simple-updater/server.py

import os
import json
import socket
import posixpath
import urllib.parse
from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer

CONFIG_FILENAME = "config.json"


def load_config():
    config_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), CONFIG_FILENAME)
    with open(config_path, "r", encoding="utf-8") as f:
        return json.load(f)


CONFIG = load_config()
HOST = CONFIG.get("server", {}).get("host", "0.0.0.0")
PORT = CONFIG.get("server", {}).get("port", 3232)

# config.json keeps client folders and access keys under two separate
# top-level maps, both keyed by the same friendly client name
# ("Main", "Test", ...):
#
#   "clients":     {"Main": "game_client", "Test": "game_client_test"}
#   "access_keys": {"Main": "<hex>",        "Test": "<hex>"}
#
# This mirrors how updater.py's CLIENT_KEYS is keyed (by display name),
# so quickstart.py can populate both from the exact same source of truth
# without the server and the updater disagreeing about what "Main" means.
# The server only cares about the resulting access_key -> folder mapping,
# built once here at startup.
_CLIENT_FOLDERS = CONFIG.get("clients", {})
_ACCESS_KEYS = CONFIG.get("access_keys", {})

CLIENTS = {}
for _name, _folder in _CLIENT_FOLDERS.items():
    _key = _ACCESS_KEYS.get(_name)
    if not _key:
        print(f"WARNING: client '{_name}' has no access_key configured in config.json - skipping it.")
        continue
    CLIENTS[_key] = _folder

# Absolute, resolved base directories for each client key, computed once at
# startup. Relative folder paths in config.json are resolved relative to
# this script's own location, not the process's current working directory,
# so `python server.py` works the same regardless of where it's launched
# from. Every request is checked against these to make sure the final path
# can never land outside the intended client folder.
SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
CLIENT_BASE_DIRS = {
    key: os.path.realpath(os.path.join(SCRIPT_DIR, folder))
    for key, folder in CLIENTS.items()
}

# A path that is guaranteed not to exist, used to force a 404 through the
# normal http.server flow instead of ever falling back to serving files
# from the script's own working directory.
NONEXISTENT_PATH = os.path.join(os.path.abspath(os.sep), "__no_such_path__")

# Simple per-IP concurrent connection cap. This is not a substitute for a
# real reverse proxy (nginx/Caddy) doing proper rate limiting, but it stops
# a single naive client (or a basic flood) from tying up every worker
# thread the process has. Put a real reverse proxy in front for anything
# internet-facing - see README.
MAX_CONNECTIONS_PER_IP = CONFIG.get("server", {}).get("max_connections_per_ip", 20)
_active_connections = {}


class MultiClientHandler(SimpleHTTPRequestHandler):
    """
    Serves files only under a URL path that starts with a known access key,
    e.g. /<hex-key>/manifest.json or /<hex-key>/some/file.

    Everything else gets a 404:
      - a bare "/" (the directory listing that exposes server.py, config.json,
        the raw client folders, etc.)
      - an unknown or missing key
      - any path that tries to escape the client folder (e.g. via "..")
      - directory listings even *inside* a valid client folder

    This is enforced by never letting execution fall through to the default
    SimpleHTTPRequestHandler behavior, which serves the process's current
    working directory.
    """

    # Keep noisy default logging off stdout in production; flip to True
    # (or add real logging) if you need request-level debugging.
    def log_message(self, format, *args):
        pass

    def _resolve_client_path(self, path):
        path = urllib.parse.urlparse(path).path
        path = urllib.parse.unquote(path)
        parts = [p for p in path.split('/') if p]

        if not parts:
            return None

        key = parts[0]
        if key not in CLIENT_BASE_DIRS:
            return None

        base_dir = CLIENT_BASE_DIRS[key]
        rel_parts = parts[1:]
        rel_path = posixpath.join(*rel_parts) if rel_parts else ""

        full_path = os.path.realpath(os.path.join(base_dir, rel_path))

        # Confirm the resolved path is still inside base_dir (blocks "..",
        # symlink tricks, etc.). commonpath needs both paths to exist on the
        # same drive/root, which realpath + os.path.join guarantees here.
        try:
            if os.path.commonpath([full_path, base_dir]) != base_dir:
                return None
        except ValueError:
            return None

        return full_path

    def translate_path(self, path):
        resolved = self._resolve_client_path(path)
        if resolved is None:
            return NONEXISTENT_PATH
        return resolved

    def list_directory(self, path):
        # Never render a directory listing, even for a path inside a valid
        # client folder - only exact file paths are servable.
        self.send_error(404, "Not Found")
        return None

    def finish(self):
        try:
            super().finish()
        finally:
            ip = self.client_address[0]
            remaining = _active_connections.get(ip, 1) - 1
            if remaining <= 0:
                _active_connections.pop(ip, None)
            else:
                _active_connections[ip] = remaining

    def handle_one_request(self):
        ip = self.client_address[0]
        current = _active_connections.get(ip, 0)
        if current >= MAX_CONNECTIONS_PER_IP:
            self.close_connection = True
            try:
                self.send_error(429, "Too Many Requests")
            except (BrokenPipeError, ConnectionResetError):
                pass
            return
        _active_connections[ip] = current + 1
        super().handle_one_request()


class Server(ThreadingHTTPServer):
    # Handle each connection in its own thread so one slow/large download
    # doesn't stall every other player's update. daemon_threads=True keeps
    # Ctrl+C responsive instead of hanging on stray worker threads.
    daemon_threads = True
    allow_reuse_address = True


if __name__ == '__main__':
    server_address = (HOST, PORT)
    httpd = Server(server_address, MultiClientHandler)
    print(f"Server running on {HOST}:{PORT}...")
    if CLIENTS:
        active_names = [name for name in _CLIENT_FOLDERS if _ACCESS_KEYS.get(name)]
        print(f"Configured clients: {', '.join(active_names)}")
    else:
        print("WARNING: no clients configured (check config.json 'clients' and 'access_keys').")
    try:
        httpd.serve_forever()
    except KeyboardInterrupt:
        pass