Make unpredictableSeed use getrandom (syscall) on Linux#10623
Make unpredictableSeed use getrandom (syscall) on Linux#10623dlang-bot merged 1 commit intodlang:masterfrom
unpredictableSeed use getrandom (syscall) on Linux#10623Conversation
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Thanks for your pull request, @0xEAB! Bugzilla referencesYour PR doesn't reference any Bugzilla issue. If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog. Testing this PR locallyIf you don't have a local development environment setup, you can use Digger to test this PR: dub run digger -- build "master + phobos#10623" |
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That function needs a warning. It is possible that the kernel may not have enough entropy stored to give a value. You want to call it sparingly and only after the system has been booted fully. |
I don’t think this is accurate.
And also:
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Yes, during booting it may be empty. Once initialized the chance of it to be empty depends upon if it has been misused. In any case, a warning is needed ;) |
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@rikkimax
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You have gone above and beyond what I was wanting! Good job. |
std/random.d
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| with $(D_PARAM unpredictableSeed) makes engines generate different | ||
| random number sequences every run. | ||
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| This function utilizes the system (CS-)PRNG where available and implemented |
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Use "(cryptographically secure) pseudo-random number generator" and introduce the acronym, and then use it throughout (rather than using the acronym first, and then spelling it out later).
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Updated to:
This function utilizes the system cryptographically-secure pseudo-random
number generator (CSPRNG) or pseudo-random number generator (PRNG)
where available and implemented (currentlyarc4randomon applicable BSD
systems orgetrandomon Linux) to generate “high quality” pseudo-random
numbers – if possible.
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You know what, I’ll take this chance that this hasn’t been merged yet to ask a question or propose a change here. |
| static assert(buffer.sizeof <= 256); | ||
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| const status = (() @trusted => getrandom(&buffer, buffer.sizeof, 0))(); | ||
| assert(status == buffer.sizeof); |
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- Are we fine that this assert might not make it into user code because of
-release? - Should we rather do
if (status != buffer.sizeof) { assert(false); }? - Should we rather do
if (status != buffer.sizeof) { return fallbackSeed(); }?
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Don't worry about it.
You get what you get when you use it.
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there is enforce for that. Is this optional by the way? so I can set it by a flag , 0, this, 1 getrandom, 2, something else kinda thing?
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Calling enforce() would make this nothrow @nogc function, well, throw and @gc.
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This function is just a way to generate a "good" seed for initializing random number engines – not a CSPRNG. (And if it were one, we definitely shouldn’t overengineer it. It could probably return an “optional”-type result then – but make it configurable – with options not applicable to all operating system –, rather nope. Also keep in mind, this thing has already been utilizing arc4random on applicable targets.)
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I think this caused a regression in 2.111: https://forum.dlang.org/post/dxgjgvfrlawgiajklzpm@forum.dlang.org |
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@dkorpel glibc 2.25 — that added |
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https://wiki.ubuntu.com/Releases If it's still being used, it's reasonable to say that we support it. |
The oldest freely available (i.e. non-ESM) version of Ubuntu is 20.04 which ships with glibc 2.31: https://packages.ubuntu.com/focal/libc-bin |
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The report on the newsgroup however was about OpenSUSE. |
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AFAICT both openSUSE Leap and Tumbleweed should come with new enough glibc versions 🤔 |
6 participants
This patch changes
unpredictableSeedto use thegetrandomsyscall on Linux.Currently,
unpredictableSeedcallsarc4random()on applicable BSD systems;for everything else it executes
RDRANDonInlineAsm_X86_Any-compatible targets or falls back to a homebrew solution.