Date: Sat, 27 Jun 1998 18:24:56 -0400 (EDT) From: jtb <jtb@pubnix.org> To: Patrick McAndrew <pfm@slack.net> Cc: Wojciech Sobczuk <sopel@hood.1lo.lublin.pl>, fpscha@schapachnik.com.ar, Niall Smart <njs3@doc.ic.ac.uk>, ncb05@uow.edu.au, security@FreeBSD.ORG Subject: Re: non-executable stack? Message-ID: <Pine.SOL.3.96.980627182039.9643A-100000@pubnix.org> In-Reply-To: <Pine.NEB.3.96.980627001158.27630A-100000@brooklyn.slack.net>
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What do you mean, checking for this is very easy, just before something
gets executed, you take argv and envp and loop through them looking for
those certain ascii characters, it's like 10-15 lines of code, if that. I
don't see why you'd think that would be cumbersome to the kernel.
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Jonathan T. Bowie ADM w00w00 WSD
jobe@sekurity.org jtb@pubnix.org jobe@dataforce.net
Independant Security Developer
Home: (603)436-5698 "I'd hate to advocate drugs, sex, alcohol, or
Cell: (603)553-6697 violence... to any one, but they've worked
for me." -- Hunter S. Thompson
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On Sat, 27 Jun 1998, Patrick McAndrew wrote:
>
>
> On Fri, 26 Jun 1998, jtb wrote:
>
> > Actually, Brian Matthews brought this idea up to me last fall, and the
> > more I've been thinking about it lately, why not just deny a handful of
> > ctrl-char's that a buffer overflow needs, i.e. 0x90, 0xff, etc. I'd have
> > to say there is a minimal number of ctrl-char's we can disallow to stop
> > your average script kiddie from sending shellcode into a process via
> > cmdline or environment arguments. This method won't really protect
> > against attacks involving sscanf()'ing data from files ala the Vixie Cron
> > bug for RH 4.x, but security will definitely be improved with minimal
> > loses funcionality-wise. Let me know what you guys think. All replies
> > are welcomed, critical or not.
>
> Why bother? Just practice good security programming and check bounds. It
> would be much easier to fix a getc() call than to write an entire function
> that checks for certain control characters that were passed.. Rember,
> "keep it simpe stupid" :)
>
> Pat
>
>
>
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