+74
-8
lines changedFilter options
+74
-8
lines changed Original file line number Diff line number Diff line change
@@ -27,7 +27,7 @@ def load(self):
27 27
session_data = None
28 28
if session_data is not None:
29 29
return session_data
30 -
self.create()
30 +
self._session_key = None
31 31
return {}
32 32 33 33
def create(self):
@@ -49,6 +49,8 @@ def create(self):
49 49
"It is likely that the cache is unavailable.")
50 50 51 51
def save(self, must_create=False):
52 +
if self.session_key is None:
53 +
return self.create()
52 54
if must_create:
53 55
func = self._cache.add
54 56
else:
@@ -60,7 +62,7 @@ def save(self, must_create=False):
60 62
raise CreateError
61 63 62 64
def exists(self, session_key):
63 -
return (KEY_PREFIX + session_key) in self._cache
65 +
return session_key and (KEY_PREFIX + session_key) in self._cache
64 66 65 67
def delete(self, session_key=None):
66 68
if session_key is None:
@@ -51,12 +51,12 @@ def load(self):
51 51
logger = logging.getLogger('django.security.%s' %
52 52
e.__class__.__name__)
53 53
logger.warning(force_text(e))
54 -
self.create()
54 +
self._session_key = None
55 55
data = {}
56 56
return data
57 57 58 58
def exists(self, session_key):
59 -
if (KEY_PREFIX + session_key) in self._cache:
59 +
if session_key and (KEY_PREFIX + session_key) in self._cache:
60 60
return True
61 61
return super(SessionStore, self).exists(session_key)
62 62
@@ -26,7 +26,7 @@ def load(self):
26 26
logger = logging.getLogger('django.security.%s' %
27 27
e.__class__.__name__)
28 28
logger.warning(force_text(e))
29 -
self.create()
29 +
self._session_key = None
30 30
return {}
31 31 32 32
def exists(self, session_key):
@@ -43,7 +43,6 @@ def create(self):
43 43
# Key wasn't unique. Try again.
44 44
continue
45 45
self.modified = True
46 -
self._session_cache = {}
47 46
return
48 47 49 48
def save(self, must_create=False):
@@ -53,6 +52,8 @@ def save(self, must_create=False):
53 52
create a *new* entry (as opposed to possibly updating an existing
54 53
entry).
55 54
"""
55 +
if self.session_key is None:
56 +
return self.create()
56 57
obj = Session(
57 58
session_key=self._get_or_create_session_key(),
58 59
session_data=self.encode(self._get_session(no_load=must_create)),
@@ -96,7 +96,7 @@ def load(self):
96 96
self.delete()
97 97
self.create()
98 98
except (IOError, SuspiciousOperation):
99 -
self.create()
99 +
self._session_key = None
100 100
return session_data
101 101 102 102
def create(self):
@@ -107,10 +107,11 @@ def create(self):
107 107
except CreateError:
108 108
continue
109 109
self.modified = True
110 -
self._session_cache = {}
111 110
return
112 111 113 112
def save(self, must_create=False):
113 +
if self.session_key is None:
114 +
return self.create()
114 115
# Get the session data now, before we start messing
115 116
# with the file it is stored within.
116 117
session_data = self._get_session(no_load=must_create)
@@ -171,6 +171,11 @@ def test_cycle(self):
171 171
self.assertNotEqual(self.session.session_key, prev_key)
172 172
self.assertEqual(list(self.session.items()), prev_data)
173 173 174 +
def test_save_doesnt_clear_data(self):
175 +
self.session['a'] = 'b'
176 +
self.session.save()
177 +
self.assertEqual(self.session['a'], 'b')
178 + 174 179
def test_invalid_key(self):
175 180
# Submitting an invalid session key (either by guessing, or if the db has
176 181
# removed the key) results in a new key being generated.
@@ -306,6 +311,21 @@ def test_actual_expiry(self):
306 311
self.session.delete(old_session_key)
307 312
self.session.delete(new_session_key)
308 313 314 +
def test_session_load_does_not_create_record(self):
315 +
"""
316 +
Loading an unknown session key does not create a session record.
317 + 318 +
Creating session records on load is a DOS vulnerability.
319 +
"""
320 +
if self.backend is CookieSession:
321 +
raise unittest.SkipTest("Cookie backend doesn't have an external store to create records in.")
322 +
session = self.backend('someunknownkey')
323 +
session.load()
324 + 325 +
self.assertFalse(session.exists(session.session_key))
326 +
# provided unknown key was cycled, not reused
327 +
self.assertNotEqual(session.session_key, 'someunknownkey')
328 + 309 329 310 330
class DatabaseSessionTests(SessionTestsMixin, TestCase):
311 331
@@ -5,3 +5,24 @@ Django 1.4.21 release notes
5 5
*July 8, 2015*
6 6 7 7
Django 1.4.21 fixes several security issues in 1.4.20.
8 + 9 +
Denial-of-service possibility by filling session store
10 +
======================================================
11 + 12 +
In previous versions of Django, the session backends created a new empty record
13 +
in the session storage anytime ``request.session`` was accessed and there was a
14 +
session key provided in the request cookies that didn't already have a session
15 +
record. This could allow an attacker to easily create many new session records
16 +
simply by sending repeated requests with unknown session keys, potentially
17 +
filling up the session store or causing other users' session records to be
18 +
evicted.
19 + 20 +
The built-in session backends now create a session record only if the session
21 +
is actually modified; empty session records are not created. Thus this
22 +
potential DoS is now only possible if the site chooses to expose a
23 +
session-modifying view to anonymous users.
24 + 25 +
As each built-in session backend was fixed separately (rather than a fix in the
26 +
core sessions framework), maintainers of third-party session backends should
27 +
check whether the same vulnerability is present in their backend and correct
28 +
it if so.
Original file line number Diff line number Diff line change
@@ -6,6 +6,27 @@ Django 1.7.9 release notes
6 6 7 7
Django 1.7.9 fixes several security issues and bugs in 1.7.8.
8 8 9 +
Denial-of-service possibility by filling session store
10 +
======================================================
11 + 12 +
In previous versions of Django, the session backends created a new empty record
13 +
in the session storage anytime ``request.session`` was accessed and there was a
14 +
session key provided in the request cookies that didn't already have a session
15 +
record. This could allow an attacker to easily create many new session records
16 +
simply by sending repeated requests with unknown session keys, potentially
17 +
filling up the session store or causing other users' session records to be
18 +
evicted.
19 + 20 +
The built-in session backends now create a session record only if the session
21 +
is actually modified; empty session records are not created. Thus this
22 +
potential DoS is now only possible if the site chooses to expose a
23 +
session-modifying view to anonymous users.
24 + 25 +
As each built-in session backend was fixed separately (rather than a fix in the
26 +
core sessions framework), maintainers of third-party session backends should
27 +
check whether the same vulnerability is present in their backend and correct
28 +
it if so.
29 + 9 30
Bugfixes
10 31
========
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