From: shyouhei@... Date: 2018-08-29T08:41:13+00:00 Subject: [ruby-core:88727] [Ruby trunk Bug#15039] Random.urandom and SecureRandom arc4random use Issue #15039 has been updated by shyouhei (Shyouhei Urabe). Freaky (Thomas Hurst) wrote: > > Or is it not about the code quality in general? Maybe the problem here is that having _any_ bits of instructions in a userland? > > It's a mix of the two, and it might be worth separating the issues. > > One is that arc4random() is pretty much only sensibly implemented on OpenBSD, as far as I know, and its use should probably be limited to that and maybe other platforms where it's *confirmed* to be not-awful. Hmm, OK. I respect your feeling that the arc4random() in FreeBSD (up to 11) is questionable. +1 to avoid using such implementation(s). > The other is clarifying the intent of `Random.urandom` and the priorities of `SecureRandom`. Following #9569, *are* they meant to be avoiding using userspace CSPRNGs? They do so on Linux and Windows, but don't on platforms with arc4random(). As far as I understand Random.urandom intends to be cryptographically secure; nothing more. My attempt when fixing #9569 was that arc4random() supposedly adequately fulfilled this property like OpenBSD's. I did not see any reason to reject such thing. Maybe is it getting hard for a "userspace CSPRNG" in general to make sense these days? That is a possible situation and I have to change my mind then. ---------------------------------------- Bug #15039: Random.urandom and SecureRandom arc4random use https://bugs.ruby-lang.org/issues/15039#change-73781 * Author: Freaky (Thomas Hurst) * Status: Open * Priority: Normal * Assignee: * Target version: * ruby -v: * Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN ---------------------------------------- Random.urandom defaults to arc4random() on a lot of platforms, including FreeBSD. On all currently released versions of FreeBSD, arc4random() is, as the name suggests, a dubious ARC4-based userspace PRNG dating from circa 1997. Given the entire point of #9569 was that using the userspace CSPRNG in OpenSSL over /dev/urandom or equivalent is a bad idea, this seems to mean it's regressed to an *even worse* state on these platforms. Even in cases where it's using something more modern (FreeBSD 12, OpenBSD), it's still a userspace CSPRNG. If that's fine, we might as well *pick a known-good one* and use that everywhere. Like, say, OpenSSL's. Since the conclusion of #9569 seems to have been otherwise, I'd suggest dropping arc4random() as a potential source for Random.urandom due to it not matching the desired semantics. Rust's OsRng seems a good template for alternative _syscall implementations: https://docs.rs/rand/0.5.5/rand/rngs/struct.OsRng.html#platform-sources -- https://bugs.ruby-lang.org/ Unsubscribe: