fix: normalize Windows backslash paths in weed admin file uploads (#7636)

fix: normalize Windows backslash paths in file uploads

When uploading files from a Windows client to a Linux server,
file paths containing backslashes were not being properly interpreted as
directory separators. This caused files intended for subdirectories to be
created in the root directory with backslashes in their filenames.

Changes:
- Add util.CleanWindowsPath and util.CleanWindowsPathBase helper functions
  in weed/util/fullpath.go for reusable path normalization
- Use path.Join/path.Clean/path.Base instead of filepath equivalents
  for URL path semantics (filepath is OS-specific)
- Apply normalization in weed admin handlers and filer upload parsing

Fixes #7628

weed/admin/handlers/file_browser_handlers.go

@@ -10,6 +10,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -21,6 +22,7 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/admin/view/layout"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
+	"github.com/seaweedfs/seaweedfs/weed/util"
 	"github.com/seaweedfs/seaweedfs/weed/util/http/client"
 )
 
@@ -267,8 +269,12 @@ func (h *FileBrowserHandlers) UploadFile(c *gin.Context) {
 			continue
 		}
 
-		// Create full path for the file
-		fullPath := filepath.Join(currentPath, fileName)
+		// Normalize Windows-style backslashes to forward slashes
+		fileName = util.CleanWindowsPath(fileName)
+
+		// Create full path for the file using path.Join for URL path semantics
+		// path.Join handles double slashes and is not OS-specific like filepath.Join
+		fullPath := path.Join(currentPath, fileName)
 		if !strings.HasPrefix(fullPath, "/") {
 			fullPath = "/" + fullPath
 		}
@@ -349,8 +355,10 @@ func (h *FileBrowserHandlers) uploadFileToFiler(filePath string, fileHeader *mul
 	var body bytes.Buffer
 	writer := multipart.NewWriter(&body)
 
-	// Create form file field
-	part, err := writer.CreateFormFile("file", fileHeader.Filename)
+	// Create form file field with normalized base filename
+	// Use path.Base (not filepath.Base) since cleanFilePath uses URL path semantics
+	baseFileName := path.Base(cleanFilePath)
+	part, err := writer.CreateFormFile("file", baseFileName)
 	if err != nil {
 		return fmt.Errorf("failed to create form file: %w", err)
 	}
@@ -452,8 +460,12 @@ func (h *FileBrowserHandlers) validateAndCleanFilePath(filePath string) (string,
 		return "", fmt.Errorf("file path cannot be empty")
 	}
 
+	// Normalize Windows-style backslashes to forward slashes
+	filePath = util.CleanWindowsPath(filePath)
+
 	// Clean the path to remove any .. or . components
-	cleanPath := filepath.Clean(filePath)
+	// Use path.Clean (not filepath.Clean) since this is a URL path
+	cleanPath := path.Clean(filePath)
 
 	// Ensure the path starts with /
 	if !strings.HasPrefix(cleanPath, "/") {