image: reimplement and adapt measurement generation in Go

image/measured-boot/measure/authentihash.go

@@ -0,0 +1,31 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package measure
+
+import (
+	"bytes"
+	"fmt"
+	"hash"
+	"io"
+
+	"github.com/foxboron/go-uefi/efi/pecoff"
+)
+
+// Authentihash returns the PE/COFF hash / Authentihash of a file.
+func Authentihash(r io.Reader, h hash.Hash) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	if _, err := buf.ReadFrom(r); err != nil {
+		return nil, fmt.Errorf("failed to read pe file: %v", err)
+	}
+
+	signingCtx := pecoff.PECOFFChecksum(buf.Bytes())
+	pecoff.PaddSigCtx(signingCtx)
+
+	h.Write(signingCtx.SigData.Bytes())
+
+	return h.Sum(nil), nil
+}