PHP simple parameter filtering code learning

/**
* Parameter filtering code
* edit bbs.it-home.org
*/
if (@get_magic_quotes_gpc ()) {
$_GET = sec ( $_GET );
$_POST = sec ( $_POST );
$_COOKIE = sec ( $_COOKIE );
$_FILES = sec ( $_FILES );
}
$_SERVER = sec ( $_SERVER );
function sec(&$array) {
//If it is an array, traverse the array and call it recursively
if (is_array ( $array )) {
foreach ( $array as $k => $v ) {
$array [$k] = sec ( $v );
}
} else if (is_string ( $array )) {
//Use the addslashes function to process
$array = addslashes ( $array );
} else if (is_numeric ( $array )) {
$array = intval ( $array );
}
return $array;
}
?>

1. Judgment of integer parameters When the input parameter YY is an integer, usually the original SQL statement in abc.asp is roughly as follows: select * from table name where field=YY, so you can use the following steps to test whether SQL injection exists. ①HTTP://xxx.xxx.xxx/abc.asp?p=YY’ (with a single quote attached), at this time the SQL statement in abc.ASP becomes select * from table name where field=YY’, abc.asp runs abnormally; ②HTTP://xxx.xxx.xxx/abc.asp?p=YY and 1=1, abc.asp runs normally, and the results are the same as HTTP://xxx.xxx.xxx/abc.asp?p=YY ; ③HTTP://xxx.xxx.xxx/abc.asp?p=YY and 1=2, abc.asp runs abnormally; If the above three steps are fully satisfied, there must be a SQL injection vulnerability in abc.asp.

An integer filter function, the code is as follows:

function num_check($id) {
if (! $id) {
die ( 'Parameter cannot be empty!' );
} // Whether it is empty Judgment
else if (inject_check ( $id )) {
die ( 'illegal parameter' );
} // Injection judgment
else if (! is_numetic ( $id )) {
die ( 'illegal parameter' );
 }
//Number judgment
$id = intval ($id);
//Integerization
return $id;
}
//Character filter function
function str_check($str ) {
if (inject_check ( $str )) {
die ( 'illegal parameter' );
}
//Injection judgment
$str = htmlspecialchars ( $str );
//Convert html
return $str;
}
function search_check($str) {
$str = str_replace ( "_", "_", $str );
//Filter out "_"
$str = str_replace ( "%", "%", $ str );
//Filter out "%"
$str = htmlspecialchars ( $str );
//Convert html
return $str;
}
//Form filter function
function post_check($str, $min, $max) {
if (isset ( $min ) && strlen ( $str ) < $min) {
die ( 'minimum $min bytes' );
} else if (isset ( $max ) && strlen ( $ str ) > $max) {
die ( 'Up to $max bytes' );
}
return stripslashes_array ( $str );
}
?>

When the input parameter YY is a string, usually the original SQL statement in abc.asp is roughly as follows: select * from table name where field='YY', so you can use the following steps to test whether SQL injection exists. ①HTTP://xxx.xxx.xxx/abc.asp?p=YY’ (with a single quote attached), at this time the SQL statement in abc.ASP becomes select * from table name where field=YY’, abc.asp runs abnormally; ②HTTP://xxx.xxx.xxx/abc.asp?p=YY&;nb … 39;1'='1', abc.asp runs normally and is the same as HTTP://xxx.xxx.xxx/abc.asp ?p=YY has the same running results; ③HTTP://xxx.xxx.xxx/abc.asp?p=YY&;nb … 39;1'='2', abc.asp runs abnormally; If the above three steps are fully satisfied, there must be a SQL injection vulnerability in abc.asp.

Attach a function to prevent sql injection:

//Anti-injection function
function inject_check($sql_str) {
return eregi ( 'select|inert|update|delete|'|/*|*|../|./ |UNION|into|load_file|outfile', $sql_str );
// Filter to prevent injection into bbs.it-home.org
}
function stripslashes_array(&$array) {
if (is_array ( $array )) {
foreach ( $array as $k => $v ) {
$array [$k] = stripslashes_array ( $v );
}
} else if (is_string ( $array )) {
$array = stripslashes ( $ array );
}
return $array;
}
?>