On 10.06.2016 21:17, Donald Stufft wrote:
On Jun 10, 2016, at 3:05 PM, David Mertz <me...@gnosis.cx
<mailto:me...@gnosis.cx>> wrote:
OK. My understanding is that Guido ruled out introducing an
os.getrandom() API in 3.5.2. But would you be happy if that
interface is added to 3.6?
It feels to me like the correct spelling in 3.6 should probably be
secrets.getrandom() or something related to that.
I am not a security expert but your reply makes it clear to me. So, for
me this makes:
os -> os-dependent and because of this varies from os to os (also
quality-wise)
random -> pseudo-random, but it works for most non-critical use-cases
secret -> that's for crypto
If don't need crypto, secret would be a waste of resources, but if you
need crypto, then os and random are unsafe. I think that's simple
enough. At least, I would understand it.
Just my 2 cents: if I need crypto, I would pay the price of blocking
rather then to get an exception (what are my alternatives? I need those
bits! ) or get unsecure bits.
Sven
Well we have
https://docs.python.org/dev/library/secrets.html#secrets.token_bytes so adding
a getrandom() function to secrets would largely be the same as that
function.
The problem of course is that the secrets library in 3.6 uses
os.urandom under the covers, so it’s security rests on the security of
os.urandom. To ensure that the secrets library is actually safe even
in early boot it’ll need to stop using os.urandom on Linux and use the
getrandom() function.
That same library exposes random.SystemRandom as secrets.SystemRandom
[1], and of course SystemRandom uses os.urandom too. So if we want
people to treat secrets.SystemRandom as “always secure” then it would
need to stop using os.urandom and start using the get random()
function on Linux as well.
[1] This is actually documented as "using the highest-quality sources
provided by the operating system” in the secrets documentation, and
I’d argue that it is not using the highest-quality source if it’s
reading from /dev/urandom or getrandom(GRD_NONBLOCK) on Linux systems
where getrandom() is available. Of course, it’s just an alias for
random.SystemRandom, and that is documented as using os.urandom.
—
Donald Stufft
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