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Web security 101

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Web security 101

  1. 1. Net security 101 Internet is hostile network Kristaps Kūlis
  2. 2. “Real” security● Security trough security, not obscurity House secured by door keys, not by putting doors on roof.● Ongoing process
  3. 3. Web applicationsBe conservative in what you do; be liberal in what you accept from others /Postels law/
  4. 4. SQL injection
  5. 5. SQL injections● Creating queries by string concatenation is “the wrong way”● MySQL dont do multiple queries.● Let DB do validation - use parametrized queries● ORM frameworks lift the burden ● It is easy to forget to validate inline SQL somewhere
  6. 6. XSS
  7. 7. XSS● Escape HTML/JS/XML special characters on output● Vulnerability can exist on client side (JS). ● It can get hairy with JS, AJAX, JSONP etc ...
  8. 8. CSRF <img src=”http://www.bank.lv/pay?to=kristaps&amount=100” />● Third party unauthorized request to web site● Include unique token into each response and validate on request.● Never update data with GET
  9. 9. Storing passwords● Do not expose DB / other credentials● MD5 is too “cheap”. SHA1 is not “expensive enough”● Make hash functions slow. ● Multiple iterations ● Bcrypt
  10. 10. Authorization vs AuthenticationAutentication: authenticating user credentials. Usually done once per session.Authorization: checks that user is authorized to do particular action. Must be done on every request.
  11. 11. Session fixation● Session cookie stealing / guessing ● Initialize sessions ● Tie sessions to IP address / User Agent ● Expire / invalidate sessions.
  12. 12. PHP specific problems
  13. 13. register_globals~50% of open source PHP app vulnerabilities works only when register_globals are on
  14. 14. safe_modeWrong place, wrong solution
  15. 15. magic_quotesGives false sense of security and no real protection
  16. 16. display_errors Gives away too much informationLog your errors, do not display them
  17. 17. One .php file as one script PHP engine has no “application” concept. Class files, configuration files, etc should not be executable …...everything that is not .php by default is dumped as plaintext in browser
  18. 18. include and require accepts URLs as parameters Remote code injection made dead easyIf you disable remote_url_fopen, you cannot open any URL (without CURL)
  19. 19. All these settings should be disabled by default On most hosting servers they are not
  20. 20. Server security enviroment matters
  21. 21. TLS (SSL)● Public-Private key infrastructure● Server verification and data encryption● Ultimate trust to Certificate Authorities (CA)● Dont use self-signed certificates. Roll out your own CA .
  22. 22. Secure / insecure protocols● HTTP sends all information in plaintext● So does FTP/IMAP/POP3/STMP● Use HTTPS / SFTP / IMAPs / POP3s / STMP over TLS● DNS is built on trust. DNSSEC is not (yet) working.
  23. 23. [D]DoS● DoS – “million” requests from one client● DDoS – “zillion” requests from “million” clients● Handle DoS at firewall level.● Try to survive DDoS at router level.
  24. 24. Shared hosting● Easy, fast, secure – pick two● “Jail” each site● Selinux / AppArmor to rescue● IDS / mod_security is slow● Test backups.
  25. 25. Real life 100% secure system Slide intentionally left blank
  26. 26. Personal security weakest chain link
  27. 27. Passwords Passwords are like underwear.You dont share them and you change them often. KeepassX
  28. 28. Think● Dont use plaintext protocols over open WiFi● Secure your home router● Check URLs and filenames● Malware doesnt expose itself anymore ● Botnet ● Information stealing● Avoid buggy and insecure software (flash and acrobat reader).
  29. 29. Securing digital communication● Skype is sort-of secure● PGP● S/MIME
  30. 30. Handling incidents● Not all hackers all bad● Preserve evidence● Presume that attacker obtained maximum information.● System is compromised● Eliminate attack vectors● Offline backups help.
  31. 31. Questions ?
  32. 32. Futher reading● www.owasp.org – knowledge● www.cert.lv – Latvia netsecurity team Books● Stealing the Network: How to Own the Box by R. Russel – hacking “fiction” book.● Art of Deception by Kevin Mitnick – hacker “memoirs”

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