Ponder The Bits

Musings and confusings. All things DFIR.

Category: Tools

Decompressing and Extracting Artifacts from Windows 8 / Server 2012+ Hibernation Files

Windows Hibernation files from a hibernated (or sometimes simply shutdown) machine can be a wealth of information in investigations, often containing a nearly complete memory image of what was running on the system prior to hibernation (shutdown). For years, many in the DFIR community have pillaged the hibernation file for a variety of artifacts, ranging from extraction of simple strings to the use of more specialized analysis tools like Mathieu Suiche’s Hibr2Bin and Volatility. However, since Windows 8, you may (or may not) have noticed that the number of artifacts extracted by the usual methods have at times ranged from substantially less to nearly nonexistent.

So, what gives? Does Microsoft simply no longer store (as many) artifacts in there anymore? I mean, if our trusted tools can’t identify/extract it, it’s surely not there, right? Well, while it would be easy to simply move on and accept the loss of artifacts, I’d like to take the time to dig a bit deeper and find out what is going on here.

Background

Windows hibernation files are compressed at shutdown. Starting in Windows XP, Microsoft began using the Xpress compression algorithm with a defined data structure of which many tools (including the aforementioned Hibr2Bin and Volatility) had down pat to properly decompress and extract/display the contained artifacts. However, beginning in Windows 8/Server 2012, Microsoft changed things up, namely adding a Huffman encoding variant and changing the data structures a bit. This, in turn, rendered existing decompression tools severely hindered without a rewrite to account for the changes. As of this writing, while it appears there is some work in progress to update both Hibr2Bin and Volatility to update the decompression methods, neither of these tools can successfully fully decompress Windows 8+ Hibernation files. Though, I believe the DFIR community eagerly awaits updates to these tools as they have both proven to be incredibly useful in their own respects.

== Sidebar ==

For those interested in the nitty gritty details of Windows hibernation files, refer to Joe T Sylve, Vico Marziale, and Golden G. Richard III’s excellent paper titled “Modern windows hibernation file analysis” that describes in great detail the various Windows hibernation file formats/structures, along with their testing methodology using Hibr2Bin to attempt to decompress each Windows version’s hibernation files. You will see the issue of the changed compression structure evident in their testing with Hibr2Bin in that they saw it only produced a subset of expected decompressed artifacts and “surmised that Hibr2Bin must only decompress the first restoration set of pages that are restored by the boot loader, ignoring the second set of kernel-restored pages.” We can assume the same and/or similar issue(s) of not yet being able to properly read and entirely parse the new data structures also apply to Volatility.

== /Sidebar ==

So, the information is still there, we just have to figure out a different way (or use a different tool) to get to it. But, before we go on, let’s recap a bit about our previous go-to Hibernation file decompression tools.

On September 20, 2016, Matthieu Suiche released (open sourced) his Hibr2bin (Hibernation file decompression) and DumpIt (memory image collection) utilities. However, as of this latest release, the Hibr2bin tool only supports comprehensive decompression of Hibernation files up through Windows 7. Though it states support for Windows 8 and 10 systems, it has been demonstrated to not fully decompress the file (of which Mathieu is currently aware). Though, the tool is open source now, so the community has full access to build these changes in themselves without relying on Mathieu to do it.

Though Volatility’s imagecopy plugin will work to decompress/convert Windows XP through Windows 7Hibernation files to a raw memory dump for analysis, it does not currently support Windows 8/Server 2012+ Hibernation file decompression (https://github.com/volatilityfoundation/volatility/issues/25). That said, it is still able to properly parse and analyze a decompressed Hibernation files through the latest version(s) of Windows 10/Server 2016, should you be able to decompress the Hibernation file by some other means/tool.

So, where does this leave us if our go-to tools no longer work to fully decompress Hibernation files from Windows 8/Server 2012+ systems? Are we up Schitt’s Creek (HILARIOUS show BTW, please do check it out) without a paddle?

Enter Arsenal Recon.

The folks that brought you Registry Recon and Arsenal Image Mounter have since developed Hibernation Recon, which as of this post appears to be the only tool currently available that supports comprehensive decompression of Windows hibernation files through the latest Windows 10 releases.

I’ve extracted the below pertinent information from their web page:

Hibernation Recon has been developed to not only support memory reconstruction from Windows XP, Vista, 7, 8/8.1, and 10 hibernation files, but to properly identify and extract massive volumes of information from the multiple types (and levels) of slack space that often exist within them…

Features:
* Windows XP, Vista, 7, 8/8.1, and 10 hibernation file support
* Active memory reconstruction
* Identification and extraction of multiple levels of slack space
* Brute force decompression of partially overwritten slack
* Segregation of extracted slack based on particular hibernations
* Proper handling of legacy hibernation data found in modern hibernation files
* NTFS metadata recovery with human-friendly decoding
* Parallel processing of multiple hibernation files”

As of the March 7, 2017 release, the team currently offers both a paid and free version…

Hibernation Recon is priced at just $399 to ensure every digital forensics expert can properly arm themselves. If Hibernation Recon is run without a license, a “Free Mode” is provided which supports the extraction of active contents from both legacy and modern Windows hibernation files.

As a major bonus and rarity for the “Free” version of a tool, the “Free Mode” version is allowed for both personal AND commercial use. NOICE! Big kudos to these guys for allowing this!

Do note that the hibernation slack & NTFS metadata recovery functionality is only available within the professional version, which I would imagine could be very useful as well. However, for the sake of brevity, access, and initial focus of my testing (i.e., successful comprehensive decompression) I am simply testing the “Free Mode” version. Perhaps I can get my hands on the Pro version at some point to test those additional recovery features…

At any rate, I downloaded the tool from the website and got on my way to testing using the “Free Mode”.

Testing

For testing, I first enabled hibernation via the command line (> powercfg -h on) and then generated three different hibernation files by performing the following procedures on my Windows 10 Pro desktop system:

Booted

  1. Enable Hibernation
  2. Hibernate the machine via Right-click Windows button -> Hibernate
  3. Boot the machine
  4. Log into the system and copy the existing hiberfil.sys via FTK Imager

Hibernated

  1. Enable Hibernation
  2. Hibernate the machine via Right-click Windows button -> Hibernate
    1. This can also be done via “shutdown /h” on the command line
  3. Boot into live linux environment and copy the existing hiberfil.sys

Shutdown

  1. Enable Hibernation
  2. Shut down the system
  3. Boot into live linux environment and copy the existing hiberfil.sys

With the 3 resulting hibernation files generated by the above methods, I could now test and measure the following:

  1. If, and how well, Hibernation Recon decompresses each Hibernation file
  2. How much information, if any, each Hibernation file contains (i.e., which collection method yields the greatest amount of artifacts and information)

With the data and aforementioned goals in hand, I ran Hibernation Recon* against each Hibernation file so that I had both a native compressed file and (supposedly) fully decompressed file for performing comparison.

*Note: I did not test Hibr2bin against these images as Sylve, Marziale, and Richard III had already done so as outlined in their previously mentioned paper on the subject.

I then ran the following tools against both the native compressed and decompressed images for each collection method (booted, hibernated, and shutdown) to collect a relatively representative set of results for quantitative comparison*:

*I’m no data scientist, I just attempted a testing methodology that I considered to have the greatest layman’s ROI

  1. GNU Strings
    Not too much to explain here, I simply wanted to identify all occurrences of strings (both unicode and ASCII) within each image.
  2. Page_Brute
    This tool is designed to run Yara signatures against each block (4096 bytes) of a pagefile. However, I wanted to test it against the Hibernation file as it also uses 4096 byte pages and well… there’s really nothing to lose in testing it. I added signatures to the default_signatures.yar ruleset file to also identify IP addresses, Email addresses, and URL’s – all useful artifacts of which we’d expect to find in a memory image and thus I figured a good method for comparison.
  3. Bulk_Extractor
    Copied/pasted directly from the user manual, “bulk_extractor operates on disk images, files or a directory of files and extracts useful
    information without parsing the file system or file system structures. The input is split into pages and processed by one or more scanners.
    ” It is a beautiful thing in that it is EXTREMELY well threaded and as such will hog as much of your system’s resources as it is allowed. Though caution must be exercised here in light of that, letting it run full throttle on a dedicated machine yields some insanely fast (not to mention very intelligent) artifact parsing and extraction. The quantity of identified and extracted artifacts are a good measure of how much decompressed data (in terms of Hibernation file decompression, not decompression of standard files like zip, rar, etc. that is also built into the tool) is available within the image.
  4. Volatility 2.6
    Run Volatility’s imagecopy plugin against the native compressed image to attempt to decompress/convert it to a raw image. Then, run Volatility with the appropriate system profile against the Volatility decompressed/converted image and the Hibernation Recon decompressed image. Various plugin output can then be compared across images to see which produces the greatest amount of artifacts parsed from the memory image.

Results

== Legend ==
JPW10_hiberfil.sys = Hibernation file from Shutdown system
JPW10_hiberfil.sys_2 = Hibernation file from Hibernated system
JPW10_hiberfil.sys_3 = Hibernation file from Booted system
ActiveMemory.bin = Decompressed and reconstructed memory image via Hibernation Recon

Strings, Page_Brute, and Bulk_Extractor data:
Hibernation_Testing_Results

“Booted” System Results
See spreadsheet for Strings, Page_Brute, and Bulk_Extractor data.

As we can verify here, the contents of the Hibernation file are zeroed upon system boot, which is stated to be the case in Windows 8+ systems. Thus, as we’d expect, no results from using any of the tools and no reason to use Hibernation Recon against the Hibernation file (nothing there to decompress).

“Hibernated” System Results
See spreadsheet for Strings, Page_Brute, and Bulk_Extractor data.

Volatility
Attempt to convert/decompress native hibernation file to use with Volatility…
$ python ~/volatility/vol.py -f Hibernated/JPW10_hiberfil.sys_2 --profile=Win10x64_14393 imagecopy -O Hibernated/Output/JPW10_hiberfil.sys_2_conv

Run pslist plugin against resulting file…
$ python ~/volatility/vol.py -f Hibernated/Output/JPW10_hiberfil.sys_2_conv --profile=Win10x64_14393 pslist
Volatility Foundation Volatility Framework 2.6
No suitable address space mapping found
Tried to open image as:
MachOAddressSpace: mac: need base
LimeAddressSpace: lime: need base
WindowsHiberFileSpace32: No base Address Space
WindowsCrashDumpSpace64BitMap: No base Address Space
WindowsCrashDumpSpace64: No base Address Space
...
IA32PagedMemory: Incompatible profile Win10x64 selected
OSXPmemELF: ELF Header signature invalid
FileAddressSpace: Must be first Address Space
ArmAddressSpace: No valid DTB found

As you can see, it was not successfully decompressed and is thus not usable.

Now, we will see what happens when we run plugins against the Hibernation Recon (HR) decompressed image…
$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin imageinfo
Volatility Foundation Volatility Framework 2.6
INFO : volatility.debug : Determining profile based on KDBG search...
Suggested Profile(s) : Win10x64_10586, Win10x64_14393, Win10x64, Win2016x64_14393
AS Layer1 : Win10AMD64PagedMemory (Kernel AS)
AS Layer2 : FileAddressSpace (/mnt/hgfs/G/Hibernation_Testing/Hibernated/Output/ActiveMemory.bin)
PAE type : No PAE
DTB : 0x1ab000L
KDBG : 0xf800a82f0500L
Number of Processors : 8
Image Type (Service Pack) : 0
KPCR for CPU 0 : 0xfffff800a8342000L
KPCR for CPU 1 : 0xffffda019e020000L
KPCR for CPU 2 : 0xffffda019e09b000L
KPCR for CPU 3 : 0xffffda019e116000L
KPCR for CPU 4 : 0xffffda019e193000L
KPCR for CPU 5 : 0xffffda019e1d2000L
KPCR for CPU 6 : 0xffffda019e291000L
KPCR for CPU 7 : 0xffffda019e310000L
KUSER_SHARED_DATA : 0xfffff78000000000L
Image date and time : 2017-03-08 02:12:21 UTC+0000
Image local date and time : 2017-03-07 18:12:21 -0800

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin kdbgscan
...
**************************************************
Instantiating KDBG using: Unnamed AS Win10x64_14393 (6.4.14393 64bit)
Offset (V) : 0xf800a82f0500
Offset (P) : 0x469cf0500
KdCopyDataBlock (V) : 0xf800a81d0e00
Block encoded : Yes
Wait never : 0xd6dc0c37f24a0453
Wait always : 0x940ac90a25873204
KDBG owner tag check : True
Profile suggestion (KDBGHeader): Win10x64_14393
Service Pack (CmNtCSDVersion) : 0
Build string (NtBuildLab) : 14393.693.amd64fre.rs1_release.1
PsActiveProcessHead : 0xfffff800a82ff3d0 (39 processes)
PsLoadedModuleList : 0xfffff800a8305060 (189 modules)
KernelBase : 0xfffff800a8000000 (Matches MZ: True)
Major (OptionalHeader) : 10
Minor (OptionalHeader) : 0
KPCR : 0xfffff800a8342000 (CPU 0)
KPCR : 0xffffda019e020000 (CPU 1)
KPCR : 0xffffda019e09b000 (CPU 2)
KPCR : 0xffffda019e116000 (CPU 3)
KPCR : 0xffffda019e193000 (CPU 4)
KPCR : 0xffffda019e1d2000 (CPU 5)
KPCR : 0xffffda019e291000 (CPU 6)
KPCR : 0xffffda019e310000 (CPU 7)
**************************************************
...

Great. We’ve successfully retrieved the kdbg/dtb addresses along with the profile from the image. Now, let’s try to run some plugins against it to see what we’ve got…

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --dtb=0x1ab000 --profile=Win10x64_14393 pslist
Volatility Foundation Volatility Framework 2.6
Offset(V) Name PID PPID Thds Hnds Sess Wow64 Start Exit
------------------ -------------------- ------ ------ ------ -------- ------ ------ ------------------------------ ------------------------------
0xffff9e04362eb6c0 System 4 0 209 0 ------ 0 2017-03-07 22:34:32 UTC+0000
0xffff9e043acbf800 smss.exe 372 4 4 0 ------ 0 2017-03-07 22:34:32 UTC+0000
0xffff9e043b4e9080 csrss.exe 540 528 13 -------- 0 0 2017-03-07 22:34:35 UTC+0000
0xffff9e043c439800 wininit.exe 628 528 4 0 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c4d8800 services.exe 708 628 33 -------- 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c540400 lsass.exe 752 628 11 -------- 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c4d4800 svchost.exe 872 708 54 0 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c4ce800 svchost.exe 936 708 16 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c472800 svchost.exe 348 708 104 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c626080 svchost.exe 388 708 54 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c683800 svchost.exe 1032 708 24 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c681800 svchost.exe 1096 708 32 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c67d800 svchost.exe 1212 708 38 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c67b800 svchost.exe 1236 708 34 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c66f800 nvvsvc.exe 1580 708 8 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c66b800 nvscpapisvr.ex 1588 708 7 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043637d080 svchost.exe 2000 708 8 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043ca1f800 svchost.exe 1292 708 12 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043ca8b800 spoolsv.exe 2056 708 32 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c042700 sched.exe 2168 708 17 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c036800 avguard.exe 2428 708 120 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c032800 armsvc.exe 2440 708 5 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c034800 Avira.ServiceH 2448 708 31 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c030800 OfficeClickToR 2476 708 29 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c02e800 IPROSetMonitor 2508 708 4 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c02c800 LogiRegistrySe 2516 708 6 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c02a800 svchost.exe 2524 708 16 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c028800 NvNetworkServi 2544 708 5 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c026800 NvStreamServic 2680 708 11 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c024800 dasHost.exe 2740 1096 26 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be64740 svchost.exe 2760 708 19 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be66800 svchost.exe 2768 708 19 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be75800 vmnetdhcp.exe 2776 708 3 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be70800 vmware-usbarbi 2792 708 5 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be72800 vmnat.exe 2808 708 6 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be74800 vmware-authd.e 2824 708 7 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be91800 MsMpEng.exe 2836 708 8 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be97800 ss_conn_servic 2844 708 6 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043beed040 MemCompression 2952 4 16 0 ------ 0 2017-03-07 22:34:38 UTC+0000

Excellent. Looks like many of the data structures are in tact to provide the types of information we’d expect from a full memory image!

So, let’s keep going…

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --dtb=0x1ab000 --profile=Win10x64_14393 hivelist
Volatility Foundation Volatility Framework 2.6
Virtual Physical Name ------------------ ------------------ ----
0xffff87063f057000 0x00000000059f3000 \REGISTRY\MACHINE\HARDWARE

Uh oh, that doesn’t look right. There should be more hives found than that.

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --dtb=0x1ab000 --profile=Win10x64_14393 userassist
Volatility Foundation Volatility Framework 2.6
The requested key could not be found in the hive(s) searched

No userassist (as it relies on the registry hives).

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --dtb=0x1ab000 --profile=Win10x64_14393 shellbags
Volatility Foundation Volatility Framework 2.6
Scanning for registries....
Gathering shellbag items and building path tree...

And, no shellbags (as it also relies on the registry hives). So, I guess the decompressed image doesn’t contain that.

Well, how about files?

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --dtb=0x1ab000 --profile=Win10x64_14393 filescan
Offset(P) #Ptr #Hnd Access Name ------------------ ------ ------ ------ ----
...
0x0000f000000f0820 3 0 RW-rwd \Device\HarddiskVolume2\$Extend\$RmMetadata\$Repair:$Corrupt:$DATA 0x0000f000000fe2d0 8 0 R--r-d \Device\HarddiskVolume6\Windows\System32\coreaudiopolicymanagerext.dll 0x0000f00000100420 12 0 R--r-d \Device\HarddiskVolume6\Windows\System32\Windows.UI.Xaml.Resources.dll 0x0000f00000100720 3 0 R--rwd \Device\HarddiskVolume6\Program Files\Microsoft Office\root\CLIPART\PUB60COR\NA02386_.WMF
0x0000f00000102ef0 15 0 R--r-d \Device\HarddiskVolume6\Windows\System32\dsreg.dll
0x0000f00000113080 32753 1 ------ \Device\DeviceApi\CMNotify
0x0000f000001132a0 15 0 R--rwd \Device\HarddiskVolume6\Windows\System32\vcruntime140.dll 0x0000f00000114cc0 15 0 R--r-d \Device\HarddiskVolume6\Windows\System32\microsoft-windows-kernel-power-events.dll
0x0000f0000011c370 32708 1 RW-r-- \Device\HarddiskVolume6\Windows\System32\winevt\Logs\Microsoft-Windows-AppXDeploymentServer%4Operational.evtx
0x0000f00000127ef0 16 0 R--r-d \Device\HarddiskVolume6\Windows\System32\DriverStore\FileRepository\iaahcic.inf_amd64_6c0fb3e072c6ec98\iaAHCIC.cat
0x0000f0000012e740 32768 1 ------ \Device\DeviceApi\CMNotify
0x0000f00000135a00 16 0 R--r-- \Device\HarddiskVolume6\Windows\INF\msgpiowin32.PNF
0x0000f00000140cd0 2 0 R--r-- \Device\HarddiskVolume6\Windows\WinSxS\Manifests\x86_microsoft.windows.i..utomation.proxystub_6595b64144ccf1df_1.0.14393.0_none_1e9c04c01886b354.manifest ...

Looks like that works, so mainly (in this short testing) we’re just missing registry hives.

While there are some anomalies here within strings (less identified ASCII and UNI strings in the decompressed hibernation file), we can see that not only does Hibernation Recon’s decompressed hibernation file yield substantially more artifacts across the board in both page_brute and Bulk_Extractor, but it also yields a memory image for use in/with Volatility. However, we can see that there are some pieces of missing information that would otherwise be resident in a memory image collected from a live system (namely registry hives as discovered in our testing, but there could be other missing items). Is Hibernation Recon missing resident information? Is Windows simply not storing that information in the hibernation file itself? I’m not certain, but would be very interested in finding out.

“Shutdown” System Results
See spreadsheet for Strings, Page_Brute, and Bulk_Extractor data.

Volatility
Attempt to convert/decompress native hibernation file to use with Volatility…
$ python ~/volatility/vol.py -f Shutdown/JPW10_hiberfil.sys --profile=Win10x64_14393 imagecopy -O Shutdown/Output/JPW10_hiberfil.sys_conv

Run pslist against the resulting file…
$ python ~/volatility/vol.py -f Shutdown/Output/JPW10_hiberfil.sys_conv --profile=Win10x64_14393 pslist

No results, showing the file wasn’t able to be successfully decompressed/parsed by Volatility.

So, let’s again move on to the HR decompressed file.

$ python ~/volatility/vol.py -f Shutdown/Output/ActiveMemory.bin imageinfo
Volatility Foundation Volatility Framework 2.6
INFO : volatility.debug : Determining profile based on KDBG search...
Suggested Profile(s) : Win10x64_14393, Win2016x64_14393
AS Layer1 : Win10AMD64PagedMemory (Kernel AS)
AS Layer2 : FileAddressSpace (/mnt/hgfs/G/Hibernation_Testing/Shutdown/Output/ActiveMemory.bin)
PAE type : No PAE
DTB : 0x1ab000L
KDBG : 0xf800a82f0500L
Number of Processors : 8
Image Type (Service Pack) : 0
KPCR for CPU 0 : 0xfffff800a8342000L
KPCR for CPU 1 : 0xffffda019e020000L
KPCR for CPU 2 : 0xffffda019e09b000L
KPCR for CPU 3 : 0xffffda019e116000L
KPCR for CPU 4 : 0xffffda019e193000L
KPCR for CPU 5 : 0xffffda019e1d2000L
KPCR for CPU 6 : 0xffffda019e291000L
KPCR for CPU 7 : 0xffffda019e310000L
KUSER_SHARED_DATA : 0xfffff78000000000L
Image date and time : 2017-03-07 22:39:53 UTC+0000
Image local date and time : 2017-03-07 14:39:53 -0800

$ python ~/volatility/vol.py -f Shutdown/Output/ActiveMemory.bin kdbgscan
Volatility Foundation Volatility Framework 2.6
**************************************************
Instantiating KDBG using: /mnt/hgfs/G/Hibernation_Testing/Shutdown/Output/ActiveMemory.bin WinXPSP2x86 (5.1.0 32bit)
Offset (P) : 0x3e0a9730
KDBG owner tag check : True
Profile suggestion (KDBGHeader): Win10x64_14393
PsActiveProcessHead : 0xa82ff3d0
PsLoadedModuleList : 0xa8305060
KernelBase : 0xfffff800a8000000
**************************************************
Instantiating KDBG using: /mnt/hgfs/G/Hibernation_Testing/Shutdown/Output/ActiveMemory.bin WinXPSP2x86 (5.1.0 32bit)
Offset (P) : 0x3e0a9730
KDBG owner tag check : True
Profile suggestion (KDBGHeader): Win2016x64_14393
PsActiveProcessHead : 0xa82ff3d0
PsLoadedModuleList : 0xa8305060
KernelBase : 0xfffff800a8000000

Again, we are able to successfully parse the HR decompressed image to get the initial offsets and profile needed to use Volatility and its plugins for analysis. So, let’s get to them.

$ python ~/volatility/vol.py -f Shutdown/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --dtb=0x1ab000 --profile=Win10x64_14393 pslist
Volatility Foundation Volatility Framework 2.6
Offset(V) Name PID PPID Thds Hnds Sess Wow64 Start Exit
------------------ -------------------- ------ ------ ------ -------- ------ ------ ------------------------------ ------------------------------
0xffff9e04362eb6c0 System 4 0 206 0 ------ 0 2017-03-07 22:34:32 UTC+0000
0xffff9e043acbf800 smss.exe 372 4 4 0 ------ 0 2017-03-07 22:34:32 UTC+0000
0xffff9e043b4e9080 csrss.exe 540 528 14 -------- 0 0 2017-03-07 22:34:35 UTC+0000
0xffff9e043c439800 wininit.exe 628 528 7 0 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c4d8800 services.exe 708 628 33 -------- 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c540400 lsass.exe 752 628 9 -------- 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c4d4800 svchost.exe 872 708 46 0 0 0 2017-03-07 22:34:36 UTC+0000
0xffff9e043c4ce800 svchost.exe 936 708 14 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c472800 svchost.exe 348 708 96 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c626080 svchost.exe 388 708 53 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c683800 svchost.exe 1032 708 23 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c681800 svchost.exe 1096 708 24 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c67d800 svchost.exe 1212 708 31 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c67b800 svchost.exe 1236 708 30 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c66f800 nvvsvc.exe 1580 708 8 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c66b800 nvscpapisvr.ex 1588 708 7 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043637d080 svchost.exe 2000 708 8 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043ca1f800 svchost.exe 1292 708 12 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043ca8b800 spoolsv.exe 2056 708 30 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c042700 sched.exe 2168 708 17 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c036800 avguard.exe 2428 708 120 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c032800 armsvc.exe 2440 708 5 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c034800 Avira.ServiceH 2448 708 28 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c030800 OfficeClickToR 2476 708 23 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c02e800 IPROSetMonitor 2508 708 4 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c02c800 LogiRegistrySe 2516 708 6 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c02a800 svchost.exe 2524 708 12 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c028800 NvNetworkServi 2544 708 5 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c026800 NvStreamServic 2680 708 10 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043c024800 dasHost.exe 2740 1096 26 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be64740 svchost.exe 2760 708 17 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be66800 svchost.exe 2768 708 14 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be75800 vmnetdhcp.exe 2776 708 3 -------- 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be70800 vmware-usbarbi 2792 708 5 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be72800 vmnat.exe 2808 708 6 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be74800 vmware-authd.e 2824 708 7 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be91800 MsMpEng.exe 2836 708 8 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043be97800 ss_conn_servic 2844 708 6 0 0 0 2017-03-07 22:34:38 UTC+0000
0xffff9e043beed040 MemCompression 2952 4 4 0 ------ 0 2017-03-07 22:34:38 UTC+0000

Great. Again, looks like we have a memory image here that we can successfully use with Volatility.

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 hivelist
Volatility Foundation Volatility Framework 2.6
Virtual Physical Name ------------------ ------------------ ----
0xffff87063f057000 0x00000000059f3000 \REGISTRY\MACHINE\HARDWARE

Uh oh (again). It can’t seem to locate many of the registry hives in memory.

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 userassist
Volatility Foundation Volatility Framework 2.6
The requested key could not be found in the hive(s) searched

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 shellbags
Volatility Foundation Volatility Framework 2.6
Scanning for registries....
Gathering shellbag items and building path tree...

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 shimcache
Volatility Foundation Volatility Framework 2.6
WARNING : volatility.debug : No ShimCache data found

Again, can’t extract the info from these plugins because of the lack of registry hives found.

However, it seems that many other plugins complete successfully.

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 filescan
Volatility Foundation Volatility Framework 2.6
Offset(P) #Ptr #Hnd Access Name ------------------ ------ ------ ------ ----
...
0x0000f000000f0820 3 0 RW-rwd \Device\HarddiskVolume2\$Extend\$RmMetadata\$Repair:$Corrupt:$DATA 0x0000f000000fe2d0 8 0 R--r-d \Device\HarddiskVolume6\Windows\System32\coreaudiopolicymanagerext.dll 0x0000f00000100420 12 0 R--r-d \Device\HarddiskVolume6\Windows\System32\Windows.UI.Xaml.Resources.dll 0x0000f00000100720 3 0 R--rwd \Device\HarddiskVolume6\Program Files\Microsoft Office\root\CLIPART\PUB60COR\NA02386_.WMF
0x0000f00000102ef0 15 0 R--r-d \Device\HarddiskVolume6\Windows\System32\dsreg.dll
0x0000f00000113080 32753 1 ------ \Device\DeviceApi\CMNotify
0x0000f000001132a0 15 0 R--rwd \Device\HarddiskVolume6\Windows\System32\vcruntime140.dll 0x0000f00000114cc0 15 0 R--r-d \Device\HarddiskVolume6\Windows\System32\microsoft-windows-kernel-power-events.dll
0x0000f0000011c370 32708 1 RW-r-- \Device\HarddiskVolume6\Windows\System32\winevt\Logs\Microsoft-Windows-AppXDeploymentServer%4Operational.evtx
0x0000f00000127ef0 16 0 R--r-d \Device\HarddiskVolume6\Windows\System32\DriverStore\FileRepository\iaahcic.inf_amd64_6c0fb3e072c6ec98\iaAHCIC.cat
0x0000f0000012e740 32768 1 ------ \Device\DeviceApi\CMNotify
0x0000f00000135a00 16 0 R--r-- \Device\HarddiskVolume6\Windows\INF\msgpiowin32.PNF
0x0000f00000140cd0 2 0 R--r-- \Device\HarddiskVolume6\Windows\WinSxS\Manifests\x86_microsoft.windows.i..utomation.proxystub_6595b64144ccf1df_1.0.14393.0_none_1e9c04c01886b354.manifest
...

I also ran the mbrparser and mftparser plugins against the image to see if that data was resident.

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 mbrparser

Verified works.

$ python ~/volatility/vol.py -f Hibernated/Output/ActiveMemory.bin --kdbg=0xf800a81d0e00 --profile=Win10x64_14393 mftparser

Verified works.

So, we seem to witness the same anomaly in strings, however it appears that the decompressed hibernation file contains more identified Unicode strings as compared to the native file. Given that strings performs a relatively arbitrary function (i.e. identify things that might be strings of an alphabet/namespace), I am simply providing it as a data point. And, again, we see that the decompressed file yields a substantial amount of additional information that was otherwise obfuscated/hidden from discovery in its native form.

Conclusion

As you can see, Arsenal’s tool was able to successfully decompress and reconstruct the provided Hibernation files (sans the zeroed file from the Booted system obviously), thus restoring a substantial amount of otherwise obfuscated/encoded data and ultimately our capability to extract useful artifacts in our investigations! Given how long it’s been since I’ve been able to easily and comprehensively decompress a Windows 8/Server 2012+ Hibernation file, I would have been satisfied with simple decompression of all strings or chunks of data. Not only do we get that, but also the restored ability to use Volatility for more comprehensive analysis of the extracted memory image (sans a few missing memory artifacts as previously noted*).

For me, it looks like I now have a new go-to tool for decompressing Hibernation files from Windows 8/Server 2012+ systems.

*If anyone has any insight, I would love to find out why we can’t seem to locate the registry hives in the reconstructed memory image, along with what else may be missing (as I didn’t test every single plugin) and why.

/JP

Did you enjoy this post? Share it!

OSX (Mac) Memory Acquisition and Analysis Using OSXpmem and Volatility

Macs don’t get much love in the forensics community, aside from @iamevltwin (Sarah Edwards), @patrickolsen (Patrick Olsen), @patrickwardle (Patrick Wardle), and a few other incredibly awesome pioneers in the field. We see blog posts all the time about Windows forensics and malware analysis techniques, along with some Linux forensic analysis, but rarely do we see any posts about Mac technical/forensic analysis or techniques. I find this odd, considering the surge in usage and deployment over the last several years, particularly within enterprises. Well, with my most recent two part Mac post as well as this one, I’m attempting to change this, my friends!

Macs need love and disk/memory analysis as well, amirite?

Let’s have a look at memory acquisition of OSX systems using a nifty tool called OSXpmem.

OSXpmem is a part of the pmem suite created by the developers of Rekall. Rekall itself is actually a very useful utility built for both memory acquisition and live memory analysis on Windows, Linux, and OSX systems. While I will be delving into Rekall in a future post, for this we will simply be focusing on OSXpmem, which is an awesome command-line utility for quickly and easily collecting RAM from a Mac system. One of its greatest features is its output to an AFF4 volume, which has a ton of useful features (likely to be discussed in a dedicated post in the future as well).

Acquiring Memory

So, what’s the easiest way to get up and running with the tool for memory acquisition?

  1. Download latest release (as of this post, the latest osxpmem release is “2.1.post4”).
  2. Unzip the package
    1. $ unzip osxpmem.osxpmem-2.1.post4.zip
  3. Run it to collect memory from the local system
    1. $ ./osxpmem.app/osxpmem -o <output_dir>

Super simple, right?

Wellll, maybe not that simple. When you run it, even as sudo/root, you may get the following error:

$ sudo osxpmem.app/osxpmem -o Memory_Captures/mem.aff4
Imaging memory
E1229 15:17:26.335978 3375588288 aff4_file.cc:289] Can not open file /dev/pmem :No such file or directory
/Users/jp/Projects/osxpmem.app/MacPmem.kext failed to load - (libkern/kext) authentication failure (file ownership/permissions); check the system/kernel logs for errors or try kextutil(8).
E1229 15:17:26.606639 3375588288 osxpmem.cc:283] Unable to load driver at /Users/jp/Projects/osxpmem.app/MacPmem.kext
E1229 15:17:26.606714 3375588288 pmem_imager.cc:328] Imaging failed with error: -8

How usefully nondescript. Let me save you some time, as searching the system/kernel logs as suggested yields nothing useful.

So, instead, let’s use the native utility kextutil’s “test” parameter (-t) to see if that gets us anywhere…

$ sudo kextutil -t osxpmem.app/MacPmem.kext/
Diagnostics for osxpmem.app/MacPmem.kext:
Authentication Failures:
File owner/permissions are incorrect (must be root:wheel, nonwritable by group/other):
osxpmem.app/MacPmem.kext
Contents
_CodeSignature
CodeResources
Info.plist
MacOS
MacPmem

Nice. It finally tells us what’s wrong. The file ownership/permissions must be changed to “root:wheel”. Easy enough…

$ sudo chown -R root:wheel osxpmem.app/

So, let’s try again…

$ sudo osxpmem.app/osxpmem -o Memory_Captures/mem.aff4
Imaging memory
Creating output AFF4 ZipFile.
Reading 0x8000 0MiB / 8095MiB 0MiB/s
Reading 0xe38000 14MiB / 8095MiB 56MiB/s
Reading 0x1c88000 28MiB / 8095MiB 56MiB/s
Reading 0x2ac0000 42MiB / 8095MiB 56MiB/s
Reading 0x3978000 57MiB / 8095MiB 58MiB/s
Reading 0x47c8000 71MiB / 8095MiB 56MiB/s
Reading 0x5678000 86MiB / 8095MiB 58MiB/s
Reading 0x6500000 101MiB / 8095MiB 57MiB/s

Reading 0x1f7478000 8052MiB / 8095MiB 39MiB/s
Reading 0x1f7d68000 8061MiB / 8095MiB 35MiB/s
Reading 0x1f8708000 8071MiB / 8095MiB 38MiB/s
Reading 0x1f9150000 8081MiB / 8095MiB 41MiB/s
Reading 0x1f9c00000 8092MiB / 8095MiB 41MiB/s

YES! It worked! As you can see, my system has 8GB of memory that was (by default) exported to an AFF4 volume/file called “mem.aff4”.

You also have the option to include additional local files within the resulting AFF4 volume/file via the “-i </path/to/file> -i </path/to/file> …” command line option(s), which can be useful in producing a singular output volume containing not only memory but other files (binaries/logs/etc.) you’d like to analyze as well. In the past, I used this option to collect the local /bin/bash file when Volatility used to require the bash shell’s memory address be provided in order to parse command history and produce associated timestamps when using the linux_bash plugin. Though the documentation still shows it as a requirement, it’s actually not needed anymore and parses it all just fine.

In addition, you may also export the memory image to a singular RAW or ELF file by using the “–format elf” or “–format raw” command line options if that suits your fancy. However, for this post, I am using the default AFF4 output so that we may explore its use and features a bit.

So, without further ado, let’s take a look at the resulting AFF4 volume/file.

$ sudo osxpmem.app/osxpmem -V Memory_Captures/mem.aff4
Password:
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix aff4: <http://aff4.org/Schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix memory: <http://aff4.org/Schema#memory/> .
<aff4://7f482355-5683-46bb-87c0-21afd75dbbeb/dev/pmem>
aff4:category memory:physical ;
aff4:stored <aff4://7f482355-5683-46bb-87c0-21afd75dbbeb> ;
a aff4:map .
<aff4://7f482355-5683-46bb-87c0-21afd75dbbeb/dev/pmem/data>
aff4:chunk_size 32768 ;
aff4:chunks_per_segment 1024 ;
aff4:compression <https://www.ietf.org/rfc/rfc1950.txt> ;
aff4:size 8488656896 ;
aff4:stored <aff4://7f482355-5683-46bb-87c0-21afd75dbbeb> ;
a aff4:image .
Objects in use:
Objects in cache:
aff4://7f482355-5683-46bb-87c0-21afd75dbbeb - 0
aff4://7f482355-5683-46bb-87c0-21afd75dbbeb/information.turtle - 0
file:///Users/jp/Projects/Memory_Captures/mem.aff4 - 0

Here, you can see that we extracted a memory image to the AFF4 stream “7f482355-5683-46bb-87c0-21afd75dbbeb/dev/pmem“.

Now, what can we do with this? Well, one thing you could do (if not using Rekall to analyze this image) might be to extract the AFF4 memory image stream into a singular raw file for parsing/analysis by other tools such as Volatility, page_brute, yara, strings, etc. To do that, we perform the following:

$ sudo osxpmem.app/osxpmem -e /dev/pmem -o Memory_Captures/mem.raw Memory_Captures/mem.aff4
Extracting aff4://7f482355-5683-46bb-87c0-21afd75dbbeb/dev/pmem into file:///Users/jp/Projects/Memory_Captures/mem.raw
Reading 0x8000 0MiB / 9968MiB 0MiB/s
Reading 0x750000 7MiB / 9968MiB 28MiB/s
Reading 0xde0000 13MiB / 9968MiB 25MiB/s
Reading 0x1480000 20MiB / 9968MiB 25MiB/s

Reading 0x26d938000 9945MiB / 9968MiB 21MiB/s
Reading 0x26deb8000 9950MiB / 9968MiB 21MiB/s
Reading 0x26e418000 9956MiB / 9968MiB 20MiB/s
Reading 0x26eab0000 9962MiB / 9968MiB 25MiB/s

$ ls -l Memory_Captures/
total 25665056
-rwxr-xr-x 1 root staff 2688302741 Dec 29 15:30 mem.aff4
-rwxr-xr-x 1 root staff 10452205568 Dec 29 16:10 mem.raw

As you can see, the raw image is uncompressed and thus substantially larger than the AFF4 volume (one of the useful features of AFF4 is its compression options). Nonetheless, there you have it. A raw memory image to parse to your heart’s content with whatever tools you like.

However, before we move on, I personally like to unload the kernel extension for one last good measure so that it’s not just hanging out there for no purpose.

$ sudo osxpmem.app/osxpmem -u
Unloading driver /Users/jp/Projects/osxpmem.app/MacPmem.kext

Creating a Memory Profile

Acquiring a memory image is great, but unfortunately is useless (with respect to Volatility) without the appropriate profile to parse it. Volatility requires a memory profile be specified when parsing a memory image via the “–profile=<profile>” command line option. By default, Volatility includes a ton of profiles for Windows, but such is not the case for Linux and Mac. Though a profiles repository has been created containing a substantial set of profiles for Linux and Mac, YMMV. In my situation, I’m running the latest MacOS Sierra release 10.12.3, for which no profile existed as of this post (nor did it for 10.12.2 until I created and submitted one to the repo as well :D). Therefore, I had to create my own profile. Luckily, the folks at Volatility do a great job walking us through building a profile on a Mac. Though, there are a few clarifications I’d like to address.

To begin, I need to provide some clarification/correction for the initial step, focusing on the part in italics:

“To create a profile, you first need to download the KernelDebugKit for the kernel you want to analyze. This can be downloaded from the Apple Developer’s website (click OS X Kernel Debug Kits on the right). This account is free and only requires a valid Email address.

After the DebugKit is downloaded, mount the dmg file. This will place the contents at “/Volumes/KernelDebugKit”.”

While the above statement is true, if you immediately dismount a package once it’s installed like I do, you should instead pay attention to the installer to see where it is putting the files for long term access. Independent of the mounted package, the KDK is installed in the following location, which will need to be referenced for future use once the package is dismounted post-install:

/Library/Developer/KDKs/KDK_<version>.kdk/

As of current, for macOS Sierra 10.12.2 and 10.12.3, the <version> will be “10.12.2_16C67” and “KDK_10.12.3_16D32.kdk“, respectively.

/Library/Developer/KDKs/KDK_10.12.2_16C67.kdk/
/Library/Developer/KDKs/KDK_10.12.3_16D32.kdk/

Thus, “Step 1” for building a 10.12.3 profile would be the following (for a 64-bit 10.12.3 system):

$ dwarfdump -arch x86_64 /Library/Developer/KDKs/KDK_10.12.3_16D32.kdk/System/Library/Kernels/kernel.dSYM > 10.12.3_x64.dwarfdump

Also note that the referenced kernel file names vary from the current instructions (e.g., “mach_kernel.dSYM” is now “kernel.dSYM”, and “mach_kernel” is now just “kernel”). So, do exercise additional caution when running the commands. For ease of reference, below should be the locations for both of these files on a macOS Sierra 10.12.3 64-bit system (but note that this may change with future versions):

/Library/Developer/KDKs/KDK_10.12.3_16D32.kdk/System/Library/Kernels/kernel
/Library/Developer/KDKs/KDK_10.12.3_16D32.kdk/System/Library/Kernels/kernel.dSYM

All of the above is actually noted during the install as well:

To save everyone a bit of time and translation from current Volatility documentation, I’ve written out the latest required steps below for relatively easy copy/paste into your terminal. For this, we are using the latest 10.12.3 release and associated KDK as an example:

  1. Check to see if a profile is already available for your particular OSX version/release
    1. https://github.com/volatilityfoundation/profiles/tree/master/Mac
  2. If not, download and install the KDK appropriate for your current (or targeted) OSX version/release
    1. http://developer.apple.com/hardwaredrivers
  3. Get the dwarf debug info from the kernel.
    1. $ dwarfdump -arch x86_64 /Library/Developer/KDKs/KDK_10.12.3_16D32.kdk/System/Library/Kernels/kernel.dSYM > 10.12.3_x64.dwarfdump
  4. Convert the dwarfdump output to Linux style output readable by Volatility
    1. $ python tools/mac/convert.py 10.12.3_x64.dwarfdump converted-10.12.3_x64.dwarfdump
  5. Create the types from the converted file
    1. $ python tools/mac/convert.py converted-10.12.3_x64.dwarfdump > 10.12.3.64bit.vtypes
  6. Generate symbol information
    1. $ dsymutil -s -arch x86_64 /Library/Developer/KDKs/KDK_10.12.3_16D32.kdk/System/Library/Kernels/kernel > 10.12.3.64bit.symbol.dsymutil
  7. Create a zip file of the *.dsymutil and *.vtypes files
    1. $ zip 10.12.3.64bit.zip 10.12.3.64bit.symbol.dsymutil 10.12.3.64bit.vtypes
    2. **See note at end of instructions**
  8. Copy the zip file to to the volatility/plugins/overlays/mac/ directory (remember, we are already inside the root /volatility directory)
    1. $ cp 10.12.3.64bit.zip volatility/plugins/overlays/mac/
  9. Verify your profile is registered and ready for use
    1. $ python vol.py --info | grep "A Profile for Mac"
      1. The profile name presented is the string you will pass to the “–profile=” parameter when analyzing a memory image from this version/release in Volatility

**Note: While I append “x64” or “64bit” to my various output files to keep track of which architecture build I’m producing, doing so for the final .zip output file yields profile names with rather weird-looking duplicate 64-bit identifiers (e.g., “Mac10_12_3_64bitx64”). If you would like cleaner looking profile names (at the cost of losing the filename identifier denoting the arch build), you should instead drop the trailing identifier and provide a name the file like the following “10.12.3.zip”, thus yielding a prettier (IMO) profile name like “Mac10_12_3x64”.

Using Volatility for Analysis

Once we have successfully created the appropriate profile for the acquired image, we can now use the plethora of native Volatility Mac OSX plugins provided to us for analysis.

To see the list of available plugins, simply type the following:

#Executed from within the root /volatility folder of a git cloned repo
$ python vol.py --info | grep "mac_"

#Using the standalone binary
$ ./volatility_2.6_mac64_standalone --info | grep "mac_"

Conclusion

That pretty much wraps it up for this post. There is certainly more to explore with OSXpmem, the AFF4 format, and Volatility. However, I encourage you to explore it on your own as I would like to save some feature exploration for future in-depth posts focused on using both Volatility and the Rekall suite.

/JP

Did you enjoy this post? Share it!

Mac Dumpster Diving – Identifying Deleted File References in the Trash (.DS_Store) Files – Part 2

In Part 1 of this post, we identified where these artifacts reside along with options for parsing them. However, we still have not addressed why/how this anomaly occurs. Thus, in Part 2 of this post, we must now test to see how/why this occurs.

The behavior we’re seeing led me to the following hypothesis for testing:

  1. Although the .DS_Store file is “deleted”, when it is re-created it is created in the same space on disk within the same previously allocated blocks on the volume.
    1. *Note: This same situation often occurs on Windows when event logs are cleared/deleted and the event log file is re-created. The re-created log file often inhabits an area on disk surrounding previously deleted entries that may or may not be relevant to the current log at hand. Thus, carving of that file for entries can yield various event entries.
  2. The .DS_Store entries are stored somewhere else on disk and/or memory and are referenced and re-populated within the file upon re-creation for some reason (what reason, I have no idea).
  3. …or another theory that might make sense. (Please share your hypothesis or factual knowledge!)

I tested #1 above by using the “stat” command to see if a deleted and then re-created .DS_Store file would occupy the same inode and it does not. However, I still leave room for the possibility that even though a new inode is associated with the file each time it is re-created, it may still be somehow occupying (some of) the same space on disk.

I tested the on-disk aspect of #2 by searching across all files on disk for any references to a file that was previously deleted (since reboot) – the installer for BlockBlock named “BlockBlock_Installer.app”. The following files stood out to me:

$ sudo sift -z -a -l --err-skip-line-length BlockBlock_Installer.app /
...
/private/var/audit/20161217022600.crash_recovery
/private/var/db/uuidtext/AC/AF78F7097534A2A72631F3DD0AFE52
/private/var/folders/q4/r796r6tx2sd7zhjsxn2bjmv00000gn/0/com.apple.LaunchServices-175-v2.csstore
/private/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/0/com.apple.LaunchServices-175-v2.csstore
/.Spotlight-V100/Store-V2/3AF86A9A-8A7B-414A-8479-E5FACBC49DF1/Cache/0000/0000/000f/997405.txt
...

While each of the above files did contain references to the given file name, none of them contained anything relevant to our research here to indicate they were the culprit of our .DS_Store file entry repopulation issue.

As an aside, the last entry was actually the Spotlight indexed (cached) Evernote page I have been using to take notes for this research 🙂 Do note that the Spotlight database and cache directories are also great places to search for references to deleted files as well, to possibly include full content that has been cached by indexing.

Moving on, I then tested the in-memory aspect of #2 by capturing a memory image (will author a separate blog post on doing this later) from my system and using Volatility’s yarascan and strings plugins to identify where in memory these entries may reside. I debated just showing the end results here, but I figure there is merit in showing how I got to the results as well. So, bonus for everyone!

Volatility’s yarascan plugin (specifically, mac_yarascan for our use on a Mac image) takes a yara rules file, finds matches across a memory image with the associated files/processes/memory areas, and (optionally) dumps the resulting files for analysis. So, this would seem rather useful for our situation here in trying to identify where in memory the historical deleted file references currently exist. To begin, I created the following yara rules file containing references to files that have been deleted from my system but whose entries still remain in the .Trash./DS_Store file.

rule ds_store_searches
{
strings:
$s1=”BlockBlock_Installer.app”
$s2=”canon-mx920-19_1_0a-ea11.dmg”
$s3=”FileZilla-Installer.app”
$s4=”SpotifyInstaller.zip”

condition:
any of them
}

As you can see, I’ve installed a few programs recently, the packages of which I deleted upon successful installation. However, these entries continue to be re-populated back into the .Trash/.DS_Store file on my system as I have not rebooted since I deleted them.

Using the latest release (2.6) of Volatility’s standalone OSX executable along with a custom macOS Sierra 10.12.2 profile I manually generated (and is now available in the Mac profiles repository for all to use!), I scanned the memory image for references to the above files using the mac_yarascan plugin as shown below.

$ ./volatility_2.6_mac64_standalone --plugins=/Users/jp/Projects/volatility/volatility/plugins/ --profile=Mac10_12_2_x64x64 -f ~/Projects/Memory_Captures/mem.raw mac_yarascan -A -y ~/Projects/Yara/ds_store.yar

I’m not going to lie to you, this ran for the better part of a day on my 2015 Core i5 MBA against an 8GB memory image. So, don’t expect speedy results from running this plugin.

=== Begin Sidebar ===

In comparison to the above, running Yara against the image took just under 3 minutes. However, the two tools are doing different things (to an extent) and producing different results.

Yara simply scanned the image and output the location(s) within memory where each hit was identified:

$ yara -s -p 8 ~/Projects/Yara/ds_store.yar mem.raw
0x1fd2cb6:$s1: BlockBlock_Installer.app
0xd380f26:$s1: BlockBlock_Installer.app
0x27b8d40c:$s1: BlockBlock_Installer.app
0x45dbd248:$s1: BlockBlock_Installer.app
0x46fa6195:$s1: BlockBlock_Installer.app

0x17efc11:$s2: canon-mx920-19_1_0a-ea11.dmg
0x1908620:$s2: canon-mx920-19_1_0a-ea11.dmg
0xd11f441:$s2: canon-mx920-19_1_0a-ea11.dmg
0x1831f101:$s2: canon-mx920-19_1_0a-ea11.dmg
0x42748dd1:$s2: canon-mx920-19_1_0a-ea11.dmg

0x1fd2c26:$s3: FileZilla-Installer.app
0x4dbb356:$s3: FileZilla-Installer.app
0x5c208e5:$s3: FileZilla-Installer.app
0x141bbf81:$s3: FileZilla-Installer.app
0x22be06cc:$s3: FileZilla-Installer.app
...
0x1fd22c6:$s4: SpotifyInstaller.zip
0xc5030c6:$s4: SpotifyInstaller.zip
0x41c95ee6:$s4: SpotifyInstaller.zip
0x54c9c5d9:$s4: SpotifyInstaller.zip
0x54c9c5f6:$s4: SpotifyInstaller.zip

These hits can be verified and further investigated by hexdump:

$ hexdump -C -s 0x1fd2cb6 -n 100 mem.raw
01fd2cb6 42 6c 6f 63 6b 42 6c 6f 63 6b 5f 49 6e 73 74 61 |BlockBlock_Insta|
01fd2cc6 6c 6c 65 72 2e 61 70 70 20 0a ad be b5 29 2e a8 |ller.app ....)..|
01fd2cd6 dd ba 80 f9 45 00 00 60 00 00 00 00 00 00 00 00 |....E..`........|
01fd2ce6 00 00 00 00 00 00 00 00 00 00 a4 fa ef 3d 33 33 |.............=33|
01fd2cf6 eb 3f 00 00 00 00 00 00 00 00 08 00 00 00 00 00 |.?..............|
01fd2d06 00 00 40 04 00 00 00 00 00 00 1b 04 00 00 00 00 |..@.............|
01fd2d16 00 00 00 98 |....|

While this is great and shows us that these historical references exist across a ton of areas within memory, it doesn’t really help us identify any useful context. Nonetheless, Yara is an incredibly useful tool that has a variety of purposes, so it’s just a matter of knowing your tools and which one you need to do a given job.

=== End Sidebar ===

Volatility’s mac_yarascan output provided a lot of useful results with context. Just what we needed! Below is a sample entry:

Task: lsd pid 230 rule ds_store_searches addr 0x10c0462bc
0x000000010c0462bc 46 69 6c 65 5a 69 6c 6c 61 2d 49 6e 73 74 61 6c FileZilla-Instal
0x000000010c0462cc 6c 65 72 2e 61 70 70 00 39 31 30 2e 2f 56 6f 6c ler.app.910./Vol
0x000000010c0462dc 75 6d 65 73 2f 52 65 63 6f 76 65 72 79 20 48 44 umes/Recovery.HD
0x000000010c0462ec 00 46 46 2d 2f 70 72 69 76 61 74 65 2f 76 61 72 .FF-/private/var
0x000000010c0462fc 2f 74 6d 70 2f 4d 50 50 5a 4c 50 52 50 00 69 6f /tmp/MPPZLPRP.io
0x000000010c04630c 6b 69 74 2e 2f 64 65 76 2f 64 69 73 6b 30 73 31 kit./dev/disk0s1
0x000000010c04631c 00 6c 79 00 2f 70 72 69 76 61 74 65 2f 74 6d 70 .ly./private/tmp
0x000000010c04632c 2f 44 64 6b 4a 57 79 6f 65 00 70 6c 2f 64 65 76 /DdkJWyoe.pl/dev
0x000000010c04633c 2f 64 69 73 6b 32 73 31 00 72 61 67 2f 56 6f 6c /disk2s1.rag/Vol
0x000000010c04634c 75 6d 65 73 2f 44 6f 63 73 00 6c 6f 2f 64 65 76 umes/Docs.lo/dev
0x000000010c04635c 2f 64 69 73 6b 32 73 31 00 00 00 00 2f 70 72 69 /disk2s1..../pri
0x000000010c04636c 76 61 74 65 2f 74 6d 70 2f 52 78 53 54 49 64 78 vate/tmp/RxSTIdx
0x000000010c04637c 41 00 63 73 2f 64 65 76 2f 64 69 73 6b 32 73 31 A.cs/dev/disk2s1
0x000000010c04638c 00 61 62 6c 2f 56 6f 6c 75 6d 65 73 2f 44 6f 63 .abl/Volumes/Doc
0x000000010c04639c 73 00 6c 6f 2f 64 65 76 2f 64 69 73 6b 32 73 31 s.lo/dev/disk2s1
0x000000010c0463ac 00 72 61 67 2f 55 73 65 72 73 2f 6a 70 2f 44 6f .rag/Users/jp/Do

While it identified references to the above files in a multitude of processes (a surprising amount, actually, that may need to be revisited in future research), we are trying to identify references to all of these files within a common process/context. So, the next step is to do a bit of analysis to see which process/context had at least 4 hits (because we had 4 file names to find). A bit of command line kung fu (gotta plug Hal Pomeranz‘s site, though *cough* he needs some new entries *cough*) yields the following:

$ grep 'Task:' ../Memory_Captures/mem.raw_yara_output | awk '{print $2}' | sort | uniq -c | sort -r
43 Finder
10 BlockBlock
6 mds
5 lsd
5 Google
2 loginwindow
2 coreservicesd
1 system_installd
1 sharingd
1 revisiond
1 pbs
1 mobileassetd
1 mdworker
1 crashpad_handler
1 configd
1 com.apple.geod
1 apsd
1 airportd
1 XprotectService
1 UserEventAgent
1 SubmitDiagInfo
1 Microsoft

We can weed out anything with less than 4 entries, leaving Google, lsd, mds, BlockBlock, and Finder. Google, lsd, and mds processes only had entries for FileZilla, so those are ruled out. BlockBlock is actually an awesome app by Patrick Wardle at Objective-See that watches for any applications that attempt persistence. So, it is of no surprise that all of these entries exist within its memory space as it has overseen each in their installation and alerted me if/when persistence (auto-start) mechanisms were implemented. Usefulness aside, it’s not our culprit here.

Now, we are left with Finder. So, let’s see what entries it found within the Finder process on my machine:

$ grep -A16 'Task: Finder' ../Memory_Captures/mem.raw_yara_output
Task: Finder pid 236 rule ds_store_searches addr 0x10ef4e2bc
0x000000010ef4e2bc 46 69 6c 65 5a 69 6c 6c 61 2d 49 6e 73 74 61 6c FileZilla-Instal
0x000000010ef4e2cc 6c 65 72 2e 61 70 70 00 39 31 30 2e 2f 56 6f 6c ler.app.910./Vol
0x000000010ef4e2dc 75 6d 65 73 2f 52 65 63 6f 76 65 72 79 20 48 44 umes/Recovery.HD
0x000000010ef4e2ec 00 46 46 2d 2f 70 72 69 76 61 74 65 2f 76 61 72 .FF-/private/var
0x000000010ef4e2fc 2f 74 6d 70 2f 4d 50 50 5a 4c 50 52 50 00 69 6f /tmp/MPPZLPRP.io
0x000000010ef4e30c 6b 69 74 2e 2f 64 65 76 2f 64 69 73 6b 30 73 31 kit./dev/disk0s1
0x000000010ef4e31c 00 6c 79 00 2f 70 72 69 76 61 74 65 2f 74 6d 70 .ly./private/tmp
0x000000010ef4e32c 2f 44 64 6b 4a 57 79 6f 65 00 70 6c 2f 64 65 76 /DdkJWyoe.pl/dev
0x000000010ef4e33c 2f 64 69 73 6b 32 73 31 00 72 61 67 2f 56 6f 6c /disk2s1.rag/Vol
0x000000010ef4e34c 75 6d 65 73 2f 44 6f 63 73 00 6c 6f 2f 64 65 76 umes/Docs.lo/dev
0x000000010ef4e35c 2f 64 69 73 6b 32 73 31 00 00 00 00 2f 70 72 69 /disk2s1..../pri
0x000000010ef4e36c 76 61 74 65 2f 74 6d 70 2f 52 78 53 54 49 64 78 vate/tmp/RxSTIdx
0x000000010ef4e37c 41 00 63 73 2f 64 65 76 2f 64 69 73 6b 32 73 31 A.cs/dev/disk2s1
0x000000010ef4e38c 00 61 62 6c 2f 56 6f 6c 75 6d 65 73 2f 44 6f 63 .abl/Volumes/Doc
0x000000010ef4e39c 73 00 6c 6f 2f 64 65 76 2f 64 69 73 6b 32 73 31 s.lo/dev/disk2s1
0x000000010ef4e3ac 00 72 61 67 2f 55 73 65 72 73 2f 6a 70 2f 44 6f .rag/Users/jp/Do
--
Task: Finder pid 236 rule ds_store_searches addr 0x6000001fd248
0x00006000001fd248 42 6c 6f 63 6b 42 6c 6f 63 6b 5f 49 6e 73 74 61 BlockBlock_Insta
0x00006000001fd258 6c 6c 65 72 2e 61 70 70 2f 1b 00 00 00 00 00 00 ller.app/.......
0x00006000001fd268 00 63 6f 6d 2e 6f 62 6a 65 63 74 69 76 65 53 65 .com.objectiveSe
0x00006000001fd278 65 2e 42 6c 6f 63 6b 42 6c 6f 63 6b 04 00 20 01 e.BlockBlock....
0x00006000001fd288 00 00 00 00 8e 00 10 00 02 00 00 00 c4 e5 c7 1d ................
0x00006000001fd298 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd2a8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd2b8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd2c8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd2d8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd2e8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd2f8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd308 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0x00006000001fd318 00 00 00 00 00 00 00 00 47 09 00 00 00 00 00 00 ........G.......
0x00006000001fd328 00 00 00 00 00 00 00 00 47 0a 00 00 00 00 00 00 ........G.......
0x00006000001fd338 47 0b 00 00 00 00 00 00 47 0c 00 00 00 00 00 00 G.......G…….
--
Task: Finder pid 236 rule ds_store_searches addr 0x60000044e501
0x000060000044e501 63 61 6e 6f 6e 2d 6d 78 39 32 30 2d 31 39 5f 31 canon-mx920-19_1
0x000060000044e511 5f 30 61 2d 65 61 31 31 2e 64 6d 67 00 00 00 71 _0a-ea11.dmg...q
0x000060000044e521 91 d8 c5 ff ff 1d 00 8c 07 00 00 01 00 00 00 15 ................
0x000060000044e531 64 6e 67 2e 61 64 6f 62 65 2e 6e 69 6b 6f 6e 64 dng.adobe.nikond
0x000060000044e541 34 2e 63 61 6d 00 00 00 00 00 00 00 00 00 00 71 4.cam..........q
0x000060000044e551 91 d8 c5 ff ff 1d 00 8c 07 00 00 01 00 00 00 14 ................
0x000060000044e561 70 65 66 2e 70 65 6e 74 61 78 2e 37 37 39 37 30 pef.pentax.77970
0x000060000044e571 2e 63 61 6d 00 00 00 00 00 00 00 00 00 00 00 71 .cam...........q
0x000060000044e581 91 d8 c5 ff ff 1d 00 8c 07 00 00 01 00 00 00 10 ................
0x000060000044e591 61 72 77 2e 73 6f 6e 79 2e 32 39 36 2e 63 61 6d arw.sony.296.cam
0x000060000044e5a1 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 11 ................
0x000060000044e5b1 9c d8 c5 ff ff 1d 00 01 00 00 00 00 00 00 00 00 ................
0x000060000044e5c1 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 02 ................
0x000060000044e5d1 00 00 00 00 00 00 00 d0 65 01 00 00 60 00 00 71 ........e...`..q
0x000060000044e5e1 91 d8 c5 ff ff 1d 00 8c 07 00 00 01 00 00 00 11 ................
0x000060000044e5f1 6e 65 66 2e 6e 69 6b 6f 6e 2e 64 39 30 2e 63 61 nef.nikon.d90.ca
--
Task: Finder pid 236 rule ds_store_searches addr 0x600000a48d41
0x0000600000a48d41 53 70 6f 74 69 66 79 49 6e 73 74 61 6c 6c 65 72 SpotifyInstaller
0x0000600000a48d51 2e 7a 69 70 00 00 00 00 00 00 00 00 00 00 00 51 .zip...........Q
0x0000600000a48d61 93 d8 c5 ff ff 1d 00 c3 14 00 00 01 00 00 00 48 ...............H
0x0000600000a48d71 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
0x0000600000a48d81 00 00 00 00 00 00 00 00 ab 1f 00 00 60 00 00 71 ............`..q
0x0000600000a48d91 91 d8 c5 ff ff 1d 00 8c 07 00 00 01 00 00 00 17 ................
0x0000600000a48da1 64 6e 67 2e 61 64 6f 62 65 2e 63 61 6e 6f 6e 65 dng.adobe.canone
0x0000600000a48db1 6f 73 6d 2e 63 61 6d 00 00 00 00 00 00 00 00 e0 osm.cam.........
0x0000600000a48dc1 41 db c5 ff 7f 00 00 01 00 00 00 00 00 00 00 c0 A...............
0x0000600000a48dd1 be 43 00 00 60 00 00 d8 be 43 00 00 60 00 00 d8 .C..`....C..`...
0x0000600000a48de1 be 43 00 00 60 00 00 00 00 00 00 00 00 00 00 71 .C..`..........q
0x0000600000a48df1 91 d8 c5 ff ff 1d 00 8c 07 00 00 0b 00 00 00 13 ................
0x0000600000a48e01 49 6e 73 74 61 6c 6c 20 53 70 6f 74 69 66 79 2e Install.Spotify.
0x0000600000a48e11 61 70 70 00 00 00 00 00 00 00 00 00 00 00 00 11 app.............
0x0000600000a48e21 9c d8 c5 ff ff 1d 00 01 00 00 00 00 00 00 00 00 ................
0x0000600000a48e31 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 02 ................
...

Sure enough, looks like we’ve likely found the harborer of our historical entries! And, it makes sense, as I surmise Finder is the process responsible for creating these .DS_Store files when they are moved to the trash. How might we be able to find out what process is responsible for creating this file? OSX has a nice little utility called fs_usage that can monitor all sorts of file system, disk, I/O aspects. For our purposes/testing here, we are going to filter on filesystem events and grep for the .Trash/.DS_Store file we care about while I go into Finder and delete (send to the Trash) a file:

$ sudo fs_usage -w -f filesystem | grep ".Trash/.DS_Store"
09:15:48.854558 fsgetpath /Users/jp/.Trash/.DS_Store 0.000010 Finder.2394967
09:15:49.357252 fsgetpath /Users/jp/.Trash/.DS_Store 0.000008 Finder.2395226
09:15:53.751509 getattrlist /Users/jp/.Trash/.DS_Store 0.000041 Finder.2395226
09:15:53.751556 fsgetpath /Users/jp/.Trash/.DS_Store 0.000008 Finder.2395226
09:15:53.751576 getattrlist /Users/jp/.Trash/.DS_Store 0.000019 Finder.2395226
09:15:53.751589 fsgetpath /Users/jp/.Trash/.DS_Store 0.000005 Finder.2395226
09:15:53.751717 fsgetpath /Users/jp/.Trash/.DS_Store 0.000007 Finder.2395226
09:15:53.751738 open F=21 (_W____) /Users/jp/.Trash/.DS_Store 0.000019 Finder.2395226
09:15:53.752898 HFS_update (__M_____) /Users/jp/.Trash/.DS_Store 0.000009 Finder.2395226
09:15:53.752905 HFS_update (__MN_c_m) /Users/jp/.Trash/.DS_Store 0.000003 Finder.2395226
09:15:53.752929 HFS_update (___N____) /Users/jp/.Trash/.DS_Store 0.000004 Finder.2395226
09:15:53.752956 HFS_update (___N_c_m) /Users/jp/.Trash/.DS_Store 0.000004 Finder.2395226
09:15:53.753005 HFS_update (_FMN_c_m) /Users/jp/.Trash/.DS_Store 0.000004 Finder.2395226
09:15:53.753157 getattrlist /Users/jp/.Trash/.DS_Store 0.000016 Finder.2395226
09:15:53.754084 WrData[AN] D=0x043832a0 B=0x5000 /dev/disk1 /Users/jp/.Trash/.DS_Store 0.001077 W Finder.2395226
09:15:53.804058 fsgetpath /Users/jp/.Trash/.DS_Store 0.000005 Finder.2395372
09:15:54.293014 lstat64 /Users/jp/.Trash/.DS_Store 0.000030 fseventsd.2395383

Sure enough, there it is. We can see Finder (re)creating the .Trash/.DS_Store file. Pretty cool, huh?

Now, why these entries are re-populated instead of just creating a blank/zero’ed file, we don’t yet quite know (this would take some more intensive inspection of the Finder code itself). Nonetheless, the Finder process definitely looks like a solid candidate responsible for (re)storing these these historical entries.

For even further testing and corroboration of our above findings (additional corroboration is ALWAYS a good idea in both investigations and research), we can use Volatility’s strings plugin. For most effective use, this plugin actually relies on a strings output file (fed as input to the plugin) with each string entry prepended with the decimal offset at which it was found (e.g., “102515331 file.dmg”). Keep in mind that in addition to the standard ASCII strings, we will also want to extract the Unicode 16-bit Big Endian strings as well.

Here we will use the GNU strings utility (gstrings on OSX via brew) to acquire this needed output. As a bit of a pro-tip, below is a great way to extract both ASCII and Unicode (16-bit Big Endian) in parallel using a FIFO queue:

$ mkfifo part-out
$ gstrings -a -td part-out > Memory_Captures/mem.raw.strings.ascii &

[1] 40780
$ cat Memory_Captures/mem.raw | tee part-out | gstrings -a -td -eb > Memory_Captures/mem.raw.strings.be

Once completed, let’s check out the format and see what it found for both the ASCII and Unicode Big-Endian strings:

$ sift "canon-mx920-19_1_0a-ea11.dmg" Memory_Captures/mem.raw.strings.ascii
25099281 canon-mx920-19_1_0a-ea11.dmg
26248704 ;/Volumes/Untitled/.Trashes/501/canon-mx920-19_1_0a-ea11.dmg
219280449 canon-mx920-19_1_0a-ea11.dmg
405926145 canon-mx920-19_1_0a-ea11.dmg
1114934737 canon-mx920-19_1_0a-ea11.dmg
1422508032 e: canon-mx920-19_1_0a-ea11.dmg
1913326497 canon-mx920-19_1_0a-ea11.dmg
4364841040 File: canon-mx920-19_1_0a-ea11.dmg
4454621776 File: canon-mx920-19_1_0a-ea11.dmg
4897694289 canon-mx920-19_1_0a-ea11.dmg
5379226560 ;/Volumes/Untitled/.Trashes/501/canon-mx920-19_1_0a-ea11.dmg
6315679704 File: canon-mx920-19_1_0a-ea11.dmg
7262910545 canon-mx920-19_1_0a-ea11.dmg
7624221584 File: canon-mx920-19_1_0a-ea11.dmg
7720217424 File: canon-mx920-19_1_0a-ea11.dmg
7720218576 File: canon-mx920-19_1_0a-ea11.dmg
8317281252 File: canon-mx920-19_1_0a-ea11.dmg
8317281288 File: canon-mx920-19_1_0a-ea11.dmg
8317283615 File: canon-mx920-19_1_0a-ea11.dmg
8317283651 File: canon-mx920-19_1_0a-ea11.dmg
8555763408 File: canon-mx920-19_1_0a-ea11.dmg
8800666640 File: canon-mx920-19_1_0a-ea11.dmg
8876241680 File: canon-mx920-19_1_0a-ea11.dmg
9351045649 canon-mx920-19_1_0a-ea11.dmg
9821317328 File: canon-mx920-19_1_0a-ea11.dmg
10051278021 $File: canon-mx920-19_1_0a-ea11.dmg
10051278106 $File: canon-mx920-19_1_0a-ea11.dmg
10058241281 canon-mx920-19_1_0a-ea11.dmg
10166913457 canon-mx920-19_1_0a-ea11.dmg
10166914465 canon-mx920-19_1_0a-ea11.dmg
10215457371 File: canon-mx920-19_1_0a-ea11.dmg
10215457407 File: canon-mx920-19_1_0a-ea11.dmg
10215459734 File: canon-mx920-19_1_0a-ea11.dmg
10215459770 File: canon-mx920-19_1_0a-ea11.dmg

And, now for Unicode Big-Endian:

$ sift "canon-mx920-19_1_0a-ea11.dmg" Memory_Captures/mem.raw.strings.be
5128627554 canon-mx920-19_1_0a-ea11.dmg
5128627664 canon-mx920-19_1_0a-ea11.dmg
5128627732 canon-mx920-19_1_0a-ea11.dmg
10079999330 canon-mx920-19_1_0a-ea11.dmg
10079999440 canon-mx920-19_1_0a-ea11.dmg
10079999508 canon-mx920-19_1_0a-ea11.dmg
10090625584 ile:///Users/jp/Downloads/canon-mx920-19_1_0a-ea11.dmg}

As we saw before when running our Yara scans against memory, we find many resident artifacts of our file name strings. A bit less in our Unicode output, but possibly useful findings nonetheless. No surprise here. But, let’s feed each of these into Volatility’s strings plugin to get some more context.

$ ./volatility_2.6_mac64_standalone --plugins=/Users/jp/Projects/volatility/volatility/plugins/ --profile=Mac10_12_2_x64x64 -f ~/Projects/Memory_Captures/mem.raw mac_strings -s ~/Projects/Memory_Captures/mem.raw.strings.ascii

And, now we wait… one day… two days… until Schrödinger’s cat got the best of me and I killed the process. After receiving a pro-tip from @attrc to filter down the strings file to just what we cared about (the 4 file names we put int our Yara rules file), I whittled it down to approximately 288 string entries (down from over 45 million – gah!) and re-ran it:

$ ./volatility_2.6_mac64_standalone --plugins=/Users/jp/Projects/volatility/volatility/plugins/ --profile=Mac10_12_2_x64x64 -f ~/Projects/Memory_Captures/mem.raw mac_strings -s ~/Projects/Memory_Captures/mem.raw.strings.ascii_FILTERED

…and waited another day before killing it and instead running it on a much faster desktop machine. Alas, it still took over a day to run on a 2.8GHz core i7 with 32GB memory, and yielded the following output:

25099281 [kernel:feacc17efc11] canon-mx920-19_1_0a-ea11.dmg
26248704 [kernel:feacc1908600] ;/Volumes/Untitled/.Trashes/501/canon-mx920-19_1_0a-ea11.dmg
33366720 [kernel:feacc1fd22c0] File: SpotifyInstaller.zip
33369120 [kernel:feacc1fd2c20] File: FileZilla-Installer.app
33369264 [kernel:feacc1fd2cb0] File: BlockBlock_Installer.app
81507152 [kernel:feacc4dbb350] File: FileZilla-Installer.app
96602320 [kernel:feacc5c208d0] +/Users/jp/Downloads/FileZilla-Installer.ap
...
10215459594 [kernel:feaf20e38b0a] File: BlockBlock_Installer.app
10215459626 [kernel:feaf20e38b2a] File: BlockBlock_Installer.app
10215459658 [kernel:feaf20e38b4a] File: BlockBlock_Installer.app
10215459734 [kernel:feaf20e38b96] File: canon-mx920-19_1_0a-ea11.dmg
10215459770 [kernel:feaf20e38bba] File: canon-mx920-19_1_0a-ea11.dmg
10230120017 [kernel:feaf21c33e51] BlockBlock_Installer.app

“kernel”? That’s it? No process association?

Well, that’s unfortunately less than useful for us. According to the wiki entry for the strings plugin, “For a given image and a file with lines of the form :, or , output the corresponding process and virtual addresses where that string can be found.” In reading that, I expected output similar to (or better than) the yarascan plugin in being able to pair the string hit(s) to the associated process. Alas, ’tis not the case.

Nonetheless, we seem to have some very useful findings to satisfy hypothesis #2.

Conclusion

In conclusion, while hypothesis #2 looks rather satisfied by our testing, we are still left with the following questions:

1) Why are these entries re-populated when a .DS_Store file is re-created?
2) What causes this behavior?
3) How is this information pulled into the re-created .DS_Store file?
4) Why are only certain files resident and not every file ever deleted from the machine?*
*My testing shows that the entries are purged upon reboot, so this last question is mostly answered. Though, we still don’t know why it happens.

If anyone has any insight into this, I would be INCREDIBLY interested to hear about it.

/JP

Did you enjoy this post? Share it!

Mac Dumpster Diving – Identifying Deleted File References in the Trash (.DS_Store) Files – Part 1

If you have ever plugged a USB drive into a Mac, done some things, then plugged it into a Windows system, you have no doubt seen (if you have viewing of hidden files enabled) various “.DS_Store” files (among others) strewn throughout the folders on the drive. Though essentially useless to a Windows system, they do in fact serve a particular purpose on an HFS+ file system.

While I won’t re-invent the wheel on describing “What is a .DS_Store File?” (here as well), I would like to highlight its possible use for DFIR in containing/referencing artifacts that may be useful to investigations – traces of deleted files, with filenames and sometimes paths!

In a nutshell, the .DS_Store file stores metadata used by Finder for folder-specific display options such as window placement, layout, custom icons, background, etc. Thus, these .DS_Store files are (theoretically) created in every folder that Finder accesses, even remote network shares and external devices. Are those annoying .DS_Store files you see in Windows on your FAT32-formatted thumb drive making more sense now?

A part of this metadata is the filename, which got me to thinking… I wonder whether or not any traces get left behind when a file is moved or deleted.

For this post/research, I focused solely on the deletion aspect of when a user deletes a file through Finder.

In testing on my systems (OS X 10.10.5 and macOS Sierra 10.12.2), when a file gets “deleted” through Finder (not via “rm” on the command line, that’s a very different story), it first gets moved to the user’s ~/.Trash/ folder. If at least one file already exists within the user’s Trash, an entry for the yet-to-be-deleted file is added to the existing ~/.Trash/.DS_Store file denoting the full path on disk where the file resided before being moved to the Trash. This entry is part of how the “Put Back” feature works. If no files currently exist in the Trash (due to the user previously emptying the trash), I assumed (more on this in a bit) a new .DS_Store file would be created (“new” meaning a clear/empty file) to again begin storing entries for “Put Back”. Upon emptying the trash (via either the “Empty Trash” or “Secure Empty Trash” option in Finder for pre-Sierra systems), the files are deleted (according to the deletion method associated with each action) from the ~/.Trash/ folder and the ~/.Trash/.DS_Store file is also “deleted” (stay tuned for why I put this in quotes). Here is a great little writeup on the HFS+ volume structure and what happens “When Mac deletes it!”.

At this point, since all of the Trash source files are deleted upon emptying the Trash, we would assume that the .DS_Store file and all of its entries would be deleted as well. But, is this the case?

Answer: Not Quite!

In my testing, while the source data files within the ~/.Trash/ folder appear to be reliably deleted (short of carving the disk), various file and path entries within the ~/.Trash/.DS_Store file do not appear to be deleted! In fact, when you move another file to the trash, the ~/.Trash/.DS_Store file is re-created and historical entries* are re-populated into the file! Even if you “Put Back” the file(s), the associated .DS_Store file and entries remain. WIN!


*Note: These appeared to only be files I’ve deleted since the last reboot of my machine. Rebooting the machine seems to finally remove all historical entries. Various hypotheses of why/how this happens and where these entries come from will be tested later in this post.

We now have the opportunity to identify references to historical file deletions (sometimes with full path)! This doesn’t just apply to the Trash’s .DS_Store files, either. This applies to any given directory’s .DS_Store file that may contain (or have contained) references to files that existed within it.

Pretty AWESOME, right? How many of you are already putting together the “find” command to identify all the .DS_Store files on your systems?

*Hint: # find / -name .DS_Store

But, we kinda started this whole story at the end, well after I had finished muddling my way through researching and experimenting to find out how to actually parse these .DS_Store files. So, let’s rewind a bit

Upon first look at a .DS_Store file, they aren’t exactly straight forward, and they can’t apparently be opened with any native system tool or application. There is no native “ds_store_viewer” utility that simply parses the file information from the command line. So, how would we be even go about trying to figure out how to parse this thing? After all, the information it contains does us no good if we can’t parse and extract it!

Your initial thought may be “strings!” That’s a solid idea to start, let’s see what that yields…

[jp@jp-mba (:) ~]$ strings -a ~/.Trash/.DS_Store
Bud1
pptbNustr
gptbLustr
xptbLustr
xptbNustr
gptbNustr
...
DSDB
gptbNustr
gptbLustr
gptbNustr
gptbLustr
gptbNustr
fptbLustr

Well, that was less than useful. Oh, wait… maybe they’re Unicode strings instead of ASCII. Let’s see what the option is for Unix strings to search for Unicode strings instead of ASCII:

[jp@jp-mba (:) ~]$ man strings

At this point you may already know what I’m about to say – the BSD strings utility does NOT have the capability to search for Unicode strings. Fail.

So, you can go a few different ways here:

  1. Stick with native utilities
  2. Install/use a third-party utility that can identify Unicode strings (particularly big-endian Unicode)
  3. Install/use a third-party utility that can directly read .DS_Store format files

Native Utilities

So, what else might exist that we can use to view strings?

When in doubt, Hex it out!

I typically use of two native hex viewers – hexdump and xxd. They are both useful in different ways, but we’ll start with hexdump.

Using hexdump, you can dump hex+ASCII by doing the following:

$ hexdump -C

[jp@jp-mba (:) ~]$ hexdump -C ~/.Trash/.DS_Store
00000000 00 00 00 01 42 75 64 31 00 00 38 00 00 00 08 00 |....Bud1..8.....|
00000010 00 00 38 00 00 00 10 0c 00 00 02 09 00 00 20 0c |..8........... .|
00000020 00 00 30 0b 00 00 00 00 00 00 00 00 00 00 08 00 |..0.............|
00000030 00 00 08 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000040 00 00 00 00 00 00 00 03 00 00 00 01 00 00 00 4e |...............N|
00000050 00 00 00 04 00 00 10 00 00 65 00 61 00 73 00 65 |.........e.a.s.e|
00000060 00 5f 00 44 00 00 00 00 00 00 00 00 00 00 00 00 |._.D............|
00000070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000200 00 00 00 00 00 00 00 02 00 00 00 02 00 00 00 04 |................|
00000210 00 00 00 30 00 50 00 6c 00 65 00 61 00 73 00 65 |...0.P.l.e.a.s.e|
00000220 00 5f 00 44 00 6f 00 63 00 75 00 53 00 69 00 67 |._.D.o.c.u.S.i.g|
00000230 00 6e 00 5f 00 74 00 68 00 69 00 73 00 5f 00 64 |.n._.t.h.i.s._.d|

Here we see the notable “Bud1” header followed by readable text. Score! But, how do we extract JUST the readable text in some effective way? You can mess around with hexdump to try to make sense of the output formats, or you could do like I did and get so overwhelmed at one point that you just use xxd to create this incredibly unpretty, certainly less than efficient, convoluted, but “working” one-liner:

$ xxd -p <path/to/.DS_Store> | sed 's/00//g' | tr -d '\n' | sed 's/\([0-9A-F]\{2\}\)/0x\1 /g' | xxd -r -p | strings | sed 's/ptb[LN]ustr//g'

Voilà. Strings output from Unicode strings only using the built-in utilities. It is very ugly and it is certainly separating at points/lines where it should not, but hey… you get what you get. At least you can more legibly make out filenames and paths that could get you somewhere.

This is an ugly hack. I do not recommend it, but sometimes ugly is better than nothing. YMMV.

Note: I would be very interested if someone who is WAY more versed in hexdump output formatting would create a much simpler way of doing the above solely using the hexdump utility.

Third-Party Utilities

GNU Strings

Believe it or not, you can actually install various GNU utilities on your Mac via a handy little thing called Homebrew. Just takes a command line one-liner to install and opens your Mac to world a new and useful utilities called “formulas”. Note that Xcode is a pre-req for installing Homebrew.

For our purposes, we want to install strings, which is a part of the GNU coreutils package. With homebrew installed, all it takes is a “brew install coreutils” and we’re up and running. Do note that various GNU utilities will be prepended with “g” due to naming conflicts. For example, the GNU strings utility must be called/run as “gstrings” (yeah, I laugh a little each time I see that).

Once installed, we now have full GNU strings capabilities, namely for searching big-endian Unicode text, a la the following:

$ gstrings -a -eb

You don’t necessarily need the “-a” option that tells strings “I don’t care whether or not you think it’s a searchable file, do it anyway”, but I add it out of habit of searching files that the system likes to gripe about.

Using FDB

https://digi.ninja/projects/fdb.php

  1. Enter CPAN shell
    1. $ perl -MCPAN -e shell
  2. Install DSStore
    1. $ cpan[1] > install Mac::Finder:DSStore
  3. Install Switch
    1. $ cpan[1] > install Switch
  4. Run FDB
    1. $ ./fdb.pl --type ds --filename /Users//.Trash/.DS_Store --base_url /Users//

Using ds_store Go Parser

https://github.com/gehaxelt/ds_store

  1. Download and Install Go
    1. Download OS X Package from here: https://golang.org/dl/
  2. Set Go Path in shell
    1. One-time (I set mine as the following but it’s up to you)
      1. $ export GOPATH=~/Projects/Go
    2. Permanent
      1. Place above line in /etc/bashrc
      2. Reload shell “source /etc/bashrc” or close and relaunch terminal
  3. Download ds_store go files
    1. $ go get github.com/gehaxelt/ds_store
  4. Change to the directory of the go project
    1. $ cd $GOPATH/src/github.com/gehaxelt/ds_store
  5. Make a directory for the new project/files (I opted to name mine “dsdump”, but feel free to alter yours) and cd to it
    1. $ mkdir -p bin/dsdump && cd "$_"
  6. (If not already done) Create a .go file (I named mine dsdump.go) and copy/paste the Example Code from https://github.com/gehaxelt/ds_store
    1. $ nano dsdump.go
    2. Copy/paste the Example Code into this file and save it
  7. Build the Go binary
    1. $ go build
  8. Run dsump
    1. $ ./dsump -i <path/to/.DS_Store>

**Note: One of the awesome things about Go is its ability to build static binaries (no additional files needed) for a variety of operating systems. For example, if you wanted to build a binary for a Windows x64 system, you would simply run “GOOS=windows GOARCH=amd64 go build -o dsdump.exe”. Then, just copy that to whatever Windows x64 system and run it. Pretty sweet, huh?

(Shout out to Slavik at Demisto for quickly getting me up and running with Go before I spent any time looking at documentation.)

Comparing the .DS_Store Parsing Solutions

At this point in my testing, I don’t think I would stick with only one solution, as each provides its own merits. A hex viewer is an invaluable tool for so many reasons, namely for assisting in identifying unknown structures, artifacts, or items within a given file. Gstrings offers an easy way to search for the appropriate strings with an easily installable pseudo-native utility. Fdb allows the option to specify the “base_url” to prepend its results with the appropriate path, based on the given .DS_Store file’s location. The ds_store Go parser does the job as well and it can be compiled to be portable to any major OS, which can be very handy in a Mac Forensics go-kit of sorts.

Regardless of why/how it occurs (which we’ll address in Part 2 of this post) and what option(s) you choose to parse/extract these items, you may now at least have an additional DFIR investigation method and artifact(s) to identify previously deleted files that are no longer resident on (allocated) disk.

Though we focused solely on .DS_Store files in this post, do note that it is not just .DS_Store files that can assist in identifying deleted files on a system. There are several other files/areas that should be searched for such investigations; however, I wanted to hone in on analysis of these files as it is possibly lesser known (at least in my research and experience).

At any rate, I hope this can be somehow useful in your investigations moving forward! As usual, YMMV, so I’m interested to hear feedback and stories of if/how this works in the field for everyone.

/JP

Did you enjoy this post? Share it!

Know Your Tools: Linux (GNU) vs. Mac (BSD) Command Line Utilities

Welcome to first post in the “Know Your Tools” series!

Without further ado…

Have you ever wondered if/how *nix command line utilities may differ across distributions? Perhaps it never even occurred to you that there was even a possibility the tools were any different. I mean, they’re basic command line tools. How and why could/would they possibly differ?

Well, I’m here to say… thy basic command line utilities art not the same across different distributions. And, the differences can range from those that can cause a simple nuisance to those that can cause oversight of critical data.

Rather than going into aspects of this discussion that have already been covered such as how Linux and BSD generally differ, I would instead like to focus on a few core utilities commonly used in/for DFIR artifact analysis and some caveats that may cause you some headache or even prevent you from getting the full set of results you’d expect. In highlighting the problems, I will also help you identify some workarounds I’ve learned and developed over the years in addressing these issues, along with an overarching solution at the end to install GNU core utilities on your Mac (should you want to go that route).

Let’s get to it.

Grep

Grep is one of the most useful command-line utilities for searching within files/content, particularly for the ability to use regular expressions for searching/matching. To some, this may be the first time you’ve even heard that term or “regex” (shortened version of it). Some of you may have been using it for a while. And, nearly everyone at some point feels like…

Amirite?

Regardless of whether this is your first time hearing about regular expressions or if you use them regularly albeit with some level of discomfort, I HIGHLY suggest you take the time to learn and/or get better at using them – they will be your most powerful and best friend for grep. Though there is a definite regex learning curve (it’s really not that bad), knowing how to use regular expressions translates directly to performing effective and efficient searches for/of artifacts during an investigation.

Nonetheless, even if you feel like a near master of regular expressions, equally critical to an expression’s success is how it is implemented within a given tool. Specifically for grep, you may or may not be aware that it uses two different methods of matching that can highly impact the usefulness (and more important, validity) of results returned – Greedy vs. Lazy Matching. Let’s explore what each of these means/does.

At a very high level, greedy matching attempts to find the last (or longest) possible match, and lazy matching attempts to find the first possible match (and stops there). More specifically, greedy matching employs what is called backtracking and look-behind’s but that is a separate discussion. Suffice to say, using an incorrect, unintended, and/or unexpected matching method can completely overlook critical data or at the very least provide an inefficient or invalid set of results.

Now having established some foundational knowledge about how grep searches can work, we will drop the knowledge bomb – the exact same grep expression on Linux (using GNU grep) may produce completely different or no results on Mac (using BSD grep), especially when using these different types of matching.

…What? Why?

The first time I found this out I spent an inordinate and unnecessary amount of time banging my head against a wall typing and re-typing the same expression across systems but seeing different results. I didn’t know what I didn’t know. And, well, now I hope to let you know what I didn’t know but painfully learned.

While there is an explanation of why, it doesn’t necessarily matter for this discussion. Rather, I will get straight to the point of what you need to know and consider when using this utility across systems to perform effective searches. While GREEDY searches execute pretty much the same across systems, the main difference comes when you are attempting to perform a LAZY search with grep.

We’ll start with GREEDY searches as there is essentially little to no difference between the systems. Let’s perform a greedy search (find the last/longest possible match) for any string/line ending in “is” using grep’s Extended Regular Expressions option (“-E”).

(Linux GNU)$ echo “thisis” | grep -Eo ‘.+is'
thisis
(Mac BSD)$ echo “thisis” | grep -Eo ‘.+is'
thisis

Both systems yield the same output using a completely transferrable command. Easy peasy.

Note: When specifying Extended Regular Expressions, you can (and I often do) just use “egrep” which implies the “-E” option.

Now, let’s look at LAZY searches. First, how do we even specify a lazy search? Well, to put it simply, you append a “?” to your matching sequence. Using the same search as before, we’ll instead use lazy matching (find the first/shortest match) for the string “is” on both the Linux (GNU) and Mac (BSD) versions of grep and see what both yield.

(Linux GNU)$ echo “thisis” | grep -Eo ‘.+?is'
thisis
(Mac BSD)$ echo “thisis” | grep -Eo ‘.+?is'
this

Here the fun begins. We did the exact same command on both systems and it returned different results.

Well, for LAZY searches, Linux (GNU) grep does NOT recognize lazy searches unless you specify the “-P” option (short for PCRE, which stands for Perl Compatible Regular Expressions). So, we’ll supply that this time:

(Linux GNU)$ echo “thisis” | grep -Po ‘.+?is'
this

There we go. That’s what we expected and hoped for.

*Note: You cannot use the implied Extended expression syntax of “egrep” here as you will get a “conflicting matchers specified” error. Extended regex and PCRE are mutually exclusive in GNU grep.

Note that Mac (BSD), on the other hand, WILL do a lazy search by default with Extended grep. No changes necessary there.

While not knowing this likely won’t lead to catastrophic misses of data, it can (and in my experience will very likely) lead to massive amounts of false positives due to greedy matches that you have to unnecessarily sift through. Ever performed a grep search and got a ton of very imprecise and unnecessarily large (though technically correct) results? This implementation difference and issue could certainly have been the cause. If only you knew then what you know now…

So, now that we know how these searches differ across systems (and what we need to modify to make them do what we want), let’s see a few examples where using lazy matching can significantly help us (note: I am using my Mac for these searches, thus the successful use of Extended expressions using “egrep” to allow for both greedy and lazy matching)…

User-Agent String Matching
Let’s say I want to identify and extract the OS version from Mozilla user-agent strings from a set of logs, the format of which I know starts with “Mozilla/“ and then contains the OS version in parenthesis. The following shows some examples:

  • Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2226.0 Safari/537.36
  • Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2227.0 Safari/537.36
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2227.1 Safari/537.36

Greedy Matching (matches more than we wanted – fails)
(Mac BSD)$ echo "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2227.1 Safari/537.36" | egrep -o 'Mozilla.+\)'
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko)

Lazy Matching
(Mac BSD)$ echo "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2227.1 Safari/537.36" | egrep -o 'Mozilla.+?\)'
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1)

Searching for Malicious Eval Statements
Let’s say I want to identify and extract all of the base64 eval statements from a possibly infected web page for analysis, so that I can then pipe it into sed to extract only the base64 element and decode it for plaintext analysis.

Greedy Matching (matches more than we wanted – fails)
(Mac BSD)$ echo "date=new Date(); eval(base64_decode(\"DQplcnJvcl9yZ=\")); var ua = navigator.userAgent.toLowerCase();" | egrep -o 'eval\(base64_decode\(.+\)'
eval(base64_decode("DQplcnJvcl9yZ=")); var ua = navigator.userAgent.toLowerCase()

Lazy Matching (matches exactly what we want)
(Mac BSD)$ echo "date=new Date(); eval(base64_decode(\"DQplcnJvcl9yZ=\")); var ua = navigator.userAgent.toLowerCase();" | egrep -o 'eval\(base64_decode\(.+?\)'
eval(base64_decode("DQplcnJvcl9yZ=“))

There you have it. Hopefully you are now a bit more informed not only about the differences between Lazy and Greedy matching, but also about the difference in requirements across systems.

Strings

Strings is an important utility for use in extracting “human-readable” strings from files/binaries. It is particularly useful in extracting strings from (suspected) malicious binaries/files to attempt to acquire some insight into what may be contained within the file, its capabilities, hard-coded domains/URL’s, commands, … the list goes on.

However, not all strings are created equal. Sometimes, Unicode strings exist within a file/program/binary for various reasons, those of which are also important to identify and extract. By default, the GNU (Linux) strings utility searches for simple ASCII encoding, but also allows you to specify additional encodings for which to search, to include Unicode. Very useful.

By default, the Mac (BSD) strings utility also searches for simple ASCII encoding; however, I regret to inform you that the Mac (BSD) version of strings does NOT have the native capability to search for Unicode strings. Do not ask why. I highly encourage you to avoid the rabbit hole of lacking logic that I endured when I first found this out. Instead, we should move on and instead just be asking ourselves, “What does this mean to me?” Well, if you’ve only been using a Mac to perform string searches using the native BSD utility, you have been MISSING ALL UNICODE STRINGS. Of all the pandas, this is a very sad one.

So, what are our options?

There are several options, but I personally use one of the following (depending no the situation and my mood) when I need to extract both Unicode and ASCII strings from a file using a Mac (BSD) system:
1. Willi Ballenthin’s Python strings tool to extract both ASCII and Unicode strings from a file
2. FireEye’s FLOSS tool (though intended for binary analysis, it can also work against other types of files)
3. GNU strings*

*Wait a minute. I just went through saying how GNU strings isn’t available as a native utility on a Mac. So, how can I possibly use GNU strings on it? Well, my friends, at the end of this post I will revisit exactly how this can be achieved using a nearly irreplaceable third-party package manager.

Now, go back and re-run the above tools against various files and binaries from your previous investigations you performed from the Mac command line. You may be delighted at what new Unicode strings are now found 🙂

Sed

Sed (short for “Stream editor”) is another useful utility to perform all sorts of useful text transformations. Though there are many uses for it, I tend to use it mostly for substitutions, deletion, and permutation (switching the order of certain things), which can be incredibly useful for log files with a bunch of text.

For example, let’s say I have a messy IIS log file that somehow lost all of its newline separators and I want to extract just the HTTP status code, method, and URI from each line and output into its own separate line (restoring readability):

…2016-08-0112:31:16HTTP200GET/owa2016-08-0112:31:17HTTP200GET/owa/profile2016-08-0112:31:18HTTP404POST/owa/test…

Looking at the pattern, we’d like to insert a newline before each instance of the date, beginning with “2016-…”. Lucky for us, we’re on a Linux box with GNU sed and it can easily handle this:

(Linux GNU)$ sed 's/ \(.+\?\)2016/\1\n2016/g' logfile.txt
2016-08-0112:31:16HTTP200GET/owa
2016-08-0112:31:17HTTP200GET/owa/profile
2016-08-0112:31:18HTTP404POST/owa/test
...

You can see that it not only handles lazy matching, but also handles ANSI-C escape sequences (e.g., \n, \r, \t, …). This statement also utilizes sed variables, the understanding of which I will leave to the reader to explore.

Sweet. Let’s try that on a Mac…

(Mac BSD)$ sed 's/\(.+\?\)\(.+\)/\1\n2016/g' logfile.txt
2016-08-0112:31:16HTTP200GET/owa2016-08-0112:31:17HTTP200GET/owa/profile2016-08-0112:31:18HTTP404POST/owa/test

… Ugh. No luck.

Believe it or not, there are actually two common problems here. The first is the lack of interpretation of ANSI-C escape sequences. BSD sed simply doesn’t recognize any (except for \n, but not within the replacement portion of the statement), which means we have to find a different way of getting a properly interpreted newline into the statement.

Below are a few options that will work around this issue (and there are more clever ways to do it as well).

1. Use the literal (i.e., for a newline, literally insert a new line in the expression)
(Mac BSD)$ sed ’s//\*Press Enter*
> /g'

2. Use bash ANSI-C Quoting (I find this the easiest and least effort, but YMMV)
(Mac BSD)$ sed 's//\'$'\n/g’
3. Use Perl
(Mac BSD)$ perl -pe ‘s||\n|g'

Unfortunately, this only solves the first of two problems, the second being that BSD sed still does not allow for lazy matching (from my testing, though I am possibly just missing something). So, even if you use #1 or #2 above, it will only match the last found pattern and not all the patterns we need it to.

“So, should I bother with using BSD sed or not?”

Well, I leave that up to your judgment. Sometimes yes, sometimes no. In cases like this where you need to use both lazy matching and ANSI-C escape sequences, it may just be easier to skip the drama and use Perl (or perhaps you know of another extremely clever solution to this issue). Options are always good.

Note: There are also other issues with BSD sed like line numbers and using the “-i” parameter. Should you be interested beyond the scope of this post, this StackExchange thread actually has some useful information on the differences between GNU and BSD sed. Though, I’ve found that YMMV on posts like this where the theory and “facts” may not necessarily match up to what you find in testing. So, when in doubt, always test for yourself.

Find

Of all commands, you might wonder how something so basic as find could differ across *nix operating systems. I mean, what could possibly differ? It’s just find, the path, the type, the name… how or why could that even be complicated? Well, for the most part they are the same, except in one rather important use case – using find with regular expressions (regex).

Let’s take for example a regex to find all current (non-archived/rotated) log files.

On a GNU Linux system this is somewhat straight forward:

(Linux GNU)$ find /var/log -type f -regextype posix-extended -regex "/var/log/[a-zA-Z\.]+(/[a-zA-Z\.]+)*"

You can see here that rather than using the standard “-name” parameter, we instead used the “-regextype” flag to enable extended expressions (remember egrep from earlier?) and then used the “-regex” flag to denote our expression to utilize. And, that’s it. Bless you, GNU!

Obviously, Mac BSD is not this straight forward, otherwise I wouldn’t be writing about it. It’s not exactly SUPER complicated, but it’s different enough to cause substantial frustration as your Google searches will show that the internet is very confused about how to do this properly. I know. Shocking. Nonetheless, there is value in traveling down the path of frustration here so that you don’t have to when it really matters. So, let’s just transfer the command verbatim over to a Mac and see what happens.

(Mac BSD)$ find /var/log -type f -regextype posix-extended -regex "/var/log/[a-zA-Z\.]+(/[a-zA-Z\.]+)*"
find: -regextype: unknown primary or operator

Great, because why would BSD find use the same operators, right? That would be too easy. By doing a “man find” (on the terminal, not in Google, as that will produce very different results from what we are looking for here) you will see that BSD find does not use that operator. Though, it still does use the “-regex” operator. Easy enough, we’ll just remove that bad boy:

(Mac BSD)$ find /var/log -type f -regex "/var/log/[a-zA-Z\.]+(/[a-zA-Z\.]+)*
(Mac BSD)$

No results. Ok. Let’s look at the manual again… ah ha, to enable extended regular expressions (brackets, parenthesis, etc.), we need to use the “-E” option. Easy enough:

(Mac BSD)$ find /var/log -E -type f -regex "/var/log/[a-zA-Z\.]+(/[a-zA-Z\.]+)*"
find: -E: unknown primary or operator

Huh? The manual says the “-E” parameter is needed, yet we get the same error message we got earlier about the parameter being an unknown option. I’ll spare you a bit of frustration and tell you that it is VERY picky about where this flag is put – it must be BEFORE the path, like so:

(Mac BSD) $> find -E /var/log -type f -regex "/var/log/[a-zA-Z\.]+(/[a-zA-Z\.]+)*"
/var/log/alf.log
/var/log/appfirewall.log
/var/log/asl/StoreData
/var/log/CDIS.custom
/var/log/corecaptured.log
/var/log/daily.out
/var/log/DiagnosticMessages/StoreData
/var/log/displaypolicyd.log
/var/log/displaypolicyd.stdout.log
/var/log/emond/StoreData
/var/log/install.log
/var/log/monthly.out
/var/log/opendirectoryd.log
/var/log/powermanagement/StoreData
/var/log/ppp.log
/var/log/SleepWakeStacks.bin
/var/log/system.log
/var/log/Tunnelblick/tunnelblickd.log
/var/log/vnetlib
/var/log/weekly.out
/var/log/wifi.log

Success. And, that’s that. Nothing earth shattering here, but different and unnecessarily difficult enough to be aware of in your switching amongst systems.

So, now what?

Are you now feeling a bit like you know too much about these little idiosyncrasies? Well, there’s no going back now. If for no other reason, maybe you can use them to sound super smart or win bets or something.

These are just a few examples relevant to the commands and utilities often used in performing DFIR. There are still plenty of other utilities that differ as well that can make life a pain. So, now that we know this, what can we do about it? Are we doomed to live in constant translation of GNU <—> BSD and live without certain GNU utility capabilities on our Macs? Fret not, there is a light at the end of the tunnel…

If you would like to not have to deal with many of these cross-platform issues on your Mac, you may be happy to know that the GNU core utilities can be rather easily installed on OS X. There are a few options to do this, but I will go with my personal favorite method (for a variety of reasons) called Homebrew.

Homebrew (or brew) has been termed “The missing package manager for OS X”, and rightfully so. It allows simple command-line installation of a huge set of incredibly useful utilities (using Formulas) that aren’t installed by default and/or easily installed via other means. And, the GNU core utilities are no exception.

As a resource, Hong’s Technology Blog provides a great walk-through of installation and considerations.

You may already be thinking, “Great! But wait… how will the system know which utility I want to run if both the BSD and GNU version are installed?” Great question! By default, homebrew installs the binaries to /usr/local/bin. So, you have a couple options, depending on which utility in particular you are using. Some GNU utilities (such as sed) are prepended with a “g” and can be run without conflict (e.g., “gsed” will launch GNU sed). Others may not have the “g” prepended. In those cases, you will need to make sure that /usr/local/bin is in your path (or has been added to it) AND that it precedes those of the standard BSD utilities’ locations of /usr/bin, /bin, etc. So, your path should look something like this:

$ echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

With that done, it will by default now launch the GNU version installed in /usr/local/bin instead of the standard system one located in /usr/bin. And, to use the native system utilities when there is a GNU version installed with the same name, you will just need to provide their full path (i.e., “/usr/bin/<utility>”).

Please feel free to sound off in the comments with any clever/ingenious solutions not covered here or stories of epic failure in switching between Linux and Mac systems 😃

/JP

Did you enjoy this post? Share it!

Powered by WordPress & Theme by Anders Norén