Re: Smashing the Stack: prevention?

[snar () CARRIER KIEV UA (Alexander Snarskii)]

> 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.