From b0b42de5f04100e9672170898cb94584309fdc39 Mon Sep 17 00:00:00 2001 From: Aaron Patterson 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