Re: [pygame] From * import * and Pygame2exe

[Andre Roberge <andre.roberge@xxxxxxxxx>]

On 7/20/05, Sami Hangaslammi <sami.hangaslammi@xxxxxxxxx> wrote:
> On 7/20/05, andrew baker <failrate@xxxxxxxxx> wrote:
> > Well, I was also thinking about running a validator somewhere in there
> > that would only allow a specific set of commands for the level
> > modules.  For example, no one should be executing file operations or
> > sys commands from within a level logic block.  In fact, they should
> > only be doing namespace data operations, comparisons and iterations.
> 
> You probably already know this, but it's fiendishly difficult to
> validate Python code like that if you are using the builtin compiler.
> The new Pythons don't have any builtin restricted execution tools
> anymore and plain string/regexp matching will probably let something
> slip (there are so many different ways to e.g. get reference to the
> os.system function).
> 
> The most realistic options are probably analyzing the abstract syntax
> tree or the compiled bytecodes. I've personally used bytecodes to
> validate untrusted Python expressions by restricting the allowed
> bytecodes to very basic operations (settings variable values mainly)
> and by restricting values for specific bytecodes (e.g. you could
> restrict the LOAD_NAME bytecode to only work on a handful of
> predefined names).
> 
> --
> Sami Hangaslammi
> 
How about doing something like the following:

def isFileSafe(file_to_import):
....unsafe = "".join(contents)
....unsafe = unsafe.replace("(", " (")
....unsafe = unsafe.split()
....bad_keywords = ["chr", "exec", "eval", "input", "raw_input",
"import", "file", "open"]
....for word in bad_keywords:
........if word in safe_list:
............return False
....return True

[add in a regular expression search for any "magic" python "word" of the form
__aName__, i.e. lead and followed by two underscores -- something I can't do on 
the spot :-(]

and only allow importing levels (through execfile()) if it's deemed to be safe?

André