image: accept md5 checksums for vendor archives

pkg/image/download.go

@@ -2,6 +2,7 @@ package image
 
 import (
 	"archive/zip"
+	"crypto/md5"
 	"crypto/sha256"
 	"encoding/hex"
 	"errors"
@@ -159,26 +160,39 @@ func decompressZIP(src, dest string) error {
 	return out.Sync()
 }
 
-// VerifyChecksum checks sha256 in the form "sha256:<hex>".
+// VerifyChecksum checks hashes in the form "sha256:<hex>" or "md5:<hex>".
 func VerifyChecksum(path, checksum string) error {
 	if checksum == "" {
 		return nil
 	}
 	parts := strings.SplitN(checksum, ":", 2)
-	if len(parts) != 2 || parts[0] != "sha256" {
-		return errors.New("unsupported checksum format; use sha256:<hex>")
+	if len(parts) != 2 {
+		return errors.New("unsupported checksum format; use sha256:<hex> or md5:<hex>")
 	}
+	algo := strings.ToLower(strings.TrimSpace(parts[0]))
 	expected := strings.ToLower(parts[1])
 	f, err := os.Open(path)
 	if err != nil {
 		return err
 	}
 	defer f.Close()
-	h := sha256.New()
-	if _, err := io.Copy(h, f); err != nil {
-		return err
+	var sum string
+	switch algo {
+	case "sha256":
+		h := sha256.New()
+		if _, err := io.Copy(h, f); err != nil {
+			return err
+		}
+		sum = hex.EncodeToString(h.Sum(nil))
+	case "md5":
+		h := md5.New()
+		if _, err := io.Copy(h, f); err != nil {
+			return err
+		}
+		sum = hex.EncodeToString(h.Sum(nil))
+	default:
+		return errors.New("unsupported checksum format; use sha256:<hex> or md5:<hex>")
 	}
-	sum := hex.EncodeToString(h.Sum(nil))
 	if sum != expected {
 		return fmt.Errorf("checksum mismatch: expected %s got %s", expected, sum)
 	}

pkg/image/download_test.go

@@ -2,6 +2,7 @@ package image
 
 import (
 	"archive/zip"
+	"crypto/md5"
 	"crypto/sha256"
 	"encoding/hex"
 	"os"
@@ -160,6 +161,18 @@ func TestDownloadAndVerifyUsesArchiveChecksumForZIP(t *testing.T) {
 	}
 }
 
+func TestVerifyChecksumAcceptsMD5(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "sample.img")
+	if err := os.WriteFile(path, []byte("metis-md5-test"), 0o644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+	sum := md5.Sum([]byte("metis-md5-test"))
+	if err := VerifyChecksum(path, "md5:"+hex.EncodeToString(sum[:])); err != nil {
+		t.Fatalf("VerifyChecksum md5: %v", err)
+	}
+}
+
 func writeTestZIP(path string, files map[string]string) error {
 	out, err := os.Create(path)
 	if err != nil {