[issue26839] Python 3.5 running on Linux kernel 3.17+ can block at startup or on importing the random module on getrandom()

[STINNER Victor]

STINNER Victor added the comment:

I spent almost my whole day to read this issue, some related issues, and some more related links. WOW! Amazing discussing. Sorry that Christian decided to quit the discussion (twice) :-(

Here is my summary: http://haypo-notes.readthedocs.io/pep_random.html

tl; dr "The issue is to find a solution to not block Python startup on such case, and keep getrandom() enhancement for os.urandom()."

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Status of Python 3.5.2: http://haypo-notes.readthedocs.io/pep_random.html#status-of-python-3-5-2

My summary: "With the changeset 9de508dc4837: Python doesn’t block at startup anymore (issues #25420 and #26839 are fixed) and os.urandom() is as secure as Python 2.7, Python 3.4 and any application reading /dev/urandom."

=> STOP! don't touch anything, it's now fine ;-) (but maybe follow my link for more information)

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To *enhance* os.urandom(), always use getrandom() syscall on Linux, I opened the issue #27266. I changed the title to "Always use getrandom() in os.random() on Linux and add block=False parameter to os.urandom()" to make my intent more explicit.

As some of you have already noticed, it's not easy to implement this issue! There are technical issues to implement os.urandom(block=False).

In fact, this issue tries to fix two different but close issues:

(a) Always use getrandom() for os.urandom() on Linux
(b) Implement os.urandom(block=False) on *all* platforms

The requirement for (a) is to not reopen the bug #25420 (block on "import random"). dstufft proposed no-urandom-by-default.diff (attached to this issue), but IMHO it makes the random module worse than before. I proposed (b) as the correct fix. It's a work-in-progress, please come on the issue #27266 to help me!

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Please contact me if we want to fix/enhance my doc http://haypo-notes.readthedocs.io/pep_random.html

Right now, I'm not interested to convert this summary to a real PEP. It looks like you agree on solutions. We should now invest our time on solutions rather than listing again all issues ;-)

I know that it's really hard, but I suggest to abandon this issue (since, again, it's closed!), and focus on more specific issues and work on fixing issues. No? What do you think?

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IMHO The problem in this discussion is that it started with a very well defined issue (Python blocks at startup on Debian Testing in a script started by systemd when running in a VM) to a wide discussion about all RNG, all kinds of issues related to RNG and a little bit to security in general.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26839>
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