Tuesday, August 25, 2015

Android SDK on 64-bit Linux

I commonly use adb and fastboot to access Android devices.  Ubuntu has packages for those tools making installation easy:
$ sudo apt-get install android-tools-adb android-tools-fastboot
But, in recent months, I have encountered instances where the adb and fastboot binaries in the Ubuntu repository are out of date for the device with which I am attempting to connect.
$ apt-cache show android-tools-adb
Package: android-tools-adb
Priority: extra
Section: universe/devel
Installed-Size: 227
Maintainer: Ubuntu Developers
Original-Maintainer: Laszlo Boszormenyi (GCS)
Architecture: amd64
Source: android-tools
Version: 4.2.2+git20130218-3ubuntu41
Depends: libc6 (>= 2.15), libssl1.0.0 (>= 1.0.0), zlib1g (>= 1:1.1.4)
Filename: pool/universe/a/android-tools/android-tools-adb_4.2.2+git20130218-3ubuntu41_amd64.deb
...

$ adb version
Android Debug Bridge version 1.0.31

Android Software Development Kit


There is another way to install adb: the Android Software Development kit.  There is an issue, though.  The development kit software is 32-bit, and modern computer systems run 64-bit operating systems.  So, one needs a way to install 32-bit libraries in 64-bit Linux to support 32-bit applications.

The Android SDK can be found here. However, before you start downloading the Android Studio displayed prominently at the top of the page, consider that Studio is large collection of software for developing Android applications.  Forensically speaking, it is overkill, and fortunately, there is an alternative download that servers our purpose better: SDK Tools Only.

I prefer to install tools not found in the Ubuntu repository in the /opt directory.  After I download the SDK, I decompress the archive:
$ sudo tar xf Downloads/android-sdk_r24.3.4-linux.tgz -C /opt
The next step in installation is to execute the Android SDK Manager.  Note: You will need java installed (java-common package) to run the application.
$ /opt/android-sdk-linux/tools/android 
The only component needed to successfully run adb and fastboot are the Android SDK tools (already installed) and Android SDK Platform-tools.  Check the later and go through the installation process.  Exit the manager when you are done.

Installing 32-bit Support in 64-bit Ubuntu


The adb and fastboot executable binaries are located in the platform-tools folder of the SDK.  However, if you try to execute the tools, you will get and error stating the that the command is not found, even though you see the tools in the directory, with proper permissions for execution, too! 
$ cd /opt/android-sdk-linux/platform-tools
$ ./adb version
bash: ./adb: No such file or directory
$ ls -l adb
-rwxr-xr-x 1 root root 1221540 Aug 25 13:05 adb
Confusing?  You bet. The issue is that you are trying to execute a 32-bit application in a 64-bit-only operating system.  There is no 32-bit support installed in Ubuntu by default.  But we can solve that:
$ sudo dpkg --add-architecture i386
$ sudo apt-get update
The specific libraries to support the SDK are installed as follows:
$ sudo apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386
$ ./adb version
Android Debug Bridge version 1.0.32
Revision 57224c5cff69-android
And, voila!  The latest SDK binary tools installed.

Easy Access


There are two simple ways to gain access to the SDK platform tools: link files or path modification.  Link files are placed in a location that is part of your system path already, and path modification places the platform tools directory in your path.  Which is best?  Welcome to freedom, friend, it's your choice.

Link files

Link files are found in all modern operating systems, so I won't bother explaining them.  First, you need to know what directories are in your path so you know where to put the links:
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
Most packages you install place their executable binaries in /usr/bin and /usr/sbin, depending on the need for administrative privileges.  Most software built and installed by the user are placed in the /usr/local/bin and /usr/locals/sbin folders.  Since we are installing the software, and it does not require admin rights to execute, /usr/local/bin is a good choice.

To create link files in Linux (symlinks are preferred for this type of operation), do the following:
$ ln -s /opt/android-sdk-linux/platform-tools/adb /usr/local/bin
$ ln -s /opt/android-sdk-linux/platform-tools/fastboot /usr/local/bin
Note: you will have a lot more success with link files if you get in the habit of using absolute paths.  There is a place for relative paths, but this is not it.

Modifying the PATH

The PATH system variable maintains the list of directories searched by the system for commands.  When you, as a user, type a command without it's full path, the list of directories in the PATH variable are queried for the command.  If the command is not located, an error results.  To place the adb and fastboot binaries into the path, we need to add the folder containing them to the PATH variable.

It is possible to modify the path, both temporarily and permanently.  For example:
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
$ which
$ PATH=/opt/android-sdk-linux/platform-tools

$ echo $PATH
/opt/android-sdk-linux/platform-tools$ which
Command 'which' is available in the following places
 * /bin/which
 * /usr/bin/which
The command could not be located because '/bin:/usr/bin' is not included in the PATH environment variable.
which: command not found
The problem about illustrates that we have to be careful setting the path.  By setting the path to /opt/android-sdk-linux/platform-tools, we removed the directories previously stored there.  The method used, however, is only a temporary change to the PATH variable.  The path can be reset by restarting the terminal window, or by resetting the PATH variable to its original contents:
$ PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
To make the change permanent, and to append to but not replace the contents of the PATH variable, we should add the following to our ~/.bashrc file (if your installation does not have the file, create it):
export PATH="$PATH:/opt/android-sdk-linux/platform-tools"
It is not necessary to have quotes in the statement above if there are no spaces in the path, but it is the safest way to execute the statement.  By placing this statement in .bashrc, the PATH variable will be expanded, have the platform-tools folder appended, and then the value will be reassigned to the PATH variable.  This will happen each time a new terminal session starts.



Monday, August 24, 2015

Riffbox and Windows 10

I decided to bite the bullet and try out Windows 10. I wanted to learn the new operating system and determine if I could run specific software/hardware combinations under the new Windows that I had been running in Windows 7, specifically Riffbox. I happy to report, that after some trial and error, I have determined a reliable way of running riffbox under Windows 10. This should work equally well under Windows 8, as the issue is the same.

Hey, What's Your Sign? 


Windows 8 and now 10 both required a driver be digitally signed by a vendor known to Microsoft of it will flat refuse to install the driver. Under Windows 7, you had the option to continue even if the driver was not digitally signed, but not so for Windows 8/10.  The only solution is to reboot the computer into "Disable device driver signing detection" mode.

Disabling Driver Signing


  1. Right-click the start menu, select Shut down or sign out.
  2. Click Restart while holding the Shift key.  The boot option will appear.
  3. Select Troubleshoot > Advanced Options > Startup Settings > Restart.
  4. In the Startup Settings menu, press F7 to disable driver signing.
The PC will now perform a one-time boot with driver signing disabled.  In this mode, it is possible to install the Riff Box software.  If the driver's do not automatically install, navigate to C:\Program Files (x86)\RIFF Box JTAG Manager\Drivers\64Bit directory and run the dpinst.exe program as Administrator.  Use Windows 7 compatibility mode if necessary.  You will be warned that the three drivers are not digitally signed, but you will have the option to install anyway.

After you install the drivers, plug in Riff Box and launch JTAG Manager.  

Common Issues


If you plug the riffbox into your Windows 10 system and the green light continually flashes, riffbox has not been properly recognized.  An easy fix for this is to right-click the Start menu icon and select 'Device Manager'.  Under 'Ports', you should find the 'RIFF BOX Control Port (COM #)' entry.

  1. Right click the entry and select Update Driver Software.
  2. Select Browse my computer for driver software.
  3. Select Let me pick from a list of device drivers on my computer.
  4. With the Show compatible hardware box checked, select RIFF BOX Control Port.
  5. Click the Next button to install the driver.  The Riff Box will now be recognized as a 'RIFF BOX Control Port.'
Note: Follow this procedure, too, if instead of the Riffbox entry, you see a generic 'USB Serial Device.'

Reboot Reincarnation


Rebooting reinstates the device driver signature requirement in Windows 8/10. Riff Box will not be recognized by JTAG Manager in normal boot mode because the unsigned drivers will not load.  Even if you follow the trouble shooting listed in the Common Issues section above, JTAG Manager will not detect Riff Box.  The only solution (to date) is to reboot into Disabled Signature Enforcement Mode.

That said, there are ways to force disabled signature enforcement mode on each boot, but do they work?

Permanently Disabling Driver Signature Enforcement


You will read that you can use the bcdedit command line tool to disable driver signing on each boot automatically.  The tool modifies the boot configuration data store which replaced the boot.ini file of windows 7 and earlier.  However, while this process will allow driver installation, it still does not allow the drivers to load when Riff Box is connected to the PC.  I include the instructions below to show you what I did in testing.

To disable driver signing mode on boot (and start in Test Mode):
  1. Right-click on the Start menu icon, select Command Prompt (admin).
  2. Run the command:
    bcdedit /set loadoptions DISABLE_INTEGRITY_CHECKS
  3. Run the command:
    bcdedit /set TESTSIGNING ON
  4. Reboot.

To reenable driver signing (and exit Test Mode):
  1. Right-click on the Start menu icon, select Command Prompt (admin).
  2. Run the command:
    bcdedit /deletevalue loadoption
  3. Run the command:
    bcdedit /set TESTSIGNING OFF
  4. Reboot
Another possible permanent solution would be to disable driver signature enforcement in the Group Policy Editor.  You will only have this tool if are running Windows Pro and higher, however.  I did not have Windows 10 pro at the time of this writing, so I have not tested the following procedure:
  1. Right-click the Start menu icon and select Run.
  2. Enter gpedit.msc and press Enter.
  3. In the editor, select User Configuration > Administrative Templates > System > Driver Installation.
  4. Double-click Code signing for device drivers.
  5. Click the Enable radio button and then select Ignore in the Options drop down.
  6. Apply the changes and reboot.
If you have success with this second method, please post a comment so others will know the solution.

Tuesday, February 24, 2015

URLs : U R Loaded with Information

In my early days of forensics, I considered URLs in web histories as nothing more than addresses to websites, and strictly speaking, that’s true. But URLs often contain form information supplied by the user and other artifacts that can be relevant to an investigation, too. Most of us in the business know this already, at least it concerns one commonly sought after ingot: the web search term.

Consider the following URL:

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

Most examiners would key in on the domain google.com and the end of the url, q=linuxsleuthing, and conclude this was a Google search for the term "linuxsleuthing", and they’d be right. But is there anything else to be gleaned from the URL? Just what do all those strings and punctuation mean, anyway?

What’s in a URL

Let’s use the URL above as our discussion focus. I’ll break down each element, and I’ll mention at least one value of the element to the forensic investigator (you may find others). Finally, I’ll identify and demonstrate a Python library to quickly dissect a URL into its constituent parts.

Protocol

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

The URL starts with the protocol, the "language" the browser must speak to communicate with the resource. In the Python urllib module that I will introduce later, the protocol is referred to as the "scheme".

Examples:

  • http: - Internet surfing

  • https: - Secure Internet surfing

  • ftp: - File transfer operations

  • file: - Local file operations

  • mailto: - Email operations

The forensics value of a protocol is that it clues you into the nature of the activity occurring at that moment with the web browser.

Domain

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

The domain can be thought of as the place "where the resource lives." Technically, it can consist of three parts: the top-level domain (TLD), second-level domain, and the host name (or subdomain). If you are more interested in those terms, I’ll leave it to you to research. Suffice it to say that we think of it as the "name" of the website, and with good reason. The names exist in this form because they can be easily memorized and recognized by humans. You may also encounter the domains evil twin in a URL, the Internet Protocol (IP) address, which domain names represent.

The Python urllib module referes to the domain as the "netloc" and identifies it by the leading "//", which is the proper introduction according to RFC 1808.

The forensic value of a domain is that you know where the resource defined in the remainder of the URL can be found or was located in the past.

Port

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

The port is not listed in this url, nor is it often included in URLs intended for human consumption. However, if you see something like www.google.com:80, the ":80" indicates communication is occurring across port 80. You’ll often see port numbers for URLs to video servers, but port numbers are by no means limited to such uses. The Python urllib module incorporates the port in the "netloc" attribute.

The chief forensic value of a port is that it can clue you intohttp://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers[the type of activity] occuring on the domain because many port numbers are well known and commonly used for specific tasks.

Path

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

In terms of a web server, the path indicates the path to the resource on the server. If the "file:" protocol is seen in the URL, then the path signifies the logical location of the file on the local machine. In fact, there will not be a domain, though the domain preamble is present, which is why you see three forward slashes for a file:

file:///path.

The Python urllib module also uses the name "path" to describe this hierarchal path on the server. Please understand that both hard paths and relative paths are possible. In addition, Python describes "params" for the last path element which are introduced by a semicolon. This should not be confused with the parameters I describe in the next section.

The principle forensic value of the path is the same as the over riding principle of real estate: location, location, location.

Parameters

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

Parameters are information passed to the web server by the browser. They are also referred to as "query strings". Parameters can include environment information, web form data, window size, and anything else the web site is coded to pass on. Parameter strings are indicated by a leading "?" followed by key:value pairs. Multiple parameters are separated by "&". Python calls parameters the "query."

Consider our sample URL. It can be seen to have four parameters:

  • sourceid=chrome-instant

  • ion=1

  • espv=2

  • ie=UTF-8

Parameters are really the meat and potatoes of URL analysis, in my opinion. It is here I find the most interesting details: the user name entered on the previous web page; in the case of mobile devices, the location of the device (lat/lon) when the Facebook post was made; the query on the search engine, etc.

Despite what I said in the preceding paragraph, note that query string is not present the case of our sample URL. The search was conducted through the Google Chrome browser address bar (sourceid=chrome-instant). Thus, it is not safe to assume that all search engine search terms or web form data are to be found in the URL parameters.

To throw a little more mud on the matter, consider that the entry point of the search and the browser make a difference in the URL:

Search for linuxsleuthing from the Ubuntu start page, FireFox
https://www.google.com/search?q=linuxsleuthing&ie=UTF-8&sa=Search&channel=fe&client=browser-ubuntu&hl=en&gws_rd=ssl

Here, we see the same search, but different parameters:

  • q=linuxsleuthing

  • ie=UTF-8

  • sa=Search

  • channel=fe

  • client=browser-ubuntu

  • hl=en

  • gws_rd=ssl

Caution
Parameters will mean different things to different sites. There is no "one-definition fits all" here, even if there be obvious commonality. It will take research and testing to know the particular meaning of any given parameter even though it may appear obvious on its face.

Anchor

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing

The anchor links to some location within the web page document itself. If you’ve ever clicked a link and found yourself halfway down a page, then you understand the purpose of the anchor. Somewhere in the html code of that page is a bookmark of sorts to which that anchor points. Python calls the anchor a "fragment."

In the case of our sample URL, the anchor is the search term I entered in the address bar of the Google Chrome browser.

The forensics value of an anchor is that you know what the user saw or should have seen when at that site. It might demonstrate a user interest or that they had knowledge of a fact, depending on your particular circumstances, of course.

Making Short Work of URL Parsing

Python includes a library for manipulating URLs named, appropriately enough, urllib. The python library identifies the components of a URL a little more precisely than I described above, which was only intended as an introduction. By way of quick demonstration, we’ll let Python address our sample URL

iPython Interative Session, Demonstrating urllib
In [1]: import urllib

In [2]: result = urllib.parse.urlparse('https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing')

In [3]: print(result)
ParseResult(scheme='https', netloc='www.google.com', path='/webhp', params='', query='sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8', fragment='q=linuxsleuthing')

In [4]: result.query
Out[4]: 'sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8'

In [5]: result.query.split('&')
Out[5]: ['sourceid=chrome-instant', 'ion=1', 'espv=2', 'ie=UTF-8']

In [6]: result.fragment
Out[6]: 'q=linuxsleuthing'
Note
The Python urllib calls the parameters I discussed a query and the anchor a fragment.

If you have a little Python knowledge, then you can see how readily you could parse a large list of urls. If not, it is not much more difficult to parse a url using BASH.

Parsing URLs using BASH variable substitution

$ url="https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=linuxsleuthing"
$ anchor=${url##*\#}
$ parameters=${url##*\?}
$ parameters=${parameters//#$anchor/}
$ echo ${parameters//&/ }
sourceid=chrome-instant ion=1 espv=2 ie=UTF-8
$ echo $anchor
q=linuxsleuthing

Finding Parameters

If you want to narrow your search for URLs containing parameters and anchors, you need only grep your list for the "&" or "#" characters. If you are processing a history database such as the Google Chrome History SQLite database, you can export the relevant urls with the following query:

SQLite query for Google Chrome History
select * from urls where url like "%?%" or url like "%#%";

What’s All the Fuss?

So, why go to all this length to study a URL? I’ll give two simple illustrations:

In the first case, I had the computer of a person suspected of drug dealing. I found little relevant data on his computer doing basic analysis, including an analysis of search engine search terms. When I examined URL parameters, however, I found searches at website vendors that demonstrated the purchase of materials for growing marijuana.

In the second case, a stolen computer was recovered in close proximity to a suspect who claimed to have no knowledge of the device. The Google Chrome browser in the guest account was used since the date of the theft, so analysis was in order. URL parameters showed a login to the suspect’s Apple account 12 hours after the left. There was no useful data in the cache, only the URL history.

Finally, bear in mind that the URL history is the only artifact you may have of secure website activity. Browsers, by default, do not cache secure elements. Understanding the contents of a URL can clue you into activity for which may find no other artifacts.

It is good to know what’s in a URL!