`load` / `loadfile` lua functions can load arbitrary bytecode
kyren opened this issue · 5 comments
AIUI this can be used to cause the interpreter to exhibit UB.
load and loadfile need to be wrapped so that the mode flag does not do anything, but unlike pcall / xpcall wrapping, this really seems to break the API of those functions.
There has to be the ability to turn these wrappers off, just like there is the ability to force load the debug library, and similarly it will have to be behind an unsafe flag.
The load and loadfile wrappers shouldn't be too bad, and configuring them could be as simple as adding a flag to StdLib that disables wrapping load / loadfile, though that breaks the StdLib <=> 'library' equivalence.
Probably this has to be a new 0.x version bump as well 😞
Also package.loadlib allows a script to load a C library, which is also really unsafe.
Am I missing any more?
I wonder if dofile will execute bytecode?
Okay, here is a list of everything that I think is potentially unsafe, some of it may simply have to be not loaded at all. Currently only debug is guarded against:
- dofile
- load
- loadfile
- os.setlocale (thread unsafety?)
- package.loadlib
- os.date (maybe, might be fixed in 5.2, might be considered a bug)
- debug (okay, technically some of debug might be safe, but is of questionable use by itself)
- package.cpath (can be used to influence
requireto load C libraries, withoutpackage.cpath, none of the default searchers inpackage.searchersshould be able to find and load a C library
It might be simpler to set package.cpath to "" and disallow package.* entirely, as package.cpath should not be allowed to be set at all. Without setting package.cpath to empty string, require becomes unsafe.