Jeff,
I see XSS as merely a subgroup of code injection attacks - and it is
important to make that distinction. While they (as in XSS) still get a lot
of press coverage, they're not particularly remarkable. The most effective
attacks abusing XSS vulnerabilities to date would probably be within
Phishing attacks - thankfully something that the press havn't focused upon.
The OWASP categories of "stored" or "reflected", while good for a basic
understanding, are a little too limited in scope to cover all XSS
vulnerabilities. They are certainly inadequate for covering much of the
code injection possibilities.
Having said all that, it still suprises me how many people think that by
testing for <script>alert('XSS')</script> - getting a positive response -
means that an application is 100% vulnerable to XSS. People need to be a
lot clearer about the types of code injection flaws a web-based application
is vulnerable to -- instead of using a Cross-site Scripting catchall tag.
Cheers,
Gunter
-----Original Message-----
From: Jeff Williams [mailto:jeff.williams@aspectsecurity.com]
Sent: 02 November 2004 20:44
To: Crispin Cowan; Gunter Ollmann
Cc: bugtraq@securityfocus.com; webappsec@securityfocus.com
Subject: Re: New Whitepaper - "Second-order Code Injection Attacks"
Gunter,
Thanks for the comprehensive treatment of this class of
vulnerabilities. The OWASP Top Ten paper breaks down XSS
flaws into "stored" and "reflected"
categories, but your paper is far closer to a complete theory
about all the ways that tainted data can undermine the
security of applications.
--Jeff
----- Original Message -----
From: "Crispin Cowan" <crispin@immunix.com>
To: "Gunter Ollmann" <gunter@ngssoftware.com>
Cc: <bugtraq@securityfocus.com>
Sent: Monday, November 01, 2004 8:45 PM
Subject: Re: New Whitepaper - "Second-order Code Injection Attacks"
I found an instance of this class of vulnerability in 1998 where an
attacker could inject code into the "locate" database,
which would later
be executed when root tried to do a locate on some path name
http://msgs.securepoint.com/cgi-bin/get/bugtraq/601/1.html
Mine was not the first such"secondary code injection"
attack. It was a
consequence of exploring a PoC by MiG for a buffer overflow
vulnerability in bash, where in a tall directory tree would overflow
bash when you try to cd into that directory and you have
the pwd set to
be part of your prompt. At the time, it did not occur to me
that it was
a special kind of buffer overflow.
Crispin
Gunter Ollmann wrote:
Hi list,
NGS Software is pleased to make available a new whitepaper about
second-order code injection attacks.
Abstract:
"Many forms of code injection targeted at web-based
applications (for
instance cross-site scripting and SQL injection) rely upon the
instantaneous
execution of the embedded code to carry out the attack
(e.g. stealing a
user's current session information or executing a modified
SQL query).
In
some cases it may be possible for an attacker to inject
their malicious
code
into a data storage area that may be executed at a later
date or time.
Depending upon the nature of the application and the way
the malicious
data
is stored or rendered, the attacker may be able to conduct
a second-order
code injection attack.
A second-order code injection attack can be classified as
the process in
which malicious code is injected into a web-based
application and not
immediately executed, but instead is stored by the
application (e.g.
temporarily cached, logged, stored in a database) and then later
retrieved,
rendered and executed by the victim."
The paper can be accessed from:
http://www.nextgenss.com/papers/SecondOrderCodeInjection.pdf
Cheers,
Gunter
------------------------------------------------------
G u n t e r O l l m a n n, MSc(Hons), BSc
Professional Services Director
Next Generation Security Software Ltd.
First Floor, 52 Throwley Way Tel: +44 (0)208 401 0089
Sutton, Surrey, SM1 4BF, UK Fax: +44 (0)208 401 0076
http://www.nextgenss.com
------------------------------------------------------
--
Crispin Cowan, Ph.D. http://immunix.com/~crispin/
CTO, Immunix http://immunix.com
