Issue #8945 has been reported by brixen (Brian Shirai).

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Bug #8945: Unmarshaling an Array containing a Bignum from a tainted String returns a frozen, tainted Bignum
https://bugs.ruby-lang.org/issues/8945

Author: brixen (Brian Shirai)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: current: 2.1.0
ruby -v: ruby 2.1.0dev (2013-09-24 trunk 43025) [x86_64-darwin13.0.0]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


In 2.1, Symbol, Fixnum, Bignum, and Float (at least) have been changed to frozen by default. Consequently, calling #taint on an instance of those classes raises a RuntimeError because a frozen object cannot be modified to be tainted. However:

sasha:rbx brian$ ruby -v
ruby 2.1.0dev (2013-09-24 trunk 43025) [x86_64-darwin13.0.0]
sasha:rbx brian$ irb
irb(main):001:0> a = 0xffff_ffff_ffff_ffff
=> 18446744073709551615
irb(main):002:0> a.class
=> Bignum
irb(main):003:0> a.frozen?
=> true
irb(main):004:0> a.tainted?
=> false
irb(main):005:0> str = Marshal.dump([a]).taint
=> "\x04\b[\x06l+\t\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"
irb(main):006:0> str.tainted?
=> true
irb(main):007:0> aa = Marshal.load(str)
=> [18446744073709551615]
irb(main):008:0> aa.first.class
=> Bignum
irb(main):009:0> aa.first.frozen?
=> true
irb(main):010:0> aa.first.tainted?
=> true
irb(main):011:0>

The behavior above is inconsistent with the results of performing the same operations on instances of Symbol, Fixnum, Float. For example:

irb(main):014:0> :a.frozen?
=> true
irb(main):015:0> :a.tainted?
=> false
irb(main):016:0> str = Marshal.dump([:a]).taint
=> "\x04\b[\x06:\x06a"
irb(main):017:0> aa = Marshal.load(str)
=> [:a]
irb(main):018:0> aa.tainted?
=> true
irb(main):019:0> aa.first.frozen?
=> true
irb(main):020:0> aa.first.tainted?
=> false



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