os.loadAPI("sha")

local passPath = "passwords" --Change this if you want a different password file

if not fs.exists(passPath) then --Create a password file
  local f = fs.open(passPath, "w")
  f.write(textutils.serialize({}))
  f.close()
end

local function secureInput( mask, prestring )
  local l = true
  term.setCursorBlink(true)
  local prestring = prestring or ""
  local str = ""
  local sx, sy = term.getCursorPos()
  while l do
        local e, a, b, c, d = os.pullEventRaw()
        if e == "char" then
          str = str .. a
        elseif e == "key" then
           if a == 14 then
                 str = str:sub(1, -2)
           elseif a == 28 then
                        l = false
                        term.setBackgroundColour( colours.black )
                        term.setTextColour( colours.white )
                        print()
                        return str
          end
        end
        term.setCursorPos(sx, sy)
        term.setBackgroundColour( colours.white )
        term.setTextColour( colours.black )
        term.clearLine()
        if mask then
          write( prestring .. " > " .. string.rep(mask, #str) )
        else
          write( prestring .. " > " .. str )
        end
  end
end

local function getPass( usr )
  local f = fs.open(passPath,"r")
  local pwds = textutils.unserialize( f.readAll() )
  f.close()
  if pwds[ usr ] then
         return pwds[ usr ]
  else
        return false
  end
end

local function login( usr, pwd )
  local info = getPass( usr )
  if info then
        if sha.sha256( pwd .. info.salt ) == info.pwd then
          return true
        else
          return false
        end
  else
        return false
  end
end

--Login script--
local loop = true
while loop do
  local username = secureInput( nil, "username" )
  local password = secureInput( "x", "password" )
  if login( username, password ) then
        print("Login successfull!")
        loop = false
        break
        --DO SOMETHING
  else
        print("Login failed.")
        --REMOVE these 2 lines below so that the loop continues after incorrect login, once proven program works.
        loop = false
        break
  end
end