fix: validate CrowdSec archive entry names with a standard local-path check

backend/internal/crowdsec/hub_sync.go

@@ -930,10 +930,11 @@ func (s *HubService) extractTarGz(ctx context.Context, archive []byte, targetDir
 		if hdr.FileInfo().Mode()&os.ModeType != 0 && !hdr.FileInfo().Mode().IsRegular() && !hdr.FileInfo().IsDir() {
 			continue
 		}
-		cleanName := filepath.Clean(hdr.Name)
-		if hasParentComponent(cleanName) || filepath.IsAbs(cleanName) {
+		// IsLocal rejects absolute, empty and ".." component names (but accepts "..foo").
+		if !filepath.IsLocal(hdr.Name) {
 			return fmt.Errorf("unsafe path %s", hdr.Name)
 		}
+		cleanName := filepath.Clean(hdr.Name)
 		if IsEngineOwnedPath(cleanName) {
 			continue
 		}
@@ -1025,14 +1026,3 @@ func isGzip(data []byte) bool {
 	}
 	return data[0] == 0x1f && data[1] == 0x8b
 }
-
-// hasParentComponent reports whether any path component equals "..".
-// Names that merely start with two dots (e.g. "..foo") are legitimate.
-func hasParentComponent(name string) bool {
-	for _, part := range strings.Split(filepath.ToSlash(name), "/") {
-		if part == ".." {
-			return true
-		}
-	}
-	return false
-}

backend/internal/crowdsec/hub_sync_test.go

@@ -2299,3 +2299,32 @@ func TestHubBaseCandidates_DistinctRolesKeepOrder(t *testing.T) {
 		defaultHubBaseURL,
 	}, svc.hubBaseCandidates())
 }
+
+func TestExtractTarGzLocalPathEdgeCases(t *testing.T) {
+	t.Parallel()
+	svc := NewHubService(nil, nil, t.TempDir())
+
+	t.Run("accepts dot directory entry", func(t *testing.T) {
+		t.Parallel()
+		targetDir := t.TempDir()
+		buf := &bytes.Buffer{}
+		gw := gzip.NewWriter(buf)
+		tw := tar.NewWriter(gw)
+		require.NoError(t, tw.WriteHeader(&tar.Header{Name: "./", Typeflag: tar.TypeDir, Mode: 0o755}))
+		require.NoError(t, tw.WriteHeader(&tar.Header{Name: "./a.txt", Mode: 0o644, Size: 2}))
+		_, err := tw.Write([]byte("ok"))
+		require.NoError(t, err)
+		require.NoError(t, tw.Close())
+		require.NoError(t, gw.Close())
+		require.NoError(t, svc.extractTarGz(context.Background(), buf.Bytes(), targetDir))
+		require.FileExists(t, filepath.Join(targetDir, "a.txt"))
+	})
+
+	t.Run("rejects empty name", func(t *testing.T) {
+		t.Parallel()
+		archive := makeTarGz(t, map[string]string{"": "bad"})
+		err := svc.extractTarGz(context.Background(), archive, t.TempDir())
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "unsafe path")
+	})
+}