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Shiny,Let’s Be Bad Guys!
Exploiting and Mitigating theTop 10 Web App Vulnerabilities
Mike Pirnat - @mpirnat
David Stanek - @dstanek
Announcements
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
VolunteeringOpportunities
• 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!
Volunteering Info
• Current needs: http://bit.ly/pycon-volunteering-status
• More information:http://bit.ly/pycon2013-volunteer
Tutorial Feedback
• Go here:• https://www.surveymonkey.com/s/
pycon2013_tutorials or
• https://goo.gl/PvHDc
• Be honest!
QWho here has vulnerable apps?
Why it Matters
• Your users
• Your data
• Your business
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
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!
Today
• Background on a type of vulnerability
• Exploit it!• Discuss prevention
• Django-specific advice where possible
Disclaimer
Setup: 1
Make a virtualenv:$ virtualenv badguys$ cd badguys$ source bin/activate
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
Setup: 3
Install dependencies:$ cd src$ pip install -r requirements.txt
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
Setup: 4
Start up the app:$ python manage.py runserver
Find a Partner
1Injection
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
Trust No One
• External users• Internal users• Administrators
Attack Vectors
• GET parameters• POST parameters• PATH_INFO • Some HTTP headers: Cookie, Host• Uploaded Files
Possible Consequences
• Creation of malicious SQL (or other queries)
• Accessing private files on disk• Arbitrary code execution
Real-World Examples
• Sony Playstation Network• Ruby on Rails• http://es.pn/Z0jnoi
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
Accessing Private Files
• File system access + unvalidated user input allows attackers to navigate the file system
• http://localhost:8000/injection/file-access
Arbitrary Code Execution
• Unsafe input is dynamically evaluated or executed
• http://localhost:8000/injection/code-execution
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.
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
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
2Broken
Authentication& Session
Management
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
Possible Consequences
• Compromised user accounts
• Compromised administrative accounts
• Unauthorized use of privileged functionality
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
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...
3Cross-Site Scripting (XSS)
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
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)
Possible Consequences
• Execute scripts in a victim’s browser• Hijack sessions• Deface sites• Insert hostile content• Redirect users• Hijack browser (install malware)
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
XSS inDynamic 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
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
XSS inForm 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
QCan you trust the database?
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!
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
4InsecureDirect Object
References
Insecure DirectObject Reference
• Expose a reference to an internal implementation object without verifying authorization
• Attacker changes URL or GET/POST parameters, cookies
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
Exercises
• Manipulate parameters in the URL to access data that doesn’t belong to you
• http://localhost:8000/direct-object-references
Prevention
• Implement access controls on any direct references to restricted resources
• Implement per-user or per-session indirect object references
Django Advice
• Use permissions architecture to lock down views
• Customize queryset for looking up objects that involve user ownership
5Security Misconfiguration
Security Misconfiguration
• Insecure application settings• Unpatched flaws• Unused pages
Possible Consequences
• Unauthorized access to some system data or functionality
• Potential complete system compromise
Exercises
• Demos and discussion• http://localhost:8000/misconfiguration
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
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
QGateway to Social Engineering?
6SensitiveData Exposure
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
Insecure Cryptographic
Storage• Not encrypting worthy data• Unsafe key generation & storage, failure to
rotate keys• Weak algorithms• Weak or unsalted hashes
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
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.
Possible Consequences
• Expose individual users’ data• Account theft
• Compromise an admin account?!• Poor SSL setup can facilitate phishing
and man-in-the-middle attacks
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 (!!!)
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
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
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/
7MissingFunction Level
Access Control
MissingFunction LevelAccess Control
• Application doesn’t protect its functions properly
• Misconfiguration• Forgot proper code checks
Attack Vectors
• Authorized user changes a URL or parameter to a privileged function
• Anonymous users could access private functions that aren’t protected
Possible Consequences
• Compromised user accounts
• Compromised administrative accounts
• Unauthorized use of privileged functionality
Exercises
• Manipulate the URL to access privileged functionality
• http://localhost:8000/missing-access-control
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
Django Advice
• Use the permissions architecture to lock down views
• Don’t use the built-in admin for normal user admin tasks
8Cross-Site Request Forgery
CSRF Attacks
• Cross-Site Request Forgery (CSRF)• Attacker tricks victim into submitting
forged HTTP requests• Attack succeeds if user is authorized/
authenticated
Attack Vectors
• Image tags• Cross-Site Scripting (XSS)• Fake buttons• Phishing forms• Other techniques
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...
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/
CSRF via Image
• Craft an “image” link that triggers some site functionality
• http://localhost:8000/csrf/image
What if...
<img src="http://example.com/transferFunds?amount=1500&destinationAccount=attackersAcct#" width="0" height="0" />
CSRF viaForm Post
• Create an innocuous-looking form that POSTs to a vulnerable location
• http://localhost:8000/csrf/third-party-site
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
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)
9Using Known Vulnerable
Components
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
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
Possible Consequences
• Full range of weaknesses are possible• Impact could be minimal, or...• Complete host takeover!• Data compromise!
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
Django Advice
When @jacobian says there are new security releases for Django, upgrade!
10Unvalidated Redirects &
Forwards
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
Possible Consequences
• Install malware
• Phishing/information disclosure• Bypass access controls
External Redirection
• Use a redirection URL to redirect to an external location
• http://localhost:8000/redirects-and-forwards/redirects
Forwards
• Manipulate a forward parameter to gain access to privileged functionality
• http://localhost:8000/redirects-and-forwards/forwards
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
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
QWho here has vulnerable apps?
Parting Thoughts
Think Likea Bad Guy
Don’t Stop at Ten
Constant Change
Think Positive
Announcements
• Lunch—moved to Exhibit Hall D
• Feedback—https://goo.gl/PvHDc
• Volunteer:http://bit.ly/pycon2013-volunteer
http://bit.ly/pycon-volunteering-status
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
Contact Us
Mike Pirnathttp://mike.pirnat.com@mpirnat
David Stanekhttp://traceback.org@dstanek