Valid Email Addresses - XSS and SQL Injection
Since there are so many valid characters for email addresses, are there any valid email addresses that can in themselves be XSS attacks or SQL injections? I couldn't find any information on this on the web.
The local-part of the e-mail address may use any of these ASCII characters:
- Uppercase and lowercase English letters (a–z, A–Z)
- Digits 0 to 9
- Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~
- Character . (dot, period, full stop) provided that it is not the last character, and provided also that it does not appear two or more times consecutively (e.g. [email protected]).
http://en.wikipedia.org/wiki/E-mail_address#RFC_specification
I'm not asking how to prevent these attacks (I'm already using parametrized queries and escaping/HTML purifier), this is more a proof-of-concept.
The first thing that came to mind was 'OR [email protected], except that spaces are not allowed. Do all SQL injections require spaces?
Answer
Spaces are allowed if they are enclosed in quotes, however, so "'OR 1=1--"@gmail.com is a valid e-mail address. Also, it's probably less of a concern, but technically speaking, these are both valid e-mail addresses:
' BAD SQL STUFF -- <[email protected]>
[email protected] (' BAD SQL STUFF --)
Even if this wasn't possible, there's still no reason that you shouldn't be using paramaterized queries and encoding all user-inputted data displayed to users.