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-rw-r--r--server/src/leap/soledad/server/auth.py16
1 files changed, 12 insertions, 4 deletions
diff --git a/server/src/leap/soledad/server/auth.py b/server/src/leap/soledad/server/auth.py
index e9d2b032..57f600a1 100644
--- a/server/src/leap/soledad/server/auth.py
+++ b/server/src/leap/soledad/server/auth.py
@@ -30,6 +30,7 @@ from abc import ABCMeta, abstractmethod
from routes.mapper import Mapper
from couchdb.client import Server
from twisted.python import log
+from hashlib import sha512
from leap.soledad.common import (
@@ -415,10 +416,17 @@ class SoledadTokenAuthMiddleware(SoledadAuthMiddleware):
server = Server(url=self._app.state.couch_url)
dbname = self.TOKENS_DB
db = server[dbname]
- token = db.get(token)
- if token is None or \
- token[self.TOKENS_TYPE_KEY] != self.TOKENS_TYPE_DEF or \
- token[self.TOKENS_USER_ID_KEY] != uuid:
+ # lookup key is a hash of the token to prevent timing attacks.
+ token = db.get(sha512(token).hexdigest())
+ if token is None:
+ raise InvalidAuthTokenError()
+ # we compare uuid hashes to avoid possible timing attacks that
+ # might exploit python's builtin comparison operator behaviour,
+ # which fails immediatelly when non-matching bytes are found.
+ couch_uuid_hash = sha512(token[self.TOKENS_USER_ID_KEY]).digest()
+ req_uuid_hash = sha512(uuid).digest()
+ if token[self.TOKENS_TYPE_KEY] != self.TOKENS_TYPE_DEF \
+ or couch_uuid_hash != req_uuid_hash:
raise InvalidAuthTokenError()
return True