From c8c660002f4b0e9606de96325f20b95248b6ff2d Mon Sep 17 00:00:00 2001 From: Guillermo Iguaran Date: Thu, 23 Oct 2014 10:56:48 -0300 Subject: Add AS::SecurityUtils.secure_compare for constant time string comparison --- activesupport/lib/active_support/security_utils.rb | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100644 activesupport/lib/active_support/security_utils.rb (limited to 'activesupport/lib/active_support') diff --git a/activesupport/lib/active_support/security_utils.rb b/activesupport/lib/active_support/security_utils.rb new file mode 100644 index 0000000000..64c4801179 --- /dev/null +++ b/activesupport/lib/active_support/security_utils.rb @@ -0,0 +1,20 @@ +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 + end +end -- cgit v1.2.3