Lack of data validation

Lack of data validation - Out of range

Need

Implementation of robust data validation to prevent unauthorized access

Context

• Usage of Python 3 for writing and executing Python code

• Usage of Django for building web applications

Description

1. Non compliant code

from django.shortcuts import render
from django.contrib.auth.decorators import login_required

@login_required
def employee_management(request):
    # Employee Management Functionality
    pass
def absolute_path_bypass(request, path):...

In the above code, we have a Django backend application with a function called `employee_management` that is supposed to be accessible only to authenticated users. This function is decorated with `@login_required` to ensure only authenticated users can access this functionality. However, there's another function `absolute_path_bypass` that takes in a `request` and a `path` as arguments. This function renders the template at the absolute path specified, without any checks for user authentication or path validation. This introduces a vulnerability where an authenticated user can bypass the restrictions put in place by the `@login_required` decorator on the `employee_management` function. They can do this by using the `absolute_path_bypass` function with the absolute path to the `employee_management` functionality. The lack of data validation, specifically path validation in this case, allows the user to access restricted functionalities by providing out-of-range inputs. This could potentially lead to unauthorized access and manipulation of data.

2. Steps

• Implement a whitelist of allowed paths that can be accessed through the 'absolute_path_bypass' function. This will prevent users from accessing restricted functionalities.

• Add a permission check in the 'absolute_path_bypass' function to ensure that the user has the necessary permissions to access the requested path.

• Consider using Django's built-in URL dispatcher instead of allowing users to specify absolute paths. This can help to prevent path traversal attacks.

• Use Django's built-in 'UserPassesTestMixin' or 'PermissionRequiredMixin' to restrict access to certain views based on user permissions.

3. Secure code example

from django.shortcuts import render
from django.contrib.auth.decorators import login_required
from django.contrib.auth.mixins import UserPassesTestMixin
from django.views import View

@login_required
def employee_management(request):
    pass...

The updated code now includes a whitelist of allowed paths that can be accessed through the 'AbsolutePathBypassView' function. This is done by overriding the 'test_func' method of the 'UserPassesTestMixin' class. If the requested path is not in the whitelist, a 403 Forbidden response is returned. The 'UserPassesTestMixin' class is a built-in Django mixin that provides a way to restrict access to certain views based on the result of a test. In this case, the test is whether the requested path is in the whitelist. The 'raise_exception' attribute is set to True so that a 403 Forbidden response is returned instead of redirecting to the login page if the test fails. The 'AbsolutePathBypassView' function is now a class-based view, which is a common pattern in Django. Class-based views provide a way to define views that can handle different HTTP methods with separate methods instead of conditional branching inside a single function. This solution prevents users from accessing restricted functionalities by using absolute paths, and it also provides a clear way to manage and update the list of allowed paths.

References

• 198. Lack of data validation - Out of range

On this page