[George Adams (gdams)]

Native validation stack

Bottom layer of stack #2666, landing on microsoft/release-branch.go1.27: this provider-aware ML-DSA fix → Azure Linux 4 matrix #2665. Auto-merge is disabled; use the native stack merge flow.

Summary

Backport provider-aware ML-DSA external-mu support to Go 1.27.

Uses merged microsoft/go-crypto-openssl#109, pinned to support-branch merge SHA 38f583a66fdfb9bfa8135f775b42094efb19980b (v0.5.1-0.20261028132133-38f583a66fdf).

• Check external-mu capability for the key’s parameter set rather than assuming every OpenSSL ML-DSA provider implements it.
• Use the existing cached Go-key fallback on providers such as Azure Linux 4 SymCrypt, while retaining ordinary native ML-DSA.
• Adapt the older Go 1.27 integration: update SupportsExternalMu(params) on all platforms/stubs and pass the backend key’s parameters at the signing call site.
• Update the OpenSSL dependency and regenerate vendor changes exclusively in patch 0001, the crypto call-site change in patch 0002, and the patch index.
• No Go submodule pointer changes or standard-library test skips.

Go 1.26 has no ML-DSA package/backend integration, so no Go 1.26 counterpart is needed.

The dependency is built from ms-go1.27-support plus the focused external-mu backport, not OpenSSL main. The OpenSSL support-branch PR is merged. The pinned support-branch build was revalidated against actual Azure Linux 4 SymCrypt.

Validation

• Built patched Go 1.27.3 inside the published Azure Linux 4 ARM64 CI image using the actual SymCrypt/OpenSSL 3.5.4 provider.
• All ML-DSA-44/65/87 TestExternalMu cases pass with cgo enabled and disabled.
• Full crypto/mldsa tests and go/build.TestDependencies pass.
• External-mu tests pass under the CI FIPS environment (OPENSSL_FORCE_FIPS_MODE=1) with both cgo settings.
• Backend shim tests, vet, targeted lint, and pipeline-generation reproducibility pass.
• Regenerated both affected patches using git go-patch extract, preserving the existing patch ownership conventions.

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[Copilot]

🔵 Needs a closer look

Obsolete OpenSSL checksum entries in cryptobackend/go.sum produce a nonempty go mod tidy diff, causing TestXCryptoDependencyIsSynced to fail.

No open issues 🎉

What changed in this PR

Backports provider-aware ML-DSA external-mu support to the Microsoft build of Go 1.27, preserving native ML-DSA while using the cached Go-key fallback when external-mu operations are unsupported.

Changes:

• Checks external-mu support for the key’s parameter set and updates all platform shims.
• Upgrades the OpenSSL dependency and regenerates vendored code.
• Updates the standard-library signing call site and patch index.

Patches are happy!

File	Description
patches/​index.json	Refreshes patch hashes and index metadata.
patches/​0002-Add-crypto-backends.patch	Passes key parameters to the signing capability check.
patches/​0001-Vendor-external-dependencies.patch	Updates vendored OpenSSL code, backend shims, and dependency metadata.
cryptobackend/​mldsa/​nobackend.go	Updates the unavailable-backend stub signature.
cryptobackend/​mldsa/​mldsa_windows.go	Updates the Windows capability signature.
cryptobackend/​mldsa/​mldsa_openssl.go	Delegates capability checks to the OpenSSL provider probe.
cryptobackend/​mldsa/​mldsa_darwin.go	Updates the Darwin capability signature.
cryptobackend/​go.sum	Adds checksums for the updated OpenSSL dependency.
cryptobackend/​go.mod	Pins the provider-aware OpenSSL revision.

_{Review effort: Balanced}