From: "John P. Linderman" <jpl.jpl@gmail.com>
To: Ken Thompson <kenbob@gmail.com>
Cc: TUHS main list <tuhs@minnie.tuhs.org>,
Douglas McIlroy <douglas.mcilroy@dartmouth.edu>
Subject: Re: [TUHS] Thompson trojan put into practice
Date: Mon, 20 Sep 2021 10:35:50 -0400 [thread overview]
Message-ID: <CAC0cEp-29zFf1Y5Sq0QB3BAmVwtxnnTNvoCDp2HjB7h4aMYoyA@mail.gmail.com> (raw)
In-Reply-To: <CAMP=X_mmx7EyGbE7-8KLa6piZgZ+Df3dRGcBtBx-=Qy+DFv6PQ@mail.gmail.com>
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My recollection is that Larry Wehr ran nm on the compiler, possibly in
response to the extra-byte quirk, and found a subroutine reference with no
appearance in the source. If Ken hadn't kept the code so modular, they
might never have noticed.
On Mon, Sep 20, 2021 at 9:53 AM Ken Thompson <kenbob@gmail.com> wrote:
>
> pwb recompiled the compiler and it got 1 byte larger.
> again, another byte. after that they played with it
> until they broke the quine part. i am not sure that
> if they ever realized what was going on.
>
> the extra byte was my bug.
>
>
> On Mon, Sep 20, 2021 at 4:58 AM Douglas McIlroy <
> douglas.mcilroy@dartmouth.edu> wrote:
>
>> >> > It's part of my academic project to work on provable compiler
>> security.
>> >> > I tried to do it according to the "Reflections on Trusting Trust" by
>> Ken
>> >> > Thompson, not only to show a compiler Trojan horse but also to prove
>> that
>> >> > we can discover it.
>> >>
>> >> Of course it can be discovered if you look for it. What was impressive
>> about
>> >> the folks who got Thompson's compiler at PWB is that they found the
>> horse
>> >> even though they weren't looking for it.
>>
>> > I had not heard this story. Can you elaborate, please? My impression
>> from having
>> > read the paper (a long time ago now) is that Ken did the experiment
>> locally only.
>>
>> Ken did it locally, but a vigilant person at PWB noticed there was an
>> experimental
>> compiler on the research machine and grabbed it. While they weren't
>> looking for
>> hidden stuff, they probably were trying to find what was new in the
>> compiler. Ken
>> may know details about what they had in the way of source and binary.
>>
>> Doug
>>
>
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next prev parent reply other threads:[~2021-09-20 14:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 11:57 Douglas McIlroy
2021-09-20 13:51 ` Ken Thompson
2021-09-20 14:35 ` John P. Linderman [this message]
2021-09-20 14:48 ` [TUHS] On UNIX Trojans Ron Natalie
-- strict thread matches above, loose matches on Subject: below --
2021-09-20 3:04 [TUHS] Thompson trojan put into practice Noel Chiappa
2021-09-20 3:21 ` David Arnold
2021-09-20 4:35 ` Earl Baugh
2021-09-20 4:36 ` Earl Baugh
2021-09-20 2:39 Douglas McIlroy
2021-09-20 2:50 ` Larry McVoy
2021-09-20 7:12 ` arnold
2021-09-19 15:46 arnold
2021-09-19 15:58 ` Al Kossow
2021-09-19 16:02 ` arnold
2021-09-19 16:10 ` John Floren
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