RE: SQL Injection

[<stevenr () mastek com>]

Hi Michael

I was just bouncing the idea off the group of encoding blindly. That would convert all HTML tags and so should mitigate 
the XSS risk to a large extent (even SQL injection, right? ). But would also play havoc with my data, specially since I 
have non-browser systems reading the data too. 

I feel the white list approach would be the only way to go.... 

Regards,
Steven Rebello

-----Original Message-----
From: Michael Silk [mailto:michaels () phg com au]
Sent: Wednesday, June 09, 2004 10:11 AM
To: Steven M. Christey; webappsec () securityfocus com
Subject: RE: SQL Injection


Hi,

        There are many many more possibilities for XSS then simply the 
        <script> tag, of course it depends on where the resulting string
        ends up, but simply replacing the <script> tag is *not* enough.

        SQL Injection, of course, can not be be mitigated by way of 
        replacing "<script>" tags either, you aren't really suggesting
        this are you ?

-- Michael

-----Original Message-----
From: Steven M. Christey [mailto:coley () mitre org]
Sent: Wednesday, 9 June 2004 7:52 AM
To: webappsec () securityfocus com
Subject: Re: SQL Injection



> BTW, any opinions on if I just encode all input without checking for any
> characters? Say converting all <script> to &lt;script&gt; Can anyone
> still do XSS or SQL Injection in that case?

Not that I can think of, but there might be implications if there's a
back end.

However...  If the routine is being coded in C or another language
that's prone to buffer overflows, then you need to make sure to
account for all the potential quoting when allocating the memory to
hold the resulting string.  "Transformation-based" buffer overflows
(my hastily coined term) are starting to become more common.  If the
transformation converts a double-quote character to a "&quote;", then
an attacker could expand the original string by a factor of 6, which
could have implications for the application itself *or* the back end.

- Steve


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