PowerShell – Random Password Generator

Similar to C# – Random Password Generator but this will work with PowerShell scripts.

This script has a minimum of four (4) characters but you can change that to whatever you would like.

.\RandomPasswordGenerator.ps1 <Password Length>

<#
    .SYNOPSIS
        New-RandomPassword generates a random password
    .DESCRIPTION
        New-RandomPassword generates a random password that meets the following rules:
            A password:
                - Needs to have at least one of each of these:
                    1. Lower case character
                    2. Upper case character
                    3. Number
                    4. Special character
                - Has a certain length.
                - Needs a random amount of each of the required types in a random order.
    .PARAMETER Length
        Length of the password
    .EXAMPLE
        New-RandomPassword 8
    .INPUTS
        System.Int32
    .OUTPUTS
        System.String
#>
 
clear
 
function New-RandomPassword($PasswordLength)
    {
        # Length of the password to be generated
        #$PasswordLength = 20

        if($PasswordLength -lt 4) {$PasswordLength = 4}
         
        # Used to store an array of characters that can be used for the password
        $CharPool = New-Object System.Collections.ArrayList
 
        # Add characters a-z to the arraylist
        for ($index = 97; $index -le 122; $index++) { [Void]$CharPool.Add([char]$index) }
 
        # Add characters A-Z to the arraylist
        for ($index = 65; $index -le 90; $index++) { [Void]$CharPool.Add([Char]$index) }
 
        # Add digits 0-9 to the arraylist
        $CharPool.AddRange(@("0","1","2","3","4","5","6","7","8","9"))
         
        # Add a range of special characters to the arraylist
        $CharPool.AddRange(@("!","""","#","$","%","&","'","(",")","*","+","-",".","/",":",";","<","=",">","?","@","[","\","]","^","_","{","|","}","~","!"))
         
        $password=""
        $rand=New-Object System.Random
         
        # Generate password by appending a random value from the array list until desired length of password is reached
        1..$PasswordLength | foreach { $password = $password + $CharPool[$rand.Next(0,$CharPool.Count)] }   
         
        #print password
        $password
}
 
$pwdLengthArg = $args[0]
$runscript = 1
 
# Check Parameter Input - Start
if($pwdLengthArg -eq $null) {
    write-host "Error: Password Length is missing"
    $runscript = 0
}
# Check Parameter Input - Stop
 
# If $runscript = 0 show instructions
if (!($runscript -eq 1))
{    
    write-host "`n .\RandomPasswordGenerator.ps1 <Password Length>`n"
}
else
{
    New-RandomPassword $pwdLengthArg
}

Reference: http://www.wisesoft.co.uk/scripts/powershell_random_password_generator.aspx

Another approach

Function Get-RandomPassword {
  Param(
    [parameter()]
    [ValidateRange(8,100)]
    [int]$Length=12,
 
    [parameter()]
    [switch]$SpecialChars
 
  )
    $aUpper      = [char[]]'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    $aLower      = [char[]]'abcdefghijklmnopqrstuvwxyz'
    $aNumber     = [char[]]'1234567890'
    $aSCharacter = [char[]]'!@#$%^&*()_+|~-=\{}[]:;<>,./' # Depending on usage, you may want to strip out some of the special characters if they are not supported
    $aClasses    = [char[]]'ULN' #represents the different classes of characters
    $thePass     = ""
    if ($SpecialChars){
        $aClasses += 'S'
    }
    $notOneOfEach = $true
    while ($notOneOfEach){
        $pPattern = ''
        for ($i=0; $i-lt $Length; $i++){
            $pPattern += get-random -InputObject $aClasses
        }
        if (($pPattern -match 'U' -and $pPattern -match 'L' -and $pPattern -match 'N' -and (-not $specialChars)) -or ($pPattern -match 'U' -and $pPattern -match 'L' -and $pPattern -match 'N' -and $pPattern -match 'S')){
            $notOneOfEach = $false
        }
    }
    foreach ($chr in [char[]]$pPattern){
        switch ($chr){
            U {$thePass += get-random -InputObject $aUpper; break}
            L {$thePass += get-random -InputObject $aLower; break}
            N {$thePass += get-random -InputObject $aNumber; break}
            S {$thePass += get-random -InputObject $aSCharacter; break}
        }
    }
    $thePass
}
 
clear
 
for ($i=0; $i -le 20; $i++){Get-RandomPassword -length 16}

Reference: http://poshcode.org/5806