Plugins: Improved handling of symlinks (#51324)

Improves how we handle symlinks in plugin management.

pkg/plugins/manager/installer/installer.go

@@ -619,7 +619,7 @@ func isSymlinkRelativeTo(basePath string, symlinkDestPath string, symlinkOrigPat
 			return false
 		}
 
-		if strings.HasPrefix(p, ".."+string(filepath.Separator)) {
+		if p == ".." || strings.HasPrefix(p, ".."+string(filepath.Separator)) {
 			return false
 		}
 	}

pkg/plugins/manager/installer/installer_test.go

@@ -280,6 +280,34 @@ func TestIsSymlinkRelativeTo(t *testing.T) {
 			symlinkOrigPath: "/dir/sub-dir/test1.txt",
 			expected:        false,
 		},
+		{
+			desc:            "Symbolic link pointing to relative file outside basePath should return false",
+			basePath:        "/dir",
+			symlinkDestPath: "../../",
+			symlinkOrigPath: "/dir/sub-sir/symlink.txt",
+			expected:        false,
+		},
+		{
+			desc:            "Symbolic link pointing to relative file outside basePath should return false",
+			basePath:        "/dir",
+			symlinkDestPath: "../..",
+			symlinkOrigPath: "/dir/sub-sir/symlink.txt",
+			expected:        false,
+		},
+		{
+			desc:            "Symbolic link pointing to relative file outside basePath should return false",
+			basePath:        "/dir",
+			symlinkDestPath: "../../",
+			symlinkOrigPath: "/dir/sub-sir/",
+			expected:        false,
+		},
+		{
+			desc:            "Symbolic link pointing to relative file outside basePath should return false",
+			basePath:        "/dir",
+			symlinkDestPath: "../..",
+			symlinkOrigPath: "/dir/sub-sir/",
+			expected:        false,
+		},
 	}
 
 	for _, tc := range tcs {