Bug #5374: Weird SecurityError with ruby1.9, File.stat/Dir.glob and $SAFE=1

• Status: Closed
• Assignee: mame (Yusuke Endoh)
• Target version: 2.0.0
• ruby -v: ruby 1.9.2p180 (2011-02-18) [i386-mingw32]

[375gnu (Hleb Valoshka)]

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?

[375gnu (Hleb Valoshka)]

• File test.rb test.rb added
• File test.log test.log added
• File gettext-test.rb gettext-test.rb added
• File gettext-debian.log gettext-debian.log added
• File gettex-win.log gettex-win.log added

[ko1 (Koichi Sasada)]

• Assignee set to mame (Yusuke Endoh)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

Does this happen with recent versions?

[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.

[nobu (Nobuyoshi Nakada)]

• Status changed from Feedback to Closed
• % Done changed from 0 to 100

This issue was solved with changeset r36373.
Hleb , thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

rb_str_new_frozen: new object if tainted/untrusted unmatch

• string.c (rb_str_new_frozen): since the result object should have
  same tainted/untrusted bits with the original object, return new
  object if the shared object unmatch. [ruby-core:39745][Bug #5374]