From: "usa (Usaku NAKAMURA)" <usa@...>
Date: 2012-12-14T17:35:51+09:00
Subject: [ruby-core:50891] [Backport93 - Backport #7325] Marshal#load taints classes if they are referenced in a marsheled object


Issue #7325 has been updated by usa (Usaku NAKAMURA).


memo: r38357 is also related.
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Backport #7325: Marshal#load taints classes if they are referenced in a marsheled object
https://bugs.ruby-lang.org/issues/7325#change-34737

Author: urielka (Uriel Katz)
Status: Assigned
Priority: Normal
Assignee: usa (Usaku NAKAMURA)
Category: 
Target version: 


=begin
= Reproducing steps:
ruby taint.rb

= Output of this script in my computer running 1.9.3-p327:
 Before marshal is tainted?: false
 After marshal is tainted?: true
 Safe level when calling tainted method using call: 4
 Safe level when calling tainted method directly: 0

= Expected:
MyObject#test shouldn't be tainted as it was defined in my own source and what was saved into the file is just a reference to MyObject class ("\u0004\bc\rMyObject")

= Actual:
MyObject#test is tainted and calling it using Method#call will make it run in safe-level 4.


= Some background on how I got to this issue:
I wrote some RPC code that accepts a class and method name and does the invocation,the way I call the method is getting the method from the instance using something like: "cls_instance.method(method_name).call" 

I used Rails.cache with FileStore (which uses Marshal#load from file) to cache a object that had references to classes.

After reading from the cache all other requests saw the classes as tainted and when calling the methods they ran at $SAFE=4 which caused it to fail (even puts doesn't work at that level :)

This issue also made me understand that there is 2 potential bugs in Rails.
=end



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