CVE-2011-2462 was published more than one month ago. It's a memory corruption vulnerability related to U3D objects in Adobe Reader and it affected all the latest versions from Adobe (<=9.4.6 and <= 10.1.1). It was discovered while it was being actively exploited in the wild, as some analysis say. Adobe released a patch for it 10 days after its publication. I'm going to analyse a PDF file exploiting this vulnerability with peepdf to show some of the new commands and functions in action.
As usual, a first look at the information of the file:
So we have several objects to explore, let's start from the /AcroForm element (object 4):
According to a Kaspersky Lab article, SEO Sploit Pack is one of the Exploit Kits which appeared in the first months of the year, being PDF and Java vulnerabilities the most used in these type of kits. That's the reason why I've chosen to analyse a malicious PDF file downloaded from a SEO Sploit Pack. The PDF file kissasszod.pdf was downloaded from hxxp://marinada3.com/88/eatavayinquisitive.php and it had a low detection rate. So taking a look at the file with peepdf we can see this information:
There is no presence of any triggers here (/OpenAction) or in the rest of the objects (/AA) so it seems that the /AcroForm element has something to say. Also, the suspicious object 21 (/EmbeddedFile) is related with this interactive form:
PPDF> references to 21
PPDF> object 28
<< /DA /Helv 0 Tf 0 g /Fields [ 22 0 R ] /XFA [ template 21 0 R ] >>
In the dictionary of the form we can see that object 21 is a template and that there is a reference to a field object (object 22). So we continue analysing the field objects:
In past November The Honeynet Project published a new challenge, this time related to PDF files. Although it's quite old I'm going to analyse it with my tool because I think it has some interesting tricks and peepdf makes the analysis easier. The PDF file can be downloaded from here.
If we launch peepdf we obtain this error:
$ ./peepdf.py -i fcexploit.pdf
Error: parsing indirect object!!
It seems that there is an error in the parsing process. Talking about malicious PDF files it's recommended to add the -f option to ignore this type of errors and continue with the analysis:
The idea is that it's possible to use some malformations in the documents, like those commented by Julia Wolf, and the PDF specification itself in order to keep the files hidden from Antivirus engines and parsers. Bad guys can effectively use it to create an undetectable exploit and use it as an attacking vector. Some of the techniques are the following:
After the Jailbreakme PDF vulnerability explanation I'm gonna publish the proof of concept of the same vulnerability for Foxit Reader. This is a patched vuln for this product so I suppose there will be no problem with that. Like I said, we can use a 116-bytes shellcode without the necessity of another exploiting stage, so I've modified this calc.exe shellcode for this PoC.
This exploit generates a PDF file which can be used against Foxit Reader in Windows XP and Windows Vista. This is functional only for the latest versions of Foxit Reader but it's very easy to modify it for other ones (there is an example in the exploit for the 3.0). You can find the python script in the Exploits section or directly here. Enjoy it!! ;)
Today has been released the source code of the Jailbreakme exploit, so maybe this explanation comes a bit late. In the update of the previous post about this subject I knew that I was right about the overflow in the arguments stack when parsing the charstrings in the Type 2 format, so here is a little more info.
After decoding the stream of the object 13 we can see the following bytes (talking about this file):
The selected bytes are the important ones for this exploit because the overflow occurs when parsing them. Like I mentioned, the Type 2 format is composed of operands, operators and numbers, and use the stack to push and pop values. This stack has a maximum size of 48 elements. We can understand better the meaning of these bytes with this tips:
Some days ago Comex published his JailbreakMe for the new iPhone 4 in the Defcon 18. The interesting thing is that in order to root the device he used a PDF exploit for Mobile Safari to execute arbitrary code and after this another kernel vuln to gain elevated privileges. I've being taking a look at the PDF files with peepdf and these are my thoughts about it.
The PDF file itself has no many objects and only one encoded stream:
The stream is encoded with a simple FlateDecode filter, without parameters, and if we decode its content we can see this strings, related to the JailbreakMe stuff:
As this object seems to contain the vulnerability we are looking for we'll take a closer look to this stream and what this is for:
Description: This script compress/decompress a specified string or file using the Zlib library and writes to the standard output. If the input is a file and the method used is decompression, then the script looks for the streams compressed with the /FlateDecode filter, so it's focused on PDF files. If there is no filters in the file, the whole file is considered as a stream.
ZeuS is still the talk of the town. It's downloaded through fake antivirus, downloaders and several exploit kits. Of course, the best-known social networking site couldn't be out of this. Last week we could see some Facebook messages like the following:
This iframe redirected the user to another web page with two more iframes: