This might be a live debate on message boards, or on the wrong stack overflow boards --- though Pornin's answer[1] on this question is one of the all-time good Stack Overflow answers --- but among practitioners, this is long settled.
[1]: https://security.stackexchange.com/questions/3936/is-a-rand-...
> I don't think you're going to find too many cryptography engineers recommending that you use...the blocking variant of getrandom(2).
It depends on what you mean by "the blocking variant". To quote Cory Benfield:
> 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.
It may (or may not) surprise you to learn that PEP 524, which uses this (sometimes blocking) variant of getrandom, has been accepted.
Here's a discussion of the matter featuring several reputable, kickass security-minded python people discussing the matter and indeed endorsing the sometimes-blocking (flags=0) variant of getrandom:
https://bugs.python.org/issue27266
For full transparency: I read your post on this topic before I posted my question and found that, as far as I was able to read, it added nothing new to the public discourse on this topic. It does not seem to overcome the very real and well-sourced concerns raised by forest in his answer to my question.
Anyway, I'm not sure what you mean by "the wrong stack overflow boards" - can you tell me which are right and which are wrong?
The link which you've provided, which of course I had already read thoroughly, as I pointed out in my question, is not from Stack Overflow, but from Security StackExchange, just like my question.
I haven't yet marked an answer correct, so if you actually have something substantive to add that you think is better than forest's answer, it's possible that you can grab the check.
But, as far as I can tell - and I do indeed write with this in mind - the movement to create applications for very fresh, naive installations such as containers or IoT devices, does indeed present a problem for purely-blocking random.
My sense is that you and others in the community encouraging blind trust of /dev/urandom need to adjust your language when consulting on this matter in the future.
Since I mostly write python, I'm happy that this has been worked out and that python now uses blocking random (via getrandom(flags=0)) in these very rare situations.
No, this doesn't need to updated for IoT or "containers" (Linux containers share the KRNG).
Right. I'm glad to hear you phrasing it this way.
And listen: I don't mean to be flamy here, and it's possible that my sense of these things is tainted by our many... colorful discussions here on HN, but the unradom orthodoxy, to which getrandom and python's os.urandom are in part a response, is something for which you are arguably a tiny bit responsible, having actually written "Use urandom. Use urandom. Use urandom. Use urandom. Use urandom. Use urandom" on your blog. That kind of punditry has no place in security engineering.
There is a need for a degree of sobriety with these sorts of security considerations. Sometimes edge cases move toward the mainstream, and that's exactly what has happened with this odd little phenomenon of programs being executed much, much earlier in the OS lifecycle in the case of containerization and IoT devices.
Yes, some containers are deployed in settings where the host KRNG can be and is used. But not all. And many IoT devices suffer from a sufficiently weak set of entropy sources as to need to block.
These are real concerns, as identified by the study I linked from the University of Michigan. The researchers there were able to replicate over 1% of the SSH keys that they found in the wild because the devices that created them had insufficient entropy at the time of the key generation.
All I'm saying is: don't treat these sorts of security issues as subject to orthodoxy. Clear thinking and solid engineering are the orders of the day.
I don't see a link to a Michigan study in this thread. If you post it again, I'll be happy to explain why it doesn't say that you should use /dev/random, or a userspace RNG.
Good day.
Everything else you have to say just reads like word salad. I should be concerned about container RNGs, but not Linux containers, unless they're the Linux containers that don't share the KRNG? Or the IOT devices where blocking somehow solves the cold-start entropy problem, and at the same time can't be done in the init scripts? Even the Python issue thread you posted --- yes, I read it --- disagrees with you. I have no idea what you're talking about and, candidly, I don't know that you do either.
I've written (until now) perhaps 1 word on this thread for every 30 of yours, and I think my comments are straightforward and make obvious points. You respond to each of them with a wall of text. Can I suggest that maybe instead of a grand disagreement, you've instead just done a poor job communicating whatever your concern might be?
Regarding that last sentence of yours (er, the one before your "good day"): I am extremely comfortable with who does and doesn't find me credible. Thanks anyways.
As for community communication and understanding: I really don't think there's any good reason that we all have to lock horns all the time. I do think that you'll find more joy in these sorts of discussions if you can be less caustic and more deliberative. It's no more difficult to be nice than it is to be mean; give it a try. And if you get to the edge of your knowledge (and, it seems to me that you do, fairly frequently, which is great - you are obviously interested in a wide variety of societal topics just like I am), don't just keep marching. Stop and acknowledge your short-comings and recognize that there are others who might have had some original / compelling / correct thoughts on these matters also.
Again, this is no skin off my nose. My current project is python, and python has wisely decided to stop using urandom in favor of getrandom(flags=0), so this is a non-issue.
But won't it be nice if the next non-issue can be handled with greater ease and less toxicity?
> getrandom(...,0) isn't the blocking version of getrandom
As I have pointed out, and Cory pointed out in that thread - getrandom(flags=0) does block in the rare occasion that blocking is needed and at no subsequent time. That's all I said.
> nor is it equivalent to /dev/random
When did I say that is was? When did I ever even mention /dev/random?
You are the only one that keeps bringing up /dev/random. Instead of refactoring my statements and then taking a nugget of knowledge in an effort to disagree with me and win a point: read what I have actually written. Please. Just slow down a little.
I really don't want to argue with you any more. I do hope that you stop hammering the "use urandom use urandom use urandom waaaahh" thing, but I can't control you.
The right answer moving forward, for almost everyone, is getrandom, not urandom.
The truth is: before I opened that stackexchange question, I was only 90% sure. But now I'm confident I have the right answer. If I'm still wrong, then by all means correct me - you have a link to the open stackexchange question.
Python has done the right thing. So have other toolchains. As far as I can tell, everything is good. We can all just chill.
Wait a minute, you have made nasty insinuation after nasty insinuation in just about every single comment you've written on this thread and then sprinkled them liberally with finely ground condescension. That's where the toxicity is coming from.
But insinuation? I think I've been very clear and explicit about my criticisms rather than insinuating anything. Is there something about which I can be more transparent that will increase the quality of this and similar discussions?
I also don't mean to condescend, and I can understand from my writings how my tone might be interpreted that way. But what is the right thing to do in these situations? Discussions on HN of security and the political ramifications are dominated by the volume and aggression of this person and s73v3r_ and others of similar style, and it is taking a toll - people who are quiter but more knowledgeable (and to be clear: I'm not saying I'm either of those things) are being shut out. Can't you see it?
It reminds me of far-right AM radio. I don't want to find myself just tuning out of HN entirely, so I'm trying to be a little more proactive.
On the other hand, I certainly don't want to respond to vitriol with vitriol, but I do want to try to find common ground so we can all learn from each other instead of bark about who's right and who's wrong on these minuscule, mundane points.
Again: Although I think I've been quite explicit rather than lean on insinuation, I apologize for portions of my tone. I'm not a mean person; I'm just trying something new in an effort to change the direction of these things.