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

[Colm Buckley]

Colm Buckley added the comment:

To clarify what the various patches do:

3.5.1 as released: os.urandom and hash secret initialization both attempt getrandom() in preference to reading /dev/urandom. Under certain circumstances, this will block, possibly indefinitely.

Changeset 9de508dc4837: both os.urandom and hash secret initialization call getrandom() in nonblocking mode, falling back to (possibly low-entropy) /dev/urandom should getrandom() block due to lack of entropy.

Changeset 9de508dc4837 + nonblocking_urandom_noraise.patch: hash secret initialization calls getrandom() in nonblocking mode (ie: will always succeed, although with a silent fallback to low-entropy data if called when the system has no entropy). os.urandom will always block until there's enough entropy.

I think this final case implements what you need for the 3.5.2 RC.

The issue of "import random" still needs to be resolved; maybe we should de-merge #25420 and pursue Donald's approach there.

Thanks,

Colm

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