Broken Authentication in APIs , APIs can make you so rich $$$

Introduction

Authentication and authorization mechanisms are the gatekeepers of APIs, ensuring that only authorized users can access specific resources and perform allowed actions. However, flaws in these mechanisms are rampant and often lead to severe security breaches. Mastering the art of finding broken authentication vulnerabilities can be a lucrative skill in the Bug Bounty world.

Understanding Authentication and Authorization

● Authentication: Verifying the identity of a user or system (e.g., username/password, tokens, biometrics).
● Authorization: Determining what actions an authenticated user or system is allowed to perform.
● Common Authentication Mechanisms:
○ Basic Authentication
○ Token-Based Authentication (JWT, OAuth)
○ API Keys
○ Session Cookies
● Common Authorization Mechanisms:
○ Role-Based Access Control (RBAC)
○ Attribute-Based Access Control (ABAC)

API Authentication and Authorization Vulnerabilities

1. Broken Authentication:
○ Weak Credentials: Easily guessable passwords, default credentials, no password complexity requirements.
○ Credential Stuffing: Attackers use lists of compromised credentials to gain access to accounts.
○ Brute-Force Attacks: Automated guessing of passwords or tokens.
○ Session Management Flaws: Session fixation, session hijacking, insecure session tokens.
○ Token Vulnerabilities: Insecure token generation, storage, or transmission.
○ Lack of Multi-Factor Authentication (MFA): Adding an extra layer of security is often missing.

2. Broken Object Level Authorization (BOLA):
○ Insecure Direct Object References (IDOR): Manipulating object IDs in API requests to access unauthorized resources.
○ Missing Function Level Authorization: Failure to restrict access to specific API functions based on user roles or permissions.

How to Find Authentication and Authorization Issues in APIs

1. Reconnaissance:
○ Analyze API Documentation: Look for authentication and authorization mechanisms, endpoints, and parameters.
○ Intercept Traffic: Use tools like Burp Suite to capture and analyze API requests and responses.
○ Test Authentication Mechanisms:
● Try weak or default credentials.
● Attempt brute-force attacks (carefully, to avoid account lockouts).
● Test for session management flaws (e.g., session fixation, session hijacking).
● Analyze token generation, storage, and transmission for vulnerabilities.
○ Test for MFA Bypass: Look for ways to bypass MFA if it's implemented.

2. Vulnerability Assessment:
○ Test for BOLA:
● Manipulate Object IDs: Change user IDs, resource IDs, or other identifiers in API requests to see if you can access unauthorized data or functions.
● Test Different User Roles: See if you can access functions or data reserved for other roles.
○ Test for Broken Function Level Authorization:
● Enumerate API Endpoints: Discover hidden endpoints that might not be properly protected.
● Try Accessing Restricted Functions: See if you can perform actions you shouldn't be able to based on your user role.

Examples of Broken Authentication and Authorization

●  BOLA:

○ Endpoint: /api/users/{userId}/profile
○ Vulnerability: An attacker can change the {userId} to view other users' profiles.
● IDOR:
○ Endpoint: /api/orders/{orderId}
○ Vulnerability: An attacker can increment or decrement the {orderId} to view other users' orders.
● Broken Authentication (Weak Credentials):
○ Endpoint: /api/login
○ Vulnerability: The API accepts weak passwords like "password123" or allows unlimited login attempts.

Tools for Finding Broken Authentication and Authorization

● Burp Suite: Intercept and modify API requests, test for injection attacks, and automate tasks.

● AuthMatrix: A Burp Suite extension for testing authorization.
● Kiterunner: Automate API testing and fuzzing.

Tips for Bug Bounty Hunters

● Focus on High-Impact Vulnerabilities: Broken authentication and authorization issues often lead to severe consequences.
● Report Clearly and Concisely: Provide detailed steps to reproduce, potential impact, and recommendations for remediation.
● Stay Ethical: Always obtain permission before testing on live systems.

By mastering the art of finding and exploiting broken authentication vulnerabilities, you can make a significant contribution to the security of web applications and potentially earn substantial rewards in Bug Bounty programs.

Happy Hacking

Author: Ayush khatkar is a cybersecurity researcher, technical writer and an enthusiastic pen-tester at Asecurity. Contact here.

#bugbounty #infosec #cybersecurity