[Python-Dev] BDFL ruling request: should we block forever waiting for high-quality random bits?

David Mertz mertz at gnosis.cx
Thu Jun 16 13:01:00 EDT 2016

On Thu, Jun 16, 2016 at 11:58 AM, Nathaniel Smith <njs at pobox.com> wrote:

> [...] no one else be able to predict what session cookie I sent [...] In
> python 2.3-3.5, the most correct way to write this code is to use
> os.urandom. The question in this thread is whether we should break that in
> 3.6, so that conscientious users are forced to switch existing code over to
> using the secrets module if they want to continue to get the most correct
> available behavior, or whether we should preserve that in 3.6, so that code
> like my hypothetical web app that was correct on 2.3-3.5 remains correct on
> 3.6
This is kinda silly.  Unless you specifically wrote your code for Python
3.5.1, and NOT for 2.3.x through 3.4.x, your code is NO WORSE in 3.5.2 than
it has been under all those prior versions.  The cases where the behavior
in everything other than 3.5.0-3.5.1 is suboptimal are *extremely limited*,
as you understand (things that run in Python very early in the boot
process, and only on recent versions of Linux, no other OS).  This does not
even remotely describe the web-server-with-cookies example that you outline.

Python 3.6 is introducing a NEW MODULE, with new APIs.  The 'secrets'
module is the very first time that Python has ever really explicitly
addressed cryptography in the standard library.  Yes, there have been
third-party modules and libraries, but any cryptographic application of
Python prior to 'secrets' is very much roll-your-own and

Yes, there has been a history of telling people to "use os.urandom()" on
StackOverflow and places like that.  That's about the best advice that was
available prior to 3.6.  Adding a new module and API is specifically
designed to allow for a better answer, otherwise there'd be no reason to
include it.  And that advice that's been on StackOverflow and wherever has
been subject to the narrow, edge-case flaw we've discussed here for at
least a decade without anyone noticing or caring.

It seems to me that backporting 'secrets' and putting it on Warehouse would
be a lot more productive than complaining about 3.5.2 reverting to (almost)
the behavior of 2.3-3.4.

Keeping medicines from the bloodstreams of the sick; food
from the bellies of the hungry; books from the hands of the
uneducated; technology from the underdeveloped; and putting
advocates of freedom in prisons.  Intellectual property is
to the 21st century what the slave trade was to the 16th.
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