Can Prepared Statements Securely Parameterize Table Names?

Prepared Statements and Table Name Security: A Critical Examination

Many developers rely on mysqli_stmt_bind_param to prevent SQL injection vulnerabilities. However, this approach presents challenges when attempting to parameterize table names.

Consider this example:

<code class="language-php">function insertRow($db, $mysqli, $new_table, $Partner, $Merchant, $ips, $score, $category, $overall, $protocol) {
    $statement = $mysqli->prepare("INSERT INTO " . $new_table . " VALUES (?,?,?,?,?,?,?);");
    mysqli_stmt_bind_param($statement, 'sssisss', $Partner, $Merchant, $ips, $score, $category, $overall, $protocol);
    $statement->execute();
}</code>

While this attempts to mitigate SQL injection by binding variables, it leaves the table name, $new_table, vulnerable. Can we use a placeholder for $new_table within the prepared statement?

No. Database prepared statements only support parameter binding for values, not for table or column identifiers. This is because the table name is integral to the SQL statement's structure and validity; changing it dynamically could lead to invalid SQL.

Even with database interfaces like PDO, which offer more flexible placeholder usage, attempting to substitute a table name directly results in invalid SQL:

<code class="language-sql">SELECT * FROM ?</code>

The correct approach involves using string interpolation:

<code class="language-php">SELECT * FROM {$mytable}</code>

However, this requires a crucial security measure: strict table whitelisting. Always validate $mytable against a predefined list of allowed table names to prevent malicious input from compromising your database. Never rely solely on prepared statements for table name security.

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