Forensic Memory AnalysisWe can remember it for you wholesale!

Michael CohenJohannes Stuettgen

Introduction

● Why memory forensics?● What can Rekall do for me?● Symbols and debugging information.

○ How does Rekall support multiple operating systems and versions?

● Memory imaging○ Linux.○ Windows.

http://bit.ly/DFRWS_2014_Rekall_Workshopshort (http://goo.gl/eLljm7)

Memory Forensics - Why?

● Live response.○ Can quickly triage a system.

● Capture of memory freezes system state.○ As memory is volatile we can minimize interference

with memory.○ Analysis does not use the system APIs.

● Memory analysis technology evolves with time.○ We used to only have grep :-)○ NIST reference image: xp-laptop-2005-06-25.img:

■ Registry dump■ Passwords■ Screenshots

Popular open source tools

● Two popular open source tools:○ Volatility - Current release 2.3.1 - supports XP-Win7,

OSX, and Linux.■ Supports many Windows versions out of the box

with embedded profiles● approx 20 different profiles WinXPSP2x86, Win7SP1x64

○ Rekall - A fork (rewrite) of Volatility from 2013.■ Vastly different design philosophy:

● Profiles are not distributed with the tool - they are hosted on a public profile repository - Fetched on demand.

● Approximately 100 different windows kernel versions from WinXP to Win8.1 for x86 and amd64 architectures.

● Profiles also contain exact symbol addresses for specific kernel releases. No need to scan, search or guess anything.

The Rekall Memory Forensics Framework.

● Project page:http://rekall-forensic.com/

○ Supports OSX, Linux, Windows XP to Win8.1.● We will be mainly using Rekall.

○ We will explain differences in the two tools throughout.

Installing Rekall

Installing Rekall for windows

● Binary Windows Installer:http://downloads.rekall.googlecode.com/git/Rekall/binaries/● For Linux and OSX:

pip install rekall

● From Source:git clone https://code.google.com/p/rekall/ cd rekallpython setup.py install

Rekall interfaces

● Command line○ Simple one shot execution.

● Text Console○ Interactive ipython console.

● Notebook○ Interactive web based document system.

● Web Console○ A new web console we implemented from scratch

with Rekall specific UI.

Command line interface

● Single shot set and forget:rekall --verbose -f myimage.dd pslist --pid 2014

● Valid plugin names depend on the profile.● Help is different depending which part it is:rekall --help rekall -f myimage.dd --help

rekall -f myimage.dd pslist --help Shows options specific to pslist

Global options Plugin name Plugin Options

Shows Global options

Shows Global options and plugins relevant to this image.

Console interface

When not providing a plugin drops into an interactive session.● Can run plugins and python code

interactively.● Interactive console is much more efficient for

real analysis due to use of caching.● Can get help and command line completion.

Rekall interactive interface

Notebook interface

● Based around the ipython notebook.○

● Can mix Rekall plugins, Python code and formatted Markdown text.

Rekall Notebook interface

Webconsole interface

● Custom webinterface to Rekall○○ starts up on

● Similar capabilities as the Notebook○ More tailored to Rekall○ Work in progress

Rekall Webconsole interface

Lets do forensics!

Imaging and Acquisition

Part 1: Imaging

● Before we can analyse memory we need to take an image of it.

● The imaging tool inserts a kernel driver which provides access to the physical memory.○ On 64 bit systems the driver must be signed.

● We can choose the format the image will be written in.○ ELF Core format is more efficient since it is sparse.○ Image can be converted later to windows

Crashdump which can be loaded by windbg.

Run Rekall as admin on Windows 8

We can call Winpmem from Rekall

Linux Memory Acquisition

● Compile pmem module on target and load it○

● Use LMAP if you can’t compile on target○

● Create Profile for target kernel○

Virtual Memory and Paging

Virtual Memory and Paging

● How does virtual memory work?● Why are images padded, what's the

difference in formats?● We can see a string in the image - where

does it come from?● Why do I get a 2gb file when I dump out a

single process address space?

Virtual Memory and Paging.

Paged out

Backed Mem

Shared Memory

Backed Mem

Page File

Physical Memory

Process AVirtual Memory

Process B Virtual Memory

Overcommited

Virt

ual A

ddre

ss

Phy

sica

l A

ddre

ss

FramesPages

Virtual Memory and Paging.

● Paging allows different processes to have their own unique view of physical memory:○ Physical memory can be shared between processes○ Physical memory can be assigned to a specific

process's use without being accessible from other processes.

○ Processes can request memory to be mapped into their virtual address space which is not yet backed by physical memory (overcommitted).

○ A process’s memory can be paged out to disk.○ A process may map a file into its address space -

the kernel will automatically read from the file when a page fault occurs.

Paging in 32 bit model.

Page Directory Index Page Table Index Byte Index

Page DirectoryPage Tables

Physical Memory

CR3

PTN

PTE

Page Frame

Directory Table Base (DTB)

Virtual Address

The CR3 register.

● Paging is done automatically by the MMU in hardware.○ All the CPU has to do is store the address of the

current Page directory table in the CR3 register.○ When the kernel switches task context (to another

process), a new value of CR3 is loaded to point at new page tables.

○ The value of CR3 is key to make sense of a physical memory image.

○ Some imaging tools also capture CR3.○ CR3 contains a physical address.

● Rekall 'cc' plugin is used to switch contexts.

The Physical Address Space

● Not continuous

● Memory Mapped I/O

● Mapped by Northbridge

Profiles and Multi OS Support.

Data Structures

typedef unsigned char uchar;

enum { OPT1, OPT2} options;

struct foobar { enum options flags; short int bar; uchar *foo;}

It is generally not possible to predict the memory layout of a C struct without knowing external factors:● Alignment● Endianess● Bit size (64/32 bit)● Compiler● Optimizations etc

Unless packed structs.

Data Structures

typedef unsigned char uchar;

enum { OPT1, OPT2} options;

struct foobar { enum options flags; short int bar; uchar *foo;}

Debugging symbols contain the exact layout of all data structures

What does a Rekall profile look like?{ "$CONSTANTS": { "CmNtCSDVersion": 718856, ... "$ENUMS": { "BUS_QUERY_ID_TYPE": { "0": "BusQueryDeviceID", "1": "BusQueryHardwareIDs", ... "$FUNCTIONS": { "ADD_MAP_REGISTERS": 606670, ... "$METADATA": { "ProfileClass": "Nt", "arch": "I386"... "$STRUCTS": { "BATTERY_REPORTING_SCALE": [8, { "Capacity": [4, ["unsigned long", {}]], ...

● File is a JSON data structure.

● Divided into Sections:○ $CONSTANTS○ $FUNCTIONS○ $METADATA○ $STRUCTS

● Usually the profile is generated from debugging symbols.

$STRUCT section.{ "_EPROCESS": [624, { "AccountingFolded": [548, ["BitField", { "end_bit": 2, "start_bit": 1, "target": "unsigned long" }]], "ActiveProcessLinks": [160, ["_LIST_ENTRY", {}]], "ActiveThreads": [376, ["unsigned long", {}]], "AddressCreationLock": [232, ["_EX_PUSH_LOCK", {}]], "AddressSpaceInitialized": [552, ["BitField", { "end_bit": 12, "start_bit": 10, "target": "unsigned long" }]], "AffinityPermanent": [548, ["BitField", { "end_bit": 19, "start_bit": 18, "target": "unsigned long"...

Struct Size

Struct Name

Member Offset

Member Type

Arguments to the member type.

$CONSTANTS and $FUNCTIONS"NtAlpcSendWaitReceivePort": 2207436, "NtAlpcSetInformation": 1805611, "NtApphelpCacheControl": 2308968, "NtAreMappedFilesTheSame": 2367400, "NtAssignProcessToJobObject": 1912487, "NtBuildGUID": 411132, "NtBuildLab": 410688, "NtBuildLabEx": 410912, ...

● These addresses come directly from Microsoft Debugging symbols.○ Identical to the way the kernel debugger works.○ No need to scan, guess or otherwise deduce symbol

addresses (Contrast with Volatility).

Constant name

Constant offset (Relative to the kernel base).

Rekall Profiles - JSON files

● A profile file is a data structure which represents all the information needed to parse OS specific memory.○ Files are stored in the public profile repository:

■ http://profiles.rekall.googlecode.com/git/○ Windows Profiles are identified by GUID.

Revision c39b14f8dca9: /nt/GUID[Project Page]

● ..● 00625D7D36754CBEBA4533BA9A0F3FE22.gz● 0100FCDAFD4049B8B06005EC07705A1F2.gz● 01DDCBD82AEB46BEAFCDC6A409E3B1D31.gz● 01DF28C698D84DEBB1A74254C3AF800E2.gz● 03185083233249D9BB747EA777B80C982.gz● 04FB9A156FF44ECCA6EBCAE9617D8DB73.gz● 05A6F49C5DD848FF983459421A78F1232.gz

Profiles for nt kernel are stored here.

Every single kernel build has a unique GUID.

Rekall vs. Volatility

● Volatility○ Contains about 20 embedded windows profiles

(OSX profiles must be downloaded manually).○ Requires the user to know which profile to select.○ Windows Profiles do not contain constants - Most

plugins scan/guess offsets of kernel globals.● Rekall

○ Profile repository contains > 300 profiles, indexed by GUID.

○ Impractical for user to specify (GUID) - profiles are usually autoselected.

○ Profiles contain exact offsets of kernel data structures in memory (Very fast).

Break!!!

Live Memory Analysis

Analyse Live memory.

1. In order to analyse live memory we need to tell winpmem to leave the driver in place after quitting:

winpmem-1.5.5.exe -l

2. Now we can connect to the live memory device and repeat the process listing.

Running Rekall on Live Memory

Examine the data

1. Pick one of the processes and examine it in memory using the hexdump module:

2. e.g. dump 0x820238e03. Calculate its physical address:4. e.g vtop 0x820238e0

1. Note that _EPROCESS objects are often allocated inside large pages.

5. Now dump the physical address from the physical address space.1. dump 0x20238e0, "P"

imageinfo - A quick overview.

win8.1.raw 22:39:56> imageinfo

Fact Value

-------------------- -----

Kernel DTB 0x1a7000

NT Build 9600.winblue_gdr.130913-2141

NT Build Ex 9600.16404.amd64fre.winblue_gdr.130913-2141

Signed Drivers -

Time (UTC) 2014-01-24 21:20:05+0000

Time (Local) 2014-01-24 21:20:05+0000

Sec Since Boot 764.359375

NtSystemRoot C:\Windows

**************** Physical Layout ****************

Physical Start Physical End Number of Pages

-------------- -------------- ---------------

0x000000001000 0x00000009f000 158

0x000000100000 0x000000102000 2

0x000000103000 0x00003fff0000 261869

When was the image acquired?

Physical address ranges of image

List following - Process listing.

Listing processes - Windows.$ ./rekall -f ~/images/win7.elf -v

win7.elf 08:33:25> pslist

-----------------> pslist()

Offset (V) Name PID PPID Thds Hnds Sess Wow64 Start Exit

-------------- -------------------- ------ ------ ------ -------- ------ ------ ------------------------ ----------------------

--

INFO:root:Detected kernel base at 0xF8000261F000

DEBUG:root:Listed 41 processes using PsActiveProcessHead

DEBUG:root:Listed 37 processes using CSRSS

DEBUG:root:Listed 41 processes using PspCidTable

DEBUG:root:Listed 39 processes using Sessions

DEBUG:root:Listed 40 processes using Handles

0xfa80008959e0 System 4 0 84 511 ------ False 2012-10-01 21:39:51+0000 -

0xfa80024f85d0 svchost.exe 236 480 19 455 0 False 2012-10-01 14:40:01+0000 -

0xfa8001994310 smss.exe 272 4 2 29 ------ False 2012-10-01 21:39:51+0000 -

Finding hidden processes - psxview

● Combines the output from several plugins○ _EPROCESS list traversal○ Pool tag scanning.○ CSRSS handles○ Thread scanning.○ Kernel debugger PspCidTable

● Results are always inconsistent○ Some processes just do not show up on some

sources.

PSXViewIn [5]: psxview

------> psxview()

Offset(P) Name PID pslist psscan thrdproc pspcdid csrss

---------- -------------------- ------ ------- ------- -------- ------- -------

0x01f67500 TaskSwitch.exe 1952 True True True True True

0x02000980 wmiprvse.exe 4080 True True True False False

0x02025608 atiptaxx.exe 2040 True True True True True

0x12cd3020 smss.exe 448 False True False False False

0x0fe5f8e0 snmp.exe 1424 False True False False False

0x01f8eb10 winlogon.exe 528 True True True True True

0x02079c18 cmd.exe 2624 True True True True True

0x02218020 PluckSvr.exe 944 True True True True True

0x01ed76b0 PluckTray.exe 2740 True True True True True

0x01f48da0 tcpsvcs.exe 1400 True True True True True

0x01f6db28 msdtc.exe 1076 True True True True True

0x020e0da0 services.exe 580 True True True True True

0x1a192a90 Fast.exe 1960 False True False False False

0x01fa8240 Smc.exe 876 True True True True True

PE Files

PE Executables

● The PE file format is specifically designed to allow fast and efficient loading of executables into memory.○ The structure of executables on disk is similar to

their structure in memory.○ Imports and Exports are resolved at load time.

PE Overview

http://code.google.com/p/corkami/downloads/detail?name=pe-20110117.pdf

The peinfo pluginwin7.elf 10:17:00> peinfo?

Docstring:

Print information about a PE binary.Dump a PE binary from memory.

Status is shown for each exported function:

- M: The function is mapped into memory.

Link:

http://epydocs.rekall.googlecode.com/git/rekall.plugins.windows.procinfo.PEInfo-class.html

Parameter Documentation

------------------------------ ----------------------------------------------------------------------

output If specified we write output to this file.

verbosity Add more output.

executable If provided we create an address space from this file.

address_space The address space to use.

image_base The base of the image.

renderer Use this renderer for the output.

The peinfo pluginIn [3]: peinfo "nt"

Machine TimeDateStamp

-------------------- -------------

Machine IMAGE_FILE_MACHINE_AMD64

TimeDateStamp 2009-07-13 23:40:48 UTC+0000

Characteristics IMAGE_FILE_EXECUTABLE_IMAGE, IMAGE_FILE_LARGE_ADDRESS_AWARE

....

Sections (Relative to 0xFFFFF8000261A000):

Perm Name VMA Size

---- -------- -------------- --------------

xr- .text 0x000000001000 0x00000019b800

xr- INITKDBG 0x00000019d000 0x000000003a00

xr- POOLMI 0x0000001a1000 0x000000001c00

....

Data Directories:

- VMA Size

---------------------------------------- -------------- --------------

IMAGE_DIRECTORY_ENTRY_EXPORT 0xfffff80002b43000 0x000000010962

IMAGE_DIRECTORY_ENTRY_IMPORT 0xfffff80002bbccec 0x000000000078

IMAGE_DIRECTORY_ENTRY_RESOURCE 0xfffff80002bbe000 0x000000035d34

...

Can reference the base of the module by using the module name.

PE Dumping from memory

● Can be done using a bunch of plugins:○ procdump - Dumps _EPROCESS images using PID.○ dlldump - Dumps DLLs.○ pedump - Generic PE dumper that is used by the

other modules.● Potential problems:

○ Rootkits can easily change the in-memory PE headers. (e.g. Section description etc).■ It is possible to corrupt the headers so the tool

blows up - too much data, huge executables.○ Import Address Table is not patched.○ Not all sections are fully mapped into memory (e.g. .

rsrc not always mapped in).

Kernel Memory management.

Window Kernel Memory Allocation

● The windows kernel uses Pools to manage allocation:○ Paged pool - can be paged to disk.○ Non paged - For use by critical components which

must not be paged (e.g. Interrupt level).● Allocations come from the pool, and are

tagged using a special identifier "Tag":○ ExAllocatePoolWithTag○ Tags are used to track memory owners and detect

leaks.

What does a pool allocation look like?win8.1.raw 16:14:59> print profile._POOL_HEADER(0xe000023aa890)

[_POOL_HEADER _POOL_HEADER] @ 0xE000023AA890

0x00 PoolIndex [BitField:PoolIndex]: 0x00000000

0x00 PreviousSize [BitField:PreviousSize]: 0x00000008

0x00 Ulong1 [unsigned long:Ulong1]: 0x02770008

0x02 BlockSize [BitField:BlockSize]: 0x00000077

0x02 PoolType [BitField:PoolType]: 0x00000002

0x04 PoolTag [unsigned long:PoolTag]: 0x636F7250

0x08 AllocatorBackTraceIndex [unsigned short:AllocatorBackTraceIndex]: 0x00000000

0x08 ProcessBilled <_EPROCESS Pointer to [0x00000000] (ProcessBilled)>

0x0A PoolTagHash [unsigned short:PoolTagHash]: 0x00000000

'Proc' in ascii

allocation size in pool blocks (0x20 bytes)

Previous block allocation size

What kinds of pool are they?

win8.1.raw 23:37:38> pools

-------------------> pools()

Type Index Size Start End Comment

-------------------- ----- ---------- -------------- -------------- -------

PagedPoolSession 0 3216352 0xf90140000000 0xf9213fffffff Session ID 0

PagedPoolSession 0 12489472 0xf90140000000 0xf9213fffffff Session ID 1

PagedPool 0 70872304 0xa80000000000 0xa81fffffffff

PagedPool 1 14192864 0xa80000000000 0xa81fffffffff

PagedPool 2 1539696 0xa80000000000 0xa81fffffffff

PagedPool 3 1635888 0xa80000000000 0xa81fffffffff

PagedPool 4 1718448 0xa80000000000 0xa81fffffffff

NonPagedPoolNx 0 29362464 0xe0000001a000 0xe00077400000 -

The Pool Trackerwin8.1.raw 22:08:03> pool_trackerTag NP Alloc NP Bytes P Alloc P Bytes---- -------------------- ---------- -------------------- ---------- DMV 1 (0) 0 0 (0) 08042 6 (4) 4048 12 (0) 0ACPI 4 (0) 0 0 (0) 0AFGp 1 (0) 0 0 (0) 0ALPC 3211 (770) 434240 0 (0) 0

…Ppin 0 (0) 0 221 (2) 4160

Ppio 10 (0) 0 11718 (0) 0

Pprl 0 (0) 0 3 (0) 0

Ppsu 0 (0) 0 1394 (223) 18512

Prcr 5 (4) 5440 13 (0) 0

Proc 137 (48) 91328 0 (0) 0

PsFn 136 (0) 0 0 (0) 0

PsIn 946 (47) 7040 0 (0) 0

PsPb 135 (0) 0 0 (0) 0

…

NtFf 62 (0) 0 306 (19) 132224

NtFm 0 (0) 0 2 (2) 16384

NtFs 7 (7) 213664 42682 (2902) 319440

NtFv 5114 (2) 288 112 (0) 0

NtTc 1 (1) 64 0 (0) 0

NtTf 3 (3) 240 0 (0) 0

Gives a nice overview of outstanding allocations of each type.

For example we know 48 outstanding _EPROCESS allocations.

The Windows Object manager.

● The windows Object Manager is responsible for managing allocation/deallocation of objects.○ An object is a managed data structure in the kernel.○ There are many types of objects - basically anything

we require the kernel to manage is an object.○ Allocation functions end up delegating to

ObCreateObject()○ Objects are allocated from specific "Types". The

Types are registered data structures that the kernel knows about.

Windows Kernel Objects

ObpObjectTypes Arraywin8.1.raw 16:22:44> object_types

-------------------> object_types()

Index Number Objects PoolType Name

----- --------------- --------------- ----

2 46 NonPagedPoolNx Type

3 42 PagedPool Directory

4 167 PagedPool SymbolicLink

5 1194 PagedPool Token

6 6 NonPagedPoolNx Job

7 48 NonPagedPoolNx Process

8 834 NonPagedPoolNx Thread

9 1 NonPagedPoolNx UserApcReserve

10 0 NonPagedPoolNx IoCompletionReserve

11 0 NonPagedPoolNx DebugObject

12 5669 NonPagedPoolNx Event

13 279 NonPagedPoolNx Mutant

14 21 NonPagedPoolNx Callback

15 1158 NonPagedPoolNx Semaphore

16 70 NonPagedPoolNx Timer

17 299 NonPagedPoolNx IRTimer

Number of allocated objects is tracked here.

We know there are 48 outstanding _EPROCESS objects.

Object Allocation Schemehttp://www.codemachine.com/article_objectheader.html

Pool Header

Optional Header

Optional Header

Object Header

Object (e.g. _EPROCESS, _FILE_OBJECT etc)

ObCreateObject()

Number of optional headers is encoded in the Object Header

The object tree - Named objects win8.1.raw 16:36:18> object_tree

-------------------> object_tree()

Offset Type Name

-------------- -------------------- --------------------

0xe000014afb30 Mutant PendingRenameMutex

0xc0000000ceb0 Directory ObjectTypes

0xe000000b7eb0 Type . TmTm

0xe000000cf640 Type . Desktop

...

0xc0000020a600 Directory Sessions

...

0xc00000e038a0 Directory . 1

...

0xc000062fb430 Directory .. BaseNamedObjects

...

0xe00001a744b0 Mutant ... ARC_CommunicationManager_Mutex

0xe0000238b280 Mutant ... _SHuassist.mtx

Named objects exist within well defined object directory paths.

Here we see some mutants exist in \Sessions\1\BaseNamedObjects\

The object tree - symbolic links

● Often a driver will add a dos symlink so the device can be accessed from CreateFile API.

● This also stores the timestamp of creation of the link - interesting from forensic perspective.

0xc0000000c6e0 Directory GLOBAL?? 0xc000004c48a0 SymbolicLink . D:-> \Device\CdRom0 (2014-01-24 22:07:26+0000)0xc0000032ea50 SymbolicLink . PhysicalDrive0-> \Device\Harddisk0\DR0 (2014-01-24 22:07:20+0000)0xc000003362f0 SymbolicLink . C:-> \Device\HarddiskVolume2 (2014-01-24 22:07:20+0000)0xc00000321830 SymbolicLink . LPT1-> \Device\Parallel0 (2014-01-24 22:07:25+0000)…0xc000034b6e00 SymbolicLink . pmem-> \Device\pmem (2014-01-24 21:20:05+0000)0xc00000009b30 SymbolicLink . Global-> \GLOBAL?? (2014-01-24 22:07:19+0000)

Symlink from the GLOBAL?? directory to the device directory allows CreateFile("\\.\pmem")

Timestamp appears to be UTC during system boot and then local time later. This might be why the time seems to be back 1 hour here.

Unloaded modules

Windows keeps a record of recently unloaded drivers - this is useful sometimes:win7.dmp 23:01:53> unloaded_modules

INFO:root:Detected kernel base at 0xF80002803000

Name Start End Time

-------------------- -------------- -------------- ----

dump_dumpfve.sys 0xf880014a5000 0xf880014b8000 2014-02-21 14:36:35+0000

dump_msahci.sys 0xf8800149a000 0xf880014a5000 2014-02-21 14:36:35+0000

dump_pciidex.sys 0xf8800148e000 0xf8800149a000 2014-02-21 14:36:35+0000

crashdmp.sys 0xf88001480000 0xf8800148e000 2014-02-21 14:36:35+0000

spsys.sys 0xf880038bc000 0xf8800392d000 2014-02-21 14:45:59+0000

pmeD3DF.tmp 0xf88003940000 0xf88003950000 2014-02-21 23:32:11+0000

Pmem driver was unloaded from a temp file name.

Scanning vs. List following

● Scanning:○ can reveal already freed structures.○ But they have no context○ Its difficult to say anything definitive about them.○ Can be susceptible to manipulations

■ Can modify memory in such a way that scanning fails.

■ Can plant evidence.● List Following

○ Much more robust - usually kernel uses the same lists so its hard to remove objects from them without destabilizing the kernel.

○ As soon as object is freed it is removed from list.

Break!!!

Kernel Process memory management

Process Memory management - The Vad Tree.

● Windows manages process memory through 2 mechanisms:○ Ultimately pages are assigned through the page

tables and the PFN database.○ The Virtual Memory Address Descriptors (VAD)

maintain a high level overview of the pages assigned to a process.

○ A binary tree in memory of virtual memory assigned to a process.

○ The kernel uses the VAD tree to manage the page tables for this process.

The VAD tree: A process-eye view of physical memory - Brendan Dolan-Gavitt digitalinvestigation 4S (2007) S62–S64

Inspecting the VADIn [2]: vad pid=4012

------> vad(pid=4012)

Pid: 4012 dd.exe

VAD lev start end com - - Protect Filename

---------- --- ---------- ---------- ---- ------- ------ -------------------- --------

0x81edc7e0 0 0x30 0x12f 3 Private READWRITE

0x8220fad0 1 0x10 0x10 1 Private READWRITE

0x81ff0398 2 0x20 0x20 1 Private READWRITE

0x820ee328 1 0x400 0x40d 2 Mapped Exe EXECUTE_WRITECOPY \dd\UnicodeRelease\dd.exe

0x82068e78 2 0x140 0x23f 12 Private READWRITE

0x81f1b548 3 0x130 0x132 0 Mapped READONLY

0x81f338b0 3 0x250 0x25f 0 Mapped READWRITE

0x81ffa408 4 0x240 0x24f 6 Private READWRITE

0x81eef6d8 6 0x2c0 0x300 0 Mapped READONLY \WINDOWS\system32\sortkey.nls

0xff94a1d0 6 0x330 0x332 0 Mapped READONLY \WINDOWS\system32\ctype.nls

0x8220e848 7 0x320 0x32f 8 Private READWRITE

0x8136f140 10 0x37f 0x37f 0 Mapped READONLY

0x82216830 2 0x7c900 0x7c9af 5 Mapped Exe EXECUTE_WRITECOPY \WINDOWS\system32\ntdll.dll

0x820c9308 3 0x7c800 0x7c8f3 5 Mapped Exe EXECUTE_WRITECOPY \WINDOWS\system32\kernel32.dll

0x81f16390 4 0x10000 0x10005 2 Mapped Exe EXECUTE_WRITECOPY \dd\UnicodeRelease\getopt.dll

Mapped DLLs are shared between processes.

Using the vad to double check loaded dlls.

● As we mentioned previously there are 3 lists of loaded dlls in the Peb:○ In loaded order.○ In Init order.○ In Memory order.

● Malware can easily unlink a module from these lists, but its harder to manipulate the VAD.○ Peb data structures are accessible from userspace.○ VAD data structures only accessible from kernel

space.

The ldrmodules plugin.$ rekall -f malwarecookbook/stuxnet.vmem ldrmodules --pid 680

Pid Process Base InLoad InInit InMem MappedPath

-------- -------------------- ---------- ------ ------ ----- ----------

1928 lsass.exe 0x00080000 False False False -

1928 lsass.exe 0x7c900000 True True True \WINDOWS\system32\ntdll.dll

1928 lsass.exe 0x77c00000 True True True \WINDOWS\system32\version.dll

1928 lsass.exe 0x01000000 True False True -

1928 lsass.exe 0x5b860000 True True True \WINDOWS\system32\netapi32.dll

1928 lsass.exe 0x76bf0000 True True True \WINDOWS\system32\psapi.dll

1928 lsass.exe 0x77c10000 True True True \WINDOWS\system32\msvcrt.dll

1928 lsass.exe 0x77dd0000 True True True \WINDOWS\system32\advapi32.dll

1928 lsass.exe 0x7c9c0000 True True True \WINDOWS\system32\shell32.dll

1928 lsass.exe 0x00870000 True True True -

1928 lsass.exe 0x76f20000 True True True \WINDOWS\system32\dnsapi.dll

1928 lsass.exe 0x5d090000 True True True \WINDOWS\system32\comctl32.dll

1928 lsass.exe 0x71aa0000 True True True \WINDOWS\system32\ws2help.dll

1928 lsass.exe 0x77b20000 True True True \WINDOWS\system32\msasn1.dll

How can we get an executable area without being in the module lists and not having file mapping?

The windows registry.

Registry Dumping

● The windows registry is a central location for configuration data.○ A rich source of evidence in a digital investigation.○ There are many tools that can analyse registry files.

● The registry is cached in memory○ Registry data is stored in hives.○ Hives are divided into HBins.○ HBins are cached in memory.

● Rekall has a full registry parser and a bunch of modules to deal with registry.

Forensic Analysis of the Windows Registry in Memory. - Brendan Dolan-Gavitt. DFRWS 2008

Registry in Memory

_CMHIVE: System _CMHIVE: SoftwareLinked list

HBIN

HBIN

HBIN

Not resident

Hive.Storage.Map[].Directory[].Table[].BlockAddress

Structure is very similar to a page table which refers to HBINS. If a HBIN is not frequently used it will be paged out (i.e. not memory resident). When a program attempts to read a key which is contained in this HBIN - the HBIN will be paged into memory.

Registry pointers are 32 bit (Even on 64 bit OS).

Registry in Memorywin8.1.raw 22:36:20> hives

Offset Name

-------------- ----

0xc00000014000 @ 0xc00000014000

0xc00000028000 \REGISTRY\MACHINE\SYSTEM @ 0xc00000028000

0xc0000004a000 \REGISTRY\MACHINE\HARDWARE @ 0xc0000004a000

0xc00000d15000 \Device\HarddiskVolume1\Boot\BCD @ 0xc00000d15000

0xc00000cac000 \SystemRoot\System32\Config\SOFTWARE @ 0xc00000cac000

0xc0000630b000 \SystemRoot\System32\Config\DEFAULT @ 0xc0000630b000

0xc00000f81000 \SystemRoot\System32\Config\SECURITY @ 0xc00000f81000

0xc00000fad000 \SystemRoot\System32\Config\SAM @ 0xc00000fad000

0xc00001021000 \??\C:\Windows\ServiceProfiles\NetworkService\NTUSER.DAT @ 0xc00001021000

0xc000010d6000 \SystemRoot\System32\Config\BBI @ 0xc000010d6000

0xc0000120e000 \??\C:\Windows\ServiceProfiles\LocalService\NTUSER.DAT @ 0xc0000120e000

0xc00001e6f000 \??\C:\Windows\AppCompat\Programs\Amcache.hve @ 0xc00001e6f000

0xc0000193f000 \??\C:\Users\test\ntuser.dat @ 0xc0000193f000

0xc000022d7000 \??\C:\Users\test\AppData\Local\Microsoft\Windows\UsrClass.dat @ 0xc000022d7000

Printing Keys from memorywin8.1.raw 22:38:20> printkey key=r"ControlSet001/services/pmem"

Legend: (S) = Stable (V) = Volatile

--------------{00000000-0000-0000-0000-000000000000}/ControlSet001/Services/pmem

Registry: \REGISTRY\MACHINE\SYSTEM @ 0xc00000028000

Key name: pmem (S) @ 0XFFFFC000004BDCA4

Last updated: 2014-01-24 21:20:05+0000

Subkeys:

Values:

0XFFFFC000004BDA3C REG_DWORD Type : (S) 1

0XFFFFC000004BDA5C REG_DWORD Start : (S) 3

0XFFFFC000004BDCFC REG_DWORD ErrorControl : (S) 1

0XFFFFC000004BDD24 REG_EXPAND_SZ ImagePath : (S) \??\C:\Users\test\AppData\Local\Temp\pmeA86F.tmp

0XFFFFC000004BDDCC REG_SZ DisplayName : (S) pmem

0XFFFFC000004BDDF4 REG_DWORD WOW64 : (S) 1

When was this service installed?

Where was the driver loaded from?

Registry analysis from memory.

● There are some excellent forensic tools for registry analysis:○ Regripper○ Registry Decoder○ Encase/FTK and other commercial tools

● But these tools typically only work with registry files...○ So we need to dump out the registry into files.

Dumping out the registryIn [11]: regdump?

regdump: Dump all registry hives into a dump directory.

Parameter Documentation

------------------------------ -----------------------------------------------------

hive_offset A list of hive offsets as found by hivelist (virtual

address). If not provided we call hivescan ourselves

and dump all hives found.

dump_dir Directory in which to dump hive files.

In [12]: regdump dump_dir="/tmp/"

**************************************************

Dumping \Device\HarddiskVolume1\WINDOWS\system32\config\system @ 0xe1035b60 into "/tmp/system @ 0xe1035b60"

Dumped 5312512 bytes

**************************************************

Dumping \Device\HarddiskVolume1\Documents and Settings\Sarah\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat @ 0xe1ecd008 into "/tmp/UsrClass_dat @ 0xe1ecd008"

Dumped 8192 bytes

System Users - Analyse the SAMwin8.1.raw 23:43:33> users

…**************************************************

Key CsiTool-CreateHive-{00000000-0000-0000-0000-000000000000}/SAM/Domains/Account/Users/000003E9

UserName test

Comment

NTHash 0300010078c8adefecd752853dbdba811f870751

LanHash 03000100

FullName

Type Default Admin User

AccountExpiration -

LoginCount 3

FailedLoginCount 0

Flags Normal user account, Password does not expire, Password not required

PasswordFailedTime -

LastLoginTime 2014-01-24 21:08:48+0000

Rid 1001

PwdResetDate 2014-01-20 21:47:06+0000

**************************************************

Password Hash

Last Login time

The RID is used to resolve SID to users.

Who launches this process?The tokens plugin.win8.1.raw 23:49:31> tokens

INFO:root:Detected kernel base at 0xF802D3019000

Process Pid Sid Comment

---------------- ----- -------------------------------------------------- -------

System 4 S-1-5-18 Local System

System 4 S-1-5-32-544 Administrators

System 4 S-1-1-0 Everyone

System 4 S-1-5-11 Authenticated Users

System 4 S-1-16-16384 System Mandatory Level

smss.exe 292 S-1-5-18 Local System

smss.exe 292 S-1-5-32-544 Administrators

…

winpmem_1.5.2. 2628 S-1-5-21-1077689984-2177008626-1601812314-1001 User: test

winpmem_1.5.2. 2628 S-1-5-21-1077689984-2177008626-1601812314-513 Domain Users

winpmem_1.5.2. 2628 S-1-1-0 Everyone

The SAM is used to resolve the SIDs here.

Handles plugin - Our own open files.

We have the driver opened.

This is a history file of ipython commands!

Timers

● Hiding a process is kind of hard to do well.● Many malware have a need to periodically

do stuff (e.g. C&C).○ System has the ability to launch tasks at specified

times or intervals: The _KTIMER facility.○ A malicious kernel driver may register a timer

callback and get called periodically.

win8.1.raw 12:04:33> timers Offset DueTime(H) DueTime Period(ms) Signaled Routine Module-------------- -------------------- ------------------------- ---------- -------- -------------- --------------------0xe00001a58708 0x0000000001f0df8a92 2014-01-24 21:33:58+0000 1000 Yes 0xf80000298480 wdf01000 + 0x84800xf802d32ecd00 0x0000000001c789ad30 2014-01-24 21:32:49+0000 0 - 0xf802d311b194 nt!CcScanDpc0xf802d32bcce0 0x0000010c0d9d767529 2015-01-01 00:12:44+0000 0 - 0xf802d32467b4 nt!ExpNextYearDpcRoutine0xf802d32ac920 0x0000000001e478b3c5 2014-01-24 21:33:38+0000 0 - 0xf802d3116abc nt!CmpLazyFlushDpcRoutine0xf80002146660 0x0000000001f3302411 2014-01-24 21:34:02+0000 43348 Yes 0xf80002140c44 bowser + 0x3C440xf8000072e320 0x00000000c877502ee7 2014-01-25 21:15:04+0000 0 - 0xf80000719230 storport + 0x232300xf800024cbb28 0x0000000001fdfb093c 2014-01-24 21:34:20+0000 28348 Yes 0xf800024af550 tunnel + 0x15500xe0000127ff40 0x0000000002f06baf46 2014-01-24 21:41:07+0000 0 - 0xf80000b31394 volsnap + 0x2394

_KTIMER offset

Due to go offName of callback address

● Rekall resolves all addresses to a standard name notation:

○ nt!ExpNextYearDpcRoutine -> The function name inside the nt module (kernel).■ Common for modules with symbols to know exact function names.

○ wdf01000 + 0x8480 -> No function name known but it is 0x8480 bytes from the start of the wdf01000 module (but still within it).

■ This is common for modules without symbols.

The windows GUI Subsystem

● Once upon a time, Windows was a single user, 16 bit operating system:○ All GUI applications used a global shared area to

pass messages to each other and render to the screen (GDI).

○ Then GDI stuff moved into kernel. Now there is a global shared area between kernel and userspace.

Application 1

Application 2

Kernel Space

2Address Space 1

win32k Shared area

GUI Applications directly read/write shared data structures.

When the GDI component moved into the kernel, the win32k shared area was directly mapped into the address space of all processes.

Pros: No context switch overhead for kernel system calls in manipulating GUI structures.

Cons: Shatter attacks - no process separation! Trivial to inject code into another process's address space.

Application 1

Application 2

Kernel Space

2Address Space 1

win32k Shared area

Attempt 1 to fix it:

Introduce windows stations to contain different processes.

Run services in non interactive windows station and enforce separation through GUI ACLs.

Theoretically non interactive desktop can not receive GUI messages from interactive desktop.

There is still the problem of the shared address space thing though :-(

Doesn't really work.

Windows Station 1 - Non Interactive

Windows Station 0 - Interactive

Application 1

Application 2

Kernel Space

2Address Space 1

win32k Shared area

Attempt 2 to fix it:

Introduce sessions to contain different processes.

Sessions are a collection of processes belonging to the same "logon event" (e.g. Terminal Services logon).

Each session has a unique memory layout, but within the same session all processes still map the session address space as before.

This means a session is a security boundary. Run services and privileged processes in Session 0 and let the user login to session 1.

Session 1 - application sees a different version of session space.

Session 0 - application sees one version of session space.

Session Space

PS: Windows 8 introduces process containers which allow further separation within the same logon session.

win8.1.raw 17:30:57> sessions**************************************************Session(V): d0002214f000 ID: 0 Processes: 31PagedPoolStart: f90140000000 PagedPoolEnd f9213fffffff Process: 380 csrss.exe 2014-01-24 22:07:32+0000 @ 0xe00001be1280 Process: 432 wininit.exe 2014-01-24 22:07:32+0000 @ 0xe000000ce080 Process: 528 services.exe 2014-01-24 22:07:34+0000 @ 0xe00001d3c080 Process: 536 lsass.exe 2014-01-24 22:07:34+0000 @ 0xe00001d2a080 Process: 588 svchost.exe 2014-01-24 22:07:37+0000 @ 0xe00001dc4080 Process: 628 svchost.exe 2014-01-24 22:07:37+0000 @ 0xe00001dea500... Process: 2924 AM_Delta.exe 2014-01-24 21:19:30+0000 @ 0xe00000815900 Process: 2276 MpSigStub.exe 2014-01-24 21:19:30+0000 @ 0xe000008cd900 Image: 0xe000014ea0d0, Address 0xf96000151003, Name: win32k.sys Image: 0xe00001ccccf0, Address 0xf960006ea003, Name: TSDDD.dll**************************************************Session(V): d00023ff7000 ID: 1 Processes: 14PagedPoolStart: f90140000000 PagedPoolEnd f9213fffffff Process: 440 csrss.exe 2014-01-24 22:07:32+0000 @ 0xe000000d9280 Process: 468 winlogon.exe 2014-01-24 22:07:33+0000 @ 0xe000000f4080... Process: 2628 winpmem_1.5.2. 2014-01-24 21:20:04+0000 @ 0xe0000204a900 Process: 3368 wermgr.exe 2014-01-24 21:20:56+0000 @ 0xe00000735900 Image: 0xe00001addd90, Address 0xf96000151003, Name: win32k.sys Image: 0xe00001ce08a0, Address 0xf96000841003, Name: cdd.dll

Session 0 is where services are running.

Session 1 is where first user logs in.

Same driver is mapped in both sessions at the same address but the data is different.

Session pool is unique to each session (But mapped at the same address).

Anti-forensics

How memory imaging works?

● Most tools call MmGetPhysicalMemoryRanges

● Lets get Rekall to disassemble this function for us - so we can understand it.○ You can use command line completion to save

typing and discover the exact name of the function.

win7.elf 12:02:43> dis "nt!MmGetPhysicalMemoryRanges" Address Rel Op Codes Instruction Comment-------------- ---- -------------------- ------------------------------ ------------- nt!MmGetPhysicalMemoryRanges ------0xf80002a8dd20 0 488bc4 MOV RAX, RSP 0xf80002a8dd23 3 48895808 MOV [RAX+0x8], RBX …0xf80002a8dd5c 3C 418bfc MOV EDI, R12D 0xf80002a8dd5f 3F eb2a JMP 0xf80002a8dd8b nt!MmGetPhysicalMemoryRanges + 0x6B0xf80002a8dd61 41 66ff8bc6010000 DEC WORD [RBX+0x1c6] 0xf80002a8dd68 48 33c0 XOR EAX, EAX 0xf80002a8dd6a 4A f04c0fb13d15f6dcff LOCK CMPXCHG [RIP-0x2309eb], R15 0x0 nt!MmDynamicMemoryLock0xf80002a8dd73 53 740c JZ 0xf80002a8dd81 nt!MmGetPhysicalMemoryRanges + 0x610xf80002a8dd75 55 488d0d0cf6dcff LEA RCX, [RIP-0x2309f4] 0x0 nt!MmDynamicMemoryLock0xf80002a8dd7c 5C e84f97beff CALL 0xf800026774d0 nt!ExfAcquirePushLockShared0xf80002a8dd81 61 808b5104000020 OR BYTE [RBX+0x451], 0x20 0xf80002a8dd88 68 418bfd MOV EDI, R13D 0xf80002a8dd8b 6B 488b05a692e3ff MOV RAX, [RIP-0x1c6d5a] 0xFFFFFA800087CFD0 nt!MmPhysicalMemoryBlock0xf80002a8dd92 72 33c9 XOR ECX, ECX

win7.elf 12:11:09> dump "nt!MmPhysicalMemoryBlock"-----------------> dump("nt!MmPhysicalMemoryBlock") Offset Hex Data Comment-------------- ------------------------------------------------ ---------------- -------0xf800028c7038 d0 cf 87 00 80 fa ff ff 01 00 01 00 fe 3d 09 a1 .............=.. nt!MmPhysicalMemoryBlock + 00xf800028c7048 e0 8d 91 00 80 fa ff ff 40 4b 89 00 80 fa ff ff ........@K...... nt!IoFileObjectType + 00xf800028c7058 00 00 00 00 01 00 00 00 8e ca 02 00 00 00 00 00 ................ nt!MmTrackLockedPages + 00xf800028c7068 00 00 00 00 40 00 00 00 04 00 00 00 00 00 00 00 ....@........... nt!HvlEnlightenments + 0

win7.elf 12:10:56> dump "*nt!MmPhysicalMemoryBlock"-----------------> dump("*nt!MmPhysicalMemoryBlock") Offset Hex Data Comment-------------- ------------------------------------------------ ---------------- -------0xfa800087cfd0 02 00 00 00 00 00 00 00 8e ca 02 00 00 00 00 00 ................ 0xfa800087cfe0 01 00 00 00 00 00 00 00 9e 00 00 00 00 00 00 00 ................ 0xfa800087cff0 00 01 00 00 00 00 00 00 f0 c9 02 00 00 00 00 00 ................ 0xfa800087d000 fe ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................ 0xfa800087d010 ff ff ff 7f 00 00 00 00 00 00 00 00 00 00 00 00 ................

win7.elf 12:15:14> print session.profile._PHYSICAL_MEMORY_DESCRIPTOR(0xfa800087cfd0)[_PHYSICAL_MEMORY_DESCRIPTOR _PHYSICAL_MEMORY_DESCRIPTOR] @ 0xFA800087CFD0 0x00 NumberOfRuns [unsigned long:NumberOfRuns]: 0x00000002 0x08 NumberOfPages [unsigned long long:NumberOfPages]: 0x0002CA8E 0x10 Run <Array 2 x _PHYSICAL_MEMORY_RUN @ 0xFA800087CFE0>

win7.elf 12:11:36> phys_map-----------------> phys_map()Physical Start Physical End Number of Pages-------------- -------------- ---------------0x000000001000 0x00000009f000 158 0x000000100000 0x00002caf0000 182768

How to break Memory Forensics by changing one byte.

1. Unload the memory driver, and reload it with the -w switch. This will enable write mode:

winpmem-1.5.5-write.exe -w -l2. Open two windows an evil one and a regular

one.3. Now we are ready to be evil.

win7.elf 12:16:57> a = session.profile._PHYSICAL_MEMORY_DESCRIPTOR(0xfa800087cfd0)

win7.elf 12:16:57> a.NumberOfRuns = 0

Challenge: Change the name of a process.

1. Start Notepad.exe.2. Press ctrl-alt-delete and bring up the task

manager.3. Your task is to change the name of notepad.

exe to foobar.exe in the task manager.

Challenge: Change the name of a process.

There are several places where the process name exists (check the source for pstree).

● task.SeAuditProcessCreationInfo.ImageFileName = "foobar.exe"

● task.Peb.ProcessParameters.CommandLine = "foobar.exe"

● task.ImageFileName = "foobar.exe"

Scripting Rekall

1. This exercise is about learning how to script the interface.

2. We will practice with DKOM - hide a process.

3. Open up notepad and write the following program:

def unlink(list_entry):

"Given a list entry - unlink it from the list."

next = list_entry.Flink.dereference()

prev = list_entry.Blink.dereference()

prev.Flink = next.obj_offset

next.Blink = prev.obj_offset

list_entry.Flink = list_entry.Blink = list_entry.obj_offset

Running script from within the shell

Type run -i myscript.pyThis will run the script within the Rekall shell namespace - this makes the new function available.● Experiment by hiding the notepad process.

Conclusions

● Memory forensics is an exciting science!● Like all forensics its easy to manipulate

when you know how.

DFRWS EU 2014

9th May

Appendix

What if the Rekall repository does not have my profile?

● Determine the exact kernel release in your image:

$ rekall -f win8.1.raw version_scan --name_regex krnl Offset (P) GUID/Version PDB -------------- -------------------------------- -------------0x000001c33ff0 FD3D00D28EDC4527BB922BCC0509D2851 ntkrnlmp.pdb0x0000056b1eac 43BFE6AC987243F59695235D5BD69A7F1 ntoskrnl.pdb0x000023f294a1 1EDDFBD3D6A04821A97C1399C11C31B41 ntoskrnl.pdb0x00003b8df534 61A9236096164FB399ACBD2A806322011 dxgkrnl.pdb

● Download the PDB file from Microsoft:$ rekall fetch_pdb -D . --guid FD3D00D28EDC4527BB922BCC0509D2851 --filename ntkrnlmp.pdb

Trying to fetch http://msdl.microsoft.com/download/symbols/ntkrnlmp.pdb/FD3D00D28EDC4527BB922BCC0509D2851/ntkrnlmp.pd_

Received 1086189 bytes

Extracting cabinet: ntkrnlmp.pd_

extracting ntkrnlmp.pdb

All done, no errors.

● Generate a Rekall profile from the MS PDB file:

$ rekall parse_pdb --filename ntkrnlmp.pdb --output ./FD3D00D28EDC4527BB922BCC0509D2851.json

Exporting 64: <unnamed-4998>

● Use the new profile directly (Instead of using the repository):

$ rekall -f ~/test_data/win8.1/win8.1.raw --profile ./FD3D00D28EDC4527BB922BCC0509D2851.json

----------------------------------------------------------------------------

The Rekall Memory Forensic framework 1.0rc7.

"We can remember it for you wholesale!"

This program is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License.

Type 'help' to get started.

----------------------------------------------------------------------------

win8.1.raw 21:35:21>

● Please also consider sharing the GUID with us. Then we can add it to the public profile repository and save a couple of minutes for the next guy

Linux profile GenerationDemo

Examine the kernel modules

1. Use the modules command to see all the loaded kernel modules.

2. Can you see anything suspicious?3. Dump the suspicious module out. What can

you say about it?4. What kinds of IRPs does the module

handle?5. Can you guess what it does? disassemble

its handlers.

The Page Frame Database

The Page Frame Number (PFN) database (Windows).

● The operating system maintains a database about the allocation status of every physical page in the system.○ Since the page tables exist in the physical address

space, but the OS can only reference the Virtual Address space, there must be a way to quickly access the PTEs that control a particular physical page.

○ The hardware can only do the forward mapping (Virtual to Physical).

○ Hence the operating system needs to keep track of the reverse mapping (Physical Page to PTE).

Paging in 32 bit model.

Page Directory Index Page Table Index Byte Index

Page DirectoryPage Tables

Physical Memory

CR3

PTN

PTE

Page Frame

Directory Table Base (DTB)

Virtual Address

PFN DB Maps PFN to PTE

The PFN Database

● An array of _MMPFN structs, one for every page of physical memory.○ The PFN database start is referenced by the symbol

MmPfnDatabase.○ To get the PFN of a physical address we just divide

by 0x1000 (i.e. its the page number).○ Index the array of _MMPFN structs (aka the PFN

database) to read the PFN record.● The PFN record contains important

information about the physical page.○ In use/Valid/Paged○ Virtual Address of the PTE which controls this page.

Physical to Virtual mapping

● Can use the PFN database to map from physical address to virtual address.○ Find the Virtual PTE address for the physical

address. (e.g. 0xF6FC40018718)○ Find the PteFrame (This is the physical address for

the PTE). (e.g. 0x00019A18)○ PTE Physical address is then 0x00019A18718.○ Because there is a virtual mapping to the PTE itself,

we can repeat the process to find the PTE controlling this PTE (i.e. the PDE).■ Use the PFN database to locate the PDE,

PDPDTE, PML4E and DTB, in turn.

ExampleIn [36]: vtop 0xf880030e3000

-------> vtop(0xf880030e3000)

Virtual 0xF880030E3000, Page Directory 0x00187000

pml4e@ 0x00187F88 = 0x2E004863

pdpte@ 0x2E004000 = 0x2E003863

pde@ 0x2E0030C0 = 0x19A18863

pte@ 0x19A18718 = 0x30E48963

PTE mapped@ 0x19A18718 = 0x30E48000

In [37]: ptov 0x30E48000

-------> ptov(0x30E48000)

Physical Address 0x0000000030E48000 => Virtual Address 0x0000F880030E3000

DTB @ 0x0000000000187000

PML4E @ 0x0000000000187F88

PDPDE @ 0x000000002E004000

PDE @ 0x000000002E0030C0

PTE @ 0x0000000019A18718

Physical Address

PFN DB is used to connect all the levels.

DTB for this page is found.

In [35]: pfn 0x30E48

-------> pfn(0x30E48)

PFN 0x00030E48 at kernel address 0x0000FA800092AD80

flink 00000000 blink / share count 0000000000000001

pteaddress (VAS) 0x0000F6FC40018718 (Phys AS) 0x0000000019A18718

reference count 0001 color 0

containing page 0x00019A18 ActiveAndValid M

Modified

Finding hidden processes using PFN

● Every process has its own address space.○ Hence every process has its own DTB.○ Perform the physical to virtual mapping of all the

physical pages, and find all the DTBs.○ Compare to the DTBs of known processes.

● This is actually very hard for a rootkit to hide.

Finding hidden processes using PFN$ python vol.py -f ~/images/win7_trial_64bit.dmp --profile=Win7SP0x64 dtbscan

DTB _EPROCESS Image Name

-------------- -------------- ----------

0x000000187000 0xfa800096a9e0 System

0x00001f915000 0xfa8001d4b630 svchost.exe

0x0000209de000 0xfa8000bbdb30 �&�.exe0x00001b2c8000 0xfa8001ea5b30 spoolsv.exe

0x0000211a4000 0xfa8001dbfb30 svchost.exe

0x00002ceb9000 0xfa8000a2d060 svchost.exe

0x00002178b000 0xfa8001db5b30 svchost.exe

0x000022e75000 0xfa8000bbd060 conhost.exe

0x000022192000 0xfa8001d03ac0 lsm.exe

0x000019295000 0xfa80020bfb30 sppsvc.exe

0x00001d3a2000 0xfa8001fd9890 svchost.exe

0x00002573b000 0xfa8001974630 winlogon.exe

-0x00000001000 -------------- Process not Found!

0x000021533000 0xfa8001e905b0 svchost.exe

0x00001d5c7000 0xfa8001dd7800 explorer.exe

.....

Some other fun plugins

● Start up internet explorer and navigate to a site.

● Use the sockets and connections plugins to observe these connections.○ Which process connects to these sites?

● On windows 7 the netstat module does a similar thing.

Services and drivers

1. Run the svcscan plugin - what suspicious service can you spot? Why is it suspicious?

2. Use the driverirp scanner to examine this driver. What do you think it does?

3. Disassemble the write handler.

While examining the driverirp output can you see a driver which hooks other drivers? Why do you think it does this?

Consoles plugins

● Shows the history buffer of the command shell host process.

● cmdscan and console.● Scary mirror looking.

References

● http://mista.nu/research/smashing_the_atom.pdf● http://codemachine.com/article_objectheader.html● http://blogs.msdn.com/b/ntdebugging/archive/2012/01/31/identifying-global-atom-table-leaks.

aspx● http://mnin.blogspot.de/2011/10/aint-nuthin-but-ktimer-thing-baby.html● http://mnin.blogspot.de/2011/10/zeroaccess-volatility-and-kernel-timers.html● http://uninformed.org/index.cgi?v=8&a=5&p=10● https://code.google.com/p/rekall/● https://code.google.com/p/volatility/● http://volatility-labs.blogspot.com/● http://rekall-forensic.blogspot.com/