Broken Authentication Testing

Purpose

Identify and exploit authentication and session management vulnerabilities in web applications. Broken authentication consistently ranks in the OWASP Top 10 and can lead to account takeover, identity theft, and unauthorized access to sensitive systems. This skill covers testing methodologies for password policies, session handling, multi-factor authentication, and credential management.

Prerequisites

Required Knowledge

• HTTP protocol and session mechanisms
• Authentication types (SFA, 2FA, MFA)
• Cookie and token handling
• Common authentication frameworks

Required Tools

• Burp Suite Professional or Community
• Hydra or similar brute-force tools
• Custom wordlists for credential testing
• Browser developer tools

Required Access

• Target application URL
• Test account credentials
• Written authorization for testing

Outputs and Deliverables

1. Authentication Assessment Report - Document all identified vulnerabilities
2. Credential Testing Results - Brute-force and dictionary attack outcomes
3. Session Security Analysis - Token randomness and timeout evaluation
4. Remediation Recommendations - Security hardening guidance

Core Workflow

Phase 1: Authentication Mechanism Analysis

Understand the application's authentication architecture:

# Identify authentication type
- Password-based (forms, basic auth, digest)
- Token-based (JWT, OAuth, API keys)
- Certificate-based (mutual TLS)
- Multi-factor (SMS, TOTP, hardware tokens)

# Map authentication endpoints
/login, /signin, /authenticate
/register, /signup
/forgot-password, /reset-password
/logout, /signout
/api/auth/*, /oauth/*

Capture and analyze authentication requests:

POST /login HTTP/1.1
Host: target.com
Content-Type: application/x-www-form-urlencoded

username=test&password=test123

Phase 2: Password Policy Testing

Evaluate password requirements and enforcement:

# Test minimum length (a, ab, abcdefgh)
# Test complexity (password, password1, Password1!)
# Test common weak passwords (123456, password, qwerty, admin)
# Test username as password (admin/admin, test/test)

Document policy gaps: Minimum length <8, no complexity, common passwords allowed, username as password.

Phase 3: Credential Enumeration

Test for username enumeration vulnerabilities:

# Compare responses for valid vs invalid usernames
# Invalid: "Invalid username" vs Valid: "Invalid password"
# Check timing differences, response codes, registration messages

Password reset

"Email sent if account exists" (secure) "No account with that email" (leaks info)

API responses

{"error": "user_not_found"} {"error": "invalid_password"}

### Phase 4: Brute Force Testing

Test account lockout and rate limiting:

Using Hydra for form-based auth

hydra -l admin -P /usr/share/wordlists/rockyou.txt \ target.com http-post-form \ "/login:username=^USER^&password=^PASS^:Invalid credentials"

Using Burp Intruder

1. Capture login request
2. Send to Intruder
3. Set payload positions on password field
4. Load wordlist
5. Start attack
6. Analyze response lengths/codes

Check for protections:

Account lockout

• After how many attempts?
• Duration of lockout?
• Lockout notification?

Rate limiting

• Requests per minute limit?
• IP-based or account-based?
• Bypass via headers (X-Forwarded-For)?

CAPTCHA

• After failed attempts?
• Easily bypassable?

### Phase 5: Credential Stuffing

Test with known breached credentials:

Credential stuffing differs from brute force

Uses known email:password pairs from breaches

Using Burp Intruder with Pitchfork attack

1. Set username and password as positions
2. Load email list as payload 1
3. Load password list as payload 2 (matched pairs)
4. Analyze for successful logins

Detection evasion

• Slow request rate
• Rotate source IPs
• Randomize user agents
• Add delays between attempts

### Phase 6: Session Management Testing

Analyze session token security:

Capture session cookie

Cookie: SESSIONID=abc123def456

Test token characteristics

1. Entropy - Is it random enough?
2. Length - Sufficient length (128+ bits)?
3. Predictability - Sequential patterns?
4. Secure flags - HttpOnly, Secure, SameSite?

Session token analysis:

#!/usr/bin/env python3 import requests import hashlib

Collect multiple session tokens

tokens = [] for i in range(100): response = requests.get("https://target.com/login") token = response.cookies.get("SESSIONID") tokens.append(token)

Analyze for patterns

Check for sequential increments

Calculate entropy

Look for timestamp components

### Phase 7: Session Fixation Testing

Test if session is regenerated after authentication:

Step 1: Get session before login

GET /login HTTP/1.1 Response: Set-Cookie: SESSIONID=abc123

Step 2: Login with same session

POST /login HTTP/1.1 Cookie: SESSIONID=ab