Hash token before storing it in Swift

Swauth uses token value as object name. Object names are logged in proxy
and object servers. Anybody with access to proxy/object server logs can
see token values. Attacker can use this token to access user's data in
Swift store. Instead of token, hashed token (with HASH_PATH_PREFIX and
HASH_PATH_SUFFIX) is used as object name now.

WARNING: In deployments without memcached this patch logs out all users
because tokens became invalid.

CVE-2017-16613

SecurityImpact
Closes-Bug: #1655781
Change-Id: I0d01e8e95400c82ef25f98e2d269532e83233c2c

swauth/middleware.py

@@ -15,6 +15,7 @@
 
 import base64
 from hashlib import sha1
+from hashlib import sha512
 import hmac
 from httplib import HTTPConnection
 from httplib import HTTPSConnection
@@ -50,6 +51,8 @@ from swift.common.middleware.acl import referrer_allowed
 from swift.common.utils import cache_from_env
 from swift.common.utils import get_logger
 from swift.common.utils import get_remote_client
+from swift.common.utils import HASH_PATH_PREFIX
+from swift.common.utils import HASH_PATH_SUFFIX
 from swift.common.utils import split_path
 from swift.common.utils import TRUE_VALUES
 from swift.common.utils import urlparse
@@ -289,6 +292,15 @@ class Swauth(object):
                 env['swift.clean_acl'] = clean_acl
         return self.app(env, start_response)
 
+    def _get_concealed_token(self, token):
+        """Returns hashed token to be used as object name in Swift.
+
+        Tokens are stored in auth account but object names are visible in Swift
+        logs. Object names are hashed from token.
+        """
+        enc_key = "%s:%s:%s" % (HASH_PATH_PREFIX, token, HASH_PATH_SUFFIX)
+        return sha512(enc_key).hexdigest()
+
     def get_groups(self, env, token):
         """Get groups for the given token.
 
@@ -397,8 +409,9 @@ class Swauth(object):
                         memcache_key, (time() + expires_from_now, groups),
                         time=expires_from_now)
             else:
+                object_name = self._get_concealed_token(token)
                 path = quote('/v1/%s/.token_%s/%s' %
-                             (self.auth_account, token[-1], token))
+                             (self.auth_account, object_name[-1], object_name))
                 resp = self.make_pre_authed_request(
                     env, 'GET', path).get_response(self.app)
                 if resp.status_int // 100 != 2:
@@ -1168,8 +1181,9 @@ class Swauth(object):
                             (path, resp.status))
         candidate_token = resp.headers.get('x-object-meta-auth-token')
         if candidate_token:
+            object_name = self._get_concealed_token(candidate_token)
             path = quote('/v1/%s/.token_%s/%s' %
-                (self.auth_account, candidate_token[-1], candidate_token))
+                (self.auth_account, object_name[-1], object_name))
             resp = self.make_pre_authed_request(
                 req.environ, 'DELETE', path).get_response(self.app)
             if resp.status_int // 100 != 2 and resp.status_int != 404:
@@ -1318,8 +1332,9 @@ class Swauth(object):
         expires = None
         candidate_token = resp.headers.get('x-object-meta-auth-token')
         if candidate_token:
+            object_name = self._get_concealed_token(candidate_token)
             path = quote('/v1/%s/.token_%s/%s' %
-                (self.auth_account, candidate_token[-1], candidate_token))
+                (self.auth_account, object_name[-1], object_name))
             delete_token = False
             try:
                 if req.headers.get('x-auth-new-token', 'false').lower() in \
@@ -1362,8 +1377,9 @@ class Swauth(object):
             # Generate new token
             token = '%stk%s' % (self.reseller_prefix, uuid4().hex)
             # Save token info
+            object_name = self._get_concealed_token(token)
             path = quote('/v1/%s/.token_%s/%s' %
-                         (self.auth_account, token[-1], token))
+                         (self.auth_account, object_name[-1], object_name))
             try:
                 token_life = min(
                     int(req.headers.get('x-auth-token-lifetime',
@@ -1439,8 +1455,9 @@ class Swauth(object):
                 if expires < time():
                     groups = None
         if not groups:
+            object_name = self._get_concealed_token(token)
             path = quote('/v1/%s/.token_%s/%s' %
-                         (self.auth_account, token[-1], token))
+                         (self.auth_account, object_name[-1], object_name))
             resp = self.make_pre_authed_request(
                 req.environ, 'GET', path).get_response(self.app)
             if resp.status_int // 100 != 2:

test/unit/test_authtypes.py

@@ -202,5 +202,6 @@ class TestSha512(unittest.TestCase):
         match = self.auth_encoder.match('keystring2', creds, **creds_dict)
         self.assertEqual(match, False)
 
+
 if __name__ == '__main__':
     unittest.main()

test/unit/test_middleware.py

@@ -4125,6 +4125,42 @@ class TestAuth(unittest.TestCase):
         # Assert that string passed to hmac.new is only the hash
         self.assertEqual(mock_hmac_new.call_args[0][0], key_hash)
 
+    def test_get_concealed_token(self):
+        auth.HASH_PATH_PREFIX = 'start'
+        auth.HASH_PATH_SUFFIX = 'end'
+        token = 'token'
+
+        # Check sha512 of "start:token:end"
+        hashed_token = self.test_auth._get_concealed_token(token)
+        self.assertEqual(hashed_token,
+                'cb320540b0b4c69eb83de2ffb80714cb6766e2d06b5579d1a35a9c4c3fb62'
+                '981ec50bcc3fb94521133e69a87d1efcb83efd78f35a06b6375e410201476'
+                '0722f6')
+
+        # Check sha512 of "start:token2:end"
+        token = 'token2'
+        hashed_token = self.test_auth._get_concealed_token(token)
+        self.assertEqual(hashed_token,
+                'ca400a6f884c168357f6af0609fda66aecd5aa613147167487495dd9f39fd'
+                '8a77288568e65857294f01e398d7f14328e855f18517ccf94185d849e7f34'
+                'f4259d')
+
+        # Check sha512 of "start2:token2:end"
+        auth.HASH_PATH_PREFIX = 'start2'
+        hashed_token = self.test_auth._get_concealed_token(token)
+        self.assertEqual(hashed_token,
+                'ad594a69f44dd6e0aad54e360b01f15bd4833ccb4dcd9116d7aba0c25fb95'
+                '670155b8cc7175def7aeeb4624a0f2bb7da5f0b204a4680ea7947d3d6a045'
+                '22bdde')
+
+        # Check sha512 of "start2:token2:end2"
+        auth.HASH_PATH_SUFFIX = 'end2'
+        hashed_token = self.test_auth._get_concealed_token(token)
+        self.assertEqual(hashed_token,
+                '446af2473ad6b28319a0fe02719a9d715b9941d12e0709851aedb4f53b890'
+                '693e7f1328e68d870fe114f35f4ed9648b16a5013182db50d3d1f79a660f2'
+                '0e078e')
+
 
 if __name__ == '__main__':
     unittest.main()