Are mysql_real_escape_string() and mysql_escape_string() Sufficient for App Security?

While these functions can provide some protection against SQL injection and other attacks, they fail to address certain vulnerabilities.

SQL Injection

Mysql_real_escape_string() can still expose your application to SQL injection if you improperly handle PHP variables within queries. Consider the following example:

$sql = "SELECT number FROM PhoneNumbers WHERE " . 
        mysql_real_escape_string($field) . " = " . mysql_real_escape_string($value);  

This query can be manipulated by an attacker to execute unauthorized SQL statements, as mysql_real_escape_string() is not designed to secure table names, column names, or LIMIT fields.

Like Attacks

Mysql_real_escape_string() is insufficient to prevent LIKE exploits. An attacker could input a malicious value such as "%%" to return all records, potentially compromising sensitive information.

Charset Exploits

Certain browsers may be vulnerable to charset exploits, allowing attackers to inject malicious characters that bypass escaping mechanisms and execute arbitrary SQL commands.

Prepared Statements: A Comprehensive Solution

To effectively secure your application, it is recommended to use prepared statements instead of mysql_real_escape_string(). Prepared statements execute SQL queries with user-supplied values by binding them as parameters. This eliminates the need for manual escaping and ensures that only authorized SQL is executed.

Here's an example of using a prepared statement in PHP:

$pdo = new PDO($dsn);

$column = 'url';
$value = 'http://www.example.com/';
$limit = 1;

// Validate the search parameter column.
$validColumns = array('url', 'last_fetched');
if (!in_array($column, $validColumns)) { $column = 'id'; }

$statement = $pdo->prepare('SELECT url FROM GrabbedURLs ' .
                           'WHERE ' . $column . '=? ' .
                           'LIMIT ' . intval($limit));
$statement->execute(array($value));
while (($data = $statement->fetch())) { }

Prepared statements offer a proactive defense mechanism by leveraging the security features of the underlying database server. They are inherently resistant to both known and unknown attacks, ensuring the integrity of your data.