From f8e1ab5fee708bea93c54b39dc802a08c7ed7e21 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 10 Jan 2018 18:01:28 +0000
Subject: [PATCH] Do bcrypt hashing in a background thread

---
 synapse/handlers/auth.py         | 24 ++++++++++++++++--------
 synapse/handlers/register.py     |  2 +-
 synapse/handlers/set_password.py |  2 +-
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 2f30f183ce..af9060fdbf 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -13,7 +13,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from twisted.internet import defer
+from twisted.internet import defer, threads
 
 from ._base import BaseHandler
 from synapse.api.constants import LoginType
@@ -22,6 +22,7 @@ from synapse.module_api import ModuleApi
 from synapse.types import UserID
 from synapse.util.async import run_on_reactor
 from synapse.util.caches.expiringcache import ExpiringCache
+from synapse.util.logcontext import make_deferred_yieldable
 
 from twisted.web.client import PartialDownloadError
 
@@ -626,7 +627,7 @@ class AuthHandler(BaseHandler):
         if not lookupres:
             defer.returnValue(None)
         (user_id, password_hash) = lookupres
-        result = self.validate_hash(password, password_hash)
+        result = yield self.validate_hash(password, password_hash)
         if not result:
             logger.warn("Failed password login for user %s", user_id)
             defer.returnValue(None)
@@ -754,10 +755,13 @@ class AuthHandler(BaseHandler):
             password (str): Password to hash.
 
         Returns:
-            Hashed password (str).
+            Deferred(str): Hashed password.
         """
-        return bcrypt.hashpw(password.encode('utf8') + self.hs.config.password_pepper,
-                             bcrypt.gensalt(self.bcrypt_rounds))
+        def _do_hash():
+            return bcrypt.hashpw(password.encode('utf8') + self.hs.config.password_pepper,
+                                 bcrypt.gensalt(self.bcrypt_rounds))
+
+        return make_deferred_yieldable(threads.deferToThread(_do_hash))
 
     def validate_hash(self, password, stored_hash):
         """Validates that self.hash(password) == stored_hash.
@@ -767,13 +771,17 @@ class AuthHandler(BaseHandler):
             stored_hash (str): Expected hash value.
 
         Returns:
-            Whether self.hash(password) == stored_hash (bool).
+            Deferred(bool): Whether self.hash(password) == stored_hash.
         """
-        if stored_hash:
+
+        def _do_validate_hash():
             return bcrypt.hashpw(password.encode('utf8') + self.hs.config.password_pepper,
                                  stored_hash.encode('utf8')) == stored_hash
+
+        if stored_hash:
+            return make_deferred_yieldable(threads.deferToThread(_do_validate_hash))
         else:
-            return False
+            return defer.succeed(False)
 
 
 class MacaroonGeneartor(object):
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index f6e7e58563..132e2052c0 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -130,7 +130,7 @@ class RegistrationHandler(BaseHandler):
         yield run_on_reactor()
         password_hash = None
         if password:
-            password_hash = self.auth_handler().hash(password)
+            password_hash = yield self.auth_handler().hash(password)
 
         if localpart:
             yield self.check_username(localpart, guest_access_token=guest_access_token)
diff --git a/synapse/handlers/set_password.py b/synapse/handlers/set_password.py
index 44414e1dc1..e057ae54c9 100644
--- a/synapse/handlers/set_password.py
+++ b/synapse/handlers/set_password.py
@@ -31,7 +31,7 @@ class SetPasswordHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def set_password(self, user_id, newpassword, requester=None):
-        password_hash = self._auth_handler.hash(newpassword)
+        password_hash = yield self._auth_handler.hash(newpassword)
 
         except_device_id = requester.device_id if requester else None
         except_access_token_id = requester.access_token_id if requester else None