Randomization

Overview

DuckyScript 3.0 includes various randomization features, from random keystroke injection to random integers. This enables everything from payload obfuscation to unique values for device mass-enrollment, and even games!

Pseudorandom

As an inherently deterministic device, USB Rubber Ducky pseudorandom number generator (PRNG) relies on an algorithm to generate a sequence of numbers which approximate the properties of random numbers. While the numbers generated by the USB Rubber Ducky are not truly random, they are sufficiently close to random allowing them to satisfy a great number of use cases.

Seed

The seed is the number which initializes the pseudorandom number generator. From this number, all future random numbers are generated. On the USB Rubber Ducky, this number is stored in the file seed.bin, which resides on the root of the devices MicroSD card storage similar to the inject.bin file.

Entropy

The randomness used to automatically generate the seed considered entropy. A higher level of entropy results in a better quality seed. Entropy may be derived from human input or the USB Rubber Ducky hardware alone.
A high entropy seed.bin file may be generated using Payload Studio. Alternatively, if no seed is generated, a low entropy seed will be automatically generated by the USB Rubber Ducky in the case that one is necessary.

Random Keystroke Injection

Random keystroke injection is possible with DuckyScript 3.0. Using the appropriate random command, a random character may be typed.
Command
Character Set
RANDOM_LOWERCASE_LETTER
abcdefghijklmnopqrstuvwxyz
RANDOM_UPPERCASE_LETTER
ABCDEFGHIJKLMNOPQRSTUVWXYZ
RANDOM_LETTER
abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
RANDOM_NUMBER
0123456789
RANDOM_SPECIAL
RANDOM_CHAR
abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ 0123456789 [email protected]#$%^&*()
Different key-maps will produce different characters on a keyboard. For example, with a US keyboard layout the key combo SHIFT 3 will produce in a pound, hash or number sign ("#"). On a UK keyboard layout, the same key combo will produce the symbol for the pound sterling currency ("£").
For this reason, when Payload Studio compiles the DuckyScript payload into an inject.bin file, the selected language map will be packed into the payload such that the correct random keys are injected.

Example

REM Example Random Keys
ATTACKMODE HID STORAGE
DELAY 2000
BUTTON_DEF
RANDOM_CHAR
END_BUTTON
STRINGLN Here are 10 random lowercase letters:
VAR $TIMES = 10
WHILE ($TIMES > 0)
RANDOM_LOWERCASE_LETTER
$TIMES = ($TIMES - 1)
END_WHILE
ENTER
ENTER
STRINGLN Here are 20 random numbers:
VAR $TIMES = 20
WHILE ($TIMES > 0)
RANDOM_NUMBER
$TIMES = ($TIMES - 1)
END_WHILE
ENTER
ENTER
STRINGLN Here are 3 random special characters:
RANDOM_SPECIAL
RANDOM_SPECIAL
RANDOM_SPECIAL
STRINGLN Press the button for a random character:

Result

  • This payload will type:
    • 10 random lowercase letters, per the while loop.
    • 20 random numbers, per the while loop.
    • 3 random special characters.
  • The payload will then instruct the user to press the button.
  • On each press of the button, the BUTTON_DEF will execute.
    • This special functions contains the RANDOM_CHARACTER command, and thus a random character will be typed.

Random Integers

As opposed to the RANDOM_NUMBER command which will keystroke inject, or type a random digit, the internal variable $_RANDOM_INT may be referenced for a random integer.
Internal Variable
Value
$_RANDOM_INT
Random integer within set range
$_RANDOM_MIN
Random integer minimum range (unsigned, 0-65535)
$_RANDOM_MAX
Random integer maximum range (unsigned, 0-65535)
$_RANDOM_SEED
Random seed from seed.bin

Example

REM Example Random Integer
LED_OFF
VAR $A = $_RANDOM_INT
WHILE ($A > 0)
LED_G
DELAY 500
LED_OFF
DELAY 500
$A = ($A - 1)
END_WHILE

Result

  • Each time this payload is executed, the LED will randomly blink between 0 and 9 times.

Minimum and maximum range

Each time the $_RANDOM_INT variable is referenced, it will produce a random integer. By default, this integer will be between 0 and 9. The range in which the integer is produced may be specified by changing the values of $_RANDOM_MIN and $_RANDOM_MAX.
As unsigned integers, the minimum and maximum values must fall within the range of 0 through 65535.

Example

REM Example Random Integer Example with Range
LED_OFF
$_RANDOM_MIN = 20
$_RANDOM_MAX = 50
VAR $A = $_RANDOM_INT
WHILE ($A > 0)
LED_G
DELAY 500
LED_OFF
DELAY 500
$A = ($A - 1)
END_WHILE

Result

  • Each time this payload is executed, the LED will blink a random number of times between 20 and 50.
The random minimum and maximum values may be changed arbitrarily as many times as needed throughout the payload.

Random and Conditional Statements

Random integers may be evaluated by conditional statement in the same way as ordinary variables.

Example

REM Example Random Integer with Conditional Statement
ATTACKMODE HID STORAGE
DELAY 2000
$_RANDOM_MIN = 1
$_RANDOM_MAX = 1000
WHILE TRUE
VAR $A = $_RANDOM_INT
IF ($A >= 500) THEN
STRINGLN The random number is greater than or equal to 500
ELSE IF $(A < 500 THEN
STRINGLN The random number is less than 500
END_IF
STRINGLN Press the button to go again!
WAIT_FOR_BUTTON_PRESS
END_WHILE

Result

  • The random range, as defined by $_RANDOM_MIN and $_RANDOM_MAX, is initialized only once at the start of the payload.
  • The remainder of the payload is carried out within the infinite loop, WHILE TRUE.
  • Each time the loop begins the variable $A will assign a new random number from the internal variable $_RANDOM_INT between the range initially defined.
  • The variable $A will be evaluated, and its condition (whether it's greater or less than 500) will be typed.
  • The loop will restart after the press of the button.

Random and ATTACKMODE

In addition to random keystroke injection and integers, the USB Rubber Ducky can randomize a number of ATTACKMODE parameters.
ATTACKMODE Parameter
Result
VID_RANDOM
Random Vendor ID
PID_RANDOM
Random Product ID
MAN_RANDOM
Random 32 alphanumeric character iManufacturer
PROD_RANDOM
Random 32 alphanumeric character iProduct
SERIAL_RANDOM
Random 12 digit serial number

Example

REM Example Random ATTACKMODE Parameters
ATTACKMODE OFF
WHILE TRUE
ATTACKMODE HID VID_RANDOM PID_RANDOM MAN_RANDOM PROD_RANDOM SERIAL_RANDOM
LED_R
DELAY 2000
STRINGLN Hello, World!
WAIT_FOR_BUTTON_PRESS
LED_G
END_WHILE
Remember, VID and PID must be used as a pair and MAN, PROD and SERIAL must be used as a trio.

Result

  • On each press of the button, the USB Rubber Ducky will re-enumerate as a new USB HID device with random VID, PID, MAN, PROD and SERIAL values.
  • The string Hello, World! may be typed.
    • Because VID and PID values may dictate device driver initialization, the USB Rubber Ducky may not be correctly enumerated as a Human Interface Device by the target OS.
Use caution when using random VID and PID values as unexpected results are likely.

Inspecting USB Device Enumeration

While performing security research with the USB Rubber Ducky, it is useful to inspect the USB device enumeration on the target operating system. These example commands and utilities are helpful in this regard.

Linux

Terminal

lsusb # and lsusb -v
# or
usb-devices

macOS

Graphical Interface

  1. 1.
    Click the Apple icon
  2. 2.
    Click About This Mac
  3. 3.
    Click System Report
  4. 4.
    Click USB
System Report showing USB Keyboard on macOS

Terminal

ioreg -p IOUSB

Windows

Graphical Interface

Microsoft USBView from the Windows SDK or the freeware Nirsoft USBDeview are graphical utilities for inspecting USB devices.
Nirsoft USBDeview

Powershell

gwmi Win32_USBControllerDevice
# or
Get-PnpDevice -PresentOnly | Where-Object { $_.InstanceId -match '^USB' } | Format-List

Random and Interaction

The random functions can be used in combination with the interactive abilities of the USB Rubber Ducky in a number of ways. This example will illustrate some of the possibilities by demonstrating a simple dice roll guessing game.
REM Example Random Dice Roll Guessing Game
REM -------------------------------------------------------
REM Set the ATTACKMODE to both HID and STORAGE so it's easy
REM to change the payload without removing the MicroSD card
REM and give the computer 2 seconds to enumerate the Ducky!
REM -------------------------------------------------------
ATTACKMODE HID STORAGE
DELAY 2000
REM ------------------------------------------------------
REM Draw some Dice ASCII art because ASCII art is awesome!
REM Credit: valkyrie via asciiart.eu
REM ------------------------------------------------------
STRINGLN ____
STRINGLN /\' .\ _____
STRINGLN /: \___\ / . /\
STRINGLN \' / . / /____/..\
STRINGLN \/___/ \' '\ /
STRINGLN \'__'\/
STRINGLN Ducky Dice Roll!
ENTER
ENTER
REM ------------------------------------------------------------
REM Initialize the variables, including the random 6 sided dice.
REM ------------------------------------------------------------
$_RANDOM_MIN = 1
$_RANDOM_MAX = 6
VAR $GUESS = 0
VAR $TIMER = 0
REM -------------------------------------------------------------
REM Change the button timeout from its default 1000 ms to 100 ms.
REM -------------------------------------------------------------
$_BUTTON_TIMEOUT = 100
REM ----------------------------------------------------
REM Define the button such that on each press the guess
REM variable will increment by one and prevent the guess
REM from going over six.
REM ----------------------------------------------------
BUTTON_DEF
IF ($GUESS == 6) THEN
STRINGLN The guess cannot be greater than 6!
ELSE
$GUESS = ($GUESS + 1)
END_IF
END_BUTTON
REM -----------------------------
REM Begin the main infinite loop.
REM -----------------------------
WHILE TRUE
STRINGLN Rolling the dice...
DELAY 2000
REM -----------------------------------------
REM Assign the $DICE variable a random value.
REM -----------------------------------------
VAR $DICE = $_RANDOM_INT
STRINGLN Guess the value by pressing the button!
STRING You have 5 seconds to enter your guess
REM -----------------------------------------------
REM Give the player 5 seconds to enter their guess,
REM typing a period for each second that goes by.
REM -----------------------------------------------
$TIMER = 5
$GUESS = 0
WHILE ($TIMER > 0)
STRING .
DELAY 1000
$TIMER = ($TIMER - 1)
END_WHILE
REM ----------------------------------------------------
REM Draw ASCII art of the dice that was randomly chosen.
REM ----------------------------------------------------
ENTER
IF ($DICE == 1) THEN
STRINGLN -----
STRINGLN | |
STRINGLN | o |
STRINGLN | |
STRINGLN -----
ELSE IF ($DICE == 2) THEN
STRINGLN -----
STRINGLN |o |
STRINGLN | |
STRINGLN | o|
STRINGLN -----
ELSE IF ($DICE == 3) THEN
STRINGLN -----
STRINGLN |o |
STRINGLN | o |
STRINGLN | o|
STRINGLN -----
ELSE IF ($DICE == 4) THEN
STRINGLN -----
STRINGLN |o o|
STRINGLN | |
STRINGLN |o o|
STRINGLN -----
ELSE IF ($DICE == 5) THEN
STRINGLN -----
STRINGLN |o o|
STRINGLN | o |
STRINGLN |o o|
STRINGLN -----
ELSE IF ($DICE == 6) THEN
STRINGLN -----
STRINGLN |o o|
STRINGLN |o o|
STRINGLN |o o|
STRINGLN -----
END_IF
ENTER
REM --------------------------------------------
REM Remind the player which number they guessed.
REM --------------------------------------------
IF ($GUESS == 0) THEN
STRINGLN You did not guess!
ELSE IF ($GUESS == 1) THEN
STRINGLN You guessed 1
ELSE IF ($GUESS == 2) THEN
STRINGLN You guessed 2
ELSE IF ($GUESS == 3) THEN
STRINGLN You guessed 3
ELSE IF ($GUESS == 4) THEN
STRINGLN You guessed 4
ELSE IF ($GUESS == 5) THEN
STRINGLN You guessed 5
ELSE IF ($GUESS == 6) THEN
STRINGLN You guessed 6
END_IF
REM ---------------------------------------------------
REM Check to see if the guess and the dice are the same
REM and let the player know if they guessed correctly.
REM ---------------------------------------------------
IF ($DICE == $GUESS) THEN
STRINGLN You were correct!
ELSE
STRINGLN You were incorrect!
END_IF
REM -------------------------------------------------------
REM Invite the player to play again by pressing the button.
REM -------------------------------------------------------
STRINGLN Press the button to play again!
WAIT_FOR_BUTTON_PRESS
END_WHILE
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On this page
Overview
Pseudorandom
Seed
Entropy
Random Keystroke Injection
Example
Random Integers
Example
Minimum and maximum range
Example
Random and Conditional Statements
Example
Random and ATTACKMODE
Example
Inspecting USB Device Enumeration
Linux
macOS
Windows
Random and Interaction