Bulgaria PHP Conference

Sanitization

Example #1 Sanitizing and validating email addresses

<?php
$a 
'joe@example.org';
$b 'bogus - at - example dot org';
$c '(bogus@example.org)';

$sanitized_a filter_var($aFILTER_SANITIZE_EMAIL);
if (
filter_var($sanitized_aFILTER_VALIDATE_EMAIL)) {
    echo 
"This (a) sanitized email address is considered valid.\n";
}

$sanitized_b filter_var($bFILTER_SANITIZE_EMAIL);
if (
filter_var($sanitized_bFILTER_VALIDATE_EMAIL)) {
    echo 
"This sanitized email address is considered valid.";
} else {
    echo 
"This (b) sanitized email address is considered invalid.\n";
}

$sanitized_c filter_var($cFILTER_SANITIZE_EMAIL);
if (
filter_var($sanitized_cFILTER_VALIDATE_EMAIL)) {
    echo 
"This (c) sanitized email address is considered valid.\n";
    echo 
"Before: $c\n";
    echo 
"After:  $sanitized_c\n";    
}
?>

The above example will output:

This (a) sanitized email address is considered valid.
This (b) sanitized email address is considered invalid.
This (c) sanitized email address is considered valid.
Before: (bogus@example.org)
After: bogus@example.org

Example #2 Configuring a default filter

filter.default = full_special_chars
filter.default_flags = 0

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User Contributed Notes 1 note

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zeeshan dot karamat dot abbas at gmail dot com
23 days ago
If we omit using a filter then PHP by default puts a filter which is FILTER_DEFAULT which will use default filter. Now the question is what is a default filter. A default filter is unsafe_raw which will allow the unsafe raw data passed on to the server. This value is available in php.ini file. It is suggested that a developer should update this value inside php.ini file as under:
filter.default = full_special_chars
filter.default_flags = 0

Whereas in php.ini file above values are by default, set as under:
;filter.default = unsafe_raw
;filter.default_flags =

Above semicolons are commented out lines so surely one needs to remove those semicolons to apply the changes made. If we do not do above things then what will happen. In that case PHP will use default filter which would surely be FILTER_UNSAFE_RAW and one can see that unsafe raw data can then be passed onto server which can make the life a hacker easier.
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