onionshare/cli/onionshare_cli/web/web.py

# -*- coding: utf-8 -*-
"""
OnionShare | https://onionshare.org/

Copyright (C) 2014-2021 Micah Lee, et al. <micah@micahflee.com>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
import logging
import os
import queue
import requests
from distutils.version import LooseVersion as Version

import flask
from flask import (
    Flask,
    request,
    render_template,
    abort,
    make_response,
    send_file,
    __version__ as flask_version,
)
from flask_httpauth import HTTPBasicAuth
from flask_socketio import SocketIO

from .share_mode import ShareModeWeb
from .receive_mode import ReceiveModeWeb, ReceiveModeWSGIMiddleware, ReceiveModeRequest
from .website_mode import WebsiteModeWeb
from .chat_mode import ChatModeWeb

# Stub out flask's show_server_banner function, to avoiding showing warnings that
# are not applicable to OnionShare
def stubbed_show_server_banner(env, debug, app_import_path, eager_loading):
    pass


try:
    flask.cli.show_server_banner = stubbed_show_server_banner
except:
    pass


class Web:
    """
    The Web object is the OnionShare web server, powered by flask
    """

    REQUEST_LOAD = 0
    REQUEST_STARTED = 1
    REQUEST_PROGRESS = 2
    REQUEST_CANCELED = 3
    REQUEST_RATE_LIMIT = 4
    REQUEST_UPLOAD_FILE_RENAMED = 5
    REQUEST_UPLOAD_SET_DIR = 6
    REQUEST_UPLOAD_FINISHED = 7
    REQUEST_UPLOAD_CANCELED = 8
    REQUEST_INDIVIDUAL_FILE_STARTED = 9
    REQUEST_INDIVIDUAL_FILE_PROGRESS = 10
    REQUEST_INDIVIDUAL_FILE_CANCELED = 11
    REQUEST_ERROR_DATA_DIR_CANNOT_CREATE = 12
    REQUEST_OTHER = 13
    REQUEST_INVALID_PASSWORD = 14

    def __init__(self, common, is_gui, mode_settings, mode="share"):
        self.common = common
        self.common.log("Web", "__init__", f"is_gui={is_gui}, mode={mode}")

        self.settings = mode_settings

        # The flask app
        self.app = Flask(
            __name__,
            static_folder=self.common.get_resource_path("static"),
            static_url_path=f"/static_{self.common.random_string(16)}",  # randomize static_url_path to avoid making /static unusable
            template_folder=self.common.get_resource_path("templates"),
        )
        self.app.secret_key = self.common.random_string(8)
        self.generate_static_url_path()
        self.auth = HTTPBasicAuth()
        self.auth.error_handler(self.error401)

        # Verbose mode?
        if self.common.verbose:
            self.verbose_mode()

        # Are we running in GUI mode?
        self.is_gui = is_gui

        # If the user stops the server while a transfer is in progress, it should
        # immediately stop the transfer. In order to make it thread-safe, stop_q
        # is a queue. If anything is in it, then the user stopped the server
        self.stop_q = queue.Queue()

        # Are we using receive mode?
        self.mode = mode
        if self.mode == "receive":
            # Use custom WSGI middleware, to modify environ
            self.app.wsgi_app = ReceiveModeWSGIMiddleware(self.app.wsgi_app, self)
            # Use a custom Request class to track upload progress
            self.app.request_class = ReceiveModeRequest

        # Starting in Flask 0.11, render_template_string autoescapes template variables
        # by default. To prevent content injection through template variables in
        # earlier versions of Flask, we force autoescaping in the Jinja2 template
        # engine if we detect a Flask version with insecure default behavior.
        if Version(flask_version) < Version("0.11"):
            # Monkey-patch in the fix from https://github.com/pallets/flask/commit/99c99c4c16b1327288fd76c44bc8635a1de452bc
            Flask.select_jinja_autoescape = self._safe_select_jinja_autoescape

        self.security_headers = [
            ("X-Frame-Options", "DENY"),
            ("X-Xss-Protection", "1; mode=block"),
            ("X-Content-Type-Options", "nosniff"),
            ("Referrer-Policy", "no-referrer"),
            ("Server", "OnionShare"),
        ]

        self.q = queue.Queue()
        self.password = None

        self.reset_invalid_passwords()

        self.done = False

        # shutting down the server only works within the context of flask, so the easiest way to do it is over http
        self.shutdown_password = self.common.random_string(16)

        # Keep track if the server is running
        self.running = False

        # Define the web app routes
        self.define_common_routes()

        # Create the mode web object, which defines its own routes
        self.share_mode = None
        self.receive_mode = None
        self.website_mode = None
        self.chat_mode = None
        if self.mode == "share":
            self.share_mode = ShareModeWeb(self.common, self)
        elif self.mode == "receive":
            self.receive_mode = ReceiveModeWeb(self.common, self)
        elif self.mode == "website":
            self.website_mode = WebsiteModeWeb(self.common, self)
        elif self.mode == "chat":
            self.socketio = SocketIO()
            self.socketio.init_app(self.app)
            self.chat_mode = ChatModeWeb(self.common, self)

    def get_mode(self):
        if self.mode == "share":
            return self.share_mode
        elif self.mode == "receive":
            return self.receive_mode
        elif self.mode == "website":
            return self.website_mode
        elif self.mode == "chat":
            return self.chat_mode
        else:
            return None

    def generate_static_url_path(self):
        # The static URL path has a 128-bit random number in it to avoid having name
        # collisions with files that might be getting shared
        self.static_url_path = f"/static_{self.common.random_string(16)}"
        self.common.log(
            "Web",
            "generate_static_url_path",
            f"new static_url_path is {self.static_url_path}",
        )

        # Update the flask route to handle the new static URL path
        self.app.static_url_path = self.static_url_path
        self.app.add_url_rule(
            self.static_url_path + "/<path:filename>",
            endpoint="static",
            view_func=self.app.send_static_file,
        )

    def define_common_routes(self):
        """
        Common web app routes between all modes.
        """

        @self.auth.get_password
        def get_pw(username):
            if username == "onionshare":
                return self.password
            else:
                return None

        @self.app.before_request
        def conditional_auth_check():
            # Allow static files without basic authentication
            if request.path.startswith(self.static_url_path + "/"):
                return None

            # If public mode is disabled, require authentication
            if not self.settings.get("general", "public"):

                @self.auth.login_required
                def _check_login():
                    return None

                return _check_login()

        @self.app.errorhandler(404)
        def not_found(e):
            mode = self.get_mode()
            history_id = mode.cur_history_id
            mode.cur_history_id += 1
            return self.error404(history_id)

        @self.app.route("/<password_candidate>/shutdown")
        def shutdown(password_candidate):
            """
            Stop the flask web server, from the context of an http request.
            """
            if password_candidate == self.shutdown_password:
                self.force_shutdown()
                return ""
            abort(404)

        if self.mode != "website":

            @self.app.route("/favicon.ico")
            def favicon():
                return send_file(
                    f"{self.common.get_resource_path('static')}/img/favicon.ico"
                )

    def error401(self):
        auth = request.authorization
        if auth:
            if (
                auth["username"] == "onionshare"
                and auth["password"] not in self.invalid_passwords
            ):
                print(f"Invalid password guess: {auth['password']}")
                self.add_request(Web.REQUEST_INVALID_PASSWORD, data=auth["password"])

                self.invalid_passwords.append(auth["password"])
                self.invalid_passwords_count += 1

                if self.invalid_passwords_count == 20:
                    self.add_request(Web.REQUEST_RATE_LIMIT)
                    self.force_shutdown()
                    print(
                        "Someone has made too many wrong attempts to guess your password, so OnionShare has stopped the server. Start sharing again and send the recipient a new address to share."
                    )

        r = make_response(
            render_template("401.html", static_url_path=self.static_url_path), 401
        )
        return self.add_security_headers(r)

    def error403(self):
        self.add_request(Web.REQUEST_OTHER, request.path)
        r = make_response(
            render_template("403.html", static_url_path=self.static_url_path), 403
        )
        return self.add_security_headers(r)

    def error404(self, history_id):
        self.add_request(
            self.REQUEST_INDIVIDUAL_FILE_STARTED,
            request.path,
            {"id": history_id, "status_code": 404},
        )

        self.add_request(Web.REQUEST_OTHER, request.path)
        r = make_response(
            render_template("404.html", static_url_path=self.static_url_path), 404
        )
        return self.add_security_headers(r)

    def error405(self, history_id):
        self.add_request(
            self.REQUEST_INDIVIDUAL_FILE_STARTED,
            request.path,
            {"id": history_id, "status_code": 405},
        )

        self.add_request(Web.REQUEST_OTHER, request.path)
        r = make_response(
            render_template("405.html", static_url_path=self.static_url_path), 405
        )
        return self.add_security_headers(r)

    def add_security_headers(self, r):
        """
        Add security headers to a request
        """
        for header, value in self.security_headers:
            r.headers.set(header, value)
        # Set a CSP header unless in website mode and the user has disabled it
        if not self.settings.get("website", "disable_csp") or self.mode != "website":
            r.headers.set(
                "Content-Security-Policy",
                "default-src 'self'; style-src 'self'; script-src 'self'; img-src 'self' data:;",
            )
        return r

    def _safe_select_jinja_autoescape(self, filename):
        if filename is None:
            return True
        return filename.endswith((".html", ".htm", ".xml", ".xhtml"))

    def add_request(self, request_type, path=None, data=None):
        """
        Add a request to the queue, to communicate with the GUI.
        """
        self.q.put({"type": request_type, "path": path, "data": data})

    def generate_password(self, saved_password=None):
        self.common.log("Web", "generate_password", f"saved_password={saved_password}")
        if saved_password != None and saved_password != "":
            self.password = saved_password
            self.common.log(
                "Web",
                "generate_password",
                f'saved_password sent, so password is: "{self.password}"',
            )
        else:
            self.password = self.common.build_password()
            self.common.log(
                "Web", "generate_password", f'built random password: "{self.password}"'
            )

    def verbose_mode(self):
        """
        Turn on verbose mode, which will log flask errors to a file.
        """
        flask_log_filename = os.path.join(self.common.build_data_dir(), "flask.log")
        log_handler = logging.FileHandler(flask_log_filename)
        log_handler.setLevel(logging.WARNING)
        self.app.logger.addHandler(log_handler)

    def reset_invalid_passwords(self):
        self.invalid_passwords_count = 0
        self.invalid_passwords = []

    def force_shutdown(self):
        """
        Stop the flask web server, from the context of the flask app.
        """
        # Shutdown the flask service
        try:
            func = request.environ.get("werkzeug.server.shutdown")
            if func is None:
                raise RuntimeError("Not running with the Werkzeug Server")
            func()
        except:
            pass
        self.running = False

    def start(self, port):
        """
        Start the flask web server.
        """
        self.common.log("Web", "start", f"port={port}")

        # Make sure the stop_q is empty when starting a new server
        while not self.stop_q.empty():
            try:
                self.stop_q.get(block=False)
            except queue.Empty:
                pass

        # In Whonix, listen on 0.0.0.0 instead of 127.0.0.1 (#220)
        if os.path.exists("/usr/share/anon-ws-base-files/workstation"):
            host = "0.0.0.0"
        else:
            host = "127.0.0.1"

        self.running = True
        if self.mode == "chat":
            self.socketio.run(self.app, host=host, port=port)
        else:
            self.app.run(host=host, port=port, threaded=True)

    def stop(self, port):
        """
        Stop the flask web server by loading /shutdown.
        """
        self.common.log("Web", "stop", "stopping server")

        # Let the mode know that the user stopped the server
        self.stop_q.put(True)

        # To stop flask, load http://shutdown:[shutdown_password]@127.0.0.1/[shutdown_password]/shutdown
        # (We're putting the shutdown_password in the path as well to make routing simpler)
        if self.running:
            if self.password:
                requests.get(
                    f"http://127.0.0.1:{port}/{self.shutdown_password}/shutdown",
                    auth=requests.auth.HTTPBasicAuth("onionshare", self.password),
                )
            else:
                requests.get(
                    f"http://127.0.0.1:{port}/{self.shutdown_password}/shutdown"
                )

        # Reset any password that was in use
        self.password = None