[Python-ideas] Secure string disposal (maybe other inmutable seq types too?)

[Chris Angelico]

On Sat, Jun 23, 2018 at 2:00 PM, Terry Reedy <tjreedy at udel.edu> wrote:
> On 6/22/2018 8:45 PM, Chris Angelico wrote:
>
>> Would it suffice to flag the string as "this contains sensitive data,
>> please overwrite its buffer when it gets deallocated"? The only
>> difference, in your example, would be that the last print would show
>> the original data, and the wipe would happen afterwards. Advantages of
>> this approach include that getpass can automatically flag the string
>> as sensitive, and the "sensitive" flag can infect other strings (so
>> <<pwd + "x">> would be automatically flagged to be wiped). Downside:
>> You can't say "I'm done with this string, destroy it immediately".
>
>
> But one can be careful about creating references, and in current CPython,
> deleting the last reference does mean destroy, and possibly wipe,
> immediately.
>

Yes, you can, for the most part. It's certainly possible to get stung
(eg exceptions retaining locals), but mostly it should be fine.

How will other Pythons handle this?

ChrisA