go/src/runtime/metrics/doc.go, branch fix-runtime-test-GOMAXPROCS

cmd/go: disable support for multiple vcs in one module

2025-07-08T18:30:38Z

Removes the somewhat redundant vcs.FromDir, "allowNesting" argument, which was always enabled, and disallow multiple VCS metadata folders being present in a single directory. This makes VCS injection attacks much more difficult. Also adds a GODEBUG, allowmultiplevcs, which re-enables this behavior. Thanks to RyotaK (https://ryotak.net) of GMO Flatt Security Inc for reporting this issue. Fixes #74380 Fixes CVE-2025-4674 Change-Id: I5787d90cdca8deb3aca6f154efb627df1e7d2789 Reviewed-on: https://go-review.googlesource.com/c/go/+/686515 LUCI-TryBot-Result: Go LUCI Reviewed-by: David Chase Commit-Queue: Carlos Amedee Reviewed-by: Carlos Amedee

crypto/x509: use truncated SHA-256 for SubjectKeyId

2025-05-21T22:09:45Z

Fixes #71746 Change-Id: I6a6a46568b092933d8ac2039df99ee9f0edf6e56 Reviewed-on: https://go-review.googlesource.com/c/go/+/674477 Reviewed-by: Daniel McCarney Reviewed-by: David Chase Reviewed-by: Roland Shoemaker Auto-Submit: Filippo Valsorda LUCI-TryBot-Result: Go LUCI

crypto/tls: disable SHA-1 signature algorithms in TLS 1.2

2025-05-21T22:09:29Z

This implements RFC 9155 by removing support for SHA-1 algorithms: - we don't advertise them in ClientHello and CertificateRequest (where supportedSignatureAlgorithms is used directly) - we don't select them in our ServerKeyExchange and CertificateVerify (where supportedSignatureAlgorithms filters signatureSchemesForCertificate) - we reject them in the peer's ServerKeyExchange and CertificateVerify (where we check against the algorithms we advertised in ClientHello and CertificateRequest) Fixes #72883 Change-Id: I6a6a4656e2aafd2c38cdd32090d3d8a9a8047818 Reviewed-on: https://go-review.googlesource.com/c/go/+/658216 LUCI-TryBot-Result: Go LUCI Auto-Submit: Filippo Valsorda Reviewed-by: David Chase Reviewed-by: Roland Shoemaker Reviewed-by: Daniel McCarney

runtime: use cgroup CPU limit to set GOMAXPROCS

2025-05-21T17:21:55Z

This CL adds two related features enabled by default via compatibility GODEBUGs containermaxprocs and updatemaxprocs. On Linux, containermaxprocs makes the Go runtime consider cgroup CPU bandwidth limits (quota/period) when setting GOMAXPROCS. If the cgroup limit is lower than the number of logical CPUs available, then the cgroup limit takes precedence. On all OSes, updatemaxprocs makes the Go runtime periodically recalculate the default GOMAXPROCS value and update GOMAXPROCS if it has changed. If GOMAXPROCS is set manually, this update does not occur. This is intended primarily to detect changes to cgroup limits, but it applies on all OSes because the CPU affinity mask can change as well. The runtime only considers the limit in the leaf cgroup (the one that actually contains the process), caching the CPU limit file descriptor(s), which are periodically reread for updates. This is a small departure from the original proposed design. It will not consider limits of parent cgroups (which may be lower than the leaf), and it will not detection cgroup migration after process start. We can consider changing this in the future, but the simpler approach is less invasive; less risk to packages that have some awareness of runtime internals. e.g., if the runtime periodically opens new files during execution, file descriptor leak detection is difficult to implement in a stable way. For #73193. Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest Change-Id: I6a6a636c631c1ae577fb8254960377ba91c5dc98 Reviewed-on: https://go-review.googlesource.com/c/go/+/670497 LUCI-TryBot-Result: Go LUCI Reviewed-by: Michael Knyszek

cmd/go: allow symlinks of non-directory files in embed

2025-03-11T14:51:38Z

We previously disallowed all non-regular files being embedded. This CL relaxes the restriction a little: if the GODEBUG embedfollowsymlinks=1 is set, we allow the leaf files being embedded (not the directories containing them) to be symlinks. The files pointed to by the symlinks must still be regular files. This will be used when a Bazel build action executing the Go command is running in a symlink-based sandbox. It's not something we want to enable in general for now, so it's behind a GODEBUG. Fixes #59924 Change-Id: I895be14c12de55b7d1b663d81bdda1df37d54804 Reviewed-on: https://go-review.googlesource.com/c/go/+/643215 LUCI-TryBot-Result: Go LUCI Reviewed-by: Alan Donovan

crypto/x509: keep RSA CRT values in ParsePKCS1PrivateKey

2024-11-30T01:49:35Z

Turns out that recomputing them (and qInv in particular) in constant time is expensive, so let's not throw them away when they are available. They are much faster to check, so we now do that on precompute. Also, thanks to the opaque crypto/internal/fips140/rsa.PrivateKey type, we now have some assurance that the values we use are always ones we checked. Recovers most of the performance loss since CL 630516 in the happy path. Also, since now we always use the CRT, if necessary by running a throwaway Precompute, which is now cheap if PrecomputedValues is filled out, we effectively fixed the JSON round-trip slowdown (#59695). goos: darwin goarch: arm64 pkg: crypto/rsa cpu: Apple M2 │ 3b42687c56 │ f017604bc6-dirty │ │ sec/op │ sec/op vs base │ ParsePKCS8PrivateKey/2048-8 26.76µ ± 1% 65.99µ ± 1% +146.64% (p=0.002 n=6) Fixes #59695 Updates #69799 For #69536 Change-Id: I507f8c5a32e69ab28990a3bf78959836b9b08cc9 Reviewed-on: https://go-review.googlesource.com/c/go/+/632478 Auto-Submit: Filippo Valsorda Reviewed-by: Russ Cox LUCI-TryBot-Result: Go LUCI Reviewed-by: Roland Shoemaker

crypto/rsa: refuse to generate and/or use keys smaller than 1024 bits

2024-11-22T01:50:32Z

Fixes #68762 Change-Id: Id89c770571d7cc27c6cf7932139ec3424383a7ef Reviewed-on: https://go-review.googlesource.com/c/go/+/629938 Reviewed-by: Roland Shoemaker Auto-Submit: Filippo Valsorda Reviewed-by: Dmitri Shuralyov LUCI-TryBot-Result: Go LUCI

crypto/x509: remove x509sha1 GODEBUG

2024-11-20T18:27:31Z

Fixes #41682 Change-Id: I37760f2186e75ec7df9674db25ae466cf453d66d Reviewed-on: https://go-review.googlesource.com/c/go/+/629676 LUCI-TryBot-Result: Go LUCI Reviewed-by: Filippo Valsorda Reviewed-by: Dmitri Shuralyov

cmd/go: re-enable build JSON from go test -json, now with GODEBUG

2024-11-19T02:39:44Z

This re-enables the behavior of CL 536399 (by effectively reverting CL 628955), so now go test -json again includes build output and failures as JSON rather than text. However, since this behavior is clearly enough to trip up some build systems, this CL includes a GODEBUG=gotestjsonbuildtext that can be set to 1 to revert to the old behavior. Fixes #70402. Updates #62067. Cq-Include-Trybots: luci.golang.try:gotip-darwin-arm64_13,gotip-linux-amd64-longtest,gotip-windows-amd64-longtest Change-Id: I84e778cd844783dacfc83433e391b5ccb5925127 Reviewed-on: https://go-review.googlesource.com/c/go/+/629335 LUCI-TryBot-Result: Go LUCI Reviewed-by: Dmitri Shuralyov Reviewed-by: Dmitri Shuralyov Auto-Submit: Austin Clements

Revert "crypto/rand: add randcrash=0 GODEBUG"

2024-10-28T14:46:33Z

A GODEBUG is actually a security risk here: most programs will start to ignore errors from Read because they can't happen (which is the intended behavior), but then if a program is run with GODEBUG=randcrash=0 it will use a partial buffer in case an error occurs, which may be catastrophic. Note that the proposal was accepted without the GODEBUG, which was only added later. This (partially) reverts CL 608435. I kept the tests. Updates #66821 Change-Id: I3fd20f9cae0d34115133fe935f0cfc7a741a2662 Reviewed-on: https://go-review.googlesource.com/c/go/+/622115 LUCI-TryBot-Result: Go LUCI Reviewed-by: Carlos Amedee Reviewed-by: Roland Shoemaker Auto-Submit: Filippo Valsorda Reviewed-by: Daniel McCarney