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501 lines
15 KiB
Python
501 lines
15 KiB
Python
""" Mailu admin app utilities
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"""
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try:
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import cPickle as pickle
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except ImportError:
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import pickle
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import dns
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import dns.resolver
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import hmac
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import secrets
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import time
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from multiprocessing import Value
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from mailu import limiter
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from flask import current_app as app
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import flask
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import flask_login
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import flask_migrate
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import flask_babel
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import ipaddress
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import redis
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from flask.sessions import SessionMixin, SessionInterface
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from itsdangerous.encoding import want_bytes
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from werkzeug.datastructures import CallbackDict
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from werkzeug.contrib import fixers
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# Login configuration
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login = flask_login.LoginManager()
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login.login_view = "sso.login"
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@login.unauthorized_handler
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def handle_needs_login():
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""" redirect unauthorized requests to login page """
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return flask.redirect(
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flask.url_for('sso.login', next=flask.request.endpoint)
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)
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# DNS stub configured to do DNSSEC enabled queries
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resolver = dns.resolver.Resolver()
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resolver.use_edns(0, 0, 1232)
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resolver.flags = dns.flags.AD | dns.flags.RD
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def has_dane_record(domain, timeout=10):
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try:
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result = resolver.query(f'_25._tcp.{domain}', dns.rdatatype.TLSA,dns.rdataclass.IN, lifetime=timeout)
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if result.response.flags & dns.flags.AD:
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for record in result:
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if isinstance(record, dns.rdtypes.ANY.TLSA.TLSA):
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record.validate()
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if record.usage in [2,3] and record.selector in [0,1] and record.mtype in [0,1,2]:
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return True
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except dns.resolver.NoNameservers:
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# If the DNSSEC data is invalid and the DNS resolver is DNSSEC enabled
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# we will receive this non-specific exception. The safe behaviour is to
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# accept to defer the email.
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app.logger.warn(f'Unable to lookup the TLSA record for {domain}. Is the DNSSEC zone okay on https://dnsviz.net/d/{domain}/dnssec/?')
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return app.config['DEFER_ON_TLS_ERROR']
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except dns.exception.Timeout:
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app.logger.warn(f'Timeout while resolving the TLSA record for {domain} ({timeout}s).')
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except dns.resolver.NXDOMAIN:
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pass # this is expected, not TLSA record is fine
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except Exception as e:
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app.logger.error(f'Error while looking up the TLSA record for {domain} {e}')
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pass
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# Rate limiter
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limiter = limiter.LimitWraperFactory()
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def extract_network_from_ip(ip):
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n = ipaddress.ip_network(ip)
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if n.version == 4:
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return str(n.supernet(prefixlen_diff=(32-int(app.config["AUTH_RATELIMIT_IP_V4_MASK"]))).network_address)
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else:
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return str(n.supernet(prefixlen_diff=(128-int(app.config["AUTH_RATELIMIT_IP_V6_MASK"]))).network_address)
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def is_exempt_from_ratelimits(ip):
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ip = ipaddress.ip_address(ip)
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return any(ip in cidr for cidr in app.config['AUTH_RATELIMIT_EXEMPTION'])
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# Application translation
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babel = flask_babel.Babel()
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@babel.localeselector
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def get_locale():
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""" selects locale for translation """
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language = flask.session.get('language')
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if not language in app.config.translations:
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language = flask.request.accept_languages.best_match(app.config.translations.keys())
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flask.session['language'] = language
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return language
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# Proxy fixer
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class PrefixMiddleware(object):
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""" fix proxy headers """
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def __init__(self):
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self.app = None
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def __call__(self, environ, start_response):
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prefix = environ.get('HTTP_X_FORWARDED_PREFIX', '')
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if prefix:
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environ['SCRIPT_NAME'] = prefix
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return self.app(environ, start_response)
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def init_app(self, app):
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self.app = fixers.ProxyFix(app.wsgi_app, x_for=1, x_proto=1)
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app.wsgi_app = self
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proxy = PrefixMiddleware()
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# Data migrate
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migrate = flask_migrate.Migrate()
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# session store (inspired by https://github.com/mbr/flask-kvsession)
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class RedisStore:
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""" Stores session data in a redis db. """
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has_ttl = True
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def __init__(self, redisstore):
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self.redis = redisstore
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def get(self, key):
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""" load item from store. """
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value = self.redis.get(key)
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if value is None:
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raise KeyError(key)
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return value
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def put(self, key, value, ttl=None):
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""" save item to store. """
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if ttl:
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self.redis.setex(key, int(ttl), value)
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else:
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self.redis.set(key, value)
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def delete(self, key):
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""" delete item from store. """
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self.redis.delete(key)
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def list(self, prefix=None):
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""" return list of keys starting with prefix """
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if prefix:
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prefix += b'*'
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return list(self.redis.scan_iter(match=prefix))
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class DictStore:
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""" Stores session data in a python dict. """
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has_ttl = False
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def __init__(self):
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self.dict = {}
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def get(self, key):
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""" load item from store. """
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return self.dict[key]
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def put(self, key, value, ttl_secs=None):
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""" save item to store. """
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self.dict[key] = value
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def delete(self, key):
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""" delete item from store. """
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try:
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del self.dict[key]
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except KeyError:
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pass
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def list(self, prefix=None):
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""" return list of keys starting with prefix """
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if prefix is None:
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return list(self.dict.keys())
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return [key for key in self.dict if key.startswith(prefix)]
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class MailuSession(CallbackDict, SessionMixin):
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""" Custom flask session storage. """
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# default modified to false
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modified = False
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def __init__(self, key=None, app=None):
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self.app = app or flask.current_app
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initial = None
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key = want_bytes(key)
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if parsed := self.app.session_config.parse_key(key, self.app):
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try:
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initial = pickle.loads(app.session_store.get(key))
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except (KeyError, EOFError, pickle.UnpicklingError):
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# either the cookie was manipulated or we did not find the
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# session in the backend or the pickled data is invalid.
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# => start new session
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pass
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else:
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(self._uid, self._sid, self._created) = parsed
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self._key = key
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if initial is None:
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# start new session
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self.new = True
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self._uid = None
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self._sid = None
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self._created = self.app.session_config.gen_created()
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self._key = None
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def _on_update(obj):
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obj.modified = True
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CallbackDict.__init__(self, initial, _on_update)
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@property
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def saved(self):
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""" this reflects if the session was saved. """
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return self._key is not None
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@property
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def sid(self):
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""" this reflects the session's id. """
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if self._sid is None or self._uid is None or self._created is None:
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return None
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return b''.join([self._uid, self._sid, self._created])
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def destroy(self):
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""" destroy session for security reasons. """
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self.delete()
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self._uid = None
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self._sid = None
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self._created = None
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self.clear()
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self.modified = True
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self.new = False
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def regenerate(self):
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""" generate new id for session to avoid `session fixation`. """
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self.delete()
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self._sid = None
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self._created = self.app.session_config.gen_created()
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self.modified = True
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def delete(self):
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""" Delete stored session. """
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if self.saved:
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self.app.session_store.delete(self._key)
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self._key = None
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def save(self):
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""" Save session to store. """
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set_cookie = False
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# set uid from dict data
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if self._uid is None:
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self._uid = self.app.session_config.gen_uid(self.get('user_id', ''))
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# create new session id for new or regenerated sessions and force setting the cookie
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if self._sid is None:
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self._sid = self.app.session_config.gen_sid()
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set_cookie = True
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# get new session key
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key = self.sid
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# delete old session if key has changed
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if key != self._key:
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self.delete()
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# remember time to refresh
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self['_refresh'] = int(time.time()) + self.app.permanent_session_lifetime.total_seconds()/2
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# save session
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self.app.session_store.put(
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key,
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pickle.dumps(dict(self)),
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self.app.permanent_session_lifetime.total_seconds()
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)
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self._key = key
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self.new = False
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self.modified = False
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return set_cookie
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def needs_refresh(self):
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""" Checks if server side session needs to be refreshed. """
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return int(time.time()) > self.get('_refresh', 0)
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class MailuSessionConfig:
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""" Stores sessions crypto config """
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# default size of session key parts
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uid_bits = 64 # default if SESSION_KEY_BITS is not set in config
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sid_bits = 128 # for now. must be multiple of 8!
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time_bits = 32 # for now. must be multiple of 8!
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def __init__(self, app=None):
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if app is None:
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app = flask.current_app
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bits = app.config.get('SESSION_KEY_BITS', self.uid_bits)
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if not 64 <= bits <= 256:
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raise ValueError('SESSION_KEY_BITS must be between 64 and 256!')
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uid_bytes = bits//8 + (bits%8>0)
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sid_bytes = self.sid_bits//8
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key = want_bytes(app.secret_key)
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self._hmac = hmac.new(hmac.digest(key, b'SESSION_UID_HASH', digest='sha256'), digestmod='sha256')
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self._uid_len = uid_bytes
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self._uid_b64 = len(self._encode(bytes(uid_bytes)))
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self._sid_len = sid_bytes
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self._sid_b64 = len(self._encode(bytes(sid_bytes)))
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self._key_min = self._uid_b64 + self._sid_b64
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self._key_max = self._key_min + len(self._encode(bytes(self.time_bits//8)))
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def gen_sid(self):
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""" Generate random session id. """
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return self._encode(secrets.token_bytes(self._sid_len))
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def gen_uid(self, uid):
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""" Generate hashed user id part of session key. """
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_hmac = self._hmac.copy()
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_hmac.update(want_bytes(uid))
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return self._encode(_hmac.digest()[:self._uid_len])
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def gen_created(self, now=None):
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""" Generate base64 representation of creation time. """
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return self._encode(int(now or time.time()).to_bytes(8, byteorder='big').lstrip(b'\0'))
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def parse_key(self, key, app=None, validate=False, now=None):
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""" Split key into sid, uid and creation time. """
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if not (isinstance(key, bytes) and self._key_min <= len(key) <= self._key_max):
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return None
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uid = key[:self._uid_b64]
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sid = key[self._uid_b64:self._key_min]
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crt = key[self._key_min:]
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# validate if parts are decodeable
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created = self._decode(crt)
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if created is None or self._decode(uid) is None or self._decode(sid) is None:
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return None
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# validate creation time when requested or store does not support ttl
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if validate or not app.session_store.has_ttl:
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if now is None:
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now = int(time.time())
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created = int.from_bytes(created, byteorder='big')
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if not created < now < created + app.permanent_session_lifetime.total_seconds():
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return None
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return (uid, sid, crt)
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def _encode(self, value):
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return secrets.base64.urlsafe_b64encode(value).rstrip(b'=')
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def _decode(self, value):
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try:
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return secrets.base64.urlsafe_b64decode(value + b'='*(4-len(value)%4))
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except secrets.binascii.Error:
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return None
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class MailuSessionInterface(SessionInterface):
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""" Custom flask session interface. """
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def open_session(self, app, request):
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""" Load or create session. """
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return MailuSession(request.cookies.get(app.config['SESSION_COOKIE_NAME'], None), app)
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def save_session(self, app, session, response):
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""" Save modified session. """
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# If the session is modified to be empty, remove the cookie.
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# If the session is empty, return without setting the cookie.
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if not session:
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if session.modified:
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session.delete()
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response.delete_cookie(
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app.session_cookie_name,
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domain=self.get_cookie_domain(app),
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path=self.get_cookie_path(app),
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)
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return
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# Add a "Vary: Cookie" header if the session was accessed
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if session.accessed:
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response.vary.add('Cookie')
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set_cookie = session.permanent and app.config['SESSION_REFRESH_EACH_REQUEST']
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need_refresh = session.needs_refresh()
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# save modified session or refresh unmodified session
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if session.modified or need_refresh:
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set_cookie |= session.save()
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# set cookie on refreshed permanent sessions
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if need_refresh and session.permanent:
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set_cookie = True
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# set or update cookie if necessary
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if set_cookie:
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response.set_cookie(
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app.session_cookie_name,
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session.sid,
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expires=self.get_expiration_time(app, session),
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httponly=self.get_cookie_httponly(app),
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domain=self.get_cookie_domain(app),
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path=self.get_cookie_path(app),
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secure=self.get_cookie_secure(app),
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samesite=self.get_cookie_samesite(app)
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)
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class MailuSessionExtension:
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""" Server side session handling """
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@staticmethod
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def cleanup_sessions(app=None):
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""" Remove invalid or expired sessions. """
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app = app or flask.current_app
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now = int(time.time())
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count = 0
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for key in app.session_store.list():
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if not app.session_config.parse_key(key, app, validate=True, now=now):
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app.session_store.delete(key)
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count += 1
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return count
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@staticmethod
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def prune_sessions(uid=None, keep=None, app=None):
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""" Remove sessions
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uid: remove all sessions (NONE) or sessions belonging to a specific user
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keep: keep listed sessions
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"""
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keep = keep or set()
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app = app or flask.current_app
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prefix = None if uid is None else app.session_config.gen_uid(uid)
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count = 0
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for key in app.session_store.list(prefix):
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if key not in keep:
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app.session_store.delete(key)
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count += 1
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return count
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def init_app(self, app):
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""" Replace session management of application. """
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if app.config.get('MEMORY_SESSIONS'):
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# in-memory session store for use in development
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app.session_store = DictStore()
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else:
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# redis-based session store for use in production
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app.session_store = RedisStore(
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redis.StrictRedis().from_url(app.config['SESSION_STORAGE_URL'])
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)
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# clean expired sessions oonce on first use in case lifetime was changed
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def cleaner():
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with cleaned.get_lock():
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if not cleaned.value:
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cleaned.value = True
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app.logger.info('cleaning session store')
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MailuSessionExtension.cleanup_sessions(app)
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app.before_first_request(cleaner)
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app.session_config = MailuSessionConfig(app)
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app.session_interface = MailuSessionInterface()
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cleaned = Value('i', False)
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session = MailuSessionExtension()
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