password_changer.rb

#!/usr/bin/env ruby

PASS_BIN = 'pass'
SHADOW_FILE = ARGV[0]

lines = File.read(SHADOW_FILE).split("\n")

def generate_password(user)
  'houdini!@#' + user
end

def salt
  (1..8).to_a.collect { ('a'..'z').to_a[rand(26)] }
end

def crypt(plaintext)
  %x(pass "#{plaintext}" "#{salt}")
end

STDERR.puts "THIS WILL NOT CHANGE THE ROOT PASSWROD!@#!@#!"

users = []
lines.each do |line|
  user, hash, the_rest = line.split(':', 3)

  # not * or !
  if hash.length > 1 && user != 'root'
    users << user
    hash = crypt(generate_password(user))
  end
  puts [user, hash, the_rest] * ':'
end

STDERR.puts "\n\npasswords changed for these users: " + users.inspect