EnCase Forensic Imager 7.10 Denial Of Service / Heap Buffer Overflow

`SEC Consult Vulnerability Lab Security Advisory < 20161128-0 >  
=======================================================================  
title: Denial of service & heap-based buffer overflow  
product: Guidance Software EnCase Forensic Imager & EnCase Forensic  
vulnerable version: EnCase Forensic Imager<= 7.10  
EnCase Forensic (tested with version 7.08.00.137)  
fixed version: -  
CVE number: -  
impact: high  
homepage: https://www.guidancesoftware.com/encase-forensic-imager  
found: 2016-09-30  
by: Wolfgang Ettlinger (Office Vienna)  
SEC Consult Vulnerability Lab  
  
An integrated part of SEC Consult  
Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow  
Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich  
  
https://www.sec-consult.com  
  
=======================================================================  
  
Vendor description:  
-------------------  
"When time is short and you need to acquire entire volumes or selected  
individual folders, EnCase Forensic Imager is your tool of choice. Based on  
trusted, industry-standard EnCase Forensic technology, EnCase Forensic Imager:  
* Is free to download and use  
* Requires no installation  
* Is a standalone product that does not require an EnCase Forensic license  
* Enables acquisition of local drives (network drives are not able to be  
acquired with Imager)  
* Provides easy viewing and browsing of potential evidence files, including  
folder structures and file metadata  
* Can be deployed via USB stick and used to perform acquisition of a live  
device"  
  
URL: https://www.guidancesoftware.com/encase-forensic-imager  
  
  
Business recommendation:  
------------------------  
SEC Consult recommends not to use Encase Forensic Imager or the Encase Forensic  
Suite until a thorough security review has been performed by security  
professionals and all identified issues have been resolved.  
  
  
Vulnerability overview/description:  
-----------------------------------  
1) Denial of Service  
Several manipulated hard disk images cause Encase Forensic Imager to crash. A  
suspect manipulating the hard drive could potentially hinder an investigator  
from using Encase Forensic Imager for creating hard disk images.  
Encase Forensic (v7) has been tested and found to be affected as well.  
  
2) Heap-based buffer overflow  
Using a manipulated ReiserFS image an attacker can overwrite heap memory on the  
investigator's machine. Because of several restrictions SEC Consult was unable  
to create an exploit that works reliably within a reasonable timeframe.  
However, as with most heap-based buffer overflow vulnerabilities it is possible  
that an attacker could gain arbitrary code execution nevertheless.  
  
  
Proof of concept:  
-----------------  
SEC Consult has created proof of concept disk images that will crash Encase. Those  
PoC images will not be released.  
  
1) Denial of Service  
The following list demonstrates cases that cause Encase to crash. The  
investigators would be unable to analyze the hard disk/partition/image using the  
affected products:  
* Ext3:  
- Several conditions cause Encase Forensic Imager to encounter an div/0  
exception. Disk images that were manipulated in the following way  
demonstrate this issue. Those crashes have not been further  
investigated as to whether code execution is possible.  
+ nummer of blocks per group: 0xFFFFFFFF  
+ total numer of blocks: 0xFFFFFFFF  
+ last mount path: 'A'*100000  
+ volume name: 'A'*100000  
+ block number of the superblock: 0  
+ FS-Id: 'A'*100000  
- Manipulating the size of the inode structure value (e.g. 0xFFFF) causes  
Encase Forensic Imager to write beyond the limits of a previously  
allocated (VirtualAlloc) segment.  
* Iso9660:  
- If the length of a file name is specified in a way that it would exceed  
the end of the last block, Encase Forensic Imager crashes while trying to  
read beyond an allocated segment.  
* ReiserFs:  
- When setting a block size of below 0x200 the application overwrites heap  
memory with attacker-supplied data.  
* GPT:  
- When specifying an overly long name (in our setup longer than 0x3fc6) for a  
partition, Encase Forensic crashes failing to read memory when trying to  
determine the length of the string. The partition table can be constructed  
in a way that it can also be used for storing data. However, an investigator  
using Encase will not be able to analyze it.  
  
2) Heap-based buffer overflow  
The manipulated ReiserFs image that causes the application to overwrite heap  
memory can be tuned to overwrite heap-data with attacker-controlled data.  
  
The application calculates a value (here called "dev_block_count") as:  
  
dev_block_count =  
blocksize from image (e.g. 0x200)  
/ blocksize of reading device (typically 0x200)  
* number of blocks  
  
.text:006F5306 mov ecx, [esi+14Ch] ; ecx = blocksize (device, 0x200)  
.text:006F530C movzx eax, [esp+90h+var_54] ; eax = blocksize (img)  
.text:006F5311 xor edx, edx  
.text:006F5313 div ecx ; div eax / ecx  
.text:006F5315 push 0  
.text:006F5317 mov edx, eax  
.text:006F5319 imul edx, [esp+94h+var_80] ; * numblocks  
  
If this value is zero (which is the case when the blocksize from the image is  
smaller than 0x200), later in the program it is corrected to the value 1  
(@0064B7AA).  
  
This causes the application to later allocate 4 bytes of memory (the corrected  
value of 1 * 4, @006F5426).  
  
Then the first block of the image is copied to the allocated 4-byte heap space.  
The length to be copied is calculated based on the number of blocks specified  
in the image (maximum 0x200).  
  
  
Vulnerable / tested versions:  
-----------------------------  
At least version 7.10 of Encase Forensic Imager has been found to be vulnerable.  
This version was the latest at the time the security vulnerabilities were  
discovered.  
  
The disk images that caused crashes for Encase Forensic Imager also caused  
crashes with Encase Forensic version 7.08.00.137. It is unknown whether  
Encase Forensic v8 is affected as well.  
  
  
Vendor contact timeline:  
------------------------  
2016-10-07: Contacting vendor (sales team) through email, requesting security  
contact, sending responsible disclosure policy & encryption keys  
2016-10-14: No answer, extending email recipient list, requesting security  
contact again  
2016-10-14: Vendor: our request has been sent to management team, they will  
follow up  
2016-10-17: Vendor: one of their security representatives will be reaching  
out shortly.  
2016-10-28: Asking again for security contact, kind reminder of latest release  
date per 2016-11-26  
2016-10-28: Vendor: Verified that request has been passed on to proper  
department, they will follow up on this  
2016-11-07: Asking again for security contact, reminding them again that  
release date is in about three weeks  
2016-11-08: Extending email recipient list again, including SVP Product  
Engineering explaining unsuccessful attempts to receive a  
security contact  
2016-11-14: Still no answer, reminding Guidance Software again about the release  
date which has been set to 2016-11-28 now. Told them that the  
initial vulnerabilities also affect Encase Forensic and not only  
Encase Forensic Imager.  
2016-11-14: Vendor: "send the alleged vulnerability to us for review" (signed  
email)  
2016-11-14: Sending the advisory encrypted to the vendor, including proof of  
concept disk images to reproduce the issues  
2016-11-14: Vendor: "We will look at the issues and will address them in future  
release(s) if necessary"  
2016-11-15: Asking if there is a hotfix planned, offering to delay the advisory  
release for a few days if necessary, otherwise we'll keep the set  
release date  
2016-11-15: Vendor: they will fix the issue later and are fine patching it after  
advisory release  
2016-11-25: Asking if any fixes are available  
2016-11-28: Releasing security advisory  
  
  
Solution:  
---------  
The vendor told SEC Consult they investigate the issues and will fix them at a  
later date.  
  
  
Workaround:  
-----------  
None  
  
  
Advisory URL:  
-------------  
https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm  
  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
SEC Consult Vulnerability Lab  
  
SEC Consult  
Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow  
Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich  
  
About SEC Consult Vulnerability Lab  
The SEC Consult Vulnerability Lab is an integrated part of SEC Consult. It  
ensures the continued knowledge gain of SEC Consult in the field of network  
and application security to stay ahead of the attacker. The SEC Consult  
Vulnerability Lab supports high-quality penetration testing and the evaluation  
of new offensive and defensive technologies for our customers. Hence our  
customers obtain the most current information about vulnerabilities and valid  
recommendation about the risk profile of new technologies.  
  
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EOF W. Ettlinger / @2016  
  
`