[#43120] [ruby-trunk - Bug #6124][Open] What is the purpose of "fake" gems in Ruby — Vit Ondruch <v.ondruch@...>

27 messages 2012/03/07

[#43142] Questions about thread performance (with benchmark included) — Rodrigo Rosenfeld Rosas <rr.rosas@...>

A while ago I've written an article entitled "How Nokogiri and JRuby

10 messages 2012/03/08

[#43148] [ruby-trunk - Feature #6126][Open] Introduce yes/no constants aliases for true/false — Egor Homakov <homakov@...>

16 messages 2012/03/09

[#43238] [ruby-trunk - Feature #6130][Open] inspect using to_s is pain — Thomas Sawyer <transfire@...>

21 messages 2012/03/11

[#43313] [ruby-trunk - Feature #6150][Open] add Enumerable#grep_v — Suraj Kurapati <sunaku@...>

17 messages 2012/03/15

[#43325] [ruby-trunk - Bug #6154][Open] Eliminate extending WaitReadable/Writable at runtime — Charles Nutter <headius@...>

25 messages 2012/03/16

[#43334] [ruby-trunk - Bug #6155][Open] Enumerable::Lazy#flat_map raises an exception when an element does not respond to #each — Dan Kubb <dan.kubb@...>

9 messages 2012/03/16

[#43370] [ruby-trunk - Feature #6166][Open] Enumerator::Lazy#pinch — Thomas Sawyer <transfire@...>

15 messages 2012/03/17

[#43373] [ruby-trunk - Bug #6168][Open] Segfault in OpenSSL bindings — Nguma Abojo <git.email.address@...>

14 messages 2012/03/17

[#43454] [ruby-trunk - Bug #6174][Open] Fix collision of ConditionVariable#wait timeout and #signal (+ other cosmetic changes) — "funny_falcon (Yura Sokolov)" <funny.falcon@...>

10 messages 2012/03/18

[#43497] [ruby-trunk - Bug #6179][Open] File::pos broken in Windows 1.9.3p125 — "jmthomas (Jason Thomas)" <jmthomas@...>

24 messages 2012/03/20

[#43502] [ruby-trunk - Feature #6180][Open] to_b for converting objects to a boolean value — "AaronLasseigne (Aaron Lasseigne)" <aaron.lasseigne@...>

17 messages 2012/03/20

[#43529] [ruby-trunk - Bug #6183][Open] Enumerator::Lazy performance issue — "gregolsen (Innokenty Mikhailov)" <anotheroneman@...>

36 messages 2012/03/21

[#43543] [ruby-trunk - Bug #6184][Open] [BUG] Segmentation fault ruby 1.9.3p165 (2012-03-18 revision 35078) [x86_64-darwin11.3.0] — "Gebor (Pierre-Henry Frohring)" <frohring.pierrehenry@...>

8 messages 2012/03/21

[#43672] [ruby-trunk - Feature #6201][Open] do_something then return :special_case (include "then" operator) — "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>

12 messages 2012/03/26

[#43678] [ruby-trunk - Bug #6203][Open] Array#values_at does not handle ranges with end index past the end of the array — "ferrous26 (Mark Rada)" <markrada26@...>

15 messages 2012/03/26

[#43794] [ruby-trunk - Feature #6216][Open] SystemStackError backtraces should not be reduced to one line — "postmodern (Hal Brodigan)" <postmodern.mod3@...>

15 messages 2012/03/28

[#43814] [ruby-trunk - Feature #6219][Open] Return value of Hash#store — "MartinBosslet (Martin Bosslet)" <Martin.Bosslet@...>

20 messages 2012/03/28

[#43858] [ruby-trunk - Feature #6222][Open] Use ++ to connect statements — "gcao (Guoliang Cao)" <gcao99@...>

12 messages 2012/03/29

[#43904] [ruby-trunk - Feature #6225][Open] Hash#+ — "trans (Thomas Sawyer)" <transfire@...>

36 messages 2012/03/29

[#43951] [ruby-trunk - Bug #6228][Open] [mingw] Errno::EBADF in ruby/test_io.rb on ruby_1_9_3 — "jonforums (Jon Forums)" <redmine@...>

28 messages 2012/03/30

[#43996] [ruby-trunk - Bug #6236][Open] WEBrick::HTTPServer swallows Exception — "regularfry (Alex Young)" <alex@...>

13 messages 2012/03/31

[ruby-core:43810] [ruby-trunk - Feature #5741] Secure Erasure of Passwords

From: "MartinBosslet (Martin Bosslet)" <Martin.Bosslet@...>
Date: 2012-03-28 19:58:47 UTC
List: ruby-core #43810
Issue #5741 has been updated by MartinBosslet (Martin Bosslet).


mame (Yusuke Endoh) wrote:
> I think that adding a method to String requires matz's approval.
> If you propose to add a method to others, such as openssl, you
> can do it at your discretion.
> 

Sure - I would appreciate to have more opinions on how this can be
done best. I haven't really had the time to think it through yet,
but unfortunately I see two major obstacles for either approach.

1. I'm having doubts if this could be handled reliably within String
   itself due to copy on write behavior. So when we finally call
   something like String#clear, we would also need to clear any
   proliferated instances, too. I haven't analyzed it yet, maybe
   someone could tell me if that's possible at all? 

2. If we implement the feature separately (SecureByteBuffer), there
   is a serious chicken & egg problem: how can we feed the password
   to the implementation without using a String first? It's not as 
   easy as it may sound and it would require massive changes in 
   existing code - I fear this could be too invasive for anyone
   to adopt it...

Any thoughts?
----------------------------------------
Feature #5741: Secure Erasure of Passwords
https://bugs.ruby-lang.org/issues/5741#change-25316

Author: MartinBosslet (Martin Bosslet)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 2.0.0


In other languages it is considered good practice to securely erase 
passwords immediately after they were used. Imagine authentication
in a web app - ultimately a String containing the password arrives
at the server, where it will be processed and compared to some 
previously stored value. After this is done, there is no need to
store these password Strings any longer, so they should be
discarded right away (more on why later).

In C, you would simply overwrite the array of bytes with zeroes or
random values. In Java, Strings are immutable, that's why there it
is common practice to use char[] for all things password and overwrite
them when done.

Currently, there is no way in Ruby to overwrite the memory that
was used by a String. String#clear and String#replace both use
str_discard internally, which only frees the underlying pointer 
without overwriting it.

The problem with not erasing passwords is this: the contents of the
String stay in memory until they are finally GC'ed. But even then
only the pointer will be freed, leaving the contents mostly intact
until the memory is reclaimed and overwritten later on.

This could be exploited if an attacker had access to the memory of
the server. This could happen in many ways: a core dump after a
crash, access to the host if the server runs in a VM, or even by
deep-freezing the DRAM :) [1]

It could be argued that given the examples above, much more 
devastating attacks would be possible since in all of those
cases you more or less have physical access to the machine. But
I would still consider this to be a valid concern, if not only
for the reason of never opening additional attack surfaces if
they can be avoided relatively easily.

I also found [2], which seems to show that Python deals with 
similar problems and it also contains more background info.

Eric Hodel and I discussed this yesterday and Eric came up with
a C extension that can be used to illustrate the problem (attached).

If you inspect the resulting core dump, you will find the following:

- the untouched String remains in memory fully intact
- the String#clear'ed String remains to a large extent, typically the
  first character is missing - so if you typed "PASSWORD", search for
  "ASSWORD" (unintentional pun) instead
- The String#clear_secure'ed will have been completely erased, no 
  traces remain

My questions:

1. Would you agree that we need this functionality?
2. Where would we ideally place it? I'm not sure whether
   String is the perfect place, but on the other hand, String
   is the only place where we have access to the implementation
   details.
3. Are there better alternative ways how we could achieve this?

[1] http://www.schneier.com/blog/archives/2008/02/cold_boot_attac.html
[2] http://stackoverflow.com/questions/728164/securely-erasing-password-in-memory-python


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