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Re: Smashing the Stack: prevention?
From: snar () CARRIER KIEV UA (Alexander Snarskii)
Date: Mon, 28 Apr 1997 22:29:17 +0300



1.  'you gotta change the code'
        This one is obvious; people must change their SUID programs'
source code to avoid nasty things like gets() sprintf() strcat() and
strcpy() using things like fgets() strncat() strncpy() as substitutes.

Just one more way: replace ususal strcpy/sprintf/strcat
in libc to check stack integrity before exit, and generate
kill(SIGSEGV,getpid()) in case of violations.
That is a 'bad thing' from the performance point of view,
but not so bad (about 1% more time with stack
level 10); and that is not portable - because
stack checker must be written in assembler.

Sometimes ago i propagated such patches to FreeBSD team,
they did'nt commit it. If anyone interested:
ftp://ftp.lucky.net/pub/unix/local/libc-letter.

--
Alexandre Snarskii
the source code is included.



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