full-disclosure - BZIP2 bomb question

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From: chows at ozemail.com.au (Gregh)
Subject: BZIP2 bomb question

----- Original Message -----
From: "Alex Shipp" <ashipp@...sagelabs.com>
To: <full-disclosure@...ts.netsys.com>
Sent: Tuesday, January 13, 2004 8:36 AM
Subject: Re: [Full-Disclosure] BZIP2 bomb question


> >----- Original Message -----
> >From: "Gregh" <chows@...mail.com.au>
> >
>
> >Please note I am not a good programmer here but here goes:
> >
> >I am wondering why, for those who HAVE to auto unpack, a script cannot be
> >written which, upon receipt of an archive of any sort, inspects it for,
as
> >an example, 100K of the same character repeated (keeping in mind that the
> >NULL character, chr$(7) etc have all been used for compressed bombs) and
if
> >there *IS* such a file, move the file to some safe location for later
> manual
> >inspection and if not, allow automatic unpacking etc.
>
> Ignoring lots of technical details (!) this can indeed be done, and can be
> used
> along with lots of other heuristics to defend against compressed bombs.
>
> There are implementaions that already do this.
>

Then perhaps the people still falling foul of the bombs might be helped out
by a few URLS here if you wouldn't mind? It just seemed a little strange to
me that an archive cant be inspected before being operated on. Thanks for
the answer!

Greg.