[ruby-core:46334] [ruby-trunk - Bug #5374] Weird SecurityError with ruby1.9, File.stat/Dir.glob and $SAFE=1

Issue #5374 has been updated by 375gnu (Hleb  Valoshka).


nobu (Nobuyoshi Nakada) wrote:
> Does this happen with recent versions?

Yes, at least with 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux].

And today I've made some investigations.

File.stat is rb_file_s_stat, which calls rb_get_path, which calls rb_get_path_check, which at very end calls rb_str_new4, which actually is rb_str_new_frozen.

As value passed to rb_str_new_frozen (filename) isn't frozen, it creates new string (see file string.c, line 679):
if (STR_SHARED_P(orig) && (str = RSTRING(orig)->as.heap.aux.shared)) {...} and that "new" string is returned to rb_get_path_check.

*This str is tainted!*

I also have found more simple way to reproduce the bug:

ruby -e '$SAFE=1;File.stat(("12345678901234567890123"+"4".taint).dup.untaint)'

Argument to stat sh'ld be at least 24 bytes on 64bit box.

I haven't checked again bug with glob on Win32, but suppose that it has the same nature but it didn't expressed itself on my Debian boxes cause they are 64bit. In few days I can check it on 32bit Debian.
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Bug #5374: Weird SecurityError with ruby1.9, File.stat/Dir.glob and $SAFE=1
https://bugs.ruby-lang.org/issues/5374#change-27953

Author: 375gnu (Hleb  Valoshka)
Status: Feedback
Priority: Normal
Assignee: mame (Yusuke Endoh)
Category: core
Target version: 2.0.0
ruby -v: ruby 1.9.2p180 (2011-02-18) [i386-mingw32]


Preface.

I've tried to find workaroud for one GetText-Ruby bug with untainted data from Dir.glob (http://rubyforge.org//tracker/?func=detail&atid=3377&aid=28336&group_id=855). 

Here it is (full text is in gettext-test.rb):

module GetText
  class MOFile
  alias :oldload :load
    def load(arg)
      arg = arg.dup.untaint if arg.kind_of? String
      oldload(arg)
    end
  end
end

It works fine with ruby 1.8, but with 1.9 with debug enabled there is a
message about exception SecurityError:

Exception `SecurityError' at /usr/lib/ruby/1.9.1/gettext/runtime/mofile.rb:75 - Insecure operation - stat

The corresponding code is
74  begin
75    st = File.stat(arg)
76    @last_modified = [st.ctime, st.mtime]
77  rescue Exception
78  end

I've put line 
warn "$SAFE == #{$SAFE}; arg.tainted? == #{arg.tainted?}"
before it, and it says:

$SAFE == 1; arg.tainted? == false

So why the exception is if arg is NOT tainted? Note: it was discovered on Debian
GNU/Linux box with 1.9.3preview1. Full log is in gettext-debian.log

Going further.

I've made very simple test program which mimics GetTExt-Ruby and workaround for
it, see test.rb in attachment.

This program was tested on Win32 box with 1.9.2-p180 and -p290.

Been run as "ruby -T1 test.rb u" output was clean. But been run as "ruby -T1
test.rb t" or "ruby -T1 test.rb t" is had an exception on files test1234.txt
and test12345.txt (see full test.log in attachment). 't' means "send tainted
object to function", 'u' means "send untainted", 'b' means "send tainted, then
untainted". But on Debian box it outputs NO error.

At last, I have run test for GetText on win box, and it failed with exception 

Exception `SecurityError' at C:/fsc.tmp/gettext/runtime/locale_path.rb:90 - Insecure operation - glob

Log is in gettext-win.log

But whether Dir.glob is insecure with $SAFE==1?




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