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vb2c.txt

vb2c.txt
Posted Dec 30, 2004
Authored by Qiao Zhang

A buffer overflow in the vb2c 0.02 parse() function allows for system compromise.

tags | advisory, overflow
SHA-256 | 71cadaf06edac8de52c4c0639698cb6e06a9945c1355327b359fc56a7bcdffea

vb2c.txt

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From djb@cr.yp.to Wed Dec 15 14:21:53 2004
Date: 15 Dec 2004 08:22:45 -0000
From: D. J. Bernstein <djb@cr.yp.to>
To: securesoftware@list.cr.yp.to, mike@mikekohn.net
Subject: [remote] [control] vb2c 0.02 parse_sub overflows token buffer

Qiao Zhang, a student in my Fall 2004 UNIX Security Holes course, has
discovered a remotely exploitable security hole in vb2c. I'm publishing
this notice, but all the discovery credits should be assigned to Zhang.

You are at risk if you take a FRM file from an email message (or a web
page or any other source that could be controlled by an attacker) and
feed that file through vb2c. (The vb2c documentation does not tell users
to avoid taking input from the network.) Whoever provides that file then
has complete control over your account: she can read and modify your
files, watch the programs you're running, etc.

Proof of concept: On an x86 computer running FreeBSD 4.10, as root, type

cd /usr/ports/devel/vb2c
make install

to download and compile the vb2c program, version 0.02 (current). Then,
as any user, save the file 34.frm attached to this message, and type

vb2c 34

with the unauthorized result that a file named EXPLOITED is created in
the current directory.

Here's the bug: In vb2c.c, parse() uses gettoken() to read any number of
bytes into a 255-byte token[] array.

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago

[ Part 2, Text/PLAIN (charset: unknown-8bit) 17 lines. ]
[ Unable to print this part. ]

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