Introduction
When it comes to web security, one of the most critical issues that organizations face is broken access control. This vulnerability, listed in the OWASP TOP 10, refers to flaws within a website or application that allow a user to gain unauthorized access to certain parts of the system. Imagine a broken gate that fails to keep intruders out – this is essentially what happens with broken access control in the digital world.
Real-life scenario of broken access control
To better understand the impact of broken access control, consider this real-life scenario: A company’s website assigns users different access levels based on their roles. For example, a customer should only view and edit their own profile, while an admin has access to sensitive functions like managing products and user accounts. However, imagine a bug in the website’s code that unintentionally allows a regular customer to access the admin panel. As a result, this breach in access control could lead to unauthorized changes, data leaks, and significant security threats to the organization.
I’d like to outline a few more scenarios that illustrate broken access control on a website as below,
Unauthenticated Access to Admin Functions
In this scenario, a flaw in the authentication process allows an attacker to access admin functions without logging in. This means that anyone, even without proper credentials, can perform actions that are typically restricted to privileged users. For example, a user might be able to delete or modify critical data, leading to data loss or system instability.
Price Manipulation
Another common example of broken access control is price manipulation. By exploiting vulnerabilities in the system, attackers can change prices of products or services to their advantage. This can result in financial losses for both the business and its customers. For instance, an attacker could purchase items at a discounted rate by manipulating the prices in their favor.
Viewing Other Users’ Orders
Broken access control can also allow unauthorized users to view sensitive information belonging to other users. For instance, a user may be able to access another user’s order details, including personal information and payment details. This poses a significant privacy risk and can lead to issues such as identity theft or fraud.
Accessing Restricted Pages
In some cases, broken access control can enable users to access restricted pages or areas of a website that they are not authorized to view. This can lead to exposure of confidential data, intellectual property theft, or disruption of services. For example, a user might gain access to a confidential document meant for internal use only.
Account Takeover via Session Hijacking
Another serious consequence of broken access control is account takeover through session hijacking. This occurs when an attacker steals a user’s session token and impersonates them, gaining full access to their account. With this level of control, the attacker can perform malicious actions on behalf of the user, such as making unauthorized transactions or changing account settings.
Escalating User Privileges
Broken access control can also result in privilege escalation, where a user gains higher levels of access than intended. For instance, a regular user exploiting a flaw in the system could elevate their privileges to that of an admin, granting them unrestricted control over the website or application. This can have severe consequences in terms of data security and system integrity.
Frequently Asked Interview Questions on Broken Access
1. What is broken access control, and why is it considered a critical security risk?
Broken access control happens when restrictions on the actions of authenticated users are not properly enforced. This failure allows attackers to access or modify data they are not authorized to handle. It is a critical issue because it can result in unauthorized data exposure, data tampering, or even the complete takeover of applications.This risk can compromise sensitive user information or business-critical resources.
2. Can you explain the difference between authentication and access control? How does broken access control relate to these concepts?
Authentication: Confirms the identity of a user (e.g., login with username and password).
Access Control: Governs what authenticated users are allowed to do (e.g., restricting access to specific resources or actions).
Broken access control occurs when authenticated users gain access to resources or perform actions they are not authorized to, violating the principle of least privilege.
3. What are some common vulnerabilities that lead to broken access control? Provide examples.
Missing or mis-configured access control policies. Example: An admin-only endpoint accessible to non-admin users.
Insecure Direct Object References (IDOR). Example: Allowing users to modify URLs to access unauthorized data (/profile?user=1234).
Privilege escalation. Example: Exploiting a bug to gain admin privileges.
Failure to restrict access to APIs or admin functionalities.
4. How can insecure direct object references (IDOR) contribute to broken access control vulnerabilities?
IDOR occurs when an application exposes object references (like file IDs or user IDs) without proper authorization checks. For example, if GET /user/1234 retrieves user data, an attacker could manipulate the URL to GET /user/5678 to access another user’s information. Without authorization checks, this leads to broken access control.
5. What are some real-world examples of broken access control exploits, and what were their consequences?
Facebook (2019): A vulnerability allowed attackers to access private photos of millions of users without permission.
Uber (2016): Attackers used IDOR to gain access to driver and rider personal information, resulting in lawsuits and fines.
These incidents resulted in data breaches, financial loss, and reputational damage.
6. What strategies or mechanisms can developers implement to prevent broken access control?
Implement Role-Based Access Control (RBAC): Ensure users only access resources appropriate to their role.
Enforce Least Privilege: Limit user permissions to what is strictly necessary.
Deny by Default: Block all access unless explicitly allowed.
Secure APIs: Use tokens, session management, and rate-limiting to restrict API access.
Conduct Regular Reviews: Audit access control policies and configurations.
7. How can access control issues be detected during security testing? Are there specific tools or methodologies you recommend?
Manual Testing: Attempt to access unauthorized resources or endpoints.
Automated Tools: Use scanners like Burp Suite, OWASP ZAP, or Postman to test for broken access control vulnerabilities.
Penetration Testing: Perform white-box and black-box testing to uncover gaps.
Code Reviews: Review code for missing or incorrect access control logic.
8. What is the principle of least privilege, and how does it help prevent broken access control?
The principle of least privilege ensures users only have the minimum permissions required to perform their tasks. For example, a customer support agent should only access customer records, not admin settings. By limiting permissions, the risk of accidental or malicious access to sensitive resources is reduced.
9. How does implementing security headers (like CORS or CSP) help in mitigating broken access control issues?
Security headers like CORS (Cross-Origin Resource Sharing) prevent unauthorized cross-origin requests by restricting allowed domains. While these headers do not enforce access control directly, they add a layer of defense by mitigating certain attack vectors like CSRF or unauthorized API usage.
10. Can you describe how logging and monitoring help in mitigating the impact of broken access control?
Logging: Tracks unauthorized access attempts and identifies patterns of misuse.
Monitoring: Alerts administrators in real-time about suspicious activities or access violations.
These practices help detect and respond to access control breaches quickly, limiting damage.
Conclusion
In conclusion, broken access control poses a significant risk to the security and integrity of websites and applications. By understanding the various scenarios in which this vulnerability can manifest, organizations can take proactive measures to prevent unauthorized access and protect sensitive data. It is imperative for businesses to prioritize security measures, implement robust access controls, and stay vigilant against potential threats to mitigate the risks associated with broken access control.
