Local VM image building

storage/hash.go

@@ -0,0 +1,45 @@
+package storage
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/pkg/errors"
+)
+
+func validateFileHash(path string, hash []byte) error {
+	f, err := os.OpenFile(path, os.O_RDONLY, 0400)
+	if err != nil {
+		return errors.Wrap(err, "open file")
+	}
+
+	defer func() { _ = f.Close() }()
+
+	h := sha256.New()
+	block := make([]byte, 1024)
+	for {
+		read, err := f.Read(block)
+		if read > 0 {
+			h.Write(block[:read])
+		}
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				break
+			}
+
+			return errors.Wrap(err, "read file block")
+		}
+	}
+
+	sum := h.Sum(nil)
+
+	if !bytes.Equal(sum, hash) {
+		return fmt.Errorf("hash mismatch: want '%v', have '%v'", hex.EncodeToString(hash), hex.EncodeToString(sum))
+	}
+
+	return nil
+}