do
 _G.userlib = {}
 local ut = {}
 function userlib.users()
  local t = {}
  for k,v in pairs(ut) do
   t[#t+1] = k
  end
  return t
 end
 function userlib.verify(username,pass)
  if ut[username] then
   if sha.sha256(pass..ut[username][2]) == ut[username][1] then
    return true
   end
  end
  return false
 end
 function userlib.gensalt(len)
  local S = ""
  for i = 1, len do
   S=S..string.char(math.random(32,126))
  end
  return S
 end
 function userlib.setuser(username,hpass,salt,...)
  ut[username] = {hpass, salt,...}
 end
 function userlib.deluser(username)
  ut[username] = nil
 end
 function userlib.readpwd(path)
  local f=io.open(path,"rb")
  if not f then return false end
  local C=f:read("*a")
  for line in C:gmatch("[^\n]+") do
   local username,hpass,salt = line:match("(.+)\t(.+)\t(.+)")
   log(username,hpass,salt)
   if username and hpass and salt then
    ut[username] = {hpass,salt}
   end
  end
 end
 function userlib.writepwd()
  local S=""
  for k,v in pairs(ut) do
   S=S..k.."\t"..v[1].."\t"..v[2].."\n"
  end
  return S
 end
 function userlib.write(path)
  local f=io.open(path,"wb")
  if not f then return false end
  f:write(userlib.writepwd())
  f:close()
 end
 spawn("load users",function() userlib.readpwd("/boot/sys/users.dat") end)
end