Generating complex passwords in powershell

Occasionally I'm required to create a password for a user and have never bothered to get around to using a proper random generation system. I decided to check around for powershell examples of this. There is one good example on google that uses [System.Web.Security.Membership]::GeneratePassword(), but apparently I need to upgrade .NET framework everywhere to get that one to work. There are a few longer and so-so examples out there. I decided to whip together something of my own to avoid the use of certain characters, while giving some flexibility as to content and length.

#Generate password

#Requires -Version 2
Param(
 [parameter(mandatory=$false)][int]$length=8,
 [parameter(mandatory=$false)][switch][alias("u")]$upper,
 [parameter(mandatory=$false)][switch][alias("n")]$numeric,
 [parameter(mandatory=$false)][switch][alias("s")]$symbol,
 [parameter(mandatory=$false)][switch][alias("m")]$maxcomplexity
)

function get-digit {
 return (Get-Random -Minimum 0 -Maximum 10)
}

function get-letter([bool]$is_upper) {
 if ($is_upper) {
  $letter = [char](Get-Random -Minimum 65 -Maximum 91)
 } else {
  $letter = [char](get-random -minimum 97 -maximum 123)
 }
 return $letter 
}

function get-validsymbol([int]$set) {
 #get a symbol from the ASCII table, but skip using *, \, `, ", and '
 switch($set) {
  1 { $symbol = Get-Random -Minimum 33 -Maximum 48}
  2 { $symbol = Get-Random -Minimum 58 -Maximum 65}
  3 { $symbol = Get-Random -Minimum 91 -Maximum 97}
  4 { $symbol = Get-Random -Minimum 123 -Maximum 127}  
 }
 while($symbol -match "34|42|44|92|96") {
  $symbol = get-validsymbol $set
 }
 return $symbol
}

function get-symbol {
 $setnum = Get-Random -Minimum 1 -Maximum 5
 return ([char](get-validsymbol $setnum))
}

#main

#look at input parameters and generate available charset limits
$values = @()
if ($maxcomplexity) {
 $values = (1,2,3,4)
} else {
 $values += 1
 if ($upper) {
  $values += 2
 }
 if ($numeric) {
  $values += 3
 }
 if ($symbol) {
  $values += 4
 }
}
$values
Write-Host
$password = ""
for ($i = 0; $i -lt $length; $i++) {
 $set = Get-Random -Minimum 1 -Maximum ($values.length+1)
 $values[$set-1]
 switch ($values[$set-1]) {
  1 { $char = get-letter $false }
  2 { $char = get-letter $true }
  3 { $char = get-digit }
  4 { $char = get-symbol }
 }
 $password += $char
}
return $password


<#
.SYNOPSIS

generate-password.  Create a random password. 

.DESCRIPTION

Generate a random password which by default contains only lowercase letters.  Additionally
you can specify length, use of uppercase letters, numeric characters, and use of symbols.

.PARAMETER length

Length of the password

.PARAMETER upper

User upper case and lower case letters (alias u)

.PARAMETER numeric

Use numbers (alias n)

.PARAMETER symbol

Use symboles (alias s)

.PARAMETER Maxcomplexity

Use all forms of password complexity (alias m)

.EXAMPLE

generate-password

Create an 8 char password of lower case letters.

.EXAMPLE

generate-password -length 6 -m

Create a 6 char password with letters (upper/lower), numbers and symbols

#>