NYCPHP Meetup

[nycphp-talk] User Input Data scrubbing

Elijah Insua tmpvar at gmail.com
Fri Nov 28 15:26:59 EST 2008


Michele,


SQL injection and Html injection are two separate issues.

SQL injection is something like a user posting ';DELETE FROM users;  where
it deletes all of your user accounts.

Html/Cross Site Scripting is more along the lines of what you are talking
about.  There are tons of libraries out there
that attempt to kill off as many of these as possible.

As far as your 255 character theory, it is not completely true.  There are
other character sets such as UTF-8 which allow
for 65 thousand characters.  I would seriously invest some time into finding
a library that you can integrate.

- Elijah


On Fri, Nov 28, 2008 at 3:04 PM, Michele Waldman <mmwaldman at nyc.rr.com>wrote:

>  Could ya'll repost any responses to this.  Apparently, my new email
> address wasn't subscribed to the mailing list.
>
>
>  ------------------------------
>
> *From:* Michele Waldman [mailto:mmwaldman at nyc.rr.com]
> *Sent:* Friday, November 28, 2008 2:06 PM
> *To:* 'NYPHP Talk'
> *Subject:* User Input Data scrubbing
>
>
>
> I'm trying to scrub data input to insert into a database which I will later
> display on the website.
>
>
>
> In order to prevent sql injections and html injections into the code, I
> figured I'd just replace non alphanumeric characters with their html special
> character codes and remove any control characters all together except
> carriage return.
>
>
>
> The ascii character codes only go up to 255.
>
>
>
> However, there are lots more characters in html.
>
>
>
> If the user creates a string from which was generated using html using
> characters outside of the ascii character codes, what do those get
> translated to in the string?  A garage character?
>
>
>
> Is that a concern?  Or is my only concern those 255 characters in the ascii
> chart?  I'm thinking the 255 characters covers it all.  The characters are a
> finite set which were long ago predefined, unless that changes in the
> future, right?  This means scrubbing the data is a short function.
>
>
>
> I'm not using mysql_real_escape_string, because I replace all ' and " with
> their html character code.
>
>
>
> I'm not using htmlspecialchars, because it wasn't thorough enough.  I
> simply wrote a function that replaces just about every character with it's
> html character code.
>
>
>
> I'm doing this in php after the data is passed to me.
>
>
>
> Now, in the case of ajax, I just need to come up with a good approach for
> checking the data received from php, which may vary depending on the type of
> ajax used.
>
>
>
> Michele
>
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