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On 06/10/2016 11:55 AM, Donald Stufft wrote:

Ok, so you�re looking for how would you replicate the blocking behavior of os.urandom that exists in 3.5.0 and 3.5.1?

In that case, it�s hard. I don�t think linux provides any way to externally determine if /dev/urandom has been initialized or not. Probably the easiest thing to do would be to interface with the getrandom() function using a c-ext, CFFI, or ctypes. If you�re looking for a way of doing this without calling the getrandom() function.. I believe the answer is you can�t.

I'm certain you're correct: you can't perform any operation on /dev/urandom to determine whether or not the urandom device has been initialized.� That's one of the reasons why Mr. Ts'o added getrandom()--you can use it to test exactly that (getrandom(GRND\_NONBLOCK)).

That's also why I proposed adding os.getrandom() in 3.5.2, to make it possible to block until urandom was initialized (without using ctypes etc as you suggest).� However, none of the cryptography guys jumped up and said they wanted it, and in any case it was overruled by Guido, so we're not adding it to 3.5.2.

/arry