fix permanent sessions. hash uid using SECRET_KEY

clean session in redis only once when starting
master
Alexander Graf 3 years ago
parent 4b8bbf760b
commit 731ce8ede9

@ -10,6 +10,8 @@ import hashlib
import secrets
import time
from multiprocessing import Value
from mailu import limiter
import flask
@ -87,10 +89,10 @@ class RedisStore:
raise KeyError(key)
return value
def put(self, key, value, ttl_secs=None):
def put(self, key, value, ttl=None):
""" save item to store. """
if ttl_secs:
self.redis.setex(key, int(ttl_secs), value)
if ttl:
self.redis.setex(key, int(ttl), value)
else:
self.redis.set(key, value)
@ -171,6 +173,11 @@ class MailuSession(CallbackDict, SessionMixin):
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. """
@ -181,9 +188,7 @@ class MailuSession(CallbackDict, SessionMixin):
def destroy(self):
""" destroy session for security reasons. """
if self._key is not None:
self.app.session_store.delete(self._key)
self._key = None
self.delete()
self._uid = None
self._sid = None
@ -191,28 +196,28 @@ class MailuSession(CallbackDict, SessionMixin):
self.clear()
self.modified = False
self.modified = True
self.new = False
def regenerate(self):
""" generate new id for session to avoid `session fixation`. """
if self._key is not None:
self.app.session_store.delete(self._key)
self._key = None
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. """
# don't save if session was destroyed or is not modified
if self._created is None or not self.modified:
return False
# set uid from dict data
if self._uid is None:
self._uid = self.app.session_config.gen_uid(self.get('user_id', ''))
@ -221,25 +226,18 @@ class MailuSession(CallbackDict, SessionMixin):
if self._sid is None:
self._sid = self.app.session_config.gen_sid()
# set created if permanent state changed
if self.permanent:
if self._created:
self._created = b''
elif not self._created:
self._created = self.app.session_config.gen_created()
# get new session key
key = self.sid
# delete old session if key has changed
if key != self._key and self._key is not None:
self.app.session_store.delete(self._key)
if key != self._key:
self.delete()
# save session
self.app.session_store.put(
key,
pickle.dumps(dict(self)),
None if self.permanent else self.app.permanent_session_lifetime.total_seconds()
self.app.permanent_session_lifetime.total_seconds()
)
self._key = key
@ -247,8 +245,6 @@ class MailuSession(CallbackDict, SessionMixin):
self.new = False
self.modified = False
return True
class MailuSessionConfig:
""" Stores sessions crypto config """
@ -264,8 +260,9 @@ class MailuSessionConfig:
hash_bytes = bits//8 + (bits%8>0)
time_bytes = 4 # 32 bit timestamp for now
shaker = hashlib.shake_256 if bits>128 else hashlib.shake_128
self._shake_fn = hashlib.shake_256 if bits>128 else hashlib.shake_128
self._shaker = shaker(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
@ -277,13 +274,15 @@ class MailuSessionConfig:
def gen_uid(self, uid):
""" Generate hashed user id part of session key. """
return self._encode(self._shake_fn(want_bytes(uid)).digest(self._hash_len))
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, now=None):
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):
@ -299,13 +298,12 @@ class MailuSessionConfig:
return None
# validate creation time when requested or store does not support ttl
if now is not None or not app.session_store.has_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 created > 0:
if now is None:
now = int(time.time())
if created < now < created + app.permanent_session_lifetime.total_seconds():
return None
if not (created < now < created + app.permanent_session_lifetime.total_seconds()):
return None
return (uid, sid, crt)
@ -328,17 +326,40 @@ class MailuSessionInterface(SessionInterface):
def save_session(self, app, session, response):
""" Save modified session. """
if session.save():
# session saved. update cookie
response.set_cookie(
key=app.config['SESSION_COOKIE_NAME'],
value=session.sid,
expires=self.get_expiration_time(app, session),
path=self.get_cookie_path(app),
domain=self.get_cookie_domain(app),
secure=app.config['SESSION_COOKIE_SECURE'],
httponly=app.config['SESSION_COOKIE_HTTPONLY']
)
# 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 """
@ -352,36 +373,29 @@ class MailuSessionExtension:
count = 0
for key in app.session_store.list():
if not app.session_config.parse_key(key, app, now):
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_permanent=False, keep=None, app=None):
def prune_sessions(uid=None, keep=None, app=None):
""" Remove sessions
uid: remove all sessions (NONE) or sessions belonging to a specific user
keep_permanent: also delete permanent sessions?
keep: keep listed sessions
"""
keep = keep or set()
app = app or flask.current_app
now = int(time.time())
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 in keep:
continue
if keep_permanent:
if parsed := app.session_config.parse_key(key, app, now):
if not parsed[2]:
continue
app.session_store.delete(key)
count += 1
if key not in keep:
app.session_store.delete(key)
count += 1
return count
@ -398,14 +412,18 @@ class MailuSessionExtension:
redis.StrictRedis().from_url(app.config['SESSION_STORAGE_URL'])
)
# clean expired sessions on first use in case lifetime was changed
# clean expired sessions oonce on first use in case lifetime was changed
def cleaner():
MailuSessionExtension.cleanup_sessions(app)
with cleaned.get_lock():
if not cleaned.value:
cleaned.value = True
flask.current_app.logger.error('cleaning')
MailuSessionExtension.cleanup_sessions(app)
# TODO: hmm. this will clean once per gunicorn worker
app.before_first_request(cleaner)
app.session_config = MailuSessionConfig(app)
app.session_interface = MailuSessionInterface()
cleaned = Value('i', False)
session = MailuSessionExtension()

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