Domain Driven Security Jfokus 2016

Arm yourself with Domain Driven Security.
It’s time to slay some security trolls…
@danbjson, @DanielDeogun
Omegapoint
Jfokus
Stockholm February 2016

About Us…
Umeå
Malmö
Göteborg
Falun
New York
Stockholm
Daniel Deogun
Security Paratrooper
Dan Bergh Johnsson
Secure Domain Philosopher
Omegapoint

Key Take Aways
• DDSec helps one to design secure software without actively thinking
about security
• Treat injection ﬂaws as a modelling problem rather than a validation
problem
• Context mapping is essential to avoid XSS and other 2nd order
injection attacks
• Micro-services will be scary as hell, unless the world gets a grip on
context mapping

Attacks From A DDD
Perspective
Complex Technical
Complex
Domain
Simple Domain
Simple
Technical

Purchasing
“Unencyclopedia”
[Encyclopedia]

Technical Approach
• OWASP “indata validation”
• if(value < 0) -> don’t accept
• Encourage separation of validation and data
• Problem whack-a-mole ahead!

Analysis á la DDD
• Observation
• Quantity is modelled as integer
• Quantity is an implicit concept
• Analysis
• Modelling is incomplete or missing

Analysis á la DDD
-1 : Integer
-1 : Quantity
OrderLine {ISBN, Quantity}

Quantity made explicit -
a good start
public final class Quantity {
public final int value;
public Quantity(final int value) {
isTrue(value > 0, "Quantity must be greater than zero. Got: %s", value);
this.value = value;
}
…

Ubiqutous Domain
Primitives
• Library of domain primitives
• Consolidates business rules
• Raises the ﬂoor
void buyBook(String, int) -> buyBook(ISBN, Quantity)

Another concept made explicit
public final class EmailAddress {
public final String value;
public EmailAddress(final String value) {
isTrue( ?????????, “Not valid email. Got: %s", value);
this.value = value;
}
…

Email according to spec
• RFC 5322 3.4 Address Speciﬁcation (RFC 821, RFC 2821)
• Some OK examples
• root@127.0.0.1
• !#$%&'*+-/=?^_`{|}~@omegapoint.se
• ”Åsa Sjölander”@omegapoint.se
• Regexp : (?:(?:rn)?[ t])*(?:(?:(?:[^()<>@,;:".[] 000-031]+(?:(?:(?:rn)?[ t])+|Z|(?=[
["()<>@,;:".[]]))|"(?:[^"r]|.|(?:(?:rn)?[ t]))*"(?:(?:rn)?[ t])*)(?:.(?:(?:rn)?[ t])*(?:
[^()<>@,;:".[] 000-031]+(?:(?:(?:rn)?[ t])+|Z|(?=[["()<>@,;:".[]]))|"(?:[^"r]|.|(?:(?:r
n)?[ t]))*"(?:(?:rn)?[ t])*))*@(?:(?:rn)?[ t])*(?:[^()<>@,;:".[] 000-031]+(?:(?:(?:rn)?[ t])
+|Z|(?=[["()<>@,;:".[]]))|[([^[]r]|.)*](?:(?:rn)?[ t])*)(?:.(?:(?:rn)?[ t])*(?:[^()<>@,;:
".[] 000-031]+(?:(?:(?:rn)?[ t])+|Z|(?=[["()<>@,;:".[]]))|[([^[]r]|.)*](?:(?:rn)?
[ t])*))*|(?:[^()<>@,;:".[] 000-031]+(?:(?:(?:rn)?[ t])+|Z|(?=[["()<>@,;:".[]]))|"(?:[^"r
]|.|(?:(?:rn)?[ t]))*"(?:(?:rn) /… 6424 chars

You define Your domain
• Bounded Context - bounded by what you need
• Is “root@127.0.0.1” sensible to you?
• Strength not by “how wide” but by “how speciﬁc”
• Start simple - limit to your core cases
• E.g. “daniel.deogun@omegapoint.se”
• Let the model grow

What is DDSec?
“Domain Driven Security is about taking ideas from
DDD and using them as tools to address security
concerns, even though the tools were not originally
designed speciﬁcally for security issues.”
- Dan Bergh Johnsson, Dr. John Wilander [2009]
http://dearjunior.blogspot.be/2009/09/introducing-domain-driven-security.html

History of DDSec
2009 20162010
Dan Bergh Johnsson
John Wilander
Erland Oftedal 
@Webtonull
OWASP Europe
Daniel Deogun
Industry PracticeDDSec Coined
JavaZone
Jfokus
OPKoKo
Devoxx
DDD Europe
Jfokus
DDD Summit
Daniel Sawano
Book about DDSec

Injection Flaw
“Injection ﬂaws, such as SQL, OS, and LDAP injection
occur when untrusted data is sent to an interpreter as
part of a command or query. The attacker’s hostile data
can trick the interpreter into executing unintended
commands or accessing data without proper
authorization.”
- OWASP top 10

The Classics -
Dynamic SQL String
SELECT … FROM Users
WHERE username = ’<?username>’
AND password = ’<?password>’
danbj catsarecute
WHERE username = ’danbj’
AND password = ’catsarecute’
Warning! This is just an example. Do not store passwords in plain text.
Do not use relational databases for user management.

SQL Injection
SELECT … FROM Users  
WHERE username = ’<?username>’
AND password = ’<?password>’
evilhaxxOr ’OR 1=1 --
WHERE username = ’evilhaxxOr’
AND password = ’’OR 1=1 --’
SELECT … FROM Users  
WHERE username = ’’OR 1=1 --’  
AND password = ’doesnotmatteranymore’
Warning! This is just an example. Do not store passwords in plain text.
Do not use relational databases for user management.

What’s the problem?
and solution?
• ‘OR 1=1 -- is not a valid username
• This is implicit in the code
• Needs to be made explicit
• Modelling required

Prepared Statements
AKA Parametrised Queries
• SQL Injection is solved by prepared
statements
• But what if the query structure is dynamic?
• Other Injection Flaws
• LDAP, Command, XPath, HTTP header …

HTTP Response with Cookie
[https://www.owasp.org/index.php/HTTP_Response_Splitting]
String author = … /* request, database, user setting … */
...
Cookie cookie = new Cookie("author", author);
cookie.setMaxAge(cookieExpiration);
response.addCookie(cookie);
HTTP/1.1 200 OK
...
Set-Cookie: author=Jane Smith
…
<html><head><title>The real content</title> ...

HTTP Injection
Hacked ‘author’ value into database/setting …
author : "Wiley HackerrnHTTP/1.1 200 OKrn..."
HTTP/1.1 200 OK
...
Set-Cookie: author=Wiley Hacker
HTTP/1.1 200 OK
…
<html><head><title>Hacked content</title> …
...
<html><head><title>The real content</title> ...
[https://www.owasp.org/index.php/HTTP_Response_Splitting]

RFC 2616 HTTP/1.1
Ch 4 HTTP Message
HTTP-message = Request | Response ; HTTP/1.1 messages
generic-message = start-line
*(message-header CRLF)
CRLF
[ message-body ]
start-line = Request-Line | Status-Line
message-header = field-name ":" [ field-value ]
field-name = token
field-value = *( field-content | LWS )
field-content = <the OCTETs making up the field-value
and consisting of either *TEXT or combinations
of token, separators, and quoted-string>
http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4

DDSec to the Rescue on
Injection Flaw
• DDD helps one to separate data from
code
• Validating with respect to the model is
crucial

A Quick Note On
Validation
• Validation order
• Origin
• Length
• (Lexeme, content text)
• Parsing, content structure
• Semantics
- Dr. John Wilander

Cross Site Scripting (XSS)
“XSS ﬂaws occur whenever an application takes untrusted
data and sends it to a web browser without proper
validation or escaping. XSS allows attackers to execute
scripts in the victim’s browser which can hijack user
sessions, deface web sites, or redirect the user to malicious
sites.”
- OWASP top 10

Demo
Cross Site Scripting (XSS)

Domain Perspective
Text
Comment
Text

Domain Perspective
Text
Text
Code
Comment

Fix the Broken Mapping
<script>
<script>
Text
Code
<script>

Code
SQL Injection vs XSS
Code

2nd order injection
Web
Srv
DB
Log
Log
Adm

Preventing Data Leakage 
read once object [Daniel Sawano]
public final class SensitiveValue implements Externalizable {
private final AtomicReference<String> value;
public SensitiveValue(final String value) {
this.value = new AtomicReference<>(validated(value));
}
public String value() {
return notNull(value.getAndSet(null), "Sensitive value has already been consumed");
}
@Override
public String toString() {
return "SensitiveValue value = *****";
}
@Override
public void read / writeExternal(final ObjectOutput out) throws IOException {
throw new UnsupportedOperationException("Not allowed on sensitive value");
}

How did DDSec Help Us?
• DDD gave deeper insight in nature of XSS
• Context mapping allows one to “detect” possible
broken maps
• Modeling conﬁdentiality protects against accidental
disclosure of sensitive data

Complex Domain Attack
Order
Finance Storage Shipping
-1
-1
-1

Micro-servicing the
Monolith
Payment
Policy

Payment
Micro-servicing the
Monolith
Payment
Policy
InsurancePurchase

Making a change with
surgical precision
Payment
Policy
Payment
Conﬁrm
Reject
Giro Bounce
Giro Conﬁrm
Purchase
Bank
Insurance

What we would have done
Payment
Policy
Cash Payment
Conﬁrm
Reject
Giro Bounce
Giro Conﬁrm
Purchase
Bank
Insurance
Giro Payment

Micro-Service Hell
• We’re moving towards more and more
micro-services
• Implemented by separate teams
• How do we guarantee correct context
mappings?

Current State,
Future Direction
• Academic research on DDSec
• Two master’s thesis projects in cooperation with Royal Institute of Technology
(KTH)
• Cooperation with Linnaeus University, computer science dept
• Industry practice
• Practice every day
• more needed - especially regarding how to handle micro-services
• investigating DDSec as applicable to DDOS-attacks
• Writing
• Early stage of book by Dan Bergh Johnsson, Daniel Deogun and Daniel Sawano.

Thanks
@danbjson, @DanielDeogun

Image References
• [Questions - https://flic.kr/p/9ksxQa] by Damián Navas under license https://creativecommons.org/licenses/by-nc-nd/2.0/
• [Encyclopedia - https://www.flickr.com/photos/stewart/461099066] by Stewart Butterfield under license https://creativecommons.org/licenses/by/2.0/

Domain Driven Security Jfokus 2016

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