Add Nix flake for mciasctl and mciasgrpcctl

Vendor dependencies and expose control program binaries via
nix build. Uses nixpkgs-unstable for Go 1.26 support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/go-webauthn/webauthn/protocol/metadata.go

@@ -0,0 +1,129 @@
+package protocol
+
+import (
+	"context"
+	"crypto/x509"
+	"fmt"
+
+	"github.com/google/uuid"
+
+	"github.com/go-webauthn/webauthn/metadata"
+)
+
+func ValidateMetadata(ctx context.Context, mds metadata.Provider, aaguid uuid.UUID, attestationType, attestationFormat string, x5cs []any) (protoErr *Error) {
+	if mds == nil {
+		return nil
+	}
+
+	if AttestationFormat(attestationFormat) == AttestationFormatNone {
+		return nil
+	}
+
+	var (
+		entry *metadata.Entry
+		err   error
+	)
+	if entry, err = mds.GetEntry(ctx, aaguid); err != nil {
+		return ErrMetadata.WithInfo(fmt.Sprintf("Failed to validate authenticator metadata for Authenticator Attestation GUID '%s'. Error occurred retreiving the metadata entry: %+v", aaguid, err))
+	}
+
+	if entry == nil {
+		if aaguid == uuid.Nil && mds.GetValidateEntryPermitZeroAAGUID(ctx) {
+			return nil
+		}
+
+		if mds.GetValidateEntry(ctx) {
+			return ErrMetadata.WithInfo(fmt.Sprintf("Failed to validate authenticator metadata for Authenticator Attestation GUID '%s'. The authenticator has no registered metadata.", aaguid))
+		}
+
+		return nil
+	}
+
+	if attestationType != "" && mds.GetValidateAttestationTypes(ctx) {
+		found := false
+
+		for _, atype := range entry.MetadataStatement.AttestationTypes {
+			if string(atype) == attestationType {
+				found = true
+
+				break
+			}
+		}
+
+		if !found {
+			return ErrMetadata.WithInfo(fmt.Sprintf("Failed to validate authenticator metadata for Authenticator Attestation GUID '%s'. The attestation type '%s' is not known to be used by this authenticator.", aaguid.String(), attestationType))
+		}
+	}
+
+	if mds.GetValidateStatus(ctx) {
+		if err = mds.ValidateStatusReports(ctx, entry.StatusReports); err != nil {
+			return ErrMetadata.WithInfo(fmt.Sprintf("Failed to validate authenticator metadata for Authenticator Attestation GUID '%s'. Error occurred validating the authenticator status: %+v", aaguid, err))
+		}
+	}
+
+	if mds.GetValidateTrustAnchor(ctx) {
+		if len(x5cs) == 0 {
+			return nil
+		}
+
+		var (
+			x5c, parsed *x509.Certificate
+			x5cis       []*x509.Certificate
+			raw         []byte
+			ok          bool
+		)
+
+		for i, x5cAny := range x5cs {
+			if raw, ok = x5cAny.([]byte); !ok {
+				return ErrMetadata.WithDetails(fmt.Sprintf("Failed to parse attestation certificate from x5c during attestation validation for Authenticator Attestation GUID '%s'.", aaguid)).WithInfo(fmt.Sprintf("The %s certificate in the attestation was type '%T' but '[]byte' was expected", loopOrdinalNumber(i), x5cAny))
+			}
+
+			if parsed, err = x509.ParseCertificate(raw); err != nil {
+				return ErrMetadata.WithDetails(fmt.Sprintf("Failed to parse attestation certificate from x5c during attestation validation for Authenticator Attestation GUID '%s'.", aaguid)).WithInfo(fmt.Sprintf("Error returned from x509.ParseCertificate: %+v", err)).WithError(err)
+			}
+
+			if x5c == nil {
+				x5c = parsed
+			} else {
+				x5cis = append(x5cis, parsed)
+			}
+		}
+
+		if attestationType == string(metadata.AttCA) {
+			if protoErr = tpmParseAIKAttCA(x5c, x5cis); protoErr != nil {
+				return ErrMetadata.WithDetails(protoErr.Details).WithInfo(protoErr.DevInfo).WithError(protoErr)
+			}
+		}
+
+		if x5c != nil && x5c.Subject.CommonName != x5c.Issuer.CommonName {
+			if !entry.MetadataStatement.AttestationTypes.HasBasicFull() {
+				return ErrMetadata.WithDetails(fmt.Sprintf("Failed to validate attestation statement signature during attestation validation for Authenticator Attestation GUID '%s'. Attestation was provided in the full format but the authenticator doesn't support the full attestation format.", aaguid))
+			}
+
+			if _, err = x5c.Verify(entry.MetadataStatement.Verifier(x5cis)); err != nil {
+				return ErrMetadata.WithDetails(fmt.Sprintf("Failed to validate attestation statement signature during attestation validation for Authenticator Attestation GUID '%s'. The attestation certificate could not be verified due to an error validating the trust chain against the Metadata Service.", aaguid)).WithError(err)
+			}
+		}
+	}
+
+	return nil
+}
+
+func loopOrdinalNumber(n int) string {
+	n++
+
+	if n > 9 && n < 20 {
+		return fmt.Sprintf("%dth", n)
+	}
+
+	switch n % 10 {
+	case 1:
+		return fmt.Sprintf("%dst", n)
+	case 2:
+		return fmt.Sprintf("%dnd", n)
+	case 3:
+		return fmt.Sprintf("%drd", n)
+	default:
+		return fmt.Sprintf("%dth", n)
+	}
+}