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Re: Pure Python Data Mangling or Encrypting

From Randall Smith <randall@tnr.cc>
Subject Re: Pure Python Data Mangling or Encrypting
Date 2015-06-27 12:08 -0500
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On 06/26/2015 08:21 PM, Chris Angelico wrote:
> On Sat, Jun 27, 2015 at 6:09 AM, Randall Smith <randall@tnr.cc> wrote:
>> Give me one plausible scenario where an attacker can cause malware to hit
>> the disk after bytearray.translate with a 256 byte translation table and
>> I'll be thankful to you.
>
> The entire 256-byte translation table is significant ONLY if you need
> all 256 possible bytes. Suppose I want to generate the following byte
> sequence:
>
> "\xCD\x19"
>
> (Okay, this is a slightly oversimplified example, as this attack
> doesn't work on a modern Windows. But back in the days of DOS, this
> program would reboot your computer.)
>
> How many truly different translation tables are there if I'm trying to
> produce this? Just 256*255, or 65280. If I send random two-byte files,
> there is one chance in that of my "malware" successfully landing. Once
> I've sent about 45,000 of those files, I have a fifty-fifty chance of
> having hit it. Send twice as many, I have a 75% chance of success,
> etc.
>

Yes, that's true.  It's even an issue with AES, which uses padding to 
overcome.  That said, remember these are bytes going straight to disk. 
I'm really not concerned about 2 or 3 byte malware and the probability 
plunges after that.  And remember, normal use case is AES encrypted data.

Quite interesting.

Though I didn't mention it in the description, the storage server is 
appending a CRC32 checksum for routine integrity checks.  So by the time 
the data hits the disk, it will have added both a 256 byte translation 
table and a 4 byte checksum.  I think that would interfere with any 
extremely short malware.


> Malware can be crafted to fit within certain restrictions. I saw a
> proof-of-concept and analysis document detailing a particular remote
> code execution/privilege escalation attack that involved stuffing
> "text" into an entry field and then inducing the program to read that
> into its stack, finally triggering it by some sort of buffer overflow,
> I think. The text had to be no more than X bytes long (because that's
> all the entry field was set to accept - it'd truncate after that), and
> had to not contain any NUL bytes, and there might have been other
> restrictions too. Sure, it makes it harder to write your malware...
> but imagine if you can write something in just a handful of different
> bytes, which then goes and triggers something else. You could have an
> extremely plausible attack that might need only a day's uploading to
> deliver.
>
> It makes no difference that there are 256! possible encryption keys,
> if most of them have the same result.
>
> ChrisA
>


Thankyou.  Nice points. I do think given the risks (there are always 
risks) discussed, a successful attack of this nature is not very likely. 
  Worse case, something that looks like this would land on the disk.

crc32 checksum + translation table + malware

with a generated base64 name and no extension.


Doesn't seem like much of a threat.   Much less likely than a bug in the 
standard Crytpo libraries.

-Randall

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Thread

Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-24 13:36 -0500
  Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-25 14:07 +1000
    Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-24 21:27 -0700
      Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-25 19:25 +1000
        Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-25 02:41 -0700
        Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-25 19:57 +1000
        Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-25 10:03 +0000
          Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-26 01:13 +1000
            Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-25 15:26 +0000
              Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-25 13:58 -0500
              Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-26 10:33 +1000
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-26 10:49 +0000
              Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-25 19:01 -0600
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-27 03:06 +1000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-26 15:09 -0500
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-26 23:07 +0200
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-26 21:29 +0000
                Re: Pure Python Data Mangling or Encrypting Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-26 22:55 +0100
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 00:42 +0200
                Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-26 16:26 -0700
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-27 00:21 +0000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-26 19:55 -0500
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 07:24 +0200
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-26 19:12 -0500
                Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-26 15:58 -0600
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-26 19:23 -0500
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-26 23:11 +0200
                Re: Pure Python Data Mangling or Encrypting Michael Torrie <torriem@gmail.com> - 2015-06-27 11:02 -0600
                Re: Pure Python Data Mangling or Encrypting Paul Rubin <no.email@nospam.invalid> - 2015-06-27 10:45 -0700
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-27 13:38 +1000
                Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-26 21:05 -0700
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-27 16:16 +1000
                Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-27 13:30 -0700
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-28 11:18 +1000
                Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-27 19:11 -0700
                Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-26 23:47 -0600
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-27 18:38 +1000
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-27 18:53 +1000
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 11:07 +0200
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-27 19:17 +1000
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-27 09:27 +0000
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 12:05 +0200
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-27 20:16 +1000
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 12:55 +0200
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-27 10:26 +0000
                Re: Pure Python Data Mangling or Encrypting Laura Creighton <lac@openend.se> - 2015-06-27 14:27 +0200
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 12:18 +0200
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-27 21:33 +1000
                Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-27 08:59 -0600
                Re: Pure Python Data Mangling or Encrypting Laura Creighton <lac@openend.se> - 2015-06-27 13:25 +0200
                Re: Pure Python Data Mangling or Encrypting Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-06-27 15:23 +0300
                Re: Pure Python Data Mangling or Encrypting Laura Creighton <lac@openend.se> - 2015-06-27 14:48 +0200
                Re: Pure Python Data Mangling or Encrypting Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-06-27 11:12 +0200
                Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-27 09:09 -0600
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-28 03:35 +1000
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-28 03:58 +1000
                Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-27 14:16 -0600
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-28 13:41 +0000
                Re: Pure Python Data Mangling or Encrypting Robert Kern <robert.kern@gmail.com> - 2015-06-27 08:58 +0100
                Re: Pure Python Data Mangling or Encrypting Robert Kern <robert.kern@gmail.com> - 2015-06-27 09:07 +0100
                Re: Pure Python Data Mangling or Encrypting Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-06-27 10:39 -0400
                Re: Pure Python Data Mangling or Encrypting Grant Edwards <invalid@invalid.invalid> - 2015-06-27 12:38 +0000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-27 13:22 -0500
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-28 04:51 +1000
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-28 09:05 +1000
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-27 11:21 +1000
                Re: Pure Python Data Mangling or Encrypting Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-26 23:59 -0600
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-27 09:26 +0000
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-27 16:52 +1000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-27 12:08 -0500
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-28 04:50 +1000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-29 15:52 -0500
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-06-30 13:00 +1000
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-30 12:19 +0000
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-07-01 04:17 +1000
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-07-01 04:33 +1000
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-30 18:37 +0000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-07-01 09:38 -0500
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-30 12:39 -0500
                Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve@pearwood.info> - 2015-07-01 04:59 +1000
                Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-07-01 05:20 +1000
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-30 23:25 +0000
                Re: Pure Python Data Mangling or Encrypting alister <alister.nospam.ware@ntlworld.com> - 2015-07-01 08:06 +0000
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-28 14:21 +0000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-29 15:46 -0500
                Re: Pure Python Data Mangling or Encrypting Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-29 20:49 +0000
                Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-30 12:43 -0500
                Re: Pure Python Data Mangling or Encrypting Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-07-02 10:31 +1200
              Re: Pure Python Data Mangling or Encrypting Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-26 02:17 +0100
              Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-26 12:06 +1000
              Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-26 12:05 +1000
              Re: Pure Python Data Mangling or Encrypting Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-26 03:24 +0100
              Re: Pure Python Data Mangling or Encrypting Chris Angelico <rosuav@gmail.com> - 2015-06-26 12:29 +1000
        Re: Pure Python Data Mangling or Encrypting Joonas Liik <liik.joonas@gmail.com> - 2015-06-25 13:00 +0300
        Re: Pure Python Data Mangling or Encrypting Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-06-25 03:18 -0700
    Re: Pure Python Data Mangling or Encrypting Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-25 17:05 +1000
    Re: Pure Python Data Mangling or Encrypting Randall Smith <randall@tnr.cc> - 2015-06-25 14:09 -0500

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