[George Adams (gdams)]

Native validation stack

Bottom layer of stack #2664, landing on microsoft/main: this ML-DSA fix → Azure Linux 4 matrix #2651. The top layer runs CI with this fix included. Auto-merge is disabled; use the native stack merge flow.

Summary

Fix Azure Linux 4’s crypto/mldsa.TestExternalMu failures without disabling ML-DSA or skipping standard-library tests.

Uses merged microsoft/go-crypto-openssl#108, pinned to main merge commit c9be04267896c74dd64bc75eb25869fdc037f96d (v0.5.1-0.20261028130524-c9be04267896).

• Ask the OpenSSL provider whether the key’s specific ML-DSA parameter set supports external-mu signing/verification.
• Use the existing cached Go-key fallback when that capability is unavailable. Azure Linux 4’s SymCrypt provider supports ordinary ML-DSA but rejects external-mu.
• Preserve ordinary native ML-DSA and existing Windows/Darwin behavior; update matching platform/stub signatures.
• Regenerate vendor patch 0001 and its index. No Go submodule pointer change or test skips.

Unblocks the Azure Linux 4 matrix PR #2651. Go 1.27 counterpart: #2663; Go 1.26 has no ML-DSA package/integration and needs no backport.

Validation

• Ran go generate in cryptobackend and removed stale checksums. Full go test ./... and go mod tidy -diff now pass, including the previously failing TestXCryptoDependencyIsSynced.

• Built the patched main toolchain and tested the actual published Azure Linux 4 ARM64 image with its SymCrypt/OpenSSL 3.5.4 provider.

• TestExternalMu passes for ML-DSA-44/65/87 with cgo enabled and disabled.

• Complete crypto/mldsa tests and go/build.TestDependencies pass.

• External-mu tests also pass with the CI FIPS environment (OPENSSL_FORCE_FIPS_MODE=1) in both cgo modes and with systemcrypto disabled as a control.

• Complete ML-DSA tests pass on macOS/arm64 as well.

• Backend shim tests/vet and pipeline-generation reproducibility pass.

• Source changes were squashed into the vendor commit and regenerated via git go-patch extract; patch extraction succeeds.

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🔵 Needs a closer look

Obsolete OpenSSL checksums remain in go.sum, causing go mod tidy -diff to report removals and TestXCryptoDependencyIsSynced to fail.

No open issues 🎉

What changed in this PR

Updates Microsoft Go’s ML-DSA backend to respect OpenSSL provider capabilities, allowing Azure Linux 4 external-mu operations to use the cached Go fallback without disabling ordinary native ML-DSA.

Changes:

• Checks external-mu support for the key’s specific ML-DSA parameter set.
• Updates platform and stub signatures while preserving Windows and Darwin behavior.
• Upgrades the OpenSSL dependency and regenerates the vendor patch and index.

Patches are happy!

File	Description
patches/​index.json	Refreshes vendor patch hashes and line mappings.
patches/​0001-Vendor-external-dependencies.patch	Vendors the capability probe and updated backend integration.
cryptobackend/​mldsa/​nobackend.go	Updates the unsupported-backend stub signature.
cryptobackend/​mldsa/​mldsa_windows.go	Accepts parameters while retaining native external-mu support.
cryptobackend/​mldsa/​mldsa_openssl.go	Delegates capability checks to OpenSSL.
cryptobackend/​mldsa/​mldsa_msgostd.go	Gates native signing using the key’s parameters.
cryptobackend/​mldsa/​mldsa_darwin.go	Updates the signature while retaining Go fallback behavior.
cryptobackend/​go.sum	Adds checksums for the upgraded OpenSSL dependency.
cryptobackend/​go.mod	Pins the OpenSSL revision containing the capability probe.

_{Review effort: Balanced}