diff options
| -rw-r--r-- | actionpack/lib/action_controller/metal/http_authentication.rb | 11 | ||||
| -rw-r--r-- | actionpack/lib/action_controller/metal/request_forgery_protection.rb | 4 | ||||
| -rw-r--r-- | activesupport/CHANGELOG.md | 8 | ||||
| -rw-r--r-- | activesupport/lib/active_support/security_utils.rb | 22 | ||||
| -rw-r--r-- | activesupport/test/security_utils_test.rb | 11 |
5 files changed, 37 insertions, 19 deletions
diff --git a/actionpack/lib/action_controller/metal/http_authentication.rb b/actionpack/lib/action_controller/metal/http_authentication.rb index d8bc895265..09df39db1f 100644 --- a/actionpack/lib/action_controller/metal/http_authentication.rb +++ b/actionpack/lib/action_controller/metal/http_authentication.rb @@ -70,10 +70,10 @@ module ActionController before_action(options.except(:name, :password, :realm)) do authenticate_or_request_with_http_basic(options[:realm] || "Application") do |name, password| # This comparison uses & so that it doesn't short circuit and - # uses `variable_size_secure_compare` so that length information + # uses `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]) + ActiveSupport::SecurityUtils.secure_compare(name, options[:name]) & + ActiveSupport::SecurityUtils.secure_compare(password, options[:password]) end end end @@ -348,10 +348,7 @@ module ActionController # authenticate_or_request_with_http_token do |token, options| # # Compare the tokens in a time-constant manner, to mitigate # # timing attacks. - # ActiveSupport::SecurityUtils.secure_compare( - # ::Digest::SHA256.hexdigest(token), - # ::Digest::SHA256.hexdigest(TOKEN) - # ) + # ActiveSupport::SecurityUtils.secure_compare(token, TOKEN) # end # end # end diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb index 5051c02a62..13662fc021 100644 --- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb +++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb @@ -353,7 +353,7 @@ module ActionController #:nodoc: end def compare_with_real_token(token, session) # :doc: - ActiveSupport::SecurityUtils.secure_compare(token, real_csrf_token(session)) + ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, real_csrf_token(session)) end def valid_per_form_csrf_token?(token, session) # :doc: @@ -364,7 +364,7 @@ module ActionController #:nodoc: request.request_method ) - ActiveSupport::SecurityUtils.secure_compare(token, correct_token) + ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, correct_token) else false end diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md index fc1e5516f8..8a76e011c1 100644 --- a/activesupport/CHANGELOG.md +++ b/activesupport/CHANGELOG.md @@ -1,3 +1,11 @@ +* Changed default behaviour of `ActiveSupport::SecurityUtils.secure_compare`, + to make it not leak length information even for variable length string. + + Renamed old `ActiveSupport::SecurityUtils.secure_compare` to `fixed_length_secure_compare`, + and started raising `ArgumentError` in case of length mismatch of passed strings. + + *Vipul A M* + * Add default option to module and class attribute accessors. mattr_accessor :settings, default: {} diff --git a/activesupport/lib/active_support/security_utils.rb b/activesupport/lib/active_support/security_utils.rb index b655d64449..5f5d4faa60 100644 --- a/activesupport/lib/active_support/security_utils.rb +++ b/activesupport/lib/active_support/security_utils.rb @@ -2,14 +2,12 @@ require "digest" module ActiveSupport module SecurityUtils - # Constant time string comparison. + # Constant time string comparison, for fixed length strings. # # 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 + # that have already been processed by HMAC. Raises in case of length mismatch. + def fixed_length_secure_compare(a, b) + raise ArgumentError, "string length mismatch." unless a.bytesize == b.bytesize l = a.unpack "C#{a.bytesize}" @@ -17,11 +15,15 @@ module ActiveSupport b.each_byte { |byte| res |= byte ^ l.shift } res == 0 end - module_function :secure_compare + module_function :fixed_length_secure_compare - def variable_size_secure_compare(a, b) # :nodoc: - secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b)) + # Constant time string comparison, for variable length strings. + # + # The values are first processed by SHA256, so that we don't leak length info + # via timing attacks. + def secure_compare(a, b) + fixed_length_secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b)) end - module_function :variable_size_secure_compare + module_function :secure_compare end end diff --git a/activesupport/test/security_utils_test.rb b/activesupport/test/security_utils_test.rb index e8f762da22..8d7f7d699a 100644 --- a/activesupport/test/security_utils_test.rb +++ b/activesupport/test/security_utils_test.rb @@ -11,4 +11,15 @@ class SecurityUtilsTest < ActiveSupport::TestCase assert ActiveSupport::SecurityUtils.variable_size_secure_compare("a", "a") assert_not ActiveSupport::SecurityUtils.variable_size_secure_compare("a", "b") end + + def test_fixed_length_secure_compare_should_perform_string_comparison + assert ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "a") + assert !ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "b") + end + + def test_fixed_length_secure_compare_raise_on_length_mismatch + assert_raises(ArgumentError, "string length mismatch.") do + ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "ab") + end + end end |