11 replies to this topic

[tesla1889]

I used string.dump on a function and wrote that dump into a file. When i use loadstring on the contents of the file, it gives me a function. The problem occurs when i try to use that function. I get the error "invalid object." How do you read bytecode from a file and turn it into a function?

local f = fs.open("/file","r")
if not f then
return
end
local fn = loadstring(f.readAll())
f.close()
fn() -- the error is here

[Lyqyd]

If you're using string.dump, you really should be using binary mode file operations (wb and rb for write and read, respectively). It's possible that non-binary mode usage is screwing up your function string.

[tesla1889]

thanks, i'll try that and post the results

[tesla1889]

if a file is opened in binary read mode, it only reads one byte at a time and returns the integer, so how do i reconstruct the dump of the function?

[MysticT]

You can read a byte and concatenate it to the string with string.char:

local file = fs.open("path/to/file", "rb")
if file then
  local s = ""
  local b = file.read()
  while b do
	s = s..string.char(:D/>/>
	b = file.read()
  end
  file.close()
  local f = loadstring(s)
  if f then
	f()
  end
end

[tesla1889]

still didnt work. the function comes up nil.

[MysticT]

Are you writing it to the file as binary?
Like this:

local s = string.dump(someFunction)
local file = fs.open("path", "wb")
if file then
  for i = 1, #s do
    file.write(string.byte(i))
  end
  file.close()
end

[ChunLing]

Okay, why are you doing this? I mean, you already have the working function, right?

[tesla1889]

its closed source. i wanted a way to hide security features in my work, and the only way to do that is closed source

[Orwell]

You should google 'Security by obscurity' /> if it's secure, then it shouldn't matter that people can see the code. also there are some decompilers for Lua 5.1 . So they can see it anyways.

(off-topic: in your signature: rs.setRedstone( ) is no valid CC function? )

[remiX]

Orwell, on 28 October 2012 - 05:48 AM, said:

(off-topic: in your signature: rs.setRedstone( ) is no valid CC function? )

I think he meant rs.setOutput()

[ChunLing]

Like others say, if you can use loadstring on it, then others can see the code in a form that they'll be able to figure out how it works and what the vulnerabilities are. loadstring is not the right tool for this job.