lib/rack/utils.rb in rack-1.5.1 vs lib/rack/utils.rb in rack-1.5.2

@@ -393,9 +393,21 @@
       end
       ranges
     end
     module_function :byte_ranges
 
+    # Constant time string comparison.
+    def secure_compare(a, b)
+      return false unless bytesize(a) == bytesize(b)
+
+      l = a.unpack("C*")
+
+      r, i = 0, -1
+      b.each_byte { |v| r |= v ^ l[i+=1] }
+      r == 0
+    end
+    module_function :secure_compare
+
     # Context allows the use of a compatible middleware at different points
     # in a request handling stack. A compatible middleware must define
     # #context which should take the arguments env and app. The first of which
     # would be the request environment. The second of which would be the rack
     # application that the request would be forwarded to.