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Mailu/core/admin/mailu/utils.py

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""" Mailu admin app utilities
"""
try:
import cPickle as pickle
except ImportError:
import pickle
import hashlib
import secrets
import time
from multiprocessing import Value
from mailu import limiter
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import flask
import flask_login
import flask_migrate
import flask_babel
import redis
from flask.sessions import SessionMixin, SessionInterface
from itsdangerous.encoding import want_bytes
from werkzeug.datastructures import CallbackDict
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from werkzeug.contrib import fixers
# Login configuration
login = flask_login.LoginManager()
login.login_view = "ui.login"
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@login.unauthorized_handler
def handle_needs_login():
""" redirect unauthorized requests to login page """
return flask.redirect(
flask.url_for('ui.login', next=flask.request.endpoint)
)
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# Rate limiter
limiter = limiter.LimitWraperFactory()
# Application translation
babel = flask_babel.Babel()
@babel.localeselector
def get_locale():
""" selects locale for translation """
translations = [str(translation) for translation in babel.list_translations()]
return flask.request.accept_languages.best_match(translations)
# Proxy fixer
class PrefixMiddleware(object):
""" fix proxy headers """
def __init__(self):
self.app = None
def __call__(self, environ, start_response):
prefix = environ.get('HTTP_X_FORWARDED_PREFIX', '')
if prefix:
environ['SCRIPT_NAME'] = prefix
return self.app(environ, start_response)
def init_app(self, app):
self.app = fixers.ProxyFix(app.wsgi_app, x_for=1, x_proto=1)
app.wsgi_app = self
proxy = PrefixMiddleware()
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# Data migrate
migrate = flask_migrate.Migrate()
# session store (inspired by https://github.com/mbr/flask-kvsession)
class RedisStore:
""" Stores session data in a redis db. """
has_ttl = True
def __init__(self, redisstore):
self.redis = redisstore
def get(self, key):
""" load item from store. """
value = self.redis.get(key)
if value is None:
raise KeyError(key)
return value
def put(self, key, value, ttl=None):
""" save item to store. """
if ttl:
self.redis.setex(key, int(ttl), value)
else:
self.redis.set(key, value)
def delete(self, key):
""" delete item from store. """
self.redis.delete(key)
def list(self, prefix=None):
""" return list of keys starting with prefix """
if prefix:
prefix += b'*'
return list(self.redis.scan_iter(match=prefix))
class DictStore:
""" Stores session data in a python dict. """
has_ttl = False
def __init__(self):
self.dict = {}
def get(self, key):
""" load item from store. """
return self.dict[key]
def put(self, key, value, ttl_secs=None):
""" save item to store. """
self.dict[key] = value
def delete(self, key):
""" delete item from store. """
try:
del self.dict[key]
except KeyError:
pass
def list(self, prefix=None):
""" return list of keys starting with prefix """
if prefix is None:
return list(self.dict.keys())
return [key for key in self.dict if key.startswith(prefix)]
class MailuSession(CallbackDict, SessionMixin):
""" Custom flask session storage. """
# default modified to false
modified = False
def __init__(self, key=None, app=None):
self.app = app or flask.current_app
initial = None
key = want_bytes(key)
if parsed := self.app.session_config.parse_key(key, self.app):
try:
initial = pickle.loads(app.session_store.get(key))
except (KeyError, EOFError, pickle.UnpicklingError):
# either the cookie was manipulated or we did not find the
# session in the backend or the pickled data is invalid.
# => start new session
pass
else:
(self._uid, self._sid, self._created) = parsed
self._key = key
if initial is None:
# start new session
self.new = True
self._uid = None
self._sid = None
self._created = self.app.session_config.gen_created()
self._key = None
def _on_update(obj):
obj.modified = True
CallbackDict.__init__(self, initial, _on_update)
@property
def saved(self):
""" this reflects if the session was saved. """
return self._key is not None
@property
def sid(self):
""" this reflects the session's id. """
if self._sid is None or self._uid is None or self._created is None:
return None
return b''.join([self._uid, self._sid, self._created])
def destroy(self):
""" destroy session for security reasons. """
self.delete()
self._uid = None
self._sid = None
self._created = None
self.clear()
self.modified = True
self.new = False
def regenerate(self):
""" generate new id for session to avoid `session fixation`. """
self.delete()
self._sid = None
self._created = self.app.session_config.gen_created()
self.modified = True
def delete(self):
""" Delete stored session. """
if self.saved:
self.app.session_store.delete(self._key)
self._key = None
def save(self):
""" Save session to store. """
# set uid from dict data
if self._uid is None:
self._uid = self.app.session_config.gen_uid(self.get('user_id', ''))
# create new session id for new or regenerated sessions
if self._sid is None:
self._sid = self.app.session_config.gen_sid()
# get new session key
key = self.sid
# delete old session if key has changed
if key != self._key:
self.delete()
# save session
self.app.session_store.put(
key,
pickle.dumps(dict(self)),
self.app.permanent_session_lifetime.total_seconds()
)
self._key = key
self.new = False
self.modified = False
class MailuSessionConfig:
""" Stores sessions crypto config """
def __init__(self, app=None):
if app is None:
app = flask.current_app
bits = app.config.get('SESSION_KEY_BITS', 64)
if bits < 64:
raise ValueError('Session id entropy must not be less than 64 bits!')
hash_bytes = bits//8 + (bits%8>0)
time_bytes = 4 # 32 bit timestamp for now
self._shaker = hashlib.shake_128(want_bytes(app.config.get('SECRET_KEY', '')))
self._hash_len = hash_bytes
self._hash_b64 = len(self._encode(bytes(hash_bytes)))
self._key_min = 2*self._hash_b64
self._key_max = self._key_min + len(self._encode(bytes(time_bytes)))
def gen_sid(self):
""" Generate random session id. """
return self._encode(secrets.token_bytes(self._hash_len))
def gen_uid(self, uid):
""" Generate hashed user id part of session key. """
shaker = self._shaker.copy()
shaker.update(want_bytes(uid))
return self._encode(shaker.digest(self._hash_len))
def gen_created(self, now=None):
""" Generate base64 representation of creation time. """
return self._encode(int(now or time.time()).to_bytes(8, byteorder='big').lstrip(b'\0'))
def parse_key(self, key, app=None, validate=False, now=None):
""" Split key into sid, uid and creation time. """
if not (isinstance(key, bytes) and self._key_min <= len(key) <= self._key_max):
return None
uid = key[:self._hash_b64]
sid = key[self._hash_b64:self._key_min]
crt = key[self._key_min:]
# validate if parts are decodeable
created = self._decode(crt)
if created is None or self._decode(uid) is None or self._decode(sid) is None:
return None
# validate creation time when requested or store does not support ttl
if validate or not app.session_store.has_ttl:
if now is None:
now = int(time.time())
created = int.from_bytes(created, byteorder='big')
if not (created < now < created + app.permanent_session_lifetime.total_seconds()):
return None
return (uid, sid, crt)
def _encode(self, value):
return secrets.base64.urlsafe_b64encode(value).rstrip(b'=')
def _decode(self, value):
try:
return secrets.base64.urlsafe_b64decode(value + b'='*(4-len(value)%4))
except secrets.binascii.Error:
return None
class MailuSessionInterface(SessionInterface):
""" Custom flask session interface. """
def open_session(self, app, request):
""" Load or create session. """
return MailuSession(request.cookies.get(app.config['SESSION_COOKIE_NAME'], None), app)
def save_session(self, app, session, response):
""" Save modified session. """
# If the session is modified to be empty, remove the cookie.
# If the session is empty, return without setting the cookie.
if not session:
if session.modified:
session.delete()
response.delete_cookie(
app.session_cookie_name,
domain=self.get_cookie_domain(app),
path=self.get_cookie_path(app),
)
return
# Add a "Vary: Cookie" header if the session was accessed
if session.accessed:
response.vary.add('Cookie')
# TODO: set cookie from time to time to prevent expiration in browser
# also update expire in redis
if not self.should_set_cookie(app, session):
return
# save session and update cookie
session.save()
response.set_cookie(
app.session_cookie_name,
session.sid,
expires=self.get_expiration_time(app, session),
httponly=self.get_cookie_httponly(app),
domain=self.get_cookie_domain(app),
path=self.get_cookie_path(app),
secure=self.get_cookie_secure(app),
samesite=self.get_cookie_samesite(app)
)
class MailuSessionExtension:
""" Server side session handling """
@staticmethod
def cleanup_sessions(app=None):
""" Remove invalid or expired sessions. """
app = app or flask.current_app
now = int(time.time())
count = 0
for key in app.session_store.list():
if not app.session_config.parse_key(key, app, validate=True, now=now):
app.session_store.delete(key)
count += 1
return count
@staticmethod
def prune_sessions(uid=None, keep=None, app=None):
""" Remove sessions
uid: remove all sessions (NONE) or sessions belonging to a specific user
keep: keep listed sessions
"""
keep = keep or set()
app = app or flask.current_app
prefix = None if uid is None else app.session_config.gen_uid(uid)
count = 0
for key in app.session_store.list(prefix):
if key not in keep:
app.session_store.delete(key)
count += 1
return count
def init_app(self, app):
""" Replace session management of application. """
if app.config.get('MEMORY_SESSIONS'):
# in-memory session store for use in development
app.session_store = DictStore()
else:
# redis-based session store for use in production
app.session_store = RedisStore(
redis.StrictRedis().from_url(app.config['SESSION_STORAGE_URL'])
)
# clean expired sessions oonce on first use in case lifetime was changed
def cleaner():
with cleaned.get_lock():
if not cleaned.value:
cleaned.value = True
flask.current_app.logger.error('cleaning')
MailuSessionExtension.cleanup_sessions(app)
app.before_first_request(cleaner)
app.session_config = MailuSessionConfig(app)
app.session_interface = MailuSessionInterface()
cleaned = Value('i', False)
session = MailuSessionExtension()