Bug 64408 (CVE-2004-1261)

We received the following report.
The issue is public.

The attack scenario for this one sounds rather constructed. I think
we can continue the current php update without fix for this.

From djb@cr.yp.to Wed Dec 15 14:21:44 2004
Date: 15 Dec 2004 08:21:54 -0000
From: D. J. Bernstein <djb@cr.yp.to>
To: securesoftware@list.cr.yp.to, mike@mikekohn.net
Subject: [remote] [control] asp2php 0.76.23 preparse() overflows token
    buffer; preparse() overflows temp buffer

Qiao Zhang, a student in my Fall 2004 UNIX Security Holes course, has
discovered two remotely exploitable security holes in asp2php. I'm
publishing this notice, but all the discovery credits should be assigned
to Zhang.

You are at risk if you take an ASP script from an email message (or a
web page or any other source that could be controlled by an attacker)
and feed that script through asp2php. (The asp2php documentation does
not tell users to avoid taking input from the network.) Whoever provides
that script 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, type

   wget http://downloads.mikekohn.net/asp2php/asp2php-0.76.23.tar.gz
   gunzip < asp2php-0.76.23.tar.gz | tar -xf -
   cd asp2php-0.76.23
   make

to download and compile the asp2php program, version 0.76.23 (current).
Then save the file 29-1.asp attached to this message, and type

   ./asp2php 29-1.asp

with the unauthorized result that a file named EXPLOITED is created in
the current directory. 29-2.asp is similar but uses a separate buffer
overflow. (I tested these with a 541-byte environment, as reported by
printenv | wc -c.)

Both buffer overflows can be blamed on gettoken(), which has a
fundamentally broken gets()-style API. The preparse() function calls
gettoken() to read data into a 1024-byte token[] array, and to read data
into a 1024-byte temp[] array.

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

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