Security controls bypass or absence - Data creation
Need
Enforcement of security controls for data creation
Context
- Usage of Python 3 for developing applications and scripts
- Usage of Django for building web applications in Python
Description
Non compliant code
from django.db import models
class Policy(models.Model):
name = models.CharField(max_length=100)
beneficiaries = models.ManyToManyField('Beneficiary', related_name='policies')
class Beneficiary(models.Model):
name = models.CharField(max_length=100)
The above code represents a Django model called Policy
and another model called Beneficiary
. A policy can have multiple beneficiaries, and this relationship is represented by a Many-to-Many relationship between Policy
and Beneficiary
.
The PolicyView
class is a Django view that handles the creation of policies and beneficiaries. In the post
method, it first gets the policy name and beneficiary names from the POST request. It then creates a policy with the given name and for each beneficiary name, it creates a beneficiary and adds it to the policy.
The vulnerability here is that there is no restriction on the number of beneficiaries that can be added to a policy. Despite the business rule that a policy should only have four beneficiaries, the current implementation allows the creation of a policy with any number of beneficiaries. This can lead to potential data integrity issues and can also be exploited by an attacker to create policies with a large number of beneficiaries, leading to potential denial of service.
Steps
- Create a custom save method in the Policy model.
- In the custom save method, check the count of beneficiaries before saving the policy.
- If the count of beneficiaries is more than four, raise an exception or return an error message.
- This will ensure that a policy cannot be saved with more than four beneficiaries, maintaining the integrity of the data.
Compliant code
from django.db import models
from django.core.exceptions import ValidationError
class Policy(models.Model):
name = models.CharField(max_length=100)
beneficiaries = models.ManyToManyField('Beneficiary', related_name='policies')
def save(self, *args, **kwargs):
if self.beneficiaries.count() > 4:
raise ValidationError("A policy cannot have more than four beneficiaries.")
super(Policy, self).save(*args, **kwargs)
class Beneficiary(models.Model):
name = models.CharField(max_length=100)
The code above fixes the vulnerability by adding a custom save method to the Policy
model. This method checks the count of beneficiaries
before saving the Policy
instance. If the count of beneficiaries
is more than four, it raises a ValidationError
with a message indicating that a policy cannot have more than four beneficiaries.
This ensures that the restriction on the number of beneficiaries is enforced at the model level, preventing the creation of a policy with more than four beneficiaries. This maintains the integrity of the data and prevents the bypassing of this security control.