CVE-2012-4406 (published 2012-10-22T23:55Z)

OpenStack Object Storage (swift) before 1.7.0 uses the loads function in the pickle Python module unsafely when storing and loading metadata in memcached, which allows remote attackers to execute arbitrary code via a crafted pickle object.

Severity: HIGH
CVSS v2 base score: 7.5 (AV:N/AC:L/Au:N/C:P/I:P/A:P)
CVSS v3 base score: 9.8, CRITICAL (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-502
cwe_name: Deserialization of Untrusted Data
description: The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
extended_description: 
            It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security -- which is a dangerous security assumption.
            Data that is untrusted can not be trusted to be well-formed.
            When developers place no restrictions on "gadget chains," or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.
         
         

Fix information:
repo_url: https://github.com/openstack/swift
commit_details: repo_url: https://github.com/openstack/swift
author: Vincent Untz
author_date: 2012-06-21 14:37:41+02:00
msg: Do not use pickle for serialization in memcache, but JSON

We don't want to use pickle as it can execute arbitrary code. JSON is
safer. However, note that it supports serialization for only some
specific subset of object types; this should be enough for what we need,
though.

To avoid issues on upgrades (unability to read pickled values, and cache
poisoning for old servers not understanding JSON), we add a
memcache_serialization_support configuration option, with the following
values:

 0 = older, insecure pickle serialization
 1 = json serialization but pickles can still be read (still insecure)
 2 = json serialization only (secure and the default)

To avoid an instant full cache flush, existing installations should
upgrade with 0, then set to 1 and reload, then after some time (24
hours) set to 2 and reload. Support for 0 and 1 will be removed in
future versions.

Part of bug 1006414.

Change-Id: Id7d6d547b103b4f23ebf5be98b88f09ec6027ce4
repository: repo_url: https://github.com/openstack/swift
repo_name: openstack/swift
description: OpenStack Storage (Swift). Mirror of code maintained at opendev.org.
repo_language: Python
owner: openstack
file_changes: filename: proxy-server.conf.5
change_type: ModificationType.MODIFY
diff: @@ -213,6 +213,21 @@ Logging address. The default is /dev/log.
 Enables the ability to log request headers. The default is False.
 .IP \fBmemcache_servers\fR
 If not set in the configuration file, the value for memcache_servers will be read from /etc/swift/memcache.conf (see memcache.conf-sample) or lacking that file, it will default to the value below. You can specify multiple servers separated with commas, as in: 10.1.2.3:11211,10.1.2.4:11211. This can be a list separated by commas. The default is 127.0.0.1:11211.
+.IP \fBmemcache_serialization_support\fR
+This sets how memcache values are serialized and deserialized:
+.RE
+
+.PD 0
+.RS 10
+.IP "0 = older, insecure pickle serialization"
+.IP "1 = json serialization but pickles can still be read (still insecure)"
+.IP "2 = json serialization only (secure and the default)"
+.RE
+
+.RS 10
+To avoid an instant full cache flush, existing installations should upgrade with 0, then set to 1 and reload, then after some time (24 hours) set to 2 and reload. In the future, the ability to use pickle serialization will be removed.
+
+If not set in the configuration file, the value for memcache_serialization_support will be read from /etc/swift/memcache.conf if it exists (see memcache.conf-sample). Otherwise, the default value as indicated above will be used.
 .RE
 
 

programming_language: Perl
filename: memcache.conf-sample
change_type: ModificationType.MODIFY
diff: @@ -3,3 +3,13 @@
 # several other conf files under [filter:cache] for example. You can specify
 # multiple servers separated with commas, as in: 10.1.2.3:11211,10.1.2.4:11211
 # memcache_servers = 127.0.0.1:11211
+#
+# Sets how memcache values are serialized and deserialized:
+# 0 = older, insecure pickle serialization
+# 1 = json serialization but pickles can still be read (still insecure)
+# 2 = json serialization only (secure and the default)
+# To avoid an instant full cache flush, existing installations should
+# upgrade with 0, then set to 1 and reload, then after some time (24 hours)
+# set to 2 and reload.
+# In the future, the ability to use pickle serialization will be removed.
+# memcache_serialization_support = 2

programming_language: Ruby
filename: proxy-server.conf-sample
change_type: ModificationType.MODIFY
diff: @@ -167,6 +167,18 @@ use = egg:swift#memcache
 # default to the value below. You can specify multiple servers separated with
 # commas, as in: 10.1.2.3:11211,10.1.2.4:11211
 # memcache_servers = 127.0.0.1:11211
+#
+# Sets how memcache values are serialized and deserialized:
+# 0 = older, insecure pickle serialization
+# 1 = json serialization but pickles can still be read (still insecure)
+# 2 = json serialization only (secure and the default)
+# If not set here, the value for memcache_serialization_support will be read
+# from /etc/swift/memcache.conf (see memcache.conf-sample).
+# To avoid an instant full cache flush, existing installations should
+# upgrade with 0, then set to 1 and reload, then after some time (24 hours)
+# set to 2 and reload.
+# In the future, the ability to use pickle serialization will be removed.
+# memcache_serialization_support = 2
 
 [filter:ratelimit]
 use = egg:swift#ratelimit

programming_language: Python
filename: memcached.py
change_type: ModificationType.MODIFY
diff: @@ -27,11 +27,17 @@ import time
 from bisect import bisect
 from hashlib import md5
 
+try:
+    import simplejson as json
+except ImportError:
+    import json
+
 DEFAULT_MEMCACHED_PORT = 11211
 
 CONN_TIMEOUT = 0.3
 IO_TIMEOUT = 2.0
 PICKLE_FLAG = 1
+JSON_FLAG = 2
 NODE_WEIGHT = 50
 PICKLE_PROTOCOL = 2
 TRY_COUNT = 3
@@ -57,7 +63,8 @@ class MemcacheRing(object):
     """
 
     def __init__(self, servers, connect_timeout=CONN_TIMEOUT,
-                 io_timeout=IO_TIMEOUT, tries=TRY_COUNT):
+                 io_timeout=IO_TIMEOUT, tries=TRY_COUNT,
+                 allow_pickle=False, allow_unpickle=False):
         self._ring = {}
         self._errors = dict(((serv, []) for serv in servers))
         self._error_limited = dict(((serv, 0) for serv in servers))
@@ -69,6 +76,8 @@ class MemcacheRing(object):
         self._client_cache = dict(((server, []) for server in servers))
         self._connect_timeout = connect_timeout
         self._io_timeout = io_timeout
+        self._allow_pickle = allow_pickle
+        self._allow_unpickle = allow_unpickle or allow_pickle
 
     def _exception_occurred(self, server, e, action='talking'):
         if isinstance(e, socket.timeout):
@@ -130,16 +139,21 @@ class MemcacheRing(object):
 
         :param key: key
         :param value: value
-        :param serialize: if True, value is pickled before sending to memcache
+        :param serialize: if True, value is serialized with JSON before sending
+                          to memcache, or with pickle if configured to use
+                          pickle instead of JSON (to avoid cache poisoning)
         :param timeout: ttl in memcache
         """
         key = md5hash(key)
         if timeout > 0:
             timeout += time.time()
         flags = 0
-        if serialize:
+        if serialize and self._allow_pickle:
             value = pickle.dumps(value, PICKLE_PROTOCOL)
             flags |= PICKLE_FLAG
+        elif serialize:
+            value = json.dumps(value)
+            flags |= JSON_FLAG
         for (server, fp, sock) in self._get_conns(key):
             try:
                 sock.sendall('set %s %d %d %s noreply\r\n%s\r\n' % \
@@ -151,8 +165,9 @@ class MemcacheRing(object):
 
     def get(self, key):
         """
-        Gets the object specified by key.  It will also unpickle the object
-        before returning if it is pickled in memcache.
+        Gets the object specified by key.  It will also unserialize the object
+        before returning if it is serialized in memcache with JSON, or if it
+        is pickled and unpickling is allowed.
 
         :param key: key
         :returns: value of the key in memcache
@@ -168,7 +183,12 @@ class MemcacheRing(object):
                         size = int(line[3])
                         value = fp.read(size)
                         if int(line[2]) & PICKLE_FLAG:
-                            value = pickle.loads(value)
+                            if self._allow_unpickle:
+                                value = pickle.loads(value)
+                            else:
+                                value = None
+                        elif int(line[2]) & JSON_FLAG:
+                            value = json.loads(value)
                         fp.readline()
                     line = fp.readline().strip().split()
                 self._return_conn(server, fp, sock)
@@ -258,7 +278,9 @@ class MemcacheRing(object):
         :param mapping: dictonary of keys and values to be set in memcache
         :param servery_key: key to use in determining which server in the ring
                             is used
-        :param serialize: if True, value is pickled before sending to memcache
+        :param serialize: if True, value is serialized with JSON before sending
+                          to memcache, or with pickle if configured to use
+                          pickle instead of JSON (to avoid cache poisoning)
         :param timeout: ttl for memcache
         """
         server_key = md5hash(server_key)
@@ -268,9 +290,12 @@ class MemcacheRing(object):
         for key, value in mapping.iteritems():
             key = md5hash(key)
             flags = 0
-            if serialize:
+            if serialize and self._allow_pickle:
                 value = pickle.dumps(value, PICKLE_PROTOCOL)
                 flags |= PICKLE_FLAG
+            elif serialize:
+                value = json.dumps(value)
+                flags |= JSON_FLAG
             msg += ('set %s %d %d %s noreply\r\n%s\r\n' %
                     (key, flags, timeout, len(value), value))
         for (server, fp, sock) in self._get_conns(server_key):
@@ -302,7 +327,12 @@ class MemcacheRing(object):
                         size = int(line[3])
                         value = fp.read(size)
                         if int(line[2]) & PICKLE_FLAG:
-                            value = pickle.loads(value)
+                            if self._allow_unpickle:
+                                value = pickle.loads(value)
+                            else:
+                                value = None
+                        elif int(line[2]) & JSON_FLAG:
+                            value = json.loads(value)
                         responses[line[1]] = value
                         fp.readline()
                     line = fp.readline().strip().split()

programming_language: Python
filename: memcache.py
change_type: ModificationType.MODIFY
diff: @@ -27,20 +27,36 @@ class MemcacheMiddleware(object):
     def __init__(self, app, conf):
         self.app = app
         self.memcache_servers = conf.get('memcache_servers')
-        if not self.memcache_servers:
+        serialization_format = conf.get('memcache_serialization_support')
+
+        if not self.memcache_servers or serialization_format is None:
             path = os.path.join(conf.get('swift_dir', '/etc/swift'),
                                 'memcache.conf')
             memcache_conf = ConfigParser()
             if memcache_conf.read(path):
-                try:
-                    self.memcache_servers = \
-                        memcache_conf.get('memcache', 'memcache_servers')
-                except (NoSectionError, NoOptionError):
-                    pass
+                if not self.memcache_servers:
+                    try:
+                        self.memcache_servers = \
+                            memcache_conf.get('memcache', 'memcache_servers')
+                    except (NoSectionError, NoOptionError):
+                        pass
+                if serialization_format is None:
+                    try:
+                        serialization_format = \
+                            memcache_conf.get('memcache',
+                                              'memcache_serialization_support')
+                    except (NoSectionError, NoOptionError):
+                        pass
+
         if not self.memcache_servers:
             self.memcache_servers = '127.0.0.1:11211'
+        if serialization_format is None:
+            serialization_format = 2
+
         self.memcache = MemcacheRing(
-            [s.strip() for s in self.memcache_servers.split(',') if s.strip()])
+            [s.strip() for s in self.memcache_servers.split(',') if s.strip()],
+            allow_pickle=(serialization_format == 0),
+            allow_unpickle=(serialization_format <= 1))
 
     def __call__(self, env, start_response):
         env['swift.cache'] = self.memcache

programming_language: Python
filename: test_memcache.py
change_type: ModificationType.MODIFY
diff: @@ -47,6 +47,8 @@ class SetConfigParser(object):
         if section == 'memcache':
             if option == 'memcache_servers':
                 return '1.2.3.4:5'
+            elif option == 'memcache_serialization_support':
+                return '2'
             else:
                 raise NoOptionError(option)
         else:
@@ -86,7 +88,8 @@ class TestCacheMiddleware(unittest.TestCase):
         exc = None
         try:
             app = memcache.MemcacheMiddleware(
-                    FakeApp(), {'memcache_servers': '1.2.3.4:5'})
+                    FakeApp(), {'memcache_servers': '1.2.3.4:5',
+                                'memcache_serialization_support': '2'})
         except Exception, err:
             exc = err
         finally:

programming_language: Python
filename: test_memcached.py
change_type: ModificationType.MODIFY
diff: @@ -1,3 +1,4 @@
+ # -*- coding: utf8 -*-
 # Copyright (c) 2010-2012 OpenStack, LLC.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -161,6 +162,9 @@ class TestMemcached(unittest.TestCase):
         self.assertEquals(memcache_client.get('some_key'), [1, 2, 3])
         memcache_client.set('some_key', [4, 5, 6])
         self.assertEquals(memcache_client.get('some_key'), [4, 5, 6])
+        memcache_client.set('some_key', ['simple str', 'utf8 str éà'])
+        # As per http://wiki.openstack.org/encoding, we should expect to have unicode
+        self.assertEquals(memcache_client.get('some_key'), ['simple str', u'utf8 str éà'])
         self.assert_(float(mock.cache.values()[0][1]) == 0)
         esttimeout = time.time() + 10
         memcache_client.set('some_key', [1, 2, 3], timeout=10)
@@ -239,6 +243,24 @@ class TestMemcached(unittest.TestCase):
         self.assertEquals(memcache_client.get_multi(('some_key2', 'some_key1',
             'not_exists'), 'multi_key'), [[4, 5, 6], [1, 2, 3], None])
 
+    def test_serialization(self):
+        memcache_client = memcached.MemcacheRing(['1.2.3.4:11211'],
+                                                 allow_pickle=True)
+        mock = MockMemcached()
+        memcache_client._client_cache['1.2.3.4:11211'] = [(mock, mock)] * 2
+        memcache_client.set('some_key', [1, 2, 3])
+        self.assertEquals(memcache_client.get('some_key'), [1, 2, 3])
+        memcache_client._allow_pickle = False
+        memcache_client._allow_unpickle = True
+        self.assertEquals(memcache_client.get('some_key'), [1, 2, 3])
+        memcache_client._allow_unpickle = False
+        self.assertEquals(memcache_client.get('some_key'), None)
+        memcache_client.set('some_key', [1, 2, 3])
+        self.assertEquals(memcache_client.get('some_key'), [1, 2, 3])
+        memcache_client._allow_unpickle = True
+        self.assertEquals(memcache_client.get('some_key'), [1, 2, 3])
+        memcache_client._allow_pickle = True
+        self.assertEquals(memcache_client.get('some_key'), [1, 2, 3])
 
 if __name__ == '__main__':
     unittest.main()

programming_language: Python