Make fsck behave correctly when faced with a zero-sized tree. (#753)

Author: AlCutter

cmd/fsck/main.go

@@ -47,12 +47,21 @@ func main() {
 	if err != nil {
 		klog.Exitf("Invalid --storage_url %q: %v", *storageURL, err)
 	}
-	src, err := client.NewHTTPFetcher(logURL, nil)
-	if err != nil {
-		klog.Exitf("Failed to create HTTP fetcher: %v", err)
-	}
-	if *bearerToken != "" {
-		src.SetAuthorizationHeader(fmt.Sprintf("Bearer %s", *bearerToken))
+	var src fsck.Fetcher
+
+	if logURL.Scheme == "file" {
+		src = &client.FileFetcher{
+			Root: logURL.Path,
+		}
+	} else {
+		httpSrc, err := client.NewHTTPFetcher(logURL, nil)
+		if err != nil {
+			klog.Exitf("Failed to create HTTP fetcher: %v", err)
+		}
+		if *bearerToken != "" {
+			httpSrc.SetAuthorizationHeader(fmt.Sprintf("Bearer %s", *bearerToken))
+		}
+		src = httpSrc
 	}
 	v := verifierFromFlags()
 	if *origin == "" {

fsck/fsck.go

@@ -101,7 +101,7 @@ func Check(ctx context.Context, origin string, verifier note.Verifier, f Fetcher
 	}
 
 	// Finally, check that the claimed root hash matches what we calculated.
-	gotRoot, err := fTree.tree.GetRootHash(nil)
+	gotRoot, err := fTree.GetRootHash()
 	switch {
 	case err != nil:
 		klog.Exitf("Failed to calculate root: %v", err)
@@ -160,6 +160,13 @@ func (f *fsckTree) AppendBundle(ri layout.RangeInfo, data []byte) error {
 	return nil
 }
 
+func (f *fsckTree) GetRootHash() ([]byte, error) {
+	if f.tree.End() == 0 {
+		return rfc6962.DefaultHasher.EmptyRoot(), nil
+	}
+	return f.tree.GetRootHash(nil)
+}
+
 // visit is used to populate the derived tiles as we consume entries from the log we're checking.
 func (f *fsckTree) visit(id compact.NodeID, h []byte) {
 	// We're only storing the lowest level of hash in the tiles, so early-out in other cases.