Broken Authentication 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:

```bash
# 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=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:
1. Attacker visits site, gets session: SESSIONID=attacker_session
2. Attacker sends link to victim with fixed session:
   https://target.com/login?SESSIONID=attacker_session
3. Victim logs in with attacker's session
4. Attacker now has authenticated session

Phase 8: Session Timeout Testing

Verify session expiration policies:

# Test idle timeout
1. Login and note session cookie
2. Wait without activity (15, 30, 60 minutes)
3. Attempt to use session
4. Check if session is still valid

# Test absolute timeout
1. Login and continuously use session
2. Check if forced logout after set period (8 hours, 24 hours)

# Test logout functionality
1. Login and note session
2. Click logout
3. Attempt to reuse old session cookie
4. Session should be invalidated server-side

Phase 9: Multi-Factor Authentication Testing

Assess MFA implementation security:

# OTP brute force
- 4-digit OTP = 10,000 combinations
- 6-digit OTP = 1,000,000 combinations
- Test rate limiting on OTP endpoint

# OTP bypass techniques
- Skip MFA step by direct URL access
- Modify response to indicate MFA passed
- Null/empty OTP submission
- Previous valid OTP reuse

# 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
1. Capture OTP verification request
2. Send to Intruder
3. Set OTP field as payload position
4. Use numbers payload (0000-9999)
5. Check for successful bypass

Test MFA enrollment:

# Forced enrollment
- Can MFA be skipped during setup?
- Can backup codes be accessed without verification?

# Recovery process
- Can MFA be disabled via email alone?
- Social engineering potential?

Phase 10: Password Reset Testing

Analyze password reset security:

# Token security
1. Request password reset
2. Capture reset link
3. Analyze token:
   - Length and randomness
   - Expiration time
   - Single-use enforcement
   - Account binding

# Token manipulation