[Python-ideas] Any chance on (slowly) deprecating `eval` and `exec` as builtins?
rosuav at gmail.com
Tue Nov 7 15:59:02 EST 2017
On Wed, Nov 8, 2017 at 7:33 AM, Chris Barker <chris.barker at noaa.gov> wrote:
> On Tue, Nov 7, 2017 at 6:41 AM, Steven D'Aprano <steve at pearwood.info> wrote:
>> In any case, I think that securing literal_eval is much simpler than
>> securing eval:
>> # a thousand character expression ought to be enough for
>> # any legitimate purpose...
>> value = literal_eval(tainted_string[:1000]) # untested
>> except MemoryError:
>> value = None
> sure -- though I'd use a lot more than 1000 characters -- not much these
> days, and you might want to unpack something like a JSON data package...
That's the trouble, though. It's perfectly safe to literal_eval a
large amount of well-formed data (say, a dict display with simple keys
and good-sized strings as values), but you can cause major problems by
literal_evalling a relatively small amount of malicious data (eg
"["*100 bombs out with MemoryError, and I wouldn't trust that there
isn't something far worse). If you're working with untrusted data, you
probably should be using json.loads rather than ast.literal_eval.
-1 on hiding eval/exec; these features exist in many languages, and
they're identically dangerous everywhere. Basically, use eval only
with text from the owner of the system, not from anyone untrusted.
More information about the Python-ideas