RE: New Whitepaper - "Second-order Code Injection Attacks"

["Gunter Ollmann (NGS)" <gunter () ngssoftware com>]

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