diff options
-rw-r--r-- | actionpack/lib/action_controller/metal/http_authentication.rb | 7 | ||||
-rw-r--r-- | activesupport/lib/active_support/security_utils.rb | 27 |
2 files changed, 33 insertions, 1 deletions
diff --git a/actionpack/lib/action_controller/metal/http_authentication.rb b/actionpack/lib/action_controller/metal/http_authentication.rb index fe4ab65bba..2ae516097a 100644 --- a/actionpack/lib/action_controller/metal/http_authentication.rb +++ b/actionpack/lib/action_controller/metal/http_authentication.rb @@ -1,5 +1,6 @@ require 'active_support/base64' require 'active_support/core_ext/object/blank' +require 'active_support/security_utils' module ActionController module HttpAuthentication @@ -111,7 +112,11 @@ module ActionController def http_basic_authenticate_with(options = {}) before_filter(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 new file mode 100644 index 0000000000..9be8613ada --- /dev/null +++ b/activesupport/lib/active_support/security_utils.rb @@ -0,0 +1,27 @@ +require 'digest' + +module ActiveSupport + module SecurityUtils + # Constant time string comparison. + # + # The values compared should be of fixed length, such as strings + # that have already been processed by HMAC. This should not be used + # on variable length plaintext strings because it could leak length info + # via timing attacks. + def secure_compare(a, b) + return false unless a.bytesize == b.bytesize + + l = a.unpack "C#{a.bytesize}" + + res = 0 + b.each_byte { |byte| res |= byte ^ l.shift } + 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 |