[Python-ideas] Fwd: Re: Secure unpickle

[Eric V. Smith]

On 07/23/2015 09:54 AM, Neil Girdhar wrote:
> 
> 
> On Wed, Jul 22, 2015 at 9:46 PM, Nathaniel Smith <njs at pobox.com
> <mailto:njs at pobox.com>> wrote:
> 
>     On Wed, Jul 22, 2015 at 5:27 PM, Neil Girdhar <mistersheik at gmail.com
>     <mailto:mistersheik at gmail.com>> wrote:
>     >
>     > That is so unfortunate.  Pickle is such a good solution except for the
>     > security.  Why can't we have security too?  It doesn't seem to me to be
>     > right for a project like matplotlib to be writing their own serialization
>     > library.  It would be awesome if Python had secure serialization built-in.
> 
>     The reason you can pickle/unpickle arbitrary Python objects is that
>     the pickle format is basically a structured, optimized way of
>     generating and then evaluating arbitrary Python code. Which is great
>     because it's totally general -- that's why we love pickle, you can
>     pickle anything -- but that exact feature is what makes it insecure.
>     If you want to make something secure, that means making some explicit
>     decisions about what kinds of things can be put into your data format
>     and which cannot, and write some explicit code to handle each of these
>     things instead of just handing the file format direct access to your
>     interpreter. But by the time you've done that you've done the hard
>     part of implementing a new format anyway...
> 
> 
> Wouldn't it be easier to just tell unpickle which code it's allowed to
> run (by passing a list of modules and classes)?  

unpickle can already do that, via Unpickler.find_class. There's an
example in the docs.

Eric.