Cross platform password generator

New-RandomPass.ps1

function New-RandomPass {
    <#
        .Synopsis
            Generates and returns a suitably secure password

            .EXAMPLE
            New-RandomPass

            Returns a random password as a SecureString object
            .EXAMPLE
            New-RandomPass -Length 128

            Returns a random password whose length is 128 characters as a SecureStringObject

            .EXAMPLE
            New-RandomPass -AsPlainText

            Returns a random password as plain text

    #>
    [CmdletBinding()]
    [OutputType([System.Security.SecureString])]
    param(
        [Parameter()]
        [ValidateRange(1, 128)]
        [int]$Length = 64,

        [Parameter()]
        [char[]]$AvailableCharacters = @(
            # Specifically excluding $, `, ;, #, etc such that pasting
            # passwords into support scripts will be more predictable.
            '!%()*+,-./<=>?@[\]^_'
            48..57   # 0-9
            65..90   # A-Z
            97..122  # a-z
        ).ForEach{ [char[]]$_ },

        [Parameter()]
        [Switch]
        $AsPlainText
    )
    end {
        $NewPassword = [System.Security.SecureString]::new()

        $cryptoRandom = [System.Security.Cryptography.RandomNumberGenerator]::Create()
        $bytes = [byte[]]::new(2)
        while ($NewPassword.Length -lt $Length) {
            $cryptoRandom.GetBytes($bytes)
            $index = [bitconverter]::ToUInt16($bytes, 0) % $AvailableCharacters.Count
            $NewPassword.AppendChar($AvailableCharacters[$index])
        }

        if ($AsPlainText) {
            [System.Net.NetworkCredential]::new($null, $NewPassword).Password
        } else {
            $NewPassword
        }
    }
}