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Re: Smashing the Stack: prevention?
From: merlyn () STONEHENGE COM (Randal Schwartz)
Date: Mon, 28 Apr 1997 06:31:39 -0700


"nate" == nate  <nate () MILLCOMM COM> writes:

nate> 2.  'hmm. what if you change the compiler?'
nate>         C compilers could be modified to do bounds checking, and/or
nate> problem functions could be made to complain to the user at compile time.

Not surprisingly, as a next-gen language, Perl already had this stuff
built in.  Arrays and other data structures are dynamically scalable.
And the "taint" dataflow checking (nothing *from* the outside world
could influence actions *to* the outside world without explicit
"cleansing") has been in there since Perl version 2 (1988).  Perl 5
introduced the notion of running code in an arbitrary "Safe" box,
providing interfaces that mimic system functions.  You could write a
setuid script that executes nearly everything insde the box, then
calls controlled "through the box wall" functions to perform I/O or
launch processes.

Yes, there was the CERT-able hole two years ago because Larry got an
#ifdef backwards on a platform he didn't have access to, and the
recent one where a *libc* routine couldn't handle the arbitrary-sized
data that Perl was handing it.  We have efforts going on in the Perl
developer groups to stamp the rest of those out.  (And yes, there are
apparently a few others.  Durn libc. :-)

So, if you want to write a secure toy, and you want to write it in 1/3
to 1/5 the number of lines of code of C, and you want it to be secure,
just use Perl.

--
Name: Randal L. Schwartz / Stonehenge Consulting Services (503)777-0095
Keywords: Perl training, UNIX[tm] consulting, video production, skiing, flying
Email: <merlyn () stonehenge com> Snail: (Call) PGP-Key: (finger merlyn () ora com)
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Quote: "I'm telling you, if I could have five lines in my .sig, I would!" -- me



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