Refactor session behavior, remove `Flask-Session` dep

Sessions are no longer validated using the "/session/..." route. This
created a lot of problems due to buggy/unexpected behavior coming from
the Flask-Session dependency, which is (more or less) no longer
maintained.

Sessions are also no longer strictly server-side-only. The majority of
information that was being stored in user sessions was aesthetic only,
aside from the session specific key used to encrypt URLs. This key is
still unique per user, but is not (or shouldn't be) in anyone's threat
model to keep absolutely 100% private from everyone. Especially paranoid
users of Whoogle can easily modify the code to use a randomly generated
encryption key that is reset on session invalidation (and set
invalidation time to a short enough period for their liking).

Ultimately, this should result in much more stable sessions per client.
There shouldn't be decryption issues with element URLs or queries
during result page navigation.

.gitignore

@@ -4,6 +4,7 @@ __pycache__/
 *.pyc
 *.pem
 *.conf
+*.key
 config.json
 test/static
 flask_session/

app/__init__.py

@@ -3,9 +3,9 @@ from app.request import send_tor_signal
 from app.utils.session import generate_user_key
 from app.utils.bangs import gen_bangs_json
 from app.utils.misc import gen_file_hash, read_config_bool
+from base64 import b64encode
 from datetime import datetime, timedelta
 from flask import Flask
-from flask_session import Session
 import json
 import logging.config
 import os
@@ -20,24 +20,15 @@ app = Flask(__name__, static_folder=os.path.dirname(
 
 app.wsgi_app = ProxyFix(app.wsgi_app)
 
+dot_env_path = (
+    os.path.join(os.path.dirname(os.path.abspath(__file__)),
+    '../whoogle.env'))
+
 # Load .env file if enabled
 if os.getenv('WHOOGLE_DOTENV', ''):
-    dotenv_path = '../whoogle.env'
-    load_dotenv(os.path.join(os.path.dirname(os.path.abspath(__file__)),
-                             dotenv_path))
+    load_dotenv(dot_env_path)
 
-# Session values
-# NOTE: SESSION_COOKIE_SAMESITE must be set to 'lax' to allow the user's
-# previous session to persist when accessing the instance from an external
-# link. Setting this value to 'strict' causes Whoogle to revalidate a new
-# session, and fail, resulting in cookies being disabled.
-#
-# This could be re-evaluated if Whoogle ever switches to client side
-# configuration instead.
 app.default_key = generate_user_key()
-app.config['SECRET_KEY'] = os.urandom(32)
-app.config['SESSION_TYPE'] = 'filesystem'
-app.config['SESSION_COOKIE_SAMESITE'] = 'Lax'
 
 if os.getenv('HTTPS_ONLY'):
     app.config['SESSION_COOKIE_NAME'] = '__Secure-session'
@@ -86,6 +77,36 @@ app.config['BANG_FILE'] = os.path.join(
     app.config['BANG_PATH'],
     'bangs.json')
 
+# Ensure all necessary directories exist
+if not os.path.exists(app.config['CONFIG_PATH']):
+    os.makedirs(app.config['CONFIG_PATH'])
+
+if not os.path.exists(app.config['SESSION_FILE_DIR']):
+    os.makedirs(app.config['SESSION_FILE_DIR'])
+
+if not os.path.exists(app.config['BANG_PATH']):
+    os.makedirs(app.config['BANG_PATH'])
+
+if not os.path.exists(app.config['BUILD_FOLDER']):
+    os.makedirs(app.config['BUILD_FOLDER'])
+
+# Session values
+app_key_path = os.path.join(app.config['CONFIG_PATH'], 'whoogle.key')
+if os.path.exists(app_key_path):
+    app.config['SECRET_KEY'] = open(app_key_path, 'r').read()
+else:
+    app.config['SECRET_KEY'] = str(b64encode(os.urandom(32)))
+    with open(app_key_path, 'w') as key_file:
+        key_file.write(app.config['SECRET_KEY'])
+        key_file.close()
+app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(days=365)
+
+# NOTE: SESSION_COOKIE_SAMESITE must be set to 'lax' to allow the user's
+# previous session to persist when accessing the instance from an external
+# link. Setting this value to 'strict' causes Whoogle to revalidate a new
+# session, and fail, resulting in cookies being disabled.
+app.config['SESSION_COOKIE_SAMESITE'] = 'Lax'
+
 # Config fields that are used to check for updates
 app.config['RELEASES_URL'] = 'https://github.com/' \
                              'benbusby/whoogle-search/releases'
@@ -109,15 +130,7 @@ app.config['CSP'] = 'default-src \'none\';' \
                     'media-src \'self\';' \
                     'connect-src \'self\';'
 
-if not os.path.exists(app.config['CONFIG_PATH']):
-    os.makedirs(app.config['CONFIG_PATH'])
-
-if not os.path.exists(app.config['SESSION_FILE_DIR']):
-    os.makedirs(app.config['SESSION_FILE_DIR'])
-
-# Generate DDG bang filter, and create path if it doesn't exist yet
-if not os.path.exists(app.config['BANG_PATH']):
-    os.makedirs(app.config['BANG_PATH'])
+# Generate DDG bang filter
 if not os.path.exists(app.config['BANG_FILE']):
     json.dump({}, open(app.config['BANG_FILE'], 'w'))
     bangs_thread = threading.Thread(
@@ -126,9 +139,6 @@ if not os.path.exists(app.config['BANG_FILE']):
     bangs_thread.start()
 
 # Build new mapping of static files for cache busting
-if not os.path.exists(app.config['BUILD_FOLDER']):
-    os.makedirs(app.config['BUILD_FOLDER'])
-
 cache_busting_dirs = ['css', 'js']
 for cb_dir in cache_busting_dirs:
     full_cb_dir = os.path.join(app.config['STATIC_FOLDER'], cb_dir)
@@ -155,8 +165,6 @@ app.jinja_env.globals.update(clean_query=clean_query)
 app.jinja_env.globals.update(
     cb_url=lambda f: app.config['CACHE_BUSTING_MAP'][f])
 
-Session(app)
-
 # Attempt to acquire tor identity, to determine if Tor config is available
 send_tor_signal(Signal.HEARTBEAT)
 

app/models/endpoint.py

@@ -5,7 +5,6 @@ class Endpoint(Enum):
     autocomplete = 'autocomplete'
     home = 'home'
     healthz = 'healthz'
-    session = 'session'
     config = 'config'
     opensearch = 'opensearch.xml'
     search = 'search'

app/routes.py

@@ -67,8 +67,7 @@ def auth_required(f):
 def session_required(f):
     @wraps(f)
     def decorated(*args, **kwargs):
-        if (valid_user_session(session) and
-                'cookies_disabled' not in request.args):
+        if (valid_user_session(session)):
             g.session_key = session['key']
         else:
             session.pop('_permanent', None)
@@ -113,6 +112,7 @@ def session_required(f):
 @app.before_request
 def before_request_func():
     global bang_json
+    session.permanent = True
 
     # Check for latest version if needed
     now = datetime.now()
@@ -126,43 +126,17 @@ def before_request_func():
         request.args if request.method == 'GET' else request.form
     )
 
-    # Skip pre-request actions if verifying session
-    if '/session' in request.path and not valid_user_session(session):
-        return
-
     default_config = json.load(open(app.config['DEFAULT_CONFIG'])) \
         if os.path.exists(app.config['DEFAULT_CONFIG']) else {}
 
     # Generate session values for user if unavailable
-    if (not valid_user_session(session) and
-            'cookies_disabled' not in request.args):
+    if (not valid_user_session(session)):
         session['config'] = default_config
         session['uuid'] = str(uuid.uuid4())
         session['key'] = generate_user_key()
 
-        # Skip checking for session on any searches that don't
-        # require a valid session
-        if (not Endpoint.autocomplete.in_path(request.path) and
-                not Endpoint.healthz.in_path(request.path) and
-                not Endpoint.opensearch.in_path(request.path)):
-            # reconstruct url if X-Forwarded-Host header present
-            request_url = get_proxy_host_url(request,
-                                             get_request_url(request.url))
-            return redirect(url_for(
-                'session_check',
-                session_id=session['uuid'],
-                follow=request_url), code=307)
-        else:
-            g.user_config = Config(**session['config'])
-    elif 'cookies_disabled' not in request.args:
-        # Set session as permanent
-        session.permanent = True
-        app.permanent_session_lifetime = timedelta(days=365)
-        g.user_config = Config(**session['config'])
-    else:
-        # User has cookies disabled, fall back to immutable default config
-        session.pop('_permanent', None)
-        g.user_config = Config(**default_config)
+    # Establish config values per user session
+    g.user_config = Config(**session['config'])
 
     if not g.user_config.url:
         g.user_config.url = get_request_url(request.url_root)
@@ -209,19 +183,6 @@ def healthz():
     return ''
 
 
-@app.route(f'/{Endpoint.session}/<session_id>', methods=['GET', 'PUT', 'POST'])
-def session_check(session_id):
-    if 'uuid' in session and session['uuid'] == session_id:
-        session['valid'] = True
-        return redirect(request.args.get('follow'), code=307)
-    else:
-        follow_url = request.args.get('follow')
-        req = PreparedRequest()
-        req.prepare_url(follow_url, {'cookies_disabled': 1})
-        session.pop('_permanent', None)
-        return redirect(req.url, code=307)
-
-
 @app.route('/', methods=['GET'])
 @app.route(f'/{Endpoint.home}', methods=['GET'])
 @auth_required
@@ -246,8 +207,7 @@ def index():
                                dark=g.user_config.dark),
                            config_disabled=(
                                    app.config['CONFIG_DISABLE'] or
-                                   not valid_user_session(session) or
-                                   'cookies_disabled' in request.args),
+                                   not valid_user_session(session)),
                            config=g.user_config,
                            tor_available=int(os.environ.get('TOR_AVAILABLE')),
                            version_number=app.config['VERSION_NUMBER'])

requirements.txt

@@ -9,7 +9,6 @@ cryptography==3.3.2
 cssutils==2.4.0
 defusedxml==0.7.1
 Flask==1.1.1
-Flask-Session==0.4.0
 idna==2.9
 itsdangerous==1.1.0
 Jinja2==2.11.3