Re: Unspecified behavior in C

From	James Kuyper <jameskuyper@verizon.net>
Newsgroups	comp.lang.c
Subject	Re: Unspecified behavior in C
Date	2015-07-11 12:56 -0400
Organization	Self
Message-ID	<55A14ABF.9060607@verizon.net> (permalink)
References	(6 earlier) <cb5f75e3-44fb-484d-a017-47e53b339c53@googlegroups.com> <mnmdvn$krp$1@dont-email.me> <ee9cbc5b-7faf-48cb-9b5a-97f3cf9b9fcf@googlegroups.com> <55A00286.8070301@verizon.net> <c6a24009-ba0f-4240-b509-384c28849f3d@googlegroups.com>

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On 07/11/2015 12:19 PM, David Kleinecke wrote:
...
> And I, as a potential user, object to not being able to see how these
> things are done. 
> 
> How can I, as a user be sure the implementation is not dropping
> spyware into my code? So far, I think, the spies haven't gotten that
> clever - but the potential exists.

You can't, and seeing the header files won't help. If I were writing a
compiler to insert spyware into the compiled code, I certainly wouldn't
do it through the header files, I'd put the main part in the standard
library, and all of the identifiers with external linkage that are part
of the spyware would have names that sound reasonable. The compiler
would insert calls to the spyware into the compiled object modules.
There wouldn't be a single suspicious construct anywhere in any
human-readable file.

The only way to be sure a compiler isn't doing this is read and
correctly interpret every single byte of the generated machine code, and
understand exactly what it does, to make sure it doesn't do what you
don't want it to do. I don't have enough time to do that. I don't have
enough time to do even a tiny fraction of that amount of work. Do you?
If so, you're probably better off writing machine code directly - that
way you can be sure (modulo your own coding errors) that your program
does what you want it to do, and only what you want it to do.

If you have a lot of confidence in your ability to spot malicious code
constructs, I'd recommend looking at the winning entries and runners up
in the "Underhanded C Contest", <http://underhanded-c.org/>. It should
pretty thoroughly demolish your confidence. Note: the reason why it's
the "Underhanded C Contest" and not the "Underhanded Assembler Contest"
is that doing the same thing in assembler would be far too easy.

I'm not happy about the fact that I have no reasonable alternative to
trusting a lot of software written by other people - but that doesn't
change the fact that I do not, in fact, have any reasonable alternative.
The US government requires my company to give me IT security training
every year. I know what kinds of things they consider most important for
me to do to reduce our exposure to security threats. Examining the
header files of libraries I use is never even mentioned in those
training classes, and for good reason. If you exert reasonable care
about which software vendors you use (and exerting that care is the
system administrator's responsibility), there's literally hundreds of
other ways of spending your time to improve IT security that are a more
cost-effective use of your time than looking at the details of how the
standard library is implemented.

Thread

Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-07 14:44 -0700
  Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-07 15:34 -0700
    Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 08:47 -0700
      Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-08 09:11 -0700
        Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 10:24 -0700
          Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-08 10:46 -0700
          Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 13:54 -0400
          Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-08 11:12 -0700
            Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-09 09:15 -0700
              Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-09 17:33 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 09:24 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-10 12:54 -0400
              Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-09 10:58 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 09:33 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-10 12:11 -0700
                Re: Unspecified behavior in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-10 21:05 +0000
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-10 17:14 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:32 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-11 12:59 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-11 17:21 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:23 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-11 13:03 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-11 17:15 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-12 09:52 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-12 14:13 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 09:02 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-13 13:18 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 11:09 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-13 15:06 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 08:14 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 12:02 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-13 12:03 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 07:54 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 11:16 -0400
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 16:17 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 09:16 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 12:29 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 14:57 -0400
                Re: Unspecified behavior in C Öö Tiib <ootiib@hot.ee> - 2015-07-14 13:12 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 16:30 -0400
                Re: Unspecified behavior in C Öö Tiib <ootiib@hot.ee> - 2015-07-14 15:54 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-14 21:41 -0500
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-14 21:51 -0500
                Re: Unspecified behavior in C Öö Tiib <ootiib@hot.ee> - 2015-07-15 12:42 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-15 16:13 -0500
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-16 08:49 -0500
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 10:10 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-20 13:24 -0500
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-23 02:56 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-23 11:26 -0500
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-26 11:24 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-23 19:03 -0500
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 21:19 -0700
                Re: Unspecified behavior in C Martin Shobe <martin.shobe@yahoo.com> - 2015-07-15 23:45 -0500
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 01:37 -0400
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-16 09:42 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-16 17:05 -0700
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-17 01:32 +0100
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 21:07 -0400
                We're good - don't you worry 'bout a thing, babe (Was: Unspecified behavior in C) gazelle@shell.xmission.com (Kenny McCormack) - 2015-07-17 07:21 +0000
                Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-19 20:59 +0000
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-19 22:02 +0100
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 17:59 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 23:09 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-17 18:48 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-17 23:09 -0400
                Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-19 20:57 +0000
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-19 17:22 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-19 18:57 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-19 22:16 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-19 19:30 -0700
                Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-30 14:20 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-30 15:30 -0700
                Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-30 15:53 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-30 16:46 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-31 00:59 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-31 17:15 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-31 18:28 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-31 23:28 -0400
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-04 04:07 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-04 18:02 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 21:27 -0400
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-24 09:33 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-24 17:11 -0700
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 12:44 -0700
                Re: Unspecified behavior in C Ken Brody <kenbrody@spamcop.net> - 2015-08-03 12:09 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-03 13:26 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-03 17:53 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-08-03 18:44 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-04 17:59 -0700
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-08-05 02:23 +0100
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 21:39 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-08-04 19:27 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 00:25 -0400
                Re: Unspecified behavior in C Ken Brody <kenbrody@spamcop.net> - 2015-08-04 11:55 -0400
                Re: Unspecified behavior in C Philip Lantz <prl@canterey.us> - 2015-08-04 10:31 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 13:32 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 22:46 -0400
                Re: Unspecified behavior in C Ken Brody <kenbrody@spamcop.net> - 2015-08-10 12:16 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-10 13:26 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-03 17:46 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-05 12:34 -0400
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 17:57 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 10:31 -0700
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 18:50 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 20:59 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-14 11:34 -0700
                Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-19 20:46 +0000
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-12 12:07 -0700
                Re: Unspecified behavior in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-12 19:53 +0000
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-12 16:12 -0400
              Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-09 14:20 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-09 12:18 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 09:47 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-10 13:36 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:19 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-11 12:56 -0400
                Re: Unspecified behavior in C gordonb.j19di@burditt.org (Gordon Burditt) - 2015-07-11 20:36 -0500
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-12 10:10 -0700
              Re: Unspecified behavior in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-09 20:13 +0100
          Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-09 11:17 +0000
        Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 10:37 -0700
          Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-08 10:51 -0700
          Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 14:14 -0400
          Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-08 12:19 -0700
      Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 12:14 -0400
        Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 10:40 -0700
          Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 14:29 -0400
            Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-09 11:20 +0000
      Re: Unspecified behavior in C Robert Wessel <robertwessel2@yahoo.com> - 2015-07-09 02:30 -0500
  Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-07 22:30 -0400

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