Terminate-safe DoubleLock

-- Takes a table of passwords and checks them against user input.
-- Returns 'true' if all passwords were entered correctly.
-- Returns 'false' on first wrong input.
function checkPasswords( _tPasswordList )
  -- Make sure we got a table, throw an error otherwise.
  if type( _tPasswordList ) ~= "table" then
	error( "Table expected, got "..type( _tPasswordList ).."." )
  end

  -- Iterate through all passwords in the table and compare them to the user input.
  for n = 1, #_tPasswordList do
	write( "Password #"..n..": " )
	local sInput = read( "*" )
	
	-- As soon as one password is entered incorrectly we immediately return false.
	if sInput ~= _tPasswordList[n] then
	  return false
	end
  end

  -- If we come to this point then all passwords have been entered correctly.
  return true
end

local tPasswords = { "secret", "letmein" }	-- Put your passwords in here.

local nativePullEvent = os.pullEvent	-- Backup os.pullEvent
os.pullEvent = os.pullEventRaw  -- Overwrite os.pullEvent with os.pullEventRaw
local ok, result = pcall( checkPasswords, tPasswords )
os.pullEvent = nativePullEvent  -- Restore os.pullEvent

if not ok then
  -- If ok is 'false' then checkPasswords threw an error and thus result will contain the error message.
  error( result )
elseif result then  -- If ok was 'true' then there was no error. That means we can now check result, which will contain either 'true' or 'false'.
  print( "nAll entered passwords were correct. B)/>/>" )
else
  print( "nWrong password entered! B)/>/>" )
end

local nativePullEvent = os.pullEvent	-- Backup os.pullEvent
os.pullEvent = os.pullEventRaw  -- Overwrite os.pullEvent with os.pullEventRaw
-- Do something
os.pullEvent = nativePullEvent  -- Restore os.pullEvent

Espen, on 02 March 2012 - 01:54 PM said:

As an example of how to use that code & how you can make read() - or any other function that makes use of os.pullEvent() - use os.pullEventRaw() instead of os.pullEvent(), add this code to the above (add it after the function!):

local nativePullEvent = os.pullEvent	-- Backup os.pullEvent
os.pullEvent = os.pullEventRaw  -- Overwrite os.pullEvent with os.pullEventRaw
-- Do something
os.pullEvent = nativePullEvent  -- Restore os.pullEvent

They backup the os.pullEvent function and overwrite it with os.pullEventRaw, the latter which won't listen for the 'terminate' event that e.g. CTRL+T produces. After it has fulfilled its purpose I restore it, or else os.pullEvent would stay os.pullEventRaw for all other programs as well! ^{At least until the next reboot.}
This is because we overwrite a global variable in order to make read() or sleep() not stop at CTRL+T.

Instead of doing it this way you could just as well copy the read() function out of the 'bios.lua', replace the os.pullEvent call there with an os.pullEventRaw call. That might be a lot safer, but then you'd have an additional, big function to which only three letters have been added (namely: Raw ).
It's entirely up to you.

There are many ways to skin a cat, right? :unsure:/>/>

EDIT: Clarified the comment in the code line 'elseif result then'.

local pass = "test1"
local pass2 = "test2"

term.clear()
term.setCursorPos(1,1)

-- Start program and first password chek
print("Welcome to jdpowercool's double lock system!")
print("===============================================")
write("Enter your password: ")
local state,input = pcall(read,"*") -- Pet peeve is password readers not starring the input, security risks and all
if (input == pass) then
	print("Access granted.")
	state = pcall(sleep,1)
	term.clear()
	term.setCursorPos(1,1)
else
	term.clear()
	term.setCursorPos(1,1)
	print("Wrong password.  Locking computer for 15 seconds..")
	state = pcall(sleep,15)
	os.shutdown()
end

--Start second password check
write("Enter the second password. ")
state, input = pcall(read,"*")
term.clear()
term.setCursorPos(1,1)
if (input == pass2) then
	print("Welcome!")
	rs.setOutput("left",true)
	state = pcall(sleep,2)
	rs.setOutput("left",false)
	state = pcall(sleep,1)
	os.shutdown()	
else
	print("Access Denied")
	state = pcall(sleep,2)
	os.shutdown()
end

Liraal, on 02 March 2012 - 06:17 PM said:

local is for creating a variable accessible only from within the function so that they don't mess up all your code by turning up where you'd least expect them. Just use local, okay? :unsure:/>/>

Shade25, on 02 March 2012 - 05:22 PM said:

Would another option besides overwriting base code be essentially just to run his sleep calls (since he already has his read calls going through pcall) through pcall as well?

while true do
	local ok, errMsg = pcall( sleep, 10 )
	print("Hello World")
end

function sleep( _nTime )
	local timer = os.startTimer( _nTime )
	repeat
		local sEvent, param = os.pullEvent( "timer" )
	until param == timer
end

function sleep( _nTime )
	local timer = os.startTimer( _nTime )
	repeat
		local sEvent, param = os.pullEventRaw( "timer" )
	until param == timer
end

while true do
	sleep( 10 )
	print("Hello World")
end

Espen, on 02 March 2012 - 01:54 PM said:

Instead of doing it this way you could just as well copy the read() function out of the 'bios.lua', replace the os.pullEvent call there with an os.pullEventRaw call. That might be a lot safer, but then you'd have an additional, big function to which only three letters have been added (namely: Raw ).
It's entirely up to you.

elcid534, on 15 March 2012 - 12:33 PM said:

Espen, on 02 March 2012 - 01:54 PM said:

Instead of doing it this way you could just as well copy the read() function out of the 'bios.lua', replace the os.pullEvent call there with an os.pullEventRaw call. That might be a lot safer, but then you'd have an additional, big function to which only three letters have been added (namely: Raw ).
It's entirely up to you.

now i'm no lua programmer but what if you created a copy of Read() then modify it to use os.pullEventRaw and call it ReadRaw()?
then you don't need to add the four lines of code to any lock on you minecraft/server. just have to call ReadRaw().
also possible api here called antiTerminate api that just adds the ReadRaw without modding the bios.
if someone is going to do that(because i suck at lua) plz just add my name somewhere in it.

edit: also create a SleepRaw() program

os.pullEvent = os.pullEventRaw
-- Copy this EXACTLY, and you will be protected
-- I always use this and it saves lots of time