PenTest+ Module 11 - Modifying Scripts

Bash

A command-line scripting language used for the command shell inside Unix-like systems (Linux and MacOS)

Bash is NOT object oriented

All bash scripts should start with #!/bin/bash

Bash Variables

Define a variable with varName = <value>

To use the variable, use $. $varName for example

Bash Variable Declaring

declare option VarName=<value>

Ex: declare -i PhoneNumber=1111111 (treat as integer)

Ex: declare -r Pi=3.14 (read only)

Bash Arrays

tempArray=[value1, value2, value3]

Index with $tempArray[index] (remember that in bash you reference variables with $)

Bash Named and Associative Arrays

declare -A PhoneBook (declare it first)

PhoneBook[name]=”Jason”

PhoneBook[number]=”111-1111”

${PhoneBook[name]} to get the name (named arrays use curly brackets

${PhoneBook[number]} to get the number

Bash Arithmetic Comparison

is a equal to b → if [ “$a” -eq “$b” ]

is a not equal to b → if [ “$a” -ne “$b” ]

greater than → -gt

greater than or equal to → -ge

less than → -lt

less than or equal to → le

You can use < and > but you have to use double parenthesis around the operation

((“$a” < “$b”)) for example

Bash String Comparison

if [ “$a” = “$b” ] or if [ “$a” == “$b” ] for is equal to

if [ “$a” != “$b” ] for not equal to

You can compare words with < and >. This will order based on ASCII ordering

if [ “$a” \< “$b” ] for is less than (in alphabetical order)

if [[ “$a” < “$b” ]] for is less than (remember double wrapped if using raw < and >

Bash Logical Comparison

if [condition]
  then
    # do some command
elif [condition]
  then
    # do something
else
    # do something
fi

Bash For Loop Done

for var in <list>
do
    # commands
done

Ex:

for value in {1..5}
do
    echo $value
done

echo "All done"

Bash While Do Done

while [some test]
do 
    # commands
done

Ex:

counter=1
while [$counter -lt 10]
do
    echo $counter
    ((counter++))
done

echo "All done"

Bash Until Do Done

Perform a set of commands until a test is true

until [some test]
do
    # commands
done

Ex:

counter = 1
until [$counter -gt 5]
do
    echo $counter
    ((counter++))
done

echo "All done"

Bash String Operations

The commands used to manipulate data in string format

Bash Substrings

testString = "Test String"
echo ${testString:2:4}

> st S

First number is start index, second number is how many characters from that position (including the position itself)

Bash Inputting and Outputting Data

Output with echo

Input with read

Read input into a variable: read UserName

Bash Getting Input From File

TempFile = $(<test.txt)
echo "$TempFile"

TempFile contains the contents of test.txt

Bash Outputting to a File

> overwrites what is in the file

» appends to a file

echo "hi" > hi.txt
echo "amongus" >> hi.txt

Bash Command Line Args

$1 is the first argument passed into the script

$0 is the name of the script itself

PowerShell Comments

Uses #

<# a bunch of stuff #> also works to make large multi-line comments

PowerShell Variables

All variable creation begins with $

$varName = <value>

$CustomerName = Jason

Access variables by also using the $ notation

Also allows typing

[int]$AnswerNumber = 42

[string]$AnswerString = “The life, the universe, and everything”

Constants (set the variable to read only)

Set-Variable <VarName> -Option ReadOnly -Value <value>

PowerShell Arrays

$tempArray = @() # Blank array

$TempArray = @('Jason', 'Sahra', 'Eduardo', 'Linda')

Arrays are denoted with @

Access with $tempArray[index]

PowerShell Named and Associative Arrays

$PhoneBook = @{}
$PhoneBook.name = 'Jason'
$PhoneBook.number = '321-1234'

#Reference
$PhoneBook.name

# All in one
$PhoneBook = @{'name' = 'Jason', 'number' = '321-1234'}

PowerShell Comparisons

Same as Bash, also uses -eq, -le, -ge, -lt, -gt, etc

PowerShell Conditional Statements

if (condition) {
    # Then do some command
}

if (condition) {
    # Code here
}

elseif (condition) {
    # Code here
}

else {
    # Code here
}

PowerShell For Loop

for (<Init> ; <Condition> ; <Repeat>) {

    <Statement list>
}

for ($i = 1; $1 -lt 5; $i++) {
    Write-Host $i
}

Write-Host "All done"

PowerShell Do While

Do {
    # Commands
}
While ($this -eq $that)

$i = 1
Do {
    Write-Host $i
    $i++
}
While ($i -lt 10)

Write-Host "All Done"

PowerShell Until Do

Do {
    # commands
}
Until ($this -eq $that)

$i = 1
Do {
    Write-Host $i
    $i++
}
Until ($i -gt 5)

Write-Host "All Done"

PowerShell String Operations

Print with Write-Host

Concatenation: Write-Host $testString + “2” → ”Test String2”

PowerShell Substrings

$testString = "Test String"
$testString.substring(2, 4)

> st S

First number is starting index, second number is amount of characters to include (including the starting index itself

PowerShell Get Input

Read-Host $VarName

PowerShell Read File

$TempFile = Get-Content - Path C:\Test.txt
Write-Host $TempFile

PowerShell Write to File

> overwrites

» Appends

Write-Host "Hello" > hello.txt
Write-Host "Hi" >> hello.txt

PowerShell Dead Giveaway

The cmdlets are dead giveaways that a script is PowerShell

Python Comments

Uses #

Python Variables

varName = <value>

Python Type Casting / Setting

Price = int(42) # Variable will always be an int
Price = float(42.00) # Variable will always be a float
Price = str("The life, the universe, and everything")

No need to do anything special to reference variables, just use the name

Python Constants

Use all caps to denote

PI = 3.14159

Python Arrays

tempArray = []
tempArray = [value1, value2, value3]

nameArray = ["Jason", "Mary", "Joe"] 

nameArray[0] => Jason

Python Dictionary

PhoneBook = {}
PhoneBook = {'name' = 'Jason', 'number' = "321-1234"}

PhoneBook["name"] => Jason

Python Comparisons

equal to → ==

not equal to → != or <>

greater than, less than, gte, lte → >, <, >=, <=

Python Conditional Statements

if condition:
    # code

if a == b:
    print(a)

if (condition):
    # code
elif (condition):
    # more stuff
else:
    # stuff

Python For Loop

for x in list:
    # Stuff

Python While Loop

i = 1
while i < 6:
    print(i)
    i++

print("All done")

Python Until Loop

Don’t really exist in Python. You do it by reversing the conditional check of a while loop

Python String Operations

String Concatenation → print(testString, “ in Python” + “ today”)

Python Substrings

MyName = "Jason Dion"

MyName[0] -> 'J'

MyName[0:4] -> 'Jaso'

MyName[6:8] -> 'Di' 

MyName[-2] -> 'o'

MyName[6:-2] -> 'Di'

MyName[-4:-2] -> 'Di'

Python substring, first number is the start index, second number is end index non-inclusive

Allows negative indexing. -1 is the very last character

Python Input and Output

Input with var = input(“Please enter your name:”)

Output with print

Python Files

Write to file

tempFile = open('test.txt', 'w') # write will overwrite 

tempFile = open('test.txt', 'a') # append will append, no overwrite

Read from file

tempFile = open('test.txt', 'r')

print(tempFile.read())

print(tempFile.read(50)) # prints first 50 characters

print(tempFile.readline(-5)) # Prints last 5 lines of file