[14625] in cryptography@c2.net mail archive
Re: Trusting the Tools - was Re: Open Source ...
daemon@ATHENA.MIT.EDU (kent@songbird.com)
Mon Oct 13 12:12:42 2003
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From: kent@songbird.com
Date: Sun, 12 Oct 2003 22:29:06 -0700
To: Anne & Lynn Wheeler <lynn@garlic.com>
Cc: kent@songbird.com, Bill Frantz <frantz@pwpconsult.com>,
cryptography@metzdowd.com
Mail-Followup-To: Anne & Lynn Wheeler <lynn@garlic.com>,
kent@songbird.com, Bill Frantz <frantz@pwpconsult.com>,
cryptography@metzdowd.com
In-Reply-To: <4.2.2.20031012170211.00b27980@mail.earthlink.net>
On Sun, Oct 12, 2003 at 05:13:06PM -0600, Anne & Lynn Wheeler wrote:
> well ... you can take and compare the listing file against the "txt"
> deck output of the assembler listing for each module.
[...]
> then the issue isn't if the assembler has been compromised ... it is
> whether the loader has been compromised.
You seem to be describing the characteristics of a particular assembler.
Though I may not have expressed it well, my point was really at a
different level. The entire program building system, of which the the
loader, assembler, and compiler are all parts, is susceptible.
Thompson's paper described a very clever way of embedding a trojan in a
compiler, but there are multiple places in the program building system
where compromises of a similar flavor could occur -- my favorite
hypothetical has been the binary library manager (I worked on one for
the Cray-1 series, many years ago).
> then you compare the memory
> image file against the aggregate of the txt decks ... if you've done
> the assembler listing comparison against the txt deck correctly ....
> then the memory image comparison is looking for a loader compromise ...
> not an assembler compromise.
The process you describe is a rather daunting task, especially given
that all that is really necessary is a very small bit of code to load
more code from a different file.
Kent
--
Kent Crispin "Be good, and you will be
crispin@icann.org,kent@songbird.com lonesome."
p: +1 310 823 9358 f: +1 310 823 8649 -- Mark Twain
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