Remove implicit conversion using `to_int` method.

The ISO standard does not include implicit type conversion using
`to_int`. This implicit conversion often causes vulnerability.
There will be no more attacks like #4120.

In addition, we have added internal convenience method `__to_int` which
does type check and conversion (from floats).

1 files changed, 9 insertions, 18 deletions

diff --git a/mrbgems/mruby-enum-ext/mrblib/enum.rb b/mrbgems/mruby-enum-ext/mrblib/enum.rb
index a840ade3b..e33ce2c5a 100644
--- a/mrbgems/mruby-enum-ext/mrblib/enum.rb
+++ b/mrbgems/mruby-enum-ext/mrblib/enum.rb
@@ -13,10 +13,9 @@ module Enumerable
   #    a.drop(3)             #=> [4, 5, 0]
 
   def drop(n)
-    raise TypeError, "no implicit conversion of #{n.class} into Integer" unless n.respond_to?(:to_int)
+    n = n.__to_int
     raise ArgumentError, "attempt to drop negative size" if n < 0
 
-    n = n.to_int
     ary = []
     self.each {|*val| n == 0 ? ary << val.__svalue : n -= 1 }
     ary
@@ -57,8 +56,8 @@ module Enumerable
   #    a.take(3)             #=> [1, 2, 3]
 
   def take(n)
-    raise TypeError, "no implicit conversion of #{n.class} into Integer" unless n.respond_to?(:to_int)
-    i = n.to_int
+    n = n.__to_int
+    i = n.to_i
     raise ArgumentError, "attempt to take negative size" if i < 0
     ary = []
     return ary if i == 0
@@ -113,12 +112,12 @@ module Enumerable
   #     [8, 9, 10]
 
   def each_cons(n, &block)
-    raise TypeError, "no implicit conversion of #{n.class} into Integer" unless n.respond_to?(:to_int)
+    n = n.__to_int
     raise ArgumentError, "invalid size" if n <= 0
 
     return to_enum(:each_cons,n) unless block
     ary = []
-    n = n.to_int
+    n = n.to_i
     self.each do |*val|
       ary.shift if ary.size == n
       ary << val.__svalue
@@ -141,12 +140,12 @@ module Enumerable
   #     [10]
 
   def each_slice(n, &block)
-    raise TypeError, "no implicit conversion of #{n.class} into Integer" unless n.respond_to?(:to_int)
+    n = n.__to_int
     raise ArgumentError, "invalid slice size" if n <= 0
 
     return to_enum(:each_slice,n) unless block
     ary = []
-    n = n.to_int
+    n = n.to_i
     self.each do |*val|
       ary << val.__svalue
       if ary.size == n
@@ -225,9 +224,7 @@ module Enumerable
       end
       return nil
     when 1
-      n = args[0]
-      raise TypeError, "no implicit conversion of #{n.class} into Integer" unless n.respond_to?(:to_int)
-      i = n.to_int
+      i = args[0].__to_int
       raise ArgumentError, "attempt to take negative size" if i < 0
       ary = []
       return ary if i == 0
@@ -675,13 +672,7 @@ module Enumerable
     if nv.nil?
       n = -1
     else
-      unless nv.respond_to?(:to_int)
-        raise TypeError, "no implicit conversion of #{nv.class} into Integer"
-      end
-      n = nv.to_int
-      unless n.kind_of?(Integer)
-        raise TypeError, "no implicit conversion of #{nv.class} into Integer"
-      end
+      n = nv.__to_int
       return nil if n <= 0
     end