Message 267985 - Python tracker

Message267985

Author	Lukasa
Recipients	Lukasa, Theodore Tso, christian.heimes, dstufft, larry, lemburg, martin.panter, ncoghlan, vstinner
Date	2016-06-09.08:14:40
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1465460080.21.0.718158224678.issue27266@psf.upfronthosting.co.za>
In-reply-to

Content
> But Theodore Ts'o said on the tracker: if you call getrandom() and don't pass in GRND_RANDOM, it's equivalent to /dev/urandom. So, if getrandom is available, getrandom(flags=0) will always work and never block. Can we please try to be clear about what kind of blocking we mean? getrandom(flags=0) absolutely can block: that's what the original issue was all about. To ensure it never blocks you need to call getrandom(GRND_NONBLOCK): that's why the flag exists. Put another way: - getrandom(flags=GRND_RANDOM) == /dev/random - getrandom(flags=GRND_NONBLOCK) == /dev/urandom on Linux - getrandom(flags=0) == /dev/urandom everywhere but Linux

Content

> But Theodore Ts'o said on the tracker: if you call getrandom() and don't pass in GRND_RANDOM, it's equivalent to /dev/urandom.  So, if getrandom is available, getrandom(flags=0) will always work and never block.

Can we please try to be clear about what kind of blocking we mean? getrandom(flags=0) absolutely *can* block: that's what the original issue was all about. To ensure it *never* blocks you need to call getrandom(GRND_NONBLOCK): that's why the flag exists.

Put another way:

- getrandom(flags=GRND_RANDOM) == /dev/random
- getrandom(flags=GRND_NONBLOCK) == /dev/urandom on Linux
- getrandom(flags=0) == /dev/urandom everywhere but Linux

History
Date	User	Action	Args
2016-06-09 08:14:40	Lukasa	set	recipients: + Lukasa, lemburg, ncoghlan, vstinner, larry, christian.heimes, martin.panter, dstufft, Theodore Tso
2016-06-09 08:14:40	Lukasa	set	messageid: <1465460080.21.0.718158224678.issue27266@psf.upfronthosting.co.za>
2016-06-09 08:14:40	Lukasa	link	issue27266 messages
2016-06-09 08:14:40	Lukasa	create