NETWORK                    MIDDLEWARE                   APPLICATION
  ┌────────────────┐        ┌────────────────┐           ┌────────────────┐
  │ Open DDS ports │───────▶│ Unauthenticated│──────────▶│ Hardcoded      │
  │ (7400-7500)    │        │ /cmd_vel pub   │           │ credentials    │
  │ Unsegmented LAN│        │ No msg signing │           │ Unvalidated cmd│
  └────────────────┘        └────────────────┘           └────────────────┘
  PHYSICAL                   FIRMWARE                     SUPPLY CHAIN
  ┌────────────────┐        ┌────────────────┐           ┌────────────────┐
  │ USB/debug ports│───────▶│ Unsigned       │──────────▶│ Compromised    │
  │ Serial consoles│        │ firmware OTA   │           │ ROS packages   │
  │ Exposed SBCs   │        │ No secure boot │           │ Unverified imgs│
  └────────────────┘        └────────────────┘           └────────────────┘

export ROS_SECURITY_KEYSTORE=~/sros2_keystore
ros2 security create_keystore ${ROS_SECURITY_KEYSTORE}
 
# Generate per-node enclaves (use exact fully-qualified node names)
ros2 security create_enclave ${ROS_SECURITY_KEYSTORE} /my_robot/camera_driver
ros2 security create_enclave ${ROS_SECURITY_KEYSTORE} /my_robot/navigation
ros2 security create_enclave ${ROS_SECURITY_KEYSTORE} /my_robot/motor_controller
ros2 security create_enclave ${ROS_SECURITY_KEYSTORE} /my_robot/teleop
 
# Result:
# sros2_keystore/
# ├── enclaves/my_robot/{camera_driver,navigation,...}/
# │   ├── cert.pem, key.pem          # Node identity
# │   ├── governance.p7s              # Signed governance
# │   └── permissions.p7s             # Signed permissions
# ├── public/ca.cert.pem              # CA certificate
# └── private/ca.key.pem              # CA private key — PROTECT THIS

<?xml version="1.0" encoding="UTF-8"?>
<dds xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="omg_shared_ca_governance.xsd">
  <domain_access_rules>
    <domain_rule>
      <domains><id_range><min>0</min><max>230</max></id_range></domains>
      <allow_unauthenticated_participants>false</allow_unauthenticated_participants>
      <enable_join_access_control>true</enable_join_access_control>
      <discovery_protection_kind>ENCRYPT</discovery_protection_kind>
      <liveliness_protection_kind>ENCRYPT</liveliness_protection_kind>
      <rtps_protection_kind>ENCRYPT</rtps_protection_kind>
      <topic_access_rules>
        <topic_rule>
          <topic_expression>*</topic_expression>
          <enable_discovery_protection>true</enable_discovery_protection>
          <enable_read_access_control>true</enable_read_access_control>
          <enable_write_access_control>true</enable_write_access_control>
          <metadata_protection_kind>ENCRYPT</metadata_protection_kind>
          <data_protection_kind>ENCRYPT</data_protection_kind>
        </topic_rule>
      </topic_access_rules>
    </domain_rule>
  </domain_access_rules>
</dds>

<?xml version="1.0" encoding="UTF-8"?>
<dds xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="omg_shared_ca_permissions.xsd">
  <permissions>
    <grant name="/my_robot/motor_controller">
      <subject_name>CN=/my_robot/motor_controller</subject_name>
      <validity><not_before>2024-01-01T00:00:00</not_before>
                <not_after>2026-01-01T00:00:00</not_after></validity>
      <allow_rule>
        <domains><id>0</id></domains>
        <publish><topics><topic>rt/joint_states</topic></topics></publish>
        <subscribe><topics><topic>rt/cmd_vel</topic></topics></subscribe>
      </allow_rule>
      <default>DENY</default>
    </grant>
    <grant name="/my_robot/teleop">
      <subject_name>CN=/my_robot/teleop</subject_name>
      <validity><not_before>2024-01-01T00:00:00</not_before>
                <not_after>2026-01-01T00:00:00</not_after></validity>
      <allow_rule>
        <domains><id>0</id></domains>
        <publish><topics><topic>rt/cmd_vel</topic></topics></publish>
        <subscribe><topics><topic>rt/joy</topic></topics></subscribe>
      </allow_rule>
      <default>DENY</default>
    </grant>
  </permissions>
</dds>

import os
from launch import LaunchDescription
from launch_ros.actions import Node
def generate_launch_description():
    security_env = {
        'ROS_SECURITY_KEYSTORE': os.path.expanduser('~/sros2_keystore'),
        'ROS_SECURITY_ENABLE': 'true',
        'ROS_SECURITY_STRATEGY': 'Enforce',  # Enforce=reject unauth, Permissive=warn only
    }
    return LaunchDescription([
        Node(package='my_robot_drivers', executable='motor_controller',
             name='motor_controller', namespace='my_robot',
             additional_env=security_env),
        Node(package='my_robot_nav', executable='navigation',
             name='navigation', namespace='my_robot',
             additional_env=security_env),
    ])

┌───────────────────┬──────────────────┬────────────────────────┐
│   CONTROL PLANE   │   DATA PLANE     │   MANAGEMENT PLANE     │
│   VLAN 10         │   VLAN 20        │   VLAN 30              │
│   10.10.10.0/24   │   10.10.20.0/24  │   10.10.30.0/24        │
├───────────────────┼──────────────────┼────────────────────────┤
│ /cmd_vel, /odom   │ /camera/image    │ SSH, Prometheus         │
│ /joint_states     │ /pointcloud      │ Log collection          │
│ /e_stop           │ /map, /rosbag    │ Fleet mgmt API          │
├───────────────────┼──────────────────┼────────────────────────┤
│ LOW LATENCY       │ HIGH BANDWIDTH   │ RESTRICTED ACCESS       │
│ QoS: RELIABLE     │ QoS: BEST_EFFORT │ Jump host / VPN + 2FA  │
└───────────────────┴──────────────────┴────────────────────────┘

#!/bin/bash
# firewall_ros2.sh — adapt interface names to your hardware
iptables -F && iptables -X
 
# Default: drop inbound, allow outbound
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT
 
iptables -A INPUT -i lo -j ACCEPT                                    # Loopback (intra-process DDS)
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT      # Existing connections
iptables -A INPUT -p udp --dport 7400:7500 -s 10.10.10.0/24 -j ACCEPT  # DDS discovery — control VLAN
iptables -A INPUT -p udp --dport 7500:7700 -s 10.10.10.0/24 -j ACCEPT  # DDS user traffic
iptables -A INPUT -p tcp --dport 22 -s 10.10.30.0/24 -j ACCEPT         # SSH — mgmt VLAN only
iptables -A INPUT -i wlan0 -d 239.255.0.0/16 -j DROP                   # Block multicast on WiFi
iptables -A INPUT -j LOG --log-prefix "DROPPED: " --log-level 4
iptables -A INPUT -j DROP
iptables-save > /etc/iptables/rules.v4

# /etc/netplan/01-robot-vlans.yaml
network:
  version: 2
  renderer: networkd
  ethernets:
    eth0: {dhcp4: false}
  vlans:
    vlan10:
      id: 10
      link: eth0
      addresses: [10.10.10.5/24]
    vlan20:
      id: 20
      link: eth0
      addresses: [10.10.20.5/24]
    vlan30:
      id: 30
      link: eth0
      addresses: [10.10.30.5/24]
      routes: [{to: default, via: 10.10.30.1}]

<!-- cyclonedds_secure.xml -->
<CycloneDDS>
  <Domain>
    <General><AllowMulticast>false</AllowMulticast></General>
    <Discovery>
      <Peers>
        <Peer address="10.10.10.1"/>
        <Peer address="10.10.10.2"/>
        <Peer address="10.10.10.3"/>
      </Peers>
      <ParticipantIndex>auto</ParticipantIndex>
    </Discovery>
  </Domain>
</CycloneDDS>

export CYCLONEDDS_URI=file:///etc/ros2/cyclonedds_secure.xml
export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp

# /etc/ssh/sshd_config
Port 2222
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
AuthorizedKeysFile .ssh/authorized_keys
MaxAuthTries 3
ClientAliveInterval 300
ClientAliveCountMax 2
AllowUsers robot-admin
X11Forwarding no
AllowTcpForwarding no
PermitTunnel no

sudo systemctl restart sshd
# Per-robot key pair (on management workstation)
ssh-keygen -t ed25519 -f ~/.ssh/robot_$(hostname) -C "admin@$(hostname)"
ssh-copy-id -i ~/.ssh/robot_$(hostname).pub -p 2222 robot-admin@10.10.30.5

# /etc/fail2ban/jail.local
[sshd]
enabled = true
port = 2222
filter = sshd
logpath = /var/log/auth.log
maxretry = 3
bantime = 3600
findtime = 600

sudo apt install fail2ban -y && sudo systemctl enable --now fail2ban

sudo apt install unattended-upgrades -y
sudo dpkg-reconfigure -plow unattended-upgrades
# Key settings in /etc/apt/apt.conf.d/50unattended-upgrades:
#   Allowed-Origins: "${distro_id}:${distro_codename}-security"
#   Automatic-Reboot: "false"   # NEVER auto-reboot a running robot

# Remove unnecessary packages from robot computers
sudo apt purge -y avahi-daemon cups snapd modemmanager bluetooth bluez
sudo apt autoremove -y

# BAD:
class FleetClient:
    def __init__(self):
        self.api_key = "sk-live-abc123xyz789"

# GOOD:
import os
class FleetClient:
    def __init__(self):
        self.api_key = os.environ['FLEET_API_KEY']

# BAD: credentials in params.yaml tracked by git
fleet_manager:
  ros__parameters:
    aws_secret_key: "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"

# GOOD: reference environment variables
fleet_manager:
  ros__parameters:
    aws_secret_key: "$(env AWS_SECRET_KEY)"

# /etc/systemd/system/robot-nav.service
[Service]
User=robot
Group=robot
EnvironmentFile=/etc/robot/secrets.env
ExecStart=/opt/ros/humble/bin/ros2 launch my_robot nav.launch.py
Restart=always

# /etc/robot/secrets.env
FLEET_API_KEY=sk-live-actual-key-here
ROS_SECURITY_KEYSTORE=/opt/robot/sros2_keystore
 
# Lock it down
sudo chown root:robot /etc/robot/secrets.env
sudo chmod 640 /etc/robot/secrets.env

#!/bin/bash
# rotate_certs.sh — run via cron monthly
set -euo pipefail
KEYSTORE="/opt/robot/sros2_keystore"
cp -r "${KEYSTORE}" "${KEYSTORE}_backup_$(date +%Y%m%d)"
 
for enclave in motor_controller navigation camera_driver teleop; do
    ros2 security create_enclave "${KEYSTORE}" "/my_robot/${enclave}"
done
sudo systemctl restart robot-*.service
echo "Certificates rotated at $(date)"

# /etc/cron.d/robot-cert-rotation
0 3 1 * * root /opt/robot/scripts/rotate_certs.sh >> /var/log/cert-rotation.log 2>&1

sudo chown -R root:robot /opt/robot/sros2_keystore
sudo find /opt/robot/sros2_keystore -type d -exec chmod 750 {} \;
sudo find /opt/robot/sros2_keystore -type f -exec chmod 640 {} \;
# CA private key — root only
sudo chmod 600 /opt/robot/sros2_keystore/private/ca.key.pem
sudo chown root:root /opt/robot/sros2_keystore/private/ca.key.pem

FROM ros:humble-ros-base AS runtime
RUN apt-get update && apt-get install -y --no-install-recommends \
    ros-humble-nav2-bringup && rm -rf /var/lib/apt/lists/*
RUN groupadd -g 1000 robot && useradd -u 1000 -g robot -m -s /bin/false robot
COPY --from=builder /opt/ros2_ws/install /opt/ros2_ws/install
USER robot:robot
ENTRYPOINT ["/ros_entrypoint.sh"]
CMD ["ros2", "launch", "my_robot", "nav.launch.py"]

FROM ros:humble-desktop AS builder
WORKDIR /opt/ros2_ws
COPY src/ src/
RUN . /opt/ros/humble/setup.sh && \
    colcon build --cmake-args -DCMAKE_BUILD_TYPE=Release --merge-install
 
FROM ros:humble-ros-core AS runtime
COPY --from=builder /opt/ros2_ws/install /opt/ros2_ws/install
# Remove shell and package manager — prevents interactive exploitation
RUN rm -f /bin/sh /bin/bash /bin/dash && apt-get purge -y --auto-remove apt

trivy image --severity HIGH,CRITICAL my-robot/navigation:latest
cosign sign --key cosign.key my-registry.io/my-robot/navigation:v1.2.3
cosign verify --key cosign.pub my-registry.io/my-robot/navigation:v1.2.3 || exit 1

# docker-compose.yml
services:
  motor_controller:
    image: my-robot/motor-controller:v1.0.0
    user: "1000:1000"
    read_only: true
    tmpfs: ["/tmp:size=64M", "/var/log/ros:size=32M"]
    volumes:
      - type: bind
        source: /opt/robot/sros2_keystore/enclaves/my_robot/motor_controller
        target: /keystore
        read_only: true
    security_opt: ["no-new-privileges:true"]
    cap_drop: [ALL]
    environment:
      ROS_SECURITY_KEYSTORE: /keystore
      ROS_SECURITY_ENABLE: "true"
      ROS_SECURITY_STRATEGY: Enforce

  ┌──────────┐     HARDWIRED      ┌─────────────────┐
  │ Physical  │ ─────────────────▶│ Safety Relay /   │──▶ Motor power cut
  │ E-Stop    │  Direct circuit    │ Safety PLC       │   via contactor
  │ Button    │  NO software       └─────────────────┘
  └──────────┘
  ┌──────────┐     OPTIONAL
  │ Software  │ ───(notifies)───▶ Can trigger relay, but NOT sole path
  │ E-Stop    │
  └──────────┘
  Main compute crash ──X──▶ Cannot prevent hardware e-stop
  Network failure    ──X──▶ Cannot prevent hardware e-stop

┌──────────────────────────────┬───────────────────────────────┐
│ MAIN COMPUTE (Jetson/x86)    │ SAFETY CONTROLLER (STM32/MCU) │
│ Ubuntu + ROS2                │ Bare-metal firmware            │
│ Nav, Perception, Planning    │                               │
│             ──── CAN/UART ──▶│ Validates:                    │
│                cmd_vel        │ - Max velocity                │
│                               │ - Max acceleration            │
│             ◀── joint_fb ────│ - Workspace limits            │
│                               │ - Watchdog timeout            │
│ If compromised, safety       │ Rejects out-of-bounds cmds    │
│ controller STILL enforces    │ Runs on separate hardware     │
│ physical limits.             │ Does NOT run ROS2 or Linux    │
└──────────────────────────────┴───────────────────────────────┘

# velocity_safety_gate.py
import rclpy
from rclpy.node import Node
from geometry_msgs.msg import Twist
class VelocitySafetyGate(Node):
    def __init__(self):
        super().__init__('velocity_safety_gate')
        self.declare_parameter('max_linear_vel', 1.0)   # m/s
        self.declare_parameter('max_angular_vel', 2.0)   # rad/s
        self.declare_parameter('max_linear_accel', 0.5)  # m/s^2
        self.declare_parameter('cmd_timeout_sec', 0.5)
        self.declare_parameter('max_cmd_rate_hz', 50.0)
        self.max_lin = self.get_parameter('max_linear_vel').value
        self.max_ang = self.get_parameter('max_angular_vel').value
        self.max_acc = self.get_parameter('max_linear_accel').value
        self.timeout = self.get_parameter('cmd_timeout_sec').value
        self.min_period = 1.0 / self.get_parameter('max_cmd_rate_hz').value
        self.last_cmd_time = self.get_clock().now()
        self.last_linear = 0.0
        self.last_pub_sec = 0.0
        self.sub = self.create_subscription(Twist, 'cmd_vel_raw', self.on_cmd, 10)
        self.pub = self.create_publisher(Twist, 'cmd_vel', 10)
        self.create_timer(0.1, self.watchdog_check)
    def on_cmd(self, msg: Twist):
        now = self.get_clock().now()
        now_sec = now.nanoseconds / 1e9
        if (now_sec - self.last_pub_sec) < self.min_period:
            return  # Rate limit exceeded — drop
        msg.linear.x = max(-self.max_lin, min(self.max_lin, msg.linear.x))
        msg.angular.z = max(-self.max_ang, min(self.max_ang, msg.angular.z))
        dt = (now - self.last_cmd_time).nanoseconds / 1e9
        if dt > 0:
            accel = abs(msg.linear.x - self.last_linear) / dt
            if accel > self.max_acc:
                sign = 1.0 if msg.linear.x > self.last_linear else -1.0
                msg.linear.x = self.last_linear + sign * self.max_acc * dt
        self.pub.publish(msg)
        self.last_cmd_time = now
        self.last_linear = msg.linear.x
        self.last_pub_sec = now_sec
    def watchdog_check(self):
        elapsed = (self.get_clock().now() - self.last_cmd_time).nanoseconds / 1e9
        if elapsed > self.timeout:
            self.pub.publish(Twist())  # No command → zero velocity

# Hardware watchdog — kernel resets system if not fed
import os
class HardwareWatchdog:
    """Uses /dev/watchdog. If not fed within timeout, kernel triggers reset."""
    def __init__(self):
        self.fd = os.open('/dev/watchdog', os.O_WRONLY)  # Starts countdown
    def feed(self):
        os.write(self.fd, b'\x00')  # Reset countdown
    def close(self):
        os.write(self.fd, b'V')     # Magic close — disarm gracefully
        os.close(self.fd)

# /etc/watchdog.conf
watchdog-device = /dev/watchdog
watchdog-timeout = 15
interval = 5
pidfile = /var/run/robot-safety-monitor.pid
max-load-1 = 24

# /etc/fstab
/dev/mmcblk0p2  /        ext4  ro,noatime,errors=remount-ro  0 1
tmpfs           /tmp     tmpfs nosuid,nodev,size=128M         0 0
tmpfs           /var/log tmpfs nosuid,nodev,size=128M         0 0
/dev/mmcblk0p3  /data    ext4  rw,noatime,nosuid,nodev       0 2

# Alternative: overlayroot — all writes go to tmpfs, lost on reboot
sudo apt install overlayroot -y
# /etc/overlayroot.conf → overlayroot="tmpfs:swap=1"

#!/bin/bash
set -euo pipefail
IMAGE="registry.myrobot.io/robot/navigation"
TAG="v$(cat VERSION)-$(git rev-parse --short HEAD)"
docker build -t "${IMAGE}:${TAG}" -f Dockerfile.prod .
trivy image --exit-code 1 --severity CRITICAL "${IMAGE}:${TAG}"
docker push "${IMAGE}:${TAG}"
cosign sign --key env://COSIGN_PRIVATE_KEY "${IMAGE}:${TAG}"
syft "${IMAGE}:${TAG}" -o spdx-json > sbom.json
cosign attach sbom --sbom sbom.json "${IMAGE}:${TAG}"

# LUKS + TPM2 for unattended encrypted boot
sudo cryptsetup luksFormat /dev/mmcblk0p3
sudo cryptsetup luksOpen /dev/mmcblk0p3 robot-data
sudo systemd-cryptenroll /dev/mmcblk0p3 --tpm2-device=auto --tpm2-pcrs=0+7
# Disk decrypts only on original hardware with unmodified firmware

from pathlib import Path
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives import hashes, serialization
import subprocess
def verify_and_flash(firmware: Path, signature: Path, pubkey_path: Path):
    pubkey = serialization.load_pem_public_key(pubkey_path.read_bytes())
    try:
        pubkey.verify(signature.read_bytes(), firmware.read_bytes(),
                      ec.ECDSA(hashes.SHA256()))
    except Exception:
        raise SecurityError("Firmware signature verification FAILED — aborting")
    subprocess.run(['flash-tool', '--write', str(firmware)], check=True)

# topic_auditor.py — logs publications on sensitive topics
import rclpy, json, time
from rclpy.node import Node
from geometry_msgs.msg import Twist
class TopicAuditor(Node):
    def __init__(self):
        super().__init__('topic_auditor')
        self.log = open('/var/log/ros2_audit.jsonl', 'a')
        self.create_subscription(Twist, '/cmd_vel', self.audit_cmd_vel, 10)
    def audit_cmd_vel(self, msg: Twist):
        record = {'ts': time.time(), 'topic': '/cmd_vel',
                  'lin_x': msg.linear.x, 'ang_z': msg.angular.z}
        self.log.write(json.dumps(record) + '\n')
        self.log.flush()
        if abs(msg.linear.x) > 0.8 or abs(msg.angular.z) > 1.5:
            self.get_logger().warn(f'HIGH VEL: lin={msg.linear.x:.2f} ang={msg.angular.z:.2f}')

# cmd_vel_anomaly_detector.py
import numpy as np
from collections import deque
import rclpy
from rclpy.node import Node
from geometry_msgs.msg import Twist
class CmdVelAnomalyDetector(Node):
    def __init__(self):
        super().__init__('cmd_vel_anomaly_detector')
        self.window = deque(maxlen=100)
        self.alert_pub = self.create_publisher(Twist, '/security/cmd_vel_alert', 10)
        self.create_subscription(Twist, '/cmd_vel', self.on_cmd, 10)
    def on_cmd(self, msg: Twist):
        self.window.append((msg.linear.x, msg.angular.z))
        if len(self.window) < 20:
            return
        vels = np.array(list(self.window))
        z_scores = np.abs((np.array([msg.linear.x, msg.angular.z]) - vels.mean(0)) / (vels.std(0) + 1e-6))
        if np.any(z_scores > 3.0):
            self.get_logger().error(f'ANOMALY: lin={msg.linear.x:.3f} ang={msg.angular.z:.3f} z={z_scores}')
            self.alert_pub.publish(msg)

# /etc/audit/rules.d/robot-security.rules
-w /opt/robot/sros2_keystore/ -p rwxa -k robot_keystore
-w /etc/robot/ -p wa -k robot_config
-w /home/robot-admin/.ssh/ -p wa -k ssh_keys
-w /opt/robot/firmware/ -p rwxa -k firmware_access
-w /etc/systemd/system/robot- -p wa -k robot_services
-a always,exit -F arch=b64 -F euid=0 -S execve -k root_commands
-w /dev/bus/usb/ -p rwxa -k usb_access
-w /etc/netplan/ -p wa -k network_config
-w /etc/iptables/ -p wa -k firewall_config
-w /usr/bin/docker -p x -k docker_exec

sudo auditctl -R /etc/audit/rules.d/robot-security.rules
sudo systemctl enable --now auditd
sudo ausearch -k robot_keystore --start today

# BAD: anyone on the network can do this
ros2 topic pub /cmd_vel geometry_msgs/Twist "{linear: {x: 999.0}}"

# GOOD: unauthorized publish rejected at DDS layer
export ROS_SECURITY_ENABLE=true
export ROS_SECURITY_STRATEGY=Enforce

# BAD: same key for all robots
ssh-copy-id -i ~/.ssh/fleet_key.pub robot@robot-001
ssh-copy-id -i ~/.ssh/fleet_key.pub robot@robot-002

# GOOD: SSH CA issues 8-hour certs per session
ssh-keygen -s /etc/ssh/ca_key -I "session-$(date +%s)" -n robot-admin -V +8h ~/.ssh/id_ed25519.pub

# BAD:
sudo ros2 launch my_robot bringup.launch.py

# GOOD:
sudo -u robot ros2 launch my_robot bringup.launch.py
# /etc/udev/rules.d/99-robot.rules:
# SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", MODE="0660", GROUP="robot"

# BAD: everything on 192.168.1.0/24
 
# GOOD: VLAN 10 control (wired), VLAN 20 data, VLAN 30 mgmt (jump host)

# BAD: in params.yaml tracked by git
cloud_connector:
  ros__parameters:
    aws_access_key: "AKIAIOSFODNN7EXAMPLE"

# GOOD: secrets injected at runtime via systemd EnvironmentFile
gitleaks detect --source . --verbose  # Pre-commit check

# BAD: sole e-stop is a ROS2 topic subscriber
self.create_subscription(Bool, '/e_stop', self.software_estop, 10)

# BAD: "temporary" becomes permanent
export ROS_SECURITY_ENABLE=false

# GOOD: CI enforces security
export ROS_SECURITY_ENABLE=true
export ROS_SECURITY_STRATEGY=Enforce
ros2 launch my_robot test.launch.py  # Must pass with security on