fix(storage): Fix TM download dir corner case (#14142)

This PR fixes the corner case where download file path is resolved
exactly to the download directory. The fix now checks for the parent
folder of the final resolved file path and checks the relative path
against the local directory.

Author: krishnamd-jkp

storage/transfermanager/downloader.go

@@ -994,9 +994,11 @@ func isSubPath(localDirectory, filePath string) (bool, error) {
 		return false, fmt.Errorf("cannot convert file path to absolute path: %w", err)
 	}
 
-	// The relative path from the local directory to the file path.
-	// ex: if localDirectory is /tmp/foo and filePath is /tmp/foo/bar, rel will be "bar".
-	rel, err := filepath.Rel(absLocalDirectory, absFilePath)
+	absFilePathFolder := filepath.Dir(absFilePath)
+	// The relative path from the local directory to the final file path's directory.
+	// ex 1: if localDirectory is /tmp/foo and filePath is /tmp/foo/bar, rel will be ".".
+	// ex 2: if localDirectory is /tmp/foo and filePath is /tmp/bar, rel will be "..".
+	rel, err := filepath.Rel(absLocalDirectory, absFilePathFolder)
 	if err != nil {
 		return false, err
 	}

storage/transfermanager/downloader_test.go

@@ -264,6 +264,12 @@ func TestIsSubPath(t *testing.T) {
 			name:           "filePath is the same as localDirectory",
 			localDirectory: "/tmp/foo",
 			filePath:       "/tmp/foo",
+			wantIsSub:      false,
+		},
+		{
+			name:           "local directory is /",
+			localDirectory: "/",
+			filePath:       "/../../a",
 			wantIsSub:      true,
 		},
 		{