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crypto/rand: use new Linux vDSO #69577

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FiloSottile opened this issue Sep 21, 2024 · 7 comments
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crypto/rand: use new Linux vDSO #69577

FiloSottile opened this issue Sep 21, 2024 · 7 comments
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@zx2c4
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FixPending Issues that have a fix which has not yet been reviewed or submitted. OS-Linux
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Go1.24

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@FiloSottile
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In Linux 6.11 @zx2c4 introduced a vDSO for the random number generator, which avoids the system call overhead of calling getrandom, similarly to how arc4random() works on the BSDs. The motivation is explained eloquently in the lkml patch set, but it boils down to "it would be nice to have the security of a kernel CSPRNG with the speed of a userspace CSPRNG" and indeed it would be nice if crypto/rand was so fast that no one ever reached for something else.

It was pulled in Linux 6.11 (released 2024-09-15) and Linux 6.12 will add arm64, powerpc64, powerpc32, s390x, and loongarch64 support. It doesn't seem to be documented in the kernel Documentation or in the man pages, but the patch set explains the API (and there's this LWN article, too).

I just finished mailing a chain of crypto/rand changes and I wanted to add this on top, but the vDSO mechanism is too deep in the runtime for me to feel confident wiring it in. If someone else (@ianlancetaylor maybe?) wanted to make the runtime changes to expose the vDSO function, happy to then do the crypto/rand ones.

/cc @golang/security
@FiloSottile FiloSottile added the NeedsFix The path to resolution is known, but the work has not been done. label Sep 21, 2024
@FiloSottile FiloSottile added this to the Backlog milestone Sep 21, 2024
@zx2c4
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zx2c4 commented Sep 21, 2024

I'll take a stab at it. I've got a bunch of Go backlog and this sounds like a good project to pull me back to it.

@gopherbot
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Change https://go.dev/cl/614835 mentions this issue: runtime: use vDSO for getrandom() on linux/amd64

@zx2c4
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zx2c4 commented Sep 22, 2024

Ok I did it.

@zx2c4 zx2c4 self-assigned this Sep 23, 2024
@zx2c4 zx2c4 added OS-Linux FixPending Issues that have a fix which has not yet been reviewed or submitted. and removed NeedsFix The path to resolution is known, but the work has not been done. labels Sep 23, 2024
@gopherbot
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Change https://go.dev/cl/615335 mentions this issue: unix: use vDSO for getrandom() on linux

gopherbot pushed a commit to golang/sys that referenced this issue Sep 28, 2024
@zx2c4
unix: use vDSO for getrandom() on linux
981de40 
With CL 614835 adding support in the runtime for calling into the
getrandom() vDSO function, wire up x/sys/unix's Getrandom() function to
it, so that callers can benefit from the increased speed and shared
vDSO state with the runtime.

Updates golang/go#69577.

Change-Id: I17734409982c51bb984a6337f4ffa8f60414ebee
Reviewed-on: https://go-review.googlesource.com/c/sys/+/615335
Reviewed-by: Michael Pratt <[email protected]>
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
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zx2c4 commented Sep 28, 2024

Alright, this all is now done, and everything should be wired up. I handled amd64, arm64, ppc64, loong64, and s390x. Please do remember to handle riscv in 3ish months for Linux 6.13 when that starts rolling.

@ericlagergren ericlagergren mentioned this issue Sep 28, 2024
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@dmitshur dmitshur modified the milestones: Backlog, Go1.24 Sep 28, 2024
@mateusz834 mateusz834 mentioned this issue Sep 30, 2024
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@gopherbot
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Change https://go.dev/cl/616795 mentions this issue: unix: mark vgetrandom as non-escaping

@mateusz834 mateusz834 mentioned this issue Sep 30, 2024
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@gopherbot
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Change https://go.dev/cl/616696 mentions this issue: runtime, internal/syscall/unix: mark getrandom vDSO as non-escaping

gopherbot pushed a commit that referenced this issue Sep 30, 2024
@mateusz834 @gopherbot
runtime, internal/syscall/unix: mark getrandom vDSO as non-escaping
ba10a38 
Updates #66779
Updates #69577

Change-Id: I0dea5a30aab87aaa443e7e6646c1d07aa865ac1c
GitHub-Last-Rev: 1cea46d
GitHub-Pull-Request: #69719
Reviewed-on: https://go-review.googlesource.com/c/go/+/616696
LUCI-TryBot-Result: Go LUCI <[email protected]>
Commit-Queue: Ian Lance Taylor <[email protected]>
Reviewed-by: Filippo Valsorda <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
gopherbot pushed a commit to golang/sys that referenced this issue Oct 1, 2024
@mateusz834 @gopherbot
unix: mark vgetrandom as non-escaping
23b0dab 
For golang/go#69577

Change-Id: Id1942d252c813126aa2f110e3f426714db73b9c7
GitHub-Last-Rev: 10e6a30
GitHub-Pull-Request: #220
Reviewed-on: https://go-review.googlesource.com/c/sys/+/616795
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Jason Donenfeld <[email protected]>
@The-King-of-Toasters The-King-of-Toasters mentioned this issue Oct 4, 2024
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