Shiny, Let's Be Bad Guys: Exploiting and Mitigating the Top 10 Web App Vulnerabilities

Slides from the Pycon 2013 presentation of our tutorial that walks through the OWASP Top 10 web application vulnerabilities.

Transcript

1. Text Shiny, Let’s Be Bad Guys! Exploiting and Mitigating the Top 1 0 Web App Vulnerabilities Mike Pirnat - @mpirnat David Stanek - @dstanek
2. Announcements
3. Schedule & Lunch • This session will run 9:00 AM - 12:20 PM • 20-minute break at 10:50 AM • Lunch 12:20 PM - 1:20 PM • Lunch moved to Exhibit Hall D
4. Volunteering Opportunities • Low-commitment! Fun! • SWAG bagging: Thursday 4-8 PM • Just do 10 bags! (~1/2 hr) • Registration Desk: any time • 1-2 hours helps • Friday => meet everyone!
5. Volunteering Info • Current needs: http://bit.ly/pycon-volunteering-status • More information: http://bit.ly/pycon2013-volunteer
6. Tutorial Feedback • Go here: • https://www.surveymonkey.com/s/ pycon2013_tutorials or • https://goo.gl/PvHDc • Be honest!
7. http://i.qkme.me/3r16r5.jpg
8. Q Who here has vulnerable apps?
9. Why it Matters • Your users • Your data • Your business
10. OWASP • http://www.owasp.org • Open Web Application Security Project • Non-profit focused on improving software security • Documentation and tools to help learn about security and protect your apps
11. OWASP Top Ten • Based on risk data from 8 firms • Over 500,000 vulnerabilities, hundreds of orgs, thousands of apps • Selected & prioritized by prevalence data combined with estimates of exploitability, detectability, and impact • Recently updated for 2013!
12. Today • Background on a type of vulnerability • Exploit it! • Discuss prevention • Django-specific advice where possible
13. Disclaimer
14. Setup: 1 Make a virtualenv: $ virtualenv badguys $ cd badguys $ source bin/activate
15. Setup: 2 Clone our repository: $ git clone https://github.com/ mpirnat/lets-be-bad-guys src Or pull the latest changes: $ cd src $ git pull
16. Setup: 3 Install dependencies: $ cd src $ pip install -r requirements.txt
17. Setup: 2 & 3 (Offline/USB) • Extract the project: $ mkdir src $ unzip /Volumes/BADGUYS/project/ badguys.zip -d src/ • Install dependencies: $ cd src $ pip install -r requirements.txt -i file:///Volumes/BADGUYS/software
18. Setup: 4 Start up the app: $ python manage.py runserver
19. Find a Partner
20. 1 Injection
21. Injection Attacks • When an application sends untrusted data to an interpreter • Can result in data loss/corruption, lack of accountability, denial of access • Can lead to complete host takeover
22. Trust No One • External users • Internal users • Administrators
23. Attack Vectors • GET parameters • POST parameters • PATH_INFO • Some HTTP headers: Cookie, Host • Uploaded Files
24. Possible Consequences • Creation of malicious SQL (or other queries) • Accessing private files on disk • Arbitrary code execution
25. Real-World Examples • Sony Playstation Network • Ruby on Rails • http://es.pn/Z0jnoi
26. SQL Injection • Unescaped user input causes the premature end of a SQL query and allows a malicious query to be executed... """ select * from users where username='%s'; """ • http://localhost:8000/injection/sql
27. Accessing Private Files • File system access + unvalidated user input allows attackers to navigate the file system • http://localhost:8000/injection/file- access
28. Arbitrary Code Execution • Unsafe input is dynamically evaluated or executed • http://localhost:8000/injection/code- execution
29. Prevention • Validate ALL user input • Sign cookies, don’t accept if signature is bogus/missing • Use ORMs or bind variables when talking to the database • Don’t use eval or exec, beware of pickle, user-supplied YAML, etc.
30. Django Advice • Make sure data types for your model are tight • Use Forms instead of ModelForms for stronger validation • Make new validators as needed for your application • Make sure your URL regexes for dynamic URLs are tight
31. Django Advice • Use the ORM when you can • When you can’t, use extreme caution! • Bind variables • No string concatenation/formatting of anything that came from the client
32. 2 Broken Authentication & Session Management
33. Broken Auth & Session Management • Attacker uses leaks or flaws in authentication or session management to impersonate users • Roll-your-own solutions contribute to the difficulty of finding these flaws
34. Possible Consequences • Compromised user accounts • Compromised administrative accounts • Unauthorized use of privileged functionality
35. Prevention • Hash or encrypt passwords • Don’t let credentials be easily overwritten • Don’t put session IDs in URLs • Allow session IDs to timeout/log out • Rotate session IDs after successful login • TLS connections for passwords, session IDs
36. Django Advice • Use django.contrib.auth • Consider https://github.com/yourlabs/ django-session-security middleware for timing out sessions • We’ll talk about transport layer security later on...
37. 3 Cross-Site Scripting (XSS)
38. XSS Attacks • Cross-Site Scripting (XSS) • The most prevalent web app security flaw • App includes user-supplied data in content sent to the browser without properly validating or sanitizing it
39. XSS Attacks • Stored: injected code permanently stored in database, message forum, comment, etc. • Reflected: injected code in live request to server, reflected back in error message or search result • DOM: injected code in browser DOM environment that causes scripts to run in unexpected ways (eg, reading from URL)
40. Possible Consequences • Execute scripts in a victim’s browser • Hijack sessions • Deface sites • Insert hostile content • Redirect users • Hijack browser (install malware)
41. Most Often Seen... • Places where user-created text is displayed to other users (comments, messages) • Form inputs where value is populated with user-supplied data • Script tags where user-supplied data is populated into script variables
42. XSS in Dynamic URLs • Part of the URL path is variable, isn’t validated, and gets included into the page • http://localhost:8000/cross-site- scripting/path-matching/your-path- here
43. XSS in Query String Parameters • Unvalidated user input from a query string parameter is included in the page • http://localhost:8000/cross-site- scripting/query-params?qs=awesome
44. XSS in Form Fields • The value part of an input is prematurely terminated, allowing Javascript to be injected into the element (eg, adding an onclick) • http://localhost:8000/cross-site- scripting/form-field
45. Q Can you trust the database?
46. Prevention • Escape all untrusted data based on the HTML context the data will be placed into • Whitelist input validation • Consider auto-sanitization libraries for rich content (eg, OWASP’s AntiSamy) • Update your parents’/in-laws’ browsers!
47. Django Advice • Be careful with the safe filter, django.utils.safestring, etc. • Be careful with your own template tags; django.utils.html.escape is your friend! • Use form.as_p, form.as_table, form.as_ul
48. 4 Insecure Direct Object References
49. Insecure Direct Object Reference • Expose a reference to an internal implementation object without verifying authorization • Attacker changes URL or GET/POST parameters, cookies
50. Possible Consequences • Compromise of all data that can be referenced by the vulnerable parameter • Unless the namespace is sparse, an attacker can easily access all available data of that type
51. Exercises • Manipulate parameters in the URL to access data that doesn’t belong to you • http://localhost:8000/direct-object- references
52. Prevention • Implement access controls on any direct references to restricted resources • Implement per-user or per-session indirect object references
53. Django Advice • Use permissions architecture to lock down views • Customize queryset for looking up objects that involve user ownership
54. 5 Security Misconfiguration
55. Security Misconfiguration • Insecure application settings • Unpatched flaws • Unused pages
56. Possible Consequences • Unauthorized access to some system data or functionality • Potential complete system compromise
57. Exercises • Demos and discussion • http://localhost:8000/misconfiguration
58. Prevention • Have a repeatable hardening process • Have a process for keeping on top of updates and patches • Architecture that provides secure separation between components • Periodic scans and audits
59. Django Advice • Don’t run in debug mode in production • Keep your SECRET_KEY secret! • Keep Python code out of webserver’s root • Don’t run admin publicly (if you can help it) • Don’t use the built-in admin for normal user admin tasks
60. Q Gateway to Social Engineering?
61. 6 Sensitive Data Exposure
62. Sensitive Data Exposure • Failure to properly protect credit cards, tax ids, authentication credentials, etc. • Sensitive data deserves extra protection such as encryption at rest or in transit, special precautions when exchanged with the browser
63. Insecure Cryptographic Storage • Not encrypting worthy data • Unsafe key generation & storage, failure to rotate keys • Weak algorithms • Weak or unsalted hashes
64. Insufficient Transport Layer Protection • May not authenticate, encrypt, and protect the confidentiality and integrity of sensitive network traffic • May use weak algorithms • May use expired or invalid certificates • May use certificates incorrectly
65. Possible Consequences • Compromise of all data that should have been encrypted • This can be highly sensitive information: credentials, credit cards, personal data, health records, etc.
66. Possible Consequences • Expose individual users’ data • Account theft • Compromise an admin account?! • Poor SSL setup can facilitate phishing and man-in-the-middle attacks
67. Attack Vectors • Attacker monitors network traffic of your users • Maybe in public places (Starbucks, conference wi-fi, etc.) • Maybe back end connections • Maybe inside your network (!!!)
68. Prevention • Encrypt sensitive data at rest • Encrypt offsite backups; manage keys separately • Use strong standard algorithms, strong keys • Hash passwords with strong standard algorithm & use appropriate salt • Protect passwords & keys from unauthorized access
69. Prevention • Require SSL for all sensitive pages; redirect non-SSL requests to SSL • Set the “secure” flag on sensitive cookies • Use only strong SSL algorithms • Ensure your cert is valid, not expired, not revoked, and matches your domain • SSL/encryption on the back end too
70. Django Advice • Use django.contrib.auth for proper password salting and hashing • Require SSL in Apache or Nginx • Require SSL using middleware: • http://www.redrobotstudios.com/blog/2010/02/06/ requiring-https-for-certain-paths-in-django/ • http://djangosnippets.org/snippets/2833/ • http://djangosnippets.org/snippets/1467/
71. 7 Missing Function Level Access Control
72. Missing Function Level Access Control • Application doesn’t protect its functions properly • Misconfiguration • Forgot proper code checks
73. Attack Vectors • Authorized user changes a URL or parameter to a privileged function • Anonymous users could access private functions that aren’t protected
74. Possible Consequences • Compromised user accounts • Compromised administrative accounts • Unauthorized use of privileged functionality
75. Exercises • Manipulate the URL to access privileged functionality • http://localhost:8000/missing-access- control
76. Prevention • Consider every page; public or private? • If authentication is required, make sure that checks are in place • If additional authorization is required, make sure that checks are in place • Deny all by default; explicitly grant access to users or roles
77. Django Advice • Use the permissions architecture to lock down views • Don’t use the built-in admin for normal user admin tasks
78. 8 Cross-Site Request Forgery
79. CSRF Attacks • Cross-Site Request Forgery (CSRF) • Attacker tricks victim into submitting forged HTTP requests • Attack succeeds if user is authorized/ authenticated
80. Attack Vectors • Image tags • Cross-Site Scripting (XSS) • Fake buttons • Phishing forms • Other techniques
81. Possible Consequences • Cause victim to change any data the victim is allowed to change • Cause victim to perform any function the victim is authorized to use • Impact varies based on victim’s role • Think of some possibilities...
82. Real-World Examples • Facebook: http://amolnaik4.blogspot.com/ 2012/08/facebook-csrf-worth- usd-5000.html • Google/Gmail: http://cryptogasm.com/2012/02/does- google-understand-csrf/
83. CSRF via Image • Craft an “image” link that triggers some site functionality • http://localhost:8000/csrf/image
84. What if... <img src="http://example.com/ transferFunds?amount=1500& destinationAccount=attackersAcct#" width="0" height="0" />
85. CSRF via Form Post • Create an innocuous-looking form that POSTs to a vulnerable location • http://localhost:8000/csrf/third-party- site
86. Prevention • Don’t “do” things on a GET • Include a unique token in a hidden field (often used in concert with a cookie) • Validate token to make sure the request is from on-site • Avoid putting the token into a query string
87. Django Advice • Don’t change the built-in settings! • Do use the CSRF middleware and template tag in forms • Be VERY CAREFUL about deactivating it (csrf_exempt decorator) • Be careful about APIs (Tastypie, oauth)
88. 9 Using Known Vulnerable Components
89. Components with Known Vulnerabilities • Libraries, frameworks, and other modules almost always run with full privilege • Hard to stay up to date on everything • Do you even know all the components in use, let alone their versions? • Components with known problems can be identified & exploited with automated tools
90. Attack Vectors • Attacker identifies a weak component through scanning or manual analysis • Customize exploit as needed • More difficult the deeper the component is in the application
91. Possible Consequences • Full range of weaknesses are possible • Impact could be minimal, or... • Complete host takeover! • Data compromise!
92. Prevention • Don’t use components you don’t write (unrealistic) • Keep components up to date • Identify all components and versions • Monitor security of these components
93. Django Advice When @jacobian says there are new security releases for Django, upgrade!
94. 1 0 Unvalidated Redirects & Forwards
95. Redirection Abuse • Attacker tricks user into visiting a URL that redirects or forwards the request without validating the redirect location • Users prone to click because the link is to a legitimate site
96. Possible Consequences • Install malware • Phishing/information disclosure • Bypass access controls
97. External Redirection • Use a redirection URL to redirect to an external location • http://localhost:8000/redirects-and- forwards/redirects
98. Forwards • Manipulate a forward parameter to gain access to privileged functionality • http://localhost:8000/redirects-and- forwards/forwards
99. Prevention • Don’t use redirects or forwards • Don’t involve user-supplied data to build the redirect location • Ensure the supplied value is valid and authorized for the user
100. Django Advice • Use django.utils.http.is_safe_url to check redirect URLs • Used by django.contrib.auth internally • Consider wrapping is_safe_url if you have to allow other off-domain URLs
101. Q Who here has vulnerable apps?
102. Parting Thoughts
103. Think Like a Bad Guy
104. Don’t Stop at Ten
105. Constant Change
106. Think Positive
107. Announcements • Lunch—moved to Exhibit Hall D • Feedback—https://goo.gl/PvHDc • Volunteer: http://bit.ly/pycon2013-volunteer http://bit.ly/pycon-volunteering-status
108. Links • http://www.owasp.org • https://www.owasp.org/index.php/ Category:OWASP_Top_Ten_Project • https://docs.djangoproject.com/en/dev/ topics/security/ • https://github.com/mpirnat/lets-be-bad-guys
109. Contact Us Mike Pirnat http://mike.pirnat.com @mpirnat David Stanek http://traceback.org @dstanek