avoid busy loops in bad path component (#19466)

use it in places where we are looking
for such bad path components.

cmd/admin-handlers.go

@@ -36,6 +36,7 @@ import (
 	"net/url"
 	"os"
 	"path"
+	"path/filepath"
 	"regexp"
 	"runtime"
 	"sort"
@@ -3172,11 +3173,11 @@ func (a adminAPIHandlers) InspectDataHandler(w http.ResponseWriter, r *http.Requ
 		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInvalidRequest), r.URL)
 		return
 	}
-	file = strings.ReplaceAll(file, string(os.PathSeparator), "/")
 
+	file = filepath.ToSlash(file)
 	// Reject attempts to traverse parent or absolute paths.
-	if strings.Contains(file, "..") || strings.Contains(volume, "..") {
-		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrAccessDenied), r.URL)
+	if hasBadPathComponent(volume) || hasBadPathComponent(file) {
+		writeErrorResponse(r.Context(), w, errorCodes.ToAPIErr(ErrInvalidResourceName), r.URL)
 		return
 	}
 

cmd/generic-handlers.go

@@ -310,6 +310,13 @@ func hasBadHost(host string) error {
 // Check if the incoming path has bad path components,
 // such as ".." and "."
 func hasBadPathComponent(path string) bool {
+	if len(path) > 4096 {
+		// path cannot be greater than Linux PATH_MAX
+		// this is to avoid a busy loop, that can happen
+		// if the caller sends path of following style
+		// a/a/a/a/a/a/a/a...
+		return true
+	}
 	path = filepath.ToSlash(strings.TrimSpace(path)) // For windows '\' must be converted to '/'
 	for _, p := range strings.Split(path, SlashSeparator) {
 		switch strings.TrimSpace(p) {