Tuesday, 6 April 2010

Volume Shadow Copy Forensics - the Robocopy method Part 1

There is always more than one way to skin a cat and so I make no apologies for discussing another approach to processing volume shadow copies. This approach - I'll call it the Robocopy method - has been researched and developed by the chaps over at QCC, John Douglas, Gary Evans and James Crabtree and they have kindly let me crib from their notes. This post is Part 1 - I have simplified QCC's approach but have also removed some functionality. In Part 2 I will expand on the simplified approach and add back in some functionality.

Robocopy is a robust file copying utility developed by Microsoft. This method allows us to copy out folders and files of interest from any notable shadow copies. The process will preserve folder and file paths and timestamps. The key advantages are that it is efficient -both in storage and speed.

This blog post complements my previous posts Vista Volume Shadow Copy issues and Volume Shadow Copy Forensics.. cannot see the wood for the trees? and the method documented below is similar in the early stages.

What are we going to need?
For what follows we will need a Windows 7 box (real or a VM), Encase with the PDE module and some storage space formatted NTFS. Robocopy is pre-installed within Windows 7.

Method
You will already have an Encase image of the drive you wish to investigate. When this is loaded up into an Encase case you need to gather some information in respect to the shadow copies you wish to investigate further. You will need to note the File Creation date and if you wish to be more precise establish the Shadow Copy ID stored at File Offset 144 for 16 bytes - bookmark as a GUID in Encase. Next you will have to mount the volume containing the shadow copies as an emulated disk using the Encase PDE module with caching enabled. On my box the mounted volume was allocated the drive letter I. I am using a Windows 7 box - if you are using a Windows 7 VM add the PDE mounted disk to the VM as an additional hard disk. Then on your box or in the VM:

Run a Command Prompt as Administrator and type the command (substituting I for the drive letter allocated to your mounted volume)

vssadmin list shadows /for=I:

This will result in a list of all available shadow copies on the selected volume

vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
(C) Copyright 2001-2005 Microsoft Corp.

Contents of shadow copy set ID: {2202d8a9-1326-4254-9818-252ece858b17}
Contained 1 shadow copies at creation time: 10/12/2009 14:41:25
Shadow Copy ID: {ad2e71d0-48d6-44b9-9715-f5ff6b5a5643}
Original Volume: (I:)\\?\Volume{34e5a98a-1a1d-11df-a259-00236cb6de69}\
Shadow Copy Volume: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy5
Originating Machine: Richard-MBP-Vis
Service Machine: Richard-MBP-Vis
Provider: 'Microsoft Software Shadow Copy provider 1.0'
Type: ClientAccessibleWriters
Attributes: Persistent, Client-accessible, No auto release, Differentia
l, Auto recovered

Contents of shadow copy set ID: {e13bb9d9-c522-422b-b92a-37f6d12363d9}
Contained 1 shadow copies at creation time: 15/12/2009 12:17:37
Shadow Copy ID: {d0e1c613-7892-47e1-9b7e-f638adac9d16}
Original Volume: (I:)\\?\Volume{34e5a98a-1a1d-11df-a259-00236cb6de69}\
Shadow Copy Volume: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy6
Originating Machine: Richard-MBP-Vis
Service Machine: Richard-MBP-Vis
Provider: 'Microsoft Software Shadow Copy provider 1.0'
Type: ClientAccessibleWriters
Attributes: Persistent, Client-accessible, No auto release, Differentia
l, Auto recovered

Marry up your bookmarked GUID to the Shadow Copy ID number to identify the Shadow Copy Volume you wish to process. The next step is to create a symbolic link to the selected shadow copy (ShadowCopy6 in this example) by typing the command

mklink /d C:\shadow_copy6 \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy6\

which results in the output

symbolic link created for C:\shadow_copy6 <<===>> \\?\GLOBALROOT\Device\Harddisk
VolumeShadowCopy6\

We are now going to use robocopy to copy out data from the mounted shadow copy - for this example I have created a folder called SC6 on my export volume. The command I used for this example is

robocopy C:\shadow_copy6\Users\Richard G:\SC6 /S /XJ /COPY:DAT /NFL /NDL /w:0 /r:0

This results in robocopy outputting a Job Header to the console

---------------------------------------------------------------------------
ROBOCOPY :: Robust File Copy for Windows
---------------------------------------------------------------------------
Started : Mon Apr 05 11:23:18 2010
Source : C:\shadow_copy6\Users\Richard\
Dest : G:\SC6\
Files : *.*
Options : *.* /NDL /NFL /S /COPY:DAT /XJ /R:0 /W:0
---------------------------------------------------------------------------

The header usefully sums up what I have asked robocopy to do.

  • I am copying only the Richard user profile (Users\Richard) to my export folder SC6
  • *.* indicates that I am copying all files
  • /NDL suppresses directory listings to the console
  • /NFL suppresses file listings to the console
  • /S copies the source folder and all sub folders and files
  • /COPY:DAT copies data, attributes and timestamps
  • /XJ exclude junction points
  • /R:0 number of retries on failed copies (in other words -do not re try)
  • /W:0 wait between retries

Nothing much happens at the command prompt now unless a failed file copy is encountered when you will receive output to the console similar to

2010/04/06 11:24:48 ERROR 5 (0x00000005) Copying File C:\shadow_copy6\Users\Rich
ard\AppData\Local\Temp\~DFA2ED.tmp
Access is denied.

When the copying is completed a summary is outputted to the console


It can be seen that 17 directories have been skipped. This means they have not been copied -probably because of permission issues. Also notable is the copying speed which is much quicker than imaging.

The output folder now contains a copy of the Richard users profile. Drag the contents of the export folder into Encase which processes the contents as single files. You may wish to create a logical evidence file of these single files.

Alternative Robocopy Configuration
As inferred from the Job Header above it is possible to take a fairly granular approach to what is copied out of your shadow copy. For example the command

robocopy C:\shadow_copy6\Users G:\SC6 *.jpg *.bmp *.png /S /XJ /COPY:DAT /NFL /NDL /w:0 /r:0

will copy out all jpg, bmp and png files from all User profiles. With reference to the two examples in this post and the robocopy manual it is possible to configure the copy operation in many different ways. For example you could just copy files that have timestamps in a particular range or files that are greater than a particular size.

Incorrect Function
If you play with VSCs often you will run into this rather helpful Microsoft error message. Tips to overcome it in Part 2.

References
Windows Vista/7 Recovering evidential data from Volume Shadow Copies John Douglas
http://technet.microsoft.com/en-gb/library/cc733145(WS.10).aspx
http://blogs.sans.org/computer-forensics/2009/01/08/robocopy-–-a-computer-forensics-tool/
http://42llc.net/index.php?option=com_myblog&task=tag&category=robocopy&Itemid=39




4 comments:

signon said...

Symbolic link is there only in Vista and Windows 7. How do you get around with the procedure on Windows XP?

DC1743 said...

This is why you really need a Windows 7 box (real or VM). On an XP forensic box you can try and use a MS utility called dosdev.exe however making yourself a W7 VM will be more efficient in the long run.

Troy said...

You aren't going to get to shadow copies on Vista and Windows 7 using an XP box. If you are doing Windows forensics work, you should be using WIndows 7 machines, or you will likely be leaving evidence in the image.

As for this method of working with shadow copies, I think you might find addressing the shadow copies as shares less inclined to generate copy errors.

Contact me at my office mail and I will send you my latest slides.

Thanks again for a great post.

Martin said...

try Path Too Long fixer