From f2f031fd57e0ad16c321584bae94487422d89853 Mon Sep 17 00:00:00 2001
From: Mark Haines <mark.haines@matrix.org>
Date: Fri, 16 Oct 2015 14:52:08 +0100
Subject: [PATCH] Add config for how many bcrypt rounds to use for password
 hashes

By default we leave it at the default value of 12. But now we can reduce
it for preparing users for loadtests or running integration tests.
---
 synapse/config/registration.py | 6 ++++++
 synapse/handlers/auth.py       | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index fa98eced3..f5ef36a9f 100644
--- a/synapse/config/registration.py
+++ b/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):
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 484f71925..055d395b2 100644
--- a/synapse/handlers/auth.py
+++ b/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.