Generate Complex Passwords with PowerShell

# Sample Program to demonstrate useage of the GenPwd function call
#
# September 12, 2011
# Courtesy of xb90@PoshTips.com
#
# Visit http://poshtips.com for more FREE PowerShell scripts!
#
# To Add this to YOUR script, include:
# (1) The system.web assembly (add this somewhere in your script
#     where it will only get called once
# (2) The GenPwd function
#
# That's all there is to it. Passwords will be 8 characters long;
# change the $pwdLen variable if you want a different length.
#
# The system.web.generatepassword call will guarantee that at least
# one "special" non-alphanumeric character is used but does not guarantee
# anthing more.
# To ensure other complexities are present, we test the new password
# against a regular expression that tests for:
# (1) at least one uppercase character
# (2) at least one lowercase character
# (3) at least one numeric character
# If the generated password doesn't match the regular expression,
# we keep retrying until it does.
#
# Sort of crude, but effective and regenerating passwords is very quick
#
 
[Reflection.Assembly]::LoadWithPartialName(“System.Web”) | out-null
 
function GenPwd {
    param ([int]$pwdLen=8,
           [switch]$TestMode=$false,
           [string]$TestModeNote="")
    $pwd = ""
    $pwdOk = $false
    $tries = 0
    do {
        $tries+=1
        $pwd = [System.Web.Security.Membership]::GeneratePassword($pwdLen,1)
        $pwdOk = ($pwd -match "^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{$pwdLen,$pwdLen}$")
        } until ($pwdOk)
    if ($testMode){
        # TestMode will display the following
        # 1. Content of $TestModeNote (this could be a counter, hostname, or whatever (including nothing)
        # 2. The generated password
        # 3. Number of tries it took for the GeneratePassword method to create a qualifying password
        # 4. A series of "X"'s to give a quick graphic representation of the number of tries
        write-host ("{0} : {1} : {2} {3}" -f $TestModeNote,$pwd,$tries,$("".padright($tries,"X")))
        }
    else {
        # return the password
        $pwd
        }
    }
 
#PASS 1: Run 10 iterations in TestMode
write-host "`nTest Mode:`n"
for ($i=1; $i -le 10; $i++){
    GenPwd -PwdLen 8 -TestMode $true -TestModeNote ([string]$i).padleft(2," ")
    }
write-host "`n`nReal Mode:`n"
#Pass 2: Run 10 iterations in "real" mode, and let function return values print to standard output
for ($i=1; $i -le 10; $i++){
    GenPwd
    #Note, I could also capture output as follows
    # $password = GenPwd
    }