Merge pull request #310 from matrix-org/markjh/bcrypt_rounds

Add config for how many bcrypt rounds to use for password hashes

synapse/config/registration.py

@@ -33,6 +33,7 @@ class RegistrationConfig(Config):
 
         self.registration_shared_secret = config.get("registration_shared_secret")
         self.macaroon_secret_key = config.get("macaroon_secret_key")
+        self.bcrypt_rounds = config.get("bcrypt_rounds", 12)
 
     def default_config(self, **kwargs):
         registration_shared_secret = random_string_with_symbols(50)
@@ -48,6 +49,11 @@ class RegistrationConfig(Config):
         registration_shared_secret: "%(registration_shared_secret)s"
 
         macaroon_secret_key: "%(macaroon_secret_key)s"
+
+        # Set the number of bcrypt rounds used to generate password hash.
+        # Larger numbers increase the work factor needed to generate the hash.
+        # The default number of rounds is 12.
+        bcrypt_rounds: 12
         """ % locals()
 
     def add_arguments(self, parser):

synapse/handlers/auth.py

@@ -44,6 +44,7 @@ class AuthHandler(BaseHandler):
             LoginType.EMAIL_IDENTITY: self._check_email_identity,
             LoginType.DUMMY: self._check_dummy_auth,
         }
+        self.bcrypt_rounds = hs.config.bcrypt_rounds
         self.sessions = {}
 
     @defer.inlineCallbacks
@@ -432,7 +433,7 @@ class AuthHandler(BaseHandler):
         Returns:
             Hashed password (str).
         """
-        return bcrypt.hashpw(password, bcrypt.gensalt())
+        return bcrypt.hashpw(password, bcrypt.gensalt(self.bcrypt_rounds))
 
     def validate_hash(self, password, stored_hash):
         """Validates that self.hash(password) == stored_hash.