I am just creating a registration form, and I am looking only to insert valid and safe emails into the database.
Several sites (including w3schools) recommend running FILTER_SANITIZE_EMAIL before running FILTER_VALIDATE_EMAIL to be safe; however, this could change the submitted email from an invalid into a valid email, which could not be what the user wanted, for example:
The user has the email address [email protected], but accidentally inserts jeff"@gmail.com.
FILTER_SANITIZE_EMAIL would remove the " making the email [email protected] which FILTER_VALIDATE_EMAIL would say is valid even though it's not the user's actual email address.
To avoid this problem, I plan only to run FILTER_VALIDATE_EMAIL. (assuming I don't intend to output/process any emails declared invalid)
This will tell me whether or not the email is valid. If it is then there should be no need to pass it through FILTER_SANITIZE_EMAIL because any illegal/unsafe characters, would've already caused the email to be returned invalid, correct?
I also don't know of any email approved as valid by FILTER_VALIDATE_EMAIL that could be used for injection/xss due to the fact that white spaces, parentheses () and semicolons would invalidate the email. Or am I wrong?
(note: I will be using prepared statements to insert the data in addition to this, I just wanted to clear this up)
Answer
Here's how to insert only valid emails.
<?php
$original_email = 'jeff"@gmail.com';
$clean_email = filter_var($original_email,FILTER_SANITIZE_EMAIL);
if ($original_email == $clean_email && filter_var($original_email,FILTER_VALIDATE_EMAIL)){
// now you know the original email was safe to insert.
// insert into database code go here.
}
FILTER_VALIDATE_EMAIL and FILTER_SANITIZE_EMAIL are both valuable functions and have different uses.
Validation is testing if the email is a valid format. Sanitizing is to clean the bad characters out of the email.
<?php
$email = "[email protected]";
$clean_email = "";
if (filter_var($email,FILTER_VALIDATE_EMAIL)){
$clean_email = filter_var($email,FILTER_SANITIZE_EMAIL);
}
// another implementation by request. Which is the way I would suggest
// using the filters. Clean the content and then make sure it's valid
// before you use it.
$email = "[email protected]";
$clean_email = filter_var($email,FILTER_SANITIZE_EMAIL);
if (filter_var($clean_email,FILTER_VALIDATE_EMAIL)){
// email is valid and ready for use
} else {
// email is invalid and should be rejected
}
PHP is open source, so these questions are easily answered by just using it.
Source for FILTER_SANITIZE_EMAIL:
/* {{{ php_filter_email */
#define SAFE "$-_.+"
#define EXTRA "!*'(),"
#define NATIONAL "{}|\\^~[]`"
#define PUNCTUATION "<>#%\""
#define RESERVED ";/?:@&="
void php_filter_email(PHP_INPUT_FILTER_PARAM_DECL)
{
/* Check section 6 of rfc 822 http://www.faqs.org/rfcs/rfc822.html */
const unsigned char allowed_list[] = LOWALPHA HIALPHA DIGIT "!#$%&'*+-=?^_`{|}~@.[]";
filter_map map;
filter_map_init(&map);
filter_map_update(&map, 1, allowed_list);
filter_map_apply(value, &map);
}
Source for FILTER_VALIDATE_EMAIL:
void php_filter_validate_email(PHP_INPUT_FILTER_PARAM_DECL) /* {{{ */
{
const char regexp[] = "/^(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){255,})(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}@)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-+[a-z0-9]+)*\\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-+[a-z0-9]+)*)|(?:\\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\\]))$/iD";
pcre *re = NULL;
pcre_extra *pcre_extra = NULL;
int preg_options = 0;
int ovector[150]; /* Needs to be a multiple of 3 */
int matches;
/* The maximum length of an e-mail address is 320 octets, per RFC 2821. */
if (Z_STRLEN_P(value) > 320) {
RETURN_VALIDATION_FAILED
}
re = pcre_get_compiled_regex((char *)regexp, &pcre_extra, &preg_options TSRMLS_CC);
if (!re) {
RETURN_VALIDATION_FAILED
}
matches = pcre_exec(re, NULL, Z_STRVAL_P(value), Z_STRLEN_P(value), 0, 0, ovector, 3);
/* 0 means that the vector is too small to hold all the captured substring offsets */
if (matches < 0) {
RETURN_VALIDATION_FAILED
}
}