From: Sean Russell <ser@...>
Date: 2002-04-23T00:13:18+09:00
Subject: Taintedness inheritance

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Hi,

I have a question for the Gurus on taintedness:

  a = "sean"
  a.taint
  b = a.unpack("C*")
  b.tainted?   # => false

Which means:

  b = a.unpack("C*").pack("C*")

is an efficient way of untainting a string.  Now, taintedness is a property 
of all objects, and is /sometimes/ inherited in derived objects (most 
notably Strings), but most often not:

  b = " russell"
  b.tainted?   # => false
  c = a + b
  c.tainted?   # => true
  x = [1]
  x.taint
  y = [2]
  z = x + y
  z.tainted?   # => false

  b = a.to_a
  b.tainted?   # => false
  b = ""
  b << a
  b.tainted?   # => true

Is there a document that outlines where objects derived from tainted objects 
inherit taintedness, and why?  What is the reasoning behind objects 
inheriting (or not inheriting) taintedness?  Should everything that touches 
a tainted object become tainted?  It seems sort of arbitrary at the moment; 
do only Strings inherit taintedness?

Thanks in advance,

- --- SER
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