Disallow unsafe tempurl operations to point to unauthorized data

Do not allow PUT tempurls to create pointers to other data. Specifically
disallow the creation of DLO object manifests by returning an error if a
non-safe tempurl request includes an X-Object-Manifest header regardless of
the value of the header.

This prevents discoverability attacks which can use any PUT tempurl to probe
for private data by creating a DLO object manifest and then using the PUT
tempurl to head the object which would 404 if the prefix does not match any
object data or form a valid DLO HEAD response if it does.

This also prevents a tricky and potentially unexpected consequence of PUT
tempurls which would make it unsafe to allow a user to download objects
created by tempurl (even if they just created them) because the result of
reading the object created via tempurl may not be the data which was uploaded.

[CVE-2015-5223]

Co-Authored-By: Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>

Closes-Bug: 1453948

Change-Id: I91161dfb0f089c3990aca1b4255b520299ef73c8
This commit is contained in:
Clay Gerrard 2015-07-23 22:36:21 -07:00 committed by John Dickinson
parent b7f1768a17
commit 0694e1911d
3 changed files with 85 additions and 1 deletions

View File

@ -119,11 +119,13 @@ from urllib import urlencode
from urlparse import parse_qs
from swift.proxy.controllers.base import get_account_info
from swift.common.swob import HeaderKeyDict, HTTPUnauthorized
from swift.common.swob import HeaderKeyDict, HTTPUnauthorized, HTTPBadRequest
from swift.common.utils import split_path, get_valid_utf8_str, \
register_swift_info, get_hmac, streq_const_time, quote
DISALLOWED_INCOMING_HEADERS = 'x-object-manifest'
#: Default headers to remove from incoming requests. Simply a whitespace
#: delimited list of header names and names can optionally end with '*' to
#: indicate a prefix match. DEFAULT_INCOMING_ALLOW_HEADERS is a list of
@ -227,6 +229,10 @@ class TempURL(object):
#: The methods allowed with Temp URLs.
self.methods = methods
self.disallowed_headers = set(
'HTTP_' + h.upper().replace('-', '_')
for h in DISALLOWED_INCOMING_HEADERS.split())
headers = DEFAULT_INCOMING_REMOVE_HEADERS
if 'incoming_remove_headers' in conf:
headers = conf['incoming_remove_headers']
@ -320,6 +326,13 @@ class TempURL(object):
for hmac in hmac_vals)
if not is_valid_hmac:
return self._invalid(env, start_response)
# disallowed headers prevent accidently allowing upload of a pointer
# to data that the PUT tempurl would not otherwise allow access for.
# It should be safe to provide a GET tempurl for data that an
# untrusted client just uploaded with a PUT tempurl.
resp = self._clean_disallowed_headers(env, start_response)
if resp:
return resp
self._clean_incoming_headers(env)
env['swift.authorize'] = lambda req: None
env['swift.authorize_override'] = True
@ -456,6 +469,22 @@ class TempURL(object):
body = '401 Unauthorized: Temp URL invalid\n'
return HTTPUnauthorized(body=body)(env, start_response)
def _clean_disallowed_headers(self, env, start_response):
"""
Validate the absense of disallowed headers for "unsafe" operations.
:returns: None for safe operations or swob.HTTPBadResponse if the
request includes disallowed headers.
"""
if env['REQUEST_METHOD'] in ('GET', 'HEAD', 'OPTIONS'):
return
for h in env:
if h in self.disallowed_headers:
return HTTPBadRequest(
body='The header %r is not allowed in this tempurl' %
h[len('HTTP_'):].title().replace('_', '-'))(
env, start_response)
def _clean_incoming_headers(self, env):
"""
Removes any headers from the WSGI environment as per the

View File

@ -2687,6 +2687,42 @@ class TestTempurl(Base):
self.assert_(new_obj.info(parms=put_parms,
cfg={'no_auth_token': True}))
def test_PUT_manifest_access(self):
new_obj = self.env.container.file(Utils.create_name())
# give out a signature which allows a PUT to new_obj
expires = int(time.time()) + 86400
sig = self.tempurl_sig(
'PUT', expires, self.env.conn.make_path(new_obj.path),
self.env.tempurl_key)
put_parms = {'temp_url_sig': sig,
'temp_url_expires': str(expires)}
# try to create manifest pointing to some random container
try:
new_obj.write('', {
'x-object-manifest': '%s/foo' % 'some_random_container'
}, parms=put_parms, cfg={'no_auth_token': True})
except ResponseError as e:
self.assertEqual(e.status, 400)
else:
self.fail('request did not error')
# create some other container
other_container = self.env.account.container(Utils.create_name())
if not other_container.create():
raise ResponseError(self.conn.response)
# try to create manifest pointing to new container
try:
new_obj.write('', {
'x-object-manifest': '%s/foo' % other_container
}, parms=put_parms, cfg={'no_auth_token': True})
except ResponseError as e:
self.assertEqual(e.status, 400)
else:
self.fail('request did not error')
def test_HEAD(self):
expires = int(time.time()) + 86400
sig = self.tempurl_sig(

View File

@ -623,6 +623,25 @@ class TestTempURL(unittest.TestCase):
self.assertTrue('Temp URL invalid' in resp.body)
self.assertTrue('Www-Authenticate' in resp.headers)
def test_disallowed_header_object_manifest(self):
self.tempurl = tempurl.filter_factory({})(self.auth)
method = 'PUT'
expires = int(time() + 86400)
path = '/v1/a/c/o'
key = 'abc'
hmac_body = '%s\n%s\n%s' % (method, expires, path)
sig = hmac.new(key, hmac_body, sha1).hexdigest()
req = self._make_request(
path, method='PUT', keys=[key],
headers={'x-object-manifest': 'private/secret'},
environ={'QUERY_STRING': 'temp_url_sig=%s&temp_url_expires=%s' % (
sig, expires)})
resp = req.get_response(self.tempurl)
self.assertEquals(resp.status_int, 400)
self.assertTrue('header' in resp.body)
self.assertTrue('not allowed' in resp.body)
self.assertTrue('X-Object-Manifest' in resp.body)
def test_removed_incoming_header(self):
self.tempurl = tempurl.filter_factory({
'incoming_remove_headers': 'x-remove-this'})(self.auth)