Pentesting Checklists

Authentication Bypass (403 Forbidden) Vulnerabilities

What is Authentication Bypass?

Authentication bypass, often resulting in a 403 Forbidden error when unsuccessful, is a type of vulnerability that allows an attacker to gain unauthorized access to protected resources or functionalities. These vulnerabilities occur when the authentication and authorization mechanisms of an application can be circumvented, potentially leading to severe security breaches.

Successful exploitation of auth bypass vulnerabilities can lead to unauthorized access to sensitive data, elevation of privileges, and potential compromise of the entire system. It's crucial for developers and security professionals to understand these vulnerabilities and implement robust defenses against them.

Common Auth Bypass Techniques

Below are some of the most common techniques used to attempt authentication bypass. Each technique includes examples of how it can be tested, prevention strategies, and additional details, including recommended Content Security Policy (CSP) headers.

HTTP Verb Tampering
Attempt to bypass access controls by changing the HTTP method of the request.

  • curl

    curl -X POST https://api.example.com/admin-only-resource

    Try accessing a GET-only resource using POST method.

  • Burp Suite

    Use Burp Suite's Repeater to change the HTTP method

    GitHub Page

    Intercept the request and modify the HTTP verb before sending.

Parameter Pollution
Manipulate or add parameters to the request to confuse the application's access control logic.

  • Browser Dev Tools

    Modify URL parameters: https://example.com/resource?admin=true

    Add or modify URL parameters to potentially influence server-side logic.

  • OWASP ZAP

    Use ZAP's Active Scan with Parameter Pollution policy

    GitHub Page

    Automatically test for parameter pollution vulnerabilities.

Path Traversal
Attempt to access restricted resources by manipulating file paths in the request.

  • curl

    curl https://example.com/public/../private/secret.txt

    Attempt to access files outside of the intended directory.

  • DotDotPwn

    dotdotpwn -m http -h example.com

    GitHub Page

    Automate the process of discovering and exploiting directory traversal vulnerabilities.

Forced Browsing
Attempt to access restricted resources by guessing or brute-forcing URLs and endpoints.

  • dirb

    dirb https://example.com /usr/share/dirb/wordlists/common.txt

    Use dirb to discover hidden or unlinked content on the web server.

  • Burp Suite Intruder

    Use Burp Suite's Intruder with a wordlist of common admin pages

    GitHub Page

    Automate the process of trying different URL paths to find restricted areas.

Token Manipulation
Attempt to bypass access controls by manipulating authentication tokens.

  • JWT_Tool

    python3 jwt_tool.py <your_jwt_token> -T

    GitHub Page

    Analyze and manipulate JWT tokens to test for vulnerabilities.

  • Burp Suite

    Use Burp Suite's JWT Editor extension

    GitHub Page

    Intercept and modify JWT tokens in requests to test for improper validation.

SQL Injection
Exploit SQL injection vulnerabilities to bypass authentication or elevate privileges.

  • sqlmap

    sqlmap -u "https://example.com/login?username=admin&password=password" --level=5 --risk=3

    GitHub Page

    Automatically detect and exploit SQL injection vulnerabilities in login forms.

  • Manual Testing

    ' OR '1'='1

    Try inserting this payload into login fields to bypass authentication.

Cross-Site Scripting (XSS)
Use XSS vulnerabilities to steal authentication tokens or perform actions on behalf of authenticated users.

  • XSStrike

    python xsstrike.py -u "https://example.com/search?q=test"

    GitHub Page

    Detect and exploit XSS vulnerabilities that could be used to steal auth tokens.

  • BeEF (Browser Exploitation Framework)

    ./beef

    GitHub Page

    Use BeEF to demonstrate how XSS can be leveraged for session hijacking.

Session Fixation
Exploit weak session management to force a user to use a known session identifier.

  • Manual Testing

    https://example.com/login?JSESSIONID=abcdef123456

    Attempt to set a session ID in the URL and see if it's accepted after login.

  • Burp Suite

    Use Burp Suite to intercept and modify session cookies

    GitHub Page

    Test if the application accepts pre-defined session identifiers.

Insecure Direct Object References (IDOR)
Exploit weak access controls to access or modify other users' data.

  • Burp Suite Autorize

    Use Burp Suite's Autorize extension to test for IDOR vulnerabilities

    GitHub Page

    Automate the process of detecting IDOR vulnerabilities in web applications.

  • Manual Testing

    https://example.com/api/user/123/profile

    Try changing the user ID in API requests to access other users' data.

OAuth 2.0 Vulnerabilities
Exploit weaknesses in OAuth 2.0 implementations to gain unauthorized access.

  • OAuth 2.0 Threat Model Toolkit

    python oauth2_threat_model.py --target https://example.com/oauth

    GitHub Page

    Analyze OAuth 2.0 implementations for common vulnerabilities and misconfigurations.

  • Burp Suite

    Use Burp Suite to intercept and modify OAuth 2.0 flows

    GitHub Page

    Test for vulnerabilities like token leakage, improper state validation, and redirect_uri manipulation.

Race Conditions
Exploit timing vulnerabilities in authentication or authorization processes.

  • Burp Suite Turbo Intruder

    Use Burp Suite's Turbo Intruder extension to send multiple concurrent requests

    GitHub Page

    Test for race conditions by sending many simultaneous requests to trigger timing issues.

  • Custom Script

    python race_condition_test.py https://example.com/vulnerable_endpoint

    Use a custom script to send parallel requests and analyze responses for inconsistencies.

Server-Side Request Forgery (SSRF)
Manipulate the server into making unintended requests to bypass authentication or access controls.

  • SSRFmap

    python3 ssrfmap.py -r request.txt -p url

    GitHub Page

    Automate the process of detecting and exploiting SSRF vulnerabilities.

  • Burp Suite Collaborator

    Use Burp Collaborator to detect blind SSRF vulnerabilities

    GitHub Page

    Test for SSRF by making the server send requests to a Burp Collaborator server.

General Prevention Strategies

  • Implement strong, multi-factor authentication where possible
  • Use the principle of least privilege for all user accounts and processes
  • Implement proper session management with secure session handling and timeouts
  • Regularly audit and test authentication and authorization mechanisms
  • Keep all systems, frameworks, and libraries up-to-date with the latest security patches
  • Implement proper logging and monitoring to detect potential auth bypass attempts
  • Use security headers like Content-Security-Policy (CSP) to mitigate the impact of successful attacks
  • Implement server-side validation for all authentication and authorization checks
  • Use secure password hashing algorithms (e.g., bcrypt, Argon2) for storing user credentials
  • Implement proper error handling to avoid information disclosure
  • Use secure communication protocols (HTTPS) for all authentication-related traffic
  • Implement proper access control checks at both the function and object level
  • Use secure session management techniques, including secure cookie flags and proper session invalidation
  • Implement rate limiting and account lockout mechanisms to prevent brute-force attacks
  • Regularly perform security assessments and penetration testing to identify vulnerabilities
  • Educate developers on secure coding practices and common authentication vulnerabilities

Additional Resources

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