Difference between pages "WinFE" and "Google Chrome"

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(Technical Background and Forensic Soundness)
 
(Disk Cache)
 
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{{Infobox_Software |
+
Google Chrome is a [[Web Browser|web browser]] developed by Google Inc.
  name = Windows Forensic Environment |
+
  maintainer = [[Windows Forensic Environment Project]] |
+
  os = {{Windows}} |
+
  genre = {{Live CD}} |
+
  license = unknown |
+
  website = http://winfe.wordpress.com |
+
}}
+
  
 +
== Configuration ==
 +
The Google Chrome configuration can be found in the '''Preferences''' file.
  
'''Windows Forensic Environment''' - a forensically sound bootable CD/USB to acquire electronic media or conduct forensic analysis.
+
On Linux
                                             
+
<pre>
== Windows Forensic Environment ("WinFE") ==
+
/home/$USER/.config/google-chrome/Default/Preferences
 +
</pre>
  
WinFE was developed and researched in 2008 by Troy Larson, Sr Forensic Examiner and Research at Microsoft [http://www.twine.com/item/113421dk0-g99/windows-fe].  WinFE is based off the Windows Pre-installation Environment of media being Read Only by default.
+
On MacOS-X
It works similar to Linux forensic CDs that are configured not to mount media upon booting. 
+
<pre>
However, unlike Linux boot CDs, with Win FE one can use Windows based software. Thus it is possible to include various forensic software and general portable utilities.
+
/Users/$USER/Library/Application Support/Google/Chrome/Default/Preferences
WinFE can also be configured to boot from a USB device, should the evidence computer have the ability to boot to USB.
+
</pre>
  
WinFE can be customized to the examiner's needs through batch files using the Windows Automated Install Kit (WAIK) or through 3rd party utilities such as WinBuilder [http://reboot.pro].
+
On Windows XP
+
<pre>
Some examples of Windows based forensic utilities that can run in the Windows Forensic Environment include:  
+
C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Google\Chrome\User Data\Default\Preferences
* X-Ways Forensics [http://www.x-ways.net],
+
</pre>
* AccessData FTK Imager [http://www.accessdata.com],
+
* Guidance Software Encase [http://www.guidancesoftware.com],
+
* ProDiscover [http://www.techpathways.net],
+
* RegRipper [http://www.RegRipper.wordpress.com].
+
  
A write protection tool developed by Colin Ramsden was released in 2012 that provides a GUI for disk toggling [http://www.ramsdens.org.uk/].  Colin Ramsden's write protect tool effectively replaces the command line to toggle disks on/offline or readonly/readwrite.
+
On Windows Vista and later
 +
<pre>
 +
C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\Default\Preferences
 +
</pre>
  
== Technical Background and Forensic Soundness ==
+
Or for '''Chromium'''
  
Windows FE is based on the modification of just two entries in the Windows Registry.
+
On Linux
The first key is located at "HKEY_LOCAL_MACHINE\system\ControlSet001\Services\MountMgr". The DWord "NoAutoMount" has to be set to "1".
+
<pre>
By doing this the Mount-Manager service will not automatically mount any storage device.
+
/home/$USER/.config/chromium/Default/Preferences
The second key is "HKEY_LOCAL_MACHINE\system\ControlSet001\Services\partmgr\Parameters" where "SanPolicy" has to be set to "3".
+
</pre>
While both keys will avoid the mounting of storage devices the user has to mount the storage drive manually by using the command-line tool DiskPart, while the evidence drive does not need to be mounted for imaging/forensic access.
+
  
The latest modification (New for Windows 8) to the registry is SAN policy 4.  SAN policy 4 Makes internal disks offline. Note. All external disks and the boot disk are online.
+
On MacOS-X
 +
<pre>
 +
/Users/$USER/Library/Application Support/Chromium/Default/Preferences
 +
</pre>
  
Testing has shown that mounting a '''volume''' in READ ONLY mode will write a controlling code to the disk, whereas mounting a '''disk''' in READ ONLY mode will not make any changes.  Depending on the type of filesystem there is a potential modification to the disk with a documented 4-byte change to non-user created data. This modification exists for non-Windows OS disks, where Windows (FE) will write a Windows drive signature to the disk, although it is not shown to be consistent.  Various issues with Linux Boot CDs can be compared [http://www.forensicswiki.org/wiki/Forensic_Linux_Live_CD_issues] ).
+
On Windows XP
 +
<pre>
 +
C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Chromium\User Data\Default\Preferences
 +
</pre>
  
== Resources: ==
+
On Windows Vista and later
 +
<pre>
 +
C:\Users\%USERNAME%\AppData\Local\Chromium\User Data\Default\Preferences
 +
</pre>
  
* Windows Forensic Environment blog: [http://www.winfe.wordpress.com]
+
=== Plugins ===
* Article on Win FE in Hakin9 magazine 2009-06 [http://hakin9.org]  
+
 
* step-by-step Video to create a Win FE CD [http://www.youtube.com/v/J3T5wnPiObI]
+
Information about plugins can be found under the "plugins section" of the Preferences file.
* WinPE Technical Reference: [http://technet.microsoft.com/en-us/library/dd744322(WS.10).aspx]
+
 
* Windows Automated Installation Kit:  [http://www.microsoft.com/downloads/details.aspx?familyid=696DD665-9F76-4177-A811-39C26D3B3B34&displaylang=en]
+
=== DNS Prefetching ===
* WinFE Write Protect tool [http://www.ramsdens.org.uk/]
+
 
 +
DNS is prefetched for related sites, e.g. links on the page.
 +
This behavior is controlled by the setting "Predict network actions to improve page load performance", which is enabled by default.
 +
 
 +
If enabled the Preferences file contains:
 +
<pre>
 +
  "dns_prefetching": {
 +
      "enabled": true,
 +
</pre>
 +
 
 +
If disabled the Preferences file contains:
 +
<pre>
 +
  "dns_prefetching": {
 +
      "enabled": false,
 +
</pre>
 +
 
 +
== Start-up DNS queries ==
 +
 
 +
When Chrome starts it queries for several non-existing hostnames that consists of a 10 random characters, E.g.
 +
<pre>
 +
ttrgoiknff.mydomain.com
 +
bxjhgftsyu.mydomain.com
 +
yokjbjiagd.mydomain.com
 +
</pre>
 +
 
 +
This is used to determine if your ISP is hijacking NXDOMAIN results [http://www.google.com/support/forum/p/Chrome/thread?tid=3511015c72a7b314&hl=en].
 +
 
 +
== Disk Cache ==
 +
The Google Chrome disk cache can be found in:
 +
 
 +
On Linux
 +
<pre>
 +
/home/$USER/.config/google-chrome/Default/Application Cache/Cache/
 +
</pre>
 +
 
 +
<pre>
 +
/home/$USER/.config/google-chrome/Default/Media Cache/
 +
</pre>
 +
 
 +
On MacOS-X
 +
<pre>
 +
/Users/$USER/Caches/Google/Chrome/Default/Cache/
 +
</pre>
 +
 
 +
On Windows XP
 +
<pre>
 +
C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Google\Chrome\User Data\Cache\
 +
</pre>
 +
 
 +
On Windows Vista and later
 +
<pre>
 +
C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\Default\Cache\
 +
</pre>
 +
 
 +
The Chrome Cache contains different files with the following file names:
 +
* index
 +
* data_#; where # contains a decimal digit.
 +
* f_######; where # contains a hexadecimal digit.
 +
 
 +
For more info see Chrome developers site [http://www.chromium.org/developers/design-documents/network-stack/disk-cache].
 +
 
 +
== History ==
 +
Chrome stores the history of visited sites in a file named '''History'''. This file uses the [[SQLite database format]].
 +
 
 +
The '''History''' file can be found in same location as the '''Preferences''' file.
 +
 
 +
There is also '''Archived History''' that predates information in the '''History''' file.
 +
Note that the '''Archived History''' only contains visits.
 +
 
 +
=== Timestamps ===
 +
The '''History''' file uses the different timestamps.
 +
 
 +
==== visits.visit_time ====
 +
 
 +
The '''visits.visit_time''' is in (the number of) microseconds since January 1, 1601 UTC
 +
 
 +
Some Python code to do the conversion into human readable format:
 +
<pre>
 +
date_string = datetime.datetime( 1601, 1, 1 )
 +
            + datetime.timedelta( microseconds=timestamp )
 +
</pre>
 +
 
 +
Note that this timestamp is not the same as a Windows filetime which is (the number of) 100 nanoseconds since January 1, 1601 UTC
 +
 
 +
==== downloads.start_time ====
 +
 
 +
The '''downloads.start_time''' is in (the number of) seconds since January 1, 1970 UTC
 +
 
 +
Some Python code to do the conversion into human readable format:
 +
<pre>
 +
date_string = datetime.datetime( 1970, 1, 1 )
 +
            + datetime.timedelta( seconds=timestamp )
 +
</pre>
 +
 
 +
=== Example queries ===
 +
Some example queries:
 +
 
 +
To get an overview of the visited sites:
 +
<pre>
 +
SELECT datetime(((visits.visit_time/1000000)-11644473600), "unixepoch"), urls.url, urls.title FROM urls, visits WHERE urls.id = visits.url;
 +
</pre>
 +
 
 +
Note that the visit_time conversion looses precision.
 +
 
 +
To get an overview of the downloaded files:
 +
<pre>
 +
SELECT datetime(downloads.start_time, "unixepoch"), downloads.url, downloads.full_path, downloads.received_bytes, downloads.total_bytes FROM downloads;
 +
</pre>
 +
 
 +
How the information of the downloaded files is stored in the database can vary per version of Chrome as of version 26:
 +
<pre>
 +
SELECT datetime(((downloads.start_time/1000000)-11644473600), "unixepoch"), downloads.target_path, downloads_url_chains.url, downloads.received_bytes, downloads.total_bytes \
 +
FROM downloads, downloads_url_chains WHERE downloads.id = downloads_url_chains.id;
 +
</pre>
 +
 
 +
== See Also ==
 +
 
 +
* [[SQLite database format]]
 +
 
 +
== External Links ==
 +
* [http://en.wikipedia.org/wiki/Google_Chrome Wikipedia article on Google Chrome]
 +
* [http://www.chromium.org/user-experience/user-data-directory The Chromium Projects - User Data Directory]
 +
* [http://www.chromium.org/developers/design-documents/network-stack/disk-cache Chrome Disk Cache]
 +
* [http://www.google.com/support/forum/p/Chrome/thread?tid=3511015c72a7b314&hl=en Chrome support forum article random 10 character hostnames on startup]
 +
* [http://www.useragentstring.com/pages/Chrome/ Chrome User Agent strings]
 +
* [http://computer-forensics.sans.org/blog/2010/01/21/google-chrome-forensics/ Google Chrome Forensics] by [[Kristinn Guðjónsson]], January 21, 2010
 +
* [http://linuxsleuthing.blogspot.ch/2013/02/cashing-in-on-google-chrome-cache.html?m=1 Cashing in on the Google Chrome Cache], [[John Lehr]], February 24, 2013
 +
* [http://www.obsidianforensics.com/blog/history-index-files-removed-from-chrome/ History Index files removed from Chrome v30], by Ryan Benson, October 2, 2013
 +
* [https://hindsight-internet-history.googlecode.com/files/Evolution_of_Chrome_Databases.png Evolution of Chrome Databases], by Ryan Benson, November 12, 2013
 +
 
 +
== Tools ==
 +
=== Open Source ===
 +
* [https://code.google.com/p/hindsight-internet-history/ hindsight-internet-history]
 +
 
 +
[[Category:Applications]]
 +
[[Category:Web Browsers]]

Revision as of 03:45, 29 April 2014

Google Chrome is a web browser developed by Google Inc.

Configuration

The Google Chrome configuration can be found in the Preferences file.

On Linux

/home/$USER/.config/google-chrome/Default/Preferences

On MacOS-X

/Users/$USER/Library/Application Support/Google/Chrome/Default/Preferences

On Windows XP

C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Google\Chrome\User Data\Default\Preferences

On Windows Vista and later

C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\Default\Preferences

Or for Chromium

On Linux

/home/$USER/.config/chromium/Default/Preferences

On MacOS-X

/Users/$USER/Library/Application Support/Chromium/Default/Preferences

On Windows XP

C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Chromium\User Data\Default\Preferences

On Windows Vista and later

C:\Users\%USERNAME%\AppData\Local\Chromium\User Data\Default\Preferences

Plugins

Information about plugins can be found under the "plugins section" of the Preferences file.

DNS Prefetching

DNS is prefetched for related sites, e.g. links on the page. This behavior is controlled by the setting "Predict network actions to improve page load performance", which is enabled by default.

If enabled the Preferences file contains:

   "dns_prefetching": {
      "enabled": true,

If disabled the Preferences file contains:

   "dns_prefetching": {
      "enabled": false,

Start-up DNS queries

When Chrome starts it queries for several non-existing hostnames that consists of a 10 random characters, E.g.

ttrgoiknff.mydomain.com
bxjhgftsyu.mydomain.com
yokjbjiagd.mydomain.com

This is used to determine if your ISP is hijacking NXDOMAIN results [1].

Disk Cache

The Google Chrome disk cache can be found in:

On Linux

/home/$USER/.config/google-chrome/Default/Application Cache/Cache/
/home/$USER/.config/google-chrome/Default/Media Cache/

On MacOS-X

/Users/$USER/Caches/Google/Chrome/Default/Cache/

On Windows XP

C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Google\Chrome\User Data\Cache\

On Windows Vista and later

C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\Default\Cache\

The Chrome Cache contains different files with the following file names:

  • index
  • data_#; where # contains a decimal digit.
  • f_######; where # contains a hexadecimal digit.

For more info see Chrome developers site [2].

History

Chrome stores the history of visited sites in a file named History. This file uses the SQLite database format.

The History file can be found in same location as the Preferences file.

There is also Archived History that predates information in the History file. Note that the Archived History only contains visits.

Timestamps

The History file uses the different timestamps.

visits.visit_time

The visits.visit_time is in (the number of) microseconds since January 1, 1601 UTC

Some Python code to do the conversion into human readable format:

date_string = datetime.datetime( 1601, 1, 1 )
            + datetime.timedelta( microseconds=timestamp )

Note that this timestamp is not the same as a Windows filetime which is (the number of) 100 nanoseconds since January 1, 1601 UTC

downloads.start_time

The downloads.start_time is in (the number of) seconds since January 1, 1970 UTC

Some Python code to do the conversion into human readable format:

date_string = datetime.datetime( 1970, 1, 1 )
            + datetime.timedelta( seconds=timestamp )

Example queries

Some example queries:

To get an overview of the visited sites:

SELECT datetime(((visits.visit_time/1000000)-11644473600), "unixepoch"), urls.url, urls.title FROM urls, visits WHERE urls.id = visits.url;

Note that the visit_time conversion looses precision.

To get an overview of the downloaded files:

SELECT datetime(downloads.start_time, "unixepoch"), downloads.url, downloads.full_path, downloads.received_bytes, downloads.total_bytes FROM downloads;

How the information of the downloaded files is stored in the database can vary per version of Chrome as of version 26:

SELECT datetime(((downloads.start_time/1000000)-11644473600), "unixepoch"), downloads.target_path, downloads_url_chains.url, downloads.received_bytes, downloads.total_bytes \
FROM downloads, downloads_url_chains WHERE downloads.id = downloads_url_chains.id;

See Also

External Links

Tools

Open Source