Since 1974, there has been one security attack that has been claimed to
be essentially uncounterable: the "Trusting Trust" attack. In this
attack, the compiler is subverted, which can then subvert everything
else. In 1984, Ken Thompson demonstrated it and made it widely known.
David A. Wheeler has published a paper that claims to be the antidote to
the "Trusting Trust" attack. Interestingly enough, its results are far
more helpful if your compiler is open source software.
The "trusting trust" attack subverts the compiler binary;
if the attacker succeeds, you're doomed. Well, til now.
Since 1974, there has been one security attack that has been claimed to
be uncounterable: the "Trusting Trust" attack. This attack became famous
in 1984 when Ken Thompson gave his famous speech
"Reflections on Trusting Trust." David A. Wheeler written a paper on
an approach to counter this attack,
"Countering Trusting Trust through Diverse Double-Compiling".
His approach verifies that a source and binary correspond, so that you
can then analyze the source code. This is obviously more valuable to
those who have access to the compiler source code.
Here's the abstract:
"An Air Force evaluation of Multics, and Ken Thompson's famous Turing award
lecture "Reflections on Trusting Trust," showed that compilers can be
subverted
to insert malicious Trojan horses into critical software, including
themselves.
If this attack goes undetected, even complete analysis of a system's
source code
will not find the malicious code that is running, and methods for
detecting this
particular attack are not widely known. This paper describes a practical
technique, termed diverse double-compiling (DDC),
that detects this attack and some unintended compiler defects as well.
Simply recompile the purported source code twice: once with a second
(trusted)
compiler, and again using the result of the first compilation.
If the result is bit-for-bit identical with the untrusted
binary, then the source code accurately represents the binary.
This technique has been mentioned informally, but its issues and
ramifications have not been identified or discussed in a
peer-reviewed work, nor has a public demonstration been made.
This paper describes the technique, justifies it, describes how
to overcome practical challenges, and demonstrates it."
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