill (published to ClawHub with placeholders)
Owner fills profile.md ONCE after install

Multi-Client Architecture

The guardian manages multiple clients, each with their own server fleet. SERVER_PROFILE.md defines ## Client: sections. The audit iterates ALL.

text

SERVER_PROFILE.md
├── ## Client: client-1 (7 servers)
│   ├── server-01
│   ├── server-02
│   └── ... server-07
├── ## Client: client-2 (N servers) ← add as needed
│   └── ...
└── ## Client: [NEXT-CLIENT]

All paths use <client>/<server>/ prefix:

Findings: audit/results/<client>/<server>/<severity>/
Actions: actions/<client>/<server>/auto-done/
CVEs: cve/<client>/<server>/advisories/
Reports: reports/<client>/<server>/daily/

Purpose

Agent manages complete Linux server security autonomously via SSH MCP. Every night at 1 AM IST:

Iterates all clients → all servers
Full security audit runs via SSH MCP
CVEs scanned against installed packages
Auto-fixes applied for safe issues
Critical issues queued for owner confirmation
Per-server, per-client, and master email reports delivered

Action Decision Matrix

The most important thing — what agent does vs what it asks first:

Finding Type	CVSS / Severity	Action
CVE — Critical	≥ 9.0	EMAIL ALERT immediately + queue for confirm
CVE — High	7.0–8.9	Queue for confirm + include in report
CVE — Medium	4.0–6.9	Include in report + advisory
CVE — Low	< 4.0	Info in report only
CVE — KEV (CISA)	any	Treated as CRITICAL — immediate alert + confirm within due date
CVE — KEV + Ransomware	any	🔥 HIGHEST PRIORITY — immediate alert, confirm ASAP
Kernel update available	any	Confirm required before patch
Security-only pkg update	any	Confirm required
SSH: PermitRootLogin yes	critical	Alert + confirm to fix
SSH: PasswordAuth yes	high	Alert + confirm to fix
SSH: Port 22	medium	Advisory only
Empty password account	critical	AUTO-LOCK immediately
Unknown root-uid account	critical	Alert + confirm to lock
Inactive account > 90d	medium	Alert + confirm to lock
World-writable /tmp	medium	AUTO-FIX chmod
World-writable system dir	high	Alert + confirm to fix
Unexpected SUID binary	high	Alert only (owner decides)
Failed login spike > 20/hr	high	Alert immediately
New unknown cron job	high	Alert immediately
Firewall rule change needed	any	CONFIRM REQUIRED always
Open unexpected port	high	Alert + confirm to close
Service: unnecessary running	medium	Alert + confirm to stop
SSL cert expiring < 30d	warning	Alert
SSL cert expired	critical	Alert immediately
Disk > 85% full	warning	Alert
Disk > 95% full	critical	Alert immediately
Auditd not running	high	AUTO-START + alert
fail2ban not running	high	AUTO-START + alert
Log file suspicious entry	high	Alert with extract

Audit Modules

Module	What it checks	SSH MCP Command
`01-system`	OS, kernel, uptime, last reboot, hardware	`ssh_exec(op="run", sessionId, command="uname -a; cat /etc/*release")`
`02-users`	Accounts, root access, sudo, empty passwords, inactive	`ssh_exec(op="run", sessionId, command="cat /etc/passwd; cat /etc/shadow; ...")`
`03-ssh`	sshd_config full audit — 20+ checks + weak ciphers/MACs/KexAlgorithms (CIS)	`ssh_exec(op="run", sessionId, command="cat /etc/ssh/sshd_config; sshd -T 2>/dev/null
`04-auth`	Login history, failed logins, PAM config, fail2ban auto-install + SSH jail config, password policy enforcement	`ssh_exec(op="run", sessionId, command="last; cat /var/log/auth.log")`
`05-services`	Running services, unnecessary ones, failed units	`ssh_exec(op="run", sessionId, command="systemctl list-units ...")`
`06-packages`	Pending updates, security updates count, unattended-upgrades auto-enable (security-only)	`ssh_exec(op="run", sessionId, command="apt list --upgradable 2>/dev/null")`
`07-cve`	CVE scan — remote via SSH MCP + API-based	`ssh_exec(op="run", sessionId, command="dpkg-query -W ...; curl ...")`
`08-network`	Open ports, listening services, active connections	`ssh_exec(op="run", sessionId, command="ss -tulpn; netstat -tulpn")`
`09-firewall`	iptables/nftables/ufw rules audit	`ssh_exec(op="run", sessionId, command="iptables-save 2>/dev/null")`
`10-filesystem`	SUID/SGID, world-writable, /tmp, sticky bits	`ssh_exec(op="run", sessionId, command="find / -perm -4000 ...")`
`11-kernel`	sysctl security params — 15+ checks + BPF restrictions (unprivileged_bpf_disabled, bpf_jit_enable)	`ssh_exec(op="run", sessionId, command="sysctl -a 2>/dev/null")`
`12-logs`	auth.log, syslog, kern.log — anomaly scan	`ssh_exec(op="run", sessionId, command="tail -100 /var/log/syslog")`
`13-crons`	System + user cron jobs — unknown jobs flagged	`ssh_exec(op="run", sessionId, command="cat /etc/crontab; ls -la /var/spool/cron/")`
`14-ssl`	Cert expiry check for all domains/services	`ssh_exec(op="run", sessionId, command="openssl x509 -in ... -noout -dates")`
`15-docker`	If running — image vulns, container config, daemon.json security defaults (userns-remap, no-new-privileges, seccomp)	`ssh_exec(op="run", sessionId, command="docker ps; docker images; cat /etc/docker/daemon.json")`
`16-disk`	Disk usage, inode usage	`ssh_exec(op="run", sessionId, command="df -h; df -i")`
`17-integrity`	AIDE/tripwire check if installed	`ssh_exec(op="run", sessionId, command="aide --check")`
`18-rootkit`	rkhunter/chkrootkit if installed	`ssh_exec(op="run", sessionId, command="rkhunter --check --skip-keypress")`
`19-cis-scoring`	CIS benchmark alignment score across all modules	`(aggregated from all modules)`
`20-systemd-analyze`	systemd service sandboxing — 80+ security directives per service	`ssh_exec(op="run", sessionId, command="systemd-analyze security --json=short 2>/dev/null")`
`21-mount-hardening`	Mount point security — noexec, nosuid, nodev on /tmp, /dev/shm, /var/tmp	`ssh_exec(op="run", sessionId, command="mount
`22-apparmor-selinux`	AppArmor/SELinux MAC status — enforcement mode, confined processes	`ssh_exec(op="run", sessionId, command="aa-status 2>/dev/null
`23-proc-hidepid`	/proc hidepid enforcement — process visibility isolation	`ssh_exec(op="run", sessionId, command="mount
`24-swap-encryption`	Swap partition encryption — LUKS/dm-crypt check	`ssh_exec(op="run", sessionId, command="swapon --show 2>/dev/null")`
`25-usbguard`	USB device authorization — USBGuard policy and daemon status	`ssh_exec(op="run", sessionId, command="systemctl is-active usbguard")`
`26-ipv6-audit`	IPv6 security — RA acceptance, redirects, privacy extensions, NDP hardening	`ssh_exec(op="run", sessionId, command="sysctl net.ipv6.conf.all.disable_ipv6")`

Execution rule: All commands go through ssh_exec(op="run", sessionId, command="<command>") → ssh_exec(op="logs", commandId=cmdId). No local execution.

Finding Severity Levels

Level	Color	Meaning
`CRITICAL`	🔴	Immediate risk, action required now
`HIGH`	🟠	Significant risk, fix this week
`MEDIUM`	🟡	Moderate risk, fix this month
`LOW`	🔵	Minor issue, fix when possible
`INFO`	⚪	Informational, no action needed
`PASS`	🟢	Check passed, all good

Confirmation Flow

When owner confirmation is needed:

text

Finding detected (requires confirm) on <client>/<server>
    ↓
Write to actions/<client>/<server>/pending-confirm/<client>-<server>-<id>-<slug>.md
    ↓
Include in email report under "NEEDS YOUR DECISION" with <client>/<server> context
    ↓
Owner replies with: APPROVE <id> / DENY <id> / SKIP <id>
(Full ID format: <client>-<server>-<type>-<NNN>, e.g. client-1-server-01-ACT-20260529-001)
    ↓
Search all actions/*/*/pending-confirm/ for the ID
    ↓
APPROVE → agent connects to <client>/<server> via SSH MCP → executes action → logs to history/
DENY    → action skipped, noted
SKIP    → deferred to next audit

Email Report Structure

Reports are sent per-server, per-client (summary), and master. All via email plugin/skill.

Per-Server Report

text

Subject: [Linux Guardian] <client>/<server> — YYYY-MM-DD | Score: N/100 | CRITICAL:N HIGH:N

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
LINUX SECURITY GUARDIAN — NIGHTLY REPORT
Client: <client> | Server: <server> | <IP> | YYYY-MM-DD 01:00 IST
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

EXECUTIVE SUMMARY
Security Score: N/100 | Grade: X
Critical: N | High: N | Medium: N | Low: N
Auto-fixed: N | Pending confirm: N | Passed: N

━━ 🔴 CRITICAL (immediate action needed)
[Finding details]

━━ 🟠 HIGH
[Finding details]

━━ ⚡ AUTO-ACTIONS TAKEN (safe, non-breaking)
[What was auto-fixed]

━━ 🔑 NEEDS YOUR DECISION (reply APPROVE/DENY/SKIP <id>)
[Pending confirmations with IDs — includes <client>/<server> prefix]

━━ 📦 CVE REPORT
[CVEs found by severity]

━━ 🌐 NETWORK & FIREWALL
[Port/firewall status]

━━ 🟡 MEDIUM / LOW
[Less urgent findings]

━━ 🟢 ALL PASSING
[Checks that passed]

━━ NEXT AUDIT: Tomorrow 01:00 IST

Per-Client Summary Report

text

Subject: [Linux Guardian] <client> Summary — YYYY-MM-DD | Servers: N/N | CRITICAL:N HIGH:N

Client: <client>
Servers audited: N of N total
Average score: N/100

| Server | Score | Critical | High | Score Grade |
|--------|-------|----------|------|-------------|
| ...    | ...   | ...      | ...  | ...         |

Cross-server patterns: [same vuln found on multiple servers]

Security Score Formula

text

score = 100
score -= (critical_count × 20)
score -= (high_count × 10)
score -= (medium_count × 3)
score -= (low_count × 1)
score = max(0, score)

Grade: 90-100 = A | 75-89 = B | 60-74 = C | < 60 = F

Folder Structure

text

linux-security-guardian/
  audit/
    modules/                     ← 01-system.md ... 26-ipv6-audit.md
    results/
      <client>/<server>/
        critical/  high/  warning/  info/  pass/
          YYYY-MM-DD-<check>.md  ← per-client/per-server findings

  actions/
    <client>/<server>/
      auto-done/                 ← auto-fixed actions (logged)
        YYYY-MM-DD-<slug>.md
      pending-confirm/           ← waiting for owner
        <id>-<slug>.md
      history/                   ← all approved/denied actions

  cve/
    cve-scan.sh                  ← external CVE scanner (takes --client --server)
    external-sources.md          ← all API URLs, query params, working examples
    .cache/                      ← shared cached API responses (6h TTL)
    <client>/<server>/
      scan-results/              ← YYYY-MM-DD.md
      advisories/                ← <cve-id>.md

  reports/
    <client>/<server>/
      daily/YYYY-MM-DD.md
      weekly/YYYY-WNN.md

  network/
    <client>/<server>/
      firewall-snapshots/        ← YYYY-MM-DD-rules.txt
      port-scans/                ← YYYY-MM-DD.md
      proposed-changes/          ← <id>-<change>.md

  hooks/
    audit-runner.md              ← main 1 AM audit orchestrator (multi-client loop)
    on-critical.md               ← fires on any critical finding (with client/server)
    on-confirm-reply.md          ← processes owner APPROVE/DENY/SKIP
    pre-action.md                ← safety check before any action
    post-action.md               ← verify action succeeded
    mail-sender.md               ← uses email plugin/skill to send report

  crons/
    active/
      nightly-audit.md           ← 1 AM IST permanent
    completed/

  core-extra/
    config/
      profile.md                 ← owner name, domain, email (fill ONCE, no hardcode)
    hooks/                       ← shared hooks (mirrors hooks/ structure)
    templates/                   ← shared templates

  errors/
    raw/                         ← raw error logs

  memory/
    schema.json
    index.json

  SOUL.md                        ← soul context (multi-client aware)
  AGENT.md                       ← behavioral rules (multi-client, SSH MCP hard dep)
  SERVER_PROFILE.md               ← multi-client server details
  AUDIT_LOG.md                    ← append-only master log
  BASELINE.md                     ← expected state snapshot
  STATS.md