1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238
|
From 2e47f3e401c29bc2ba5ab794d483cb0820855fb9 Mon Sep 17 00:00:00 2001
From: Carl Meyer <carl@oddbird.net>
Date: Wed, 10 Jun 2015 15:45:20 -0600
Subject: [PATCH] [1.4.x] Fixed #19324 -- Avoided creating a session record
when loading the session.
The session record is now only created if/when the session is modified. This
prevents a potential DoS via creation of many empty session records.
This is a security fix; disclosure to follow shortly.
---
django/contrib/sessions/backends/cache.py | 6 ++++--
django/contrib/sessions/backends/cached_db.py | 5 +++--
django/contrib/sessions/backends/db.py | 5 +++--
django/contrib/sessions/backends/file.py | 7 ++++---
django/contrib/sessions/tests.py | 19 +++++++++++++++++++
docs/releases/1.4.21.txt | 21 +++++++++++++++++++++
6 files changed, 54 insertions(+), 9 deletions(-)
--- a/django/contrib/sessions/backends/cache.py
+++ b/django/contrib/sessions/backends/cache.py
@@ -15,7 +15,7 @@ class SessionStore(SessionBase):
session_data = self._cache.get(KEY_PREFIX + self.session_key)
if session_data is not None:
return session_data
- self.create()
+ self._session_key = None
return {}
def create(self):
@@ -35,6 +35,8 @@ class SessionStore(SessionBase):
raise RuntimeError("Unable to create a new session key.")
def save(self, must_create=False):
+ if self._session_key is None:
+ return self.create()
if must_create:
func = self._cache.add
else:
@@ -45,7 +47,7 @@ class SessionStore(SessionBase):
raise CreateError
def exists(self, session_key):
- if self._cache.has_key(KEY_PREFIX + session_key):
+ if session_key and self._cache.has_key(KEY_PREFIX + session_key):
return True
return False
--- a/django/contrib/sessions/backends/cached_db.py
+++ b/django/contrib/sessions/backends/cached_db.py
@@ -20,16 +20,19 @@ class SessionStore(DBStore):
data = cache.get(KEY_PREFIX + self.session_key, None)
if data is None:
data = super(SessionStore, self).load()
- cache.set(KEY_PREFIX + self.session_key, data,
- settings.SESSION_COOKIE_AGE)
+ if self._session_key:
+ cache.set(KEY_PREFIX + self._session_key, data,
+ settings.SESSION_COOKIE_AGE)
return data
def exists(self, session_key):
+ if session_key and cache.has_key(KEY_PREFIX + session_key):
+ return True
return super(SessionStore, self).exists(session_key)
def save(self, must_create=False):
super(SessionStore, self).save(must_create)
- cache.set(KEY_PREFIX + self.session_key, self._session,
+ cache.set(KEY_PREFIX + self.session_key, self._session,
settings.SESSION_COOKIE_AGE)
def delete(self, session_key=None):
@@ -43,4 +46,4 @@ class SessionStore(DBStore):
"""
self.clear()
self.delete(self.session_key)
- self.create()
\ No newline at end of file
+ self.create()
--- a/django/contrib/sessions/backends/db.py
+++ b/django/contrib/sessions/backends/db.py
@@ -21,7 +21,7 @@ class SessionStore(SessionBase):
)
return self.decode(force_unicode(s.session_data))
except (Session.DoesNotExist, SuspiciousOperation):
- self.create()
+ self._session_key = None
return {}
def exists(self, session_key):
@@ -42,7 +42,6 @@ class SessionStore(SessionBase):
# Key wasn't unique. Try again.
continue
self.modified = True
- self._session_cache = {}
return
def save(self, must_create=False):
@@ -52,6 +51,8 @@ class SessionStore(SessionBase):
create a *new* entry (as opposed to possibly updating an existing
entry).
"""
+ if self.session_key is None:
+ return self.create()
obj = Session(
session_key = self.session_key,
session_data = self.encode(self._get_session(no_load=must_create)),
--- a/django/contrib/sessions/backends/file.py
+++ b/django/contrib/sessions/backends/file.py
@@ -56,11 +56,11 @@ class SessionStore(SessionBase):
try:
session_data = self.decode(file_data)
except (EOFError, SuspiciousOperation):
- self.create()
+ self._session_key = None
finally:
session_file.close()
except IOError:
- pass
+ self._session_key = None
return session_data
def create(self):
@@ -71,10 +71,11 @@ class SessionStore(SessionBase):
except CreateError:
continue
self.modified = True
- self._session_cache = {}
return
def save(self, must_create=False):
+ if self.session_key is None:
+ return self.create()
# Get the session data now, before we start messing
# with the file it is stored within.
session_data = self._get_session(no_load=must_create)
--- a/django/contrib/sessions/tests.py
+++ b/django/contrib/sessions/tests.py
@@ -40,6 +40,8 @@ False
(True, True)
>>> db_session['a'], db_session['b'] = 'c', 'd'
>>> db_session.save()
+>>> db_session['a']
+'c'
>>> prev_key = db_session.session_key
>>> prev_data = db_session.items()
>>> db_session.cycle_key()
@@ -55,6 +57,16 @@ True
>>> db_session.save()
>>> DatabaseSession('1').get('cat')
+# Loading an unknown session key does not create a session record
+# Creating session records on load is a DOS vulnerability.
+>>> session = DatabaseSession('deadbeef')
+>>> session.load()
+{}
+>>> session.exists(session.session_key)
+False
+>>> session.session_key != 'deadbeef'
+True
+
#
# Cached DB session tests
#
@@ -75,6 +87,20 @@ True
>>> cdb_session.delete(cdb_session.session_key)
>>> cdb_session.exists(cdb_session.session_key)
False
+>>> cdb_session['a'] = 'b'
+>>> cdb_session.save()
+>>> cdb_session['a']
+'b'
+
+# Loading an unknown session key does not create a session record
+# Creating session records on load is a DOS vulnerability.
+>>> session = CacheDBSession('deadbeef')
+>>> session.load()
+{}
+>>> session.exists(session.session_key)
+False
+>>> session.session_key != 'deadbeef'
+True
#
# File session tests.
@@ -117,6 +143,8 @@ False
(True, True)
>>> file_session['a'], file_session['b'] = 'c', 'd'
>>> file_session.save()
+>>> file_session['a']
+'c'
>>> prev_key = file_session.session_key
>>> prev_data = file_session.items()
>>> file_session.cycle_key()
@@ -129,6 +157,16 @@ True
>>> file_session = FileSession(file_session.session_key)
>>> file_session.save()
+# Loading an unknown session key does not create a session record
+# Creating session records on load is a DOS vulnerability.
+>>> session = FileSession('deadbeef')
+>>> session.load()
+{}
+>>> session.exists(session.session_key)
+False
+>>> session.session_key != 'deadbeef'
+True
+
# Ensure we don't allow directory traversal
>>> FileSession("a/b/c").load()
Traceback (innermost last):
@@ -186,6 +224,8 @@ False
(True, True)
>>> cache_session['a'], cache_session['b'] = 'c', 'd'
>>> cache_session.save()
+>>> cache_session['a']
+'c'
>>> prev_key = cache_session.session_key
>>> prev_data = cache_session.items()
>>> cache_session.cycle_key()
@@ -204,6 +244,16 @@ True
>>> cache_session.save()
>>> cache_session.delete(cache_session.session_key)
+# Loading an unknown session key does not create a session record
+# Creating session records on load is a DOS vulnerability.
+>>> session = CacheSession('deadbeef')
+>>> session.load()
+{}
+>>> session.exists(session.session_key)
+False
+>>> session.session_key != 'deadbeef'
+True
+
>>> s = SessionBase()
>>> s._session['some key'] = 'exists' # Pre-populate the session with some data
>>> s.accessed = False # Reset to pretend this wasn't accessed previously
|