Ken Thompson mentioned a self-reproducing program that products an
exact copy of its source code as output in his 1983 Turing paper, http://www.acm.org/classics/sep95/ . Can this be done in C? How can a
program at runtime know its compiling-time source code?
May 10 '07
11  4075 
Tor Rustad <torust_at_onli ne.nowrites:
Richard Bos wrote:
>Mind you, that trap-door only works if you assume that the compiler
will
only be used to compile itself.
Only??! It will work in more cases than that.
The seriousness here, is that system programs are typically written in
C, and C compilers are typically written in C.
If you develop a new C compiler, and use the infected compiler when
bootstrapping, the backdoor will be inherited. Also, if you create a C
cross compiler, the backdoor will be passed forward.
If I recall correctly (and it's entirely possible I don't), that's
unlikely. The trapdoor works by recognizing a certain piece of the
code being compiled, and generating special output in response to it.
An independently developed cpomiler is unlikely to contain anything
matching that pattern.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
[Can't see my response, this is a repost & possibly a duplicate message]
Keith Thompson wrote:
>
If I recall correctly (and it's entirely possible I don't), that's
unlikely. The trapdoor works by recognizing a certain piece of the
code being compiled, and generating special output in response to it.
Right. There are two parts, the "back door" and the "infecter". The back
door is targeted for some security sensitive software, e.g. SSH, while
the "infecter" is targeted the compiler, which will later be used to
compile e.g. SSH.
An independently developed cpomiler is unlikely to contain anything
matching that pattern.
Normally, compilers these days are not hand-coded, tools like lex & yacc
generate some of the C code of the compiler. These tools will leave a
signature. I have not done any prototyping of this, but it should not be
that hard to detect tokens like e.g. yyparse for the infecter.
--
Tor <torust [at] online [dot] no> This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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******************************************************************************
This posting is also available in HTML format:
http://cci.lbl.gov/~rwgk/python/adopt_init_args_2005_07_02.html
******************************************************************************
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