Penetration testing for developers

Nic Wortel
@nicwortel

About me

Software Consultant & Trainer
PHP, Symfony, Architecture, Docker, K8s, CI/CD
Co-organiser at PHPAmersfoort
Squad Leader / Instructor (reservist) at Royal NL Army

nicwortel.nl @nicwortel

Why this talk?

Goals of this talk

Improve security awareness
Know some of the tools used to attack applications
Test your own application using these tools

What is penetration testing?

A penetration test (or pentest) is an authorized simulated cyberattack performed on a computer system to evaluate its security.

Finding hidden files and directories

Google Dorks

Google search operators

site:example.com	Search in specific site
filetype:pdf or ext:pdf	Search for specific file types
intitle:foo	Search in title tag
inurl:bar	Search in URL
intext:bar	Search in page content
-foobar	Exclude from results

Google Hacking Database (GHDB)

https://www.exploit-db.com/google-hacking-database

Google Hacking Database

Focusing on a specific application

DIRB

Command line tool to look for (hidden) web pages and directories.

Wordlists

List of common filenames, passwords, usernames, etc. to use in dictionary attacks.

https://github.com/danielmiessler/SecLists

Lessons learned

Don't be low-hanging fruit
Keep sensitive files out of the web root
Disable directory listing
Enforce authorization for sensitive documents

Login brute forcing

Brute force attacks

Dictionary attacks

hydra

Supports brute force as well as dictionary attacks
Has modules to support various databases, services and systems

http-post-form module


                            "/login.php:username=^USER^&password=^PASS^:Incorrect username"

Lessons learned

Enforce the use of strong passwords (use Have I Been Pwned API)
Implement 2FA
Log authentication attempts / failures
Rate limit failed login attempts

SQL injection


                            https://example.com/dogs?id=1


                            SELECT * FROM dog WHERE id = 1

SQL injection techniques

Error-based SQL injection


                            GTID_SUBSET(@@version,0)


                            SELECT * FROM dog WHERE id = GTID_SUBSET(@@version,0)

Error message:


                                General error: 1772 Malformed GTID set specification '8.1.0'.

UNION query-based SQL injection


                            1 UNION ALL SELECT 1,@@version,3


                            SELECT * FROM dog WHERE id = 1 UNION ALL SELECT 1,@@version,3

Stacked queries SQL injection


                            1; DROP TABLE dog


                            SELECT * FROM dog WHERE id = 1; DROP TABLE dog

Boolean-based blind SQL injection


                            1 AND (SELECT COUNT(*) FROM user WHERE username = 'admin' > 0)


                            SELECT * FROM dog WHERE id = 1 AND (SELECT COUNT(*) FROM user
                              WHERE username = 'admin' > 0)

Time-based blind SQL injection


                            IF(SELECT COUNT(*) FROM user WHERE username = 'admin' > 0,
                            SLEEP(5),0)


                            SELECT * FROM dog WHERE id = 1 AND IF(SELECT COUNT(*) FROM user
                            WHERE username = 'admin' > 0,SLEEP(5),0)

sqlmap

Lessons learned

Use parameterized queries
Turn off detailed error messages
Use strong password hashing algorithms and salted passwords

Recap

Google Dorks
Web scanning with dirb
Login brute forcing with Hydra
SQL injection with sqlmap

Tools

Other tools worth mentioning

Hashcat
nmap

Operating Systems

Further resources

Cheat sheets

https://nicwortel.nl/cheat-sheets

HTB Academy

Referral link for free credits

Cheat sheets

nicwortel.nl/cheat-sheets

Questions?

Please give me feedback!

nicwortel.nl @nicwortel