From b0b42de5f04100e9672170898cb94584309fdc39 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 29 Oct 2015 10:42:44 -0700
Subject: [PATCH] use secure string comparisons for basic auth username /
password
this will avoid timing attacks against applications that use basic auth.
CVE-2015-7576
---
actionpack/lib/action_controller/metal/http_authentication.rb | 7 ++++++-
activesupport/lib/active_support/security_utils.rb | 7 +++++++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/actionpack/lib/action_controller/metal/http_authentication.rb b/actionpack/lib/action_controller/metal/http_authentication.rb
index 2ac6e37..35be6d9 100644
--- a/actionpack/lib/action_controller/metal/http_authentication.rb
+++ b/actionpack/lib/action_controller/metal/http_authentication.rb
@@ -1,4 +1,5 @@
require 'base64'
+require 'active_support/security_utils'
module ActionController
# Makes it dead easy to do HTTP Basic, Digest and Token authentication.
@@ -68,7 +69,11 @@ module ActionController
def http_basic_authenticate_with(options = {})
before_action(options.except(:name, :password, :realm)) do
authenticate_or_request_with_http_basic(options[:realm] || "Application") do |name, password|
- name == options[:name] && password == options[:password]
+ # This comparison uses & so that it doesn't short circuit and
+ # uses `variable_size_secure_compare` so that length information
+ # isn't leaked.
+ ActiveSupport::SecurityUtils.variable_size_secure_compare(name, options[:name]) &
+ ActiveSupport::SecurityUtils.variable_size_secure_compare(password, options[:password])
end
end
end
diff --git a/activesupport/lib/active_support/security_utils.rb b/activesupport/lib/active_support/security_utils.rb
index 64c4801..9be8613 100644
--- a/activesupport/lib/active_support/security_utils.rb
+++ b/activesupport/lib/active_support/security_utils.rb
@@ -1,3 +1,5 @@
+require 'digest'
+
module ActiveSupport
module SecurityUtils
# Constant time string comparison.
@@ -16,5 +18,10 @@ module ActiveSupport
res == 0
end
module_function :secure_compare
+
+ def variable_size_secure_compare(a, b) # :nodoc:
+ secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b))
+ end
+ module_function :variable_size_secure_compare
end
end
--
2.2.1