Cqcon2015

So, you wanna crypto (in AEM)
Damien Antipa (@visiongeist)
Antonio Sanso (@asanso)
Adobe Research Switzerland

Who are these guys BTW
Damien Antipa
Senior UX Engineer Adobe Research Switzerland

Who are these guys BTW
Antonio Sanso
Software Engineer Adobe Research Switzerland
Committer and PMC Member for Apache Sling
VP (Chair) for Apache Oltu (OAuth Protocol Implementation in Java)
Internet Bug Bounty, Google Security Hall of Fame, Facebook Security
Whitehat, GitHub Security Bug Bounty, Microsoft Honor Roll

What is Cryptography?
DISCLAIMER – I am not a cryptographer
Cryptography is the art of protecting information

Confidentiality vs Integrity
Encryption Sign/Validate
Integrity Protection

Encryption
Plaintext: hello
Ciphertext: ΠΞιιΘ
AES
3DES
RSA

Integrity protection
HMAC
RSA
DSA
Plaintext: hello
Plaintext: hello

Why not DIY #1?
I need to encrypt

Why not DIY #2?
Plaintext: hello
Ciphertext: ΠΞιιΘ
AES ECB
AES ECB

Encryption is NOT Authentication
★

AEM Use Case: Encapsulate Token

Encapsulated Token
Sticky session

JSON Web Token
eyJhbGciOiJIUzI1NiIs
InR5cCI6IkpXVCJ9.
eyJpc3MiOiJhZW0iLC
JzdWIiOiJhc2Fuc28iL
CJleHAiOjE0MzUwNj
g3MTEsImlhdCI6MT
QzNTA2NTExMX0.
MaGUiPg07ezuP9yA
OaVLETQH6HMOpfo
Gwg_c0-PDw
{"alg":"HS256","typ":"JWT"}Header
Claims {"iss":"aem","sub":"asanso","exp":14350
11,"iat":1435065111}
Signature HMAC
★

Encapsulated Token
JWT
{…,"sub":"asanso","exp":1435068711,"iat":1435065111, …}
★
/etc/key/hmac

Problem - CSRF
CSRF = Cross site request forgery
OWASP TOP 10

CSRF – How does the attack work?
POST http://bank.com/transfer.do HTTP/1.1
acct=BOB&amount=100
The Attack (Mallory Page)
<form action="http://bank.com/transfer.do" method="POST">
<input type="hidden" name="acct" value=”ANTONIO"/>
<input type="hidden" name=amount" value="100000"/>
<input type="submit" value=”Show pictures"/>
</form>
Browsers make requests (with cookies) to any other origin

CSRF – AEM <= 6.0 Protection
Apache Sling Referrer Filter
White list of allowed referrer
for
POST/PUT/DELETE operations
Q. IS IT SAFE ? A. YES

CSRF – AEM <= 6.0 Protection
HTTP HTTP
Referer
HTTPS HTTPS
Referer
HTTP HTTPS
Referer
HTTPS HTTP
<html>
<script>
function load() {
var postdata = '<form id=dynForm method=POST action='http://bank.com/transfer.do'>' +
'<input type=hidden name=acct value=ANTONIO />' +
'<input type=hidden name=amount value=100000 />' +
'</form>';
top.frames[0].document.body.innerHTML=postdata;
top.frames[0].document.getElementById('dynForm').submit();
}
</script>
<body onload=

CSRF – Token (Classic solution)
- Include a hidden form field
<form action="http://bank.com/transfer.do" method="POST">
...
<input type="hidden" name="csrfToken" value=“ewqakjdsa”/>
</form>
- Store the token server side in a database
- Check if the token match
- Not cachable !
- Not scalable !

Goals of the CSRF implementation
★
- Easy to use
- Transparent to application code
- No dependencies
- Auto refresh
- Available on author and publish
- No leakage to other domain
- Browser support
- IE8+
- Scalable and Cacheable
- No sticky sessions
- No HTTP Sessions

How to use it in a project
If you are building an admin UI based on Granite, you need to do:
NOTHING - we include it for you
If you are building an independent or public facing login, you to:
you need to add granite.csrf.standalone client library
In both scenarios your Javascript code does NOT need to do
anything or be aware of the CSRF token.

Ensure Integrity and Caching
- Use JSON Web Token
- Sign using system HMAC key
- Validate the token using standard JWT validation
- Short expiration time
- Asynchronous update
http://localhost:4502/libs/granite/csrf/token.json

Covered Communication
- HTML forms. Make sure the synchronous POST includes the TOKEN
- Make sure all non-GET AJAX calls include the token
- “Asynchronous” file upload for legacy IE.
Make sure that form submissions to dynamically created
iFrames include the TOKEN.

XMLHttpRequest.prototype.send = function(method) {
this.setRequestHeader('CSRF-Token', globalToken);
send.apply(this, arguments);
};

function handleForm(ev) {
var form = ev.target;
if (form.nodeName.toLowerCase() === 'form') {
input = document.createElement('input');
input.setAttribute('type', 'hidden');
input.setAttribute('name', 'CSRF-Token');
input.setAttribute('value', globalToken);
form.appendChild(input);
}
}
document.addEventListener(
'submit', handleForm, true /* capture phase */);

https://docs.adobe.com/docs/en/aem/6-
0/develop/ref/javadoc/com/adobe/granite/crypto/CryptoSupport.html
https://docs.adobe.com/docs/en/aem/6-
0/develop/ref/javadoc/com/adobe/granite/oauth/jwt/package-
summary.html
Documentation
Questions?
Damien Antipa, Senior UX Engineer
Twitter: @visiongeist
Antonio Sanso, Software Engineer
Twitter: @asanso

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