Code Injection | New Think Tank

In this PHP Security Video tutorial I continue to show you how hackers break into web applications and how to better secure your site. If you missed part 1 of this tutorial definitely watch it first here PHP Security.

Specifically in this tutorial I will show you how SQL Injection works. Don’t do this on any site that you don’t own! I then go over all of the following:

Limit What Hackers can Enter in your Input Fields
Create Encrypted Activation Codes
Validate Input Data
Verify Email Addresses
How to Act Abnormally and Confound Hackers

All of the code follows the video. If you have any other questions or comments leave them below. Feel free to use the code however you like, but I’m not stating that it is 100% secure. The fact is all code can eventually be cracked. The goal is to make the code so complicated that hackers just give up and move on to an easier target.

Code From the Video

Register.PHP Code

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Strict//EN”

“http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd”>

<head>

<title>Registration</title>

</head>

<body>

<?php
require_once(“./includes/confighamdb.php”);

if (isset($_POST[‘submitted’])) { // Handle the form.

if (preg_match (‘%^[A-Za-z\.\’ \-]{2,15}$%’, stripslashes(trim($_POST[‘first_name’])))) {

$fn = escape_data($_POST[‘first_name’]);

} else {

$fn = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter your first name!</font></p>’;

}

// Check for a last name.

if (preg_match (‘%^[A-Za-z\.\’ \-]{2,30}$%’, stripslashes(trim($_POST[‘last_name’])))) {

$ln = escape_data($_POST[‘last_name’]);

} else {

$ln = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter your last name!</font></p>’;

}

// Check for an email address.

if (preg_match (‘%^[A-Za-z0-9._\%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$%’, stripslashes(trim($_POST[’email’])))) {

$e = escape_data($_POST[’email’]);

} else {

$e = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter a valid email address!</font></p>’;

}

// Check for a street.

if (preg_match (‘%^[A-Za-z0-9\.\’ \-]{5,30}$%’, stripslashes(trim($_POST[‘street’])))) {

$s = escape_data($_POST[‘street’]);

} else {

$s = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter your street address!</font></p>’;

}

// Check for a city.

if (preg_match (‘%^[A-Za-z\.\’ \-]{2,25}$%’, stripslashes(trim($_POST[‘city’])))) {

$c = escape_data($_POST[‘city’]);

} else {

$c = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter a valid city!</font></p>’;

}

// Check for a state.

if (preg_match (‘%^(A[KLRZ]|C[AOT]|D[CE]|FL|GA|HI|I[ADLN]|K[SY]|LA|M[ADEINOST]|N[CDEHJMVY]|O[HKR]|PA|RI|S[CD]|T[NX]|UT|V[AT]|W[AIVY])$%’, stripslashes(trim($_POST[‘state’])))) {

$st = escape_data($_POST[‘state’]);

} else {

$st = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter a valid state!</font></p>’;

}

// Check for a zip code.

if (preg_match (‘%^[0-9]{5}$%’, stripslashes(trim($_POST[‘zip’])))) {

$z = escape_data($_POST[‘zip’]);

} else {

$z = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter a valid 5 digit zip code!</font></p>’;

}

// Check for a phone number.

if (preg_match (‘%^([0-9]( |-)?)?($?[0-9]{3}$?|[0-9]{3})( |-)?([0-9]{3}( |-)?[0-9]{4}|[a-zA-Z0-9]{7})$%’, stripslashes(trim($_POST[‘work_phone’])))) {

$ph = escape_data($_POST[‘work_phone’]);

} else {

$ph = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter a valid phone number!</font></p>’;

}

// Check for a password and match against the confirmed password.

if (preg_match (‘%\A(?=[-_a-zA-Z0-9]*?[A-Z])(?=[-_a-zA-Z0-9]*?[a-z])(?=[-_a-zA-Z0-9]*?[0-9])\S{6,}\z%’, stripslashes(trim($_POST[‘password1’])))) {
if ($_POST[‘password1’] == $_POST[‘password2’]) {

$p = escape_data($_POST[‘password1’]);

} else {

$p = FALSE;

echo ‘<p><font color=”red” size=”+1″>Your password did not match the confirmed password!</font></p>’;
}

} else {

$p = FALSE;

echo ‘<p><font color=”red” size=”+1″>Please enter a valid password!</font></p>’;

}

if ($fn && $ln && $e && $p && $fn && $s && $c && $st && $z && $ph) {
$query = “SELECT user_id FROM users WHERE email=’$e'”;

$result = mysql_query($query) or trigger_error(“Sorry email is taken”);

if(mysql_num_rows($result) == 0) {
$a = md5(uniqid(rand(), true));

$query = “INSERT INTO users(email, pass, first_name, last_name, active, registration_date, street, city, state, zip, work_phone) VALUES (‘$e’, SHA(‘$p’), ‘$fn’, ‘$ln’, ‘$a’, NOW(), ‘$s’, ‘$c’, ‘$st’, ‘$z’, ‘$ph’)”;

$result = mysql_query($query) or trigger_error(“Sorry an error happened”);

if(mysql_affected_rows() == 1) {

$body = “Thanks for registering. Activate account by clicking this link: <br />”;

$body .= “http://localhost/activate.php?x=” . mysql_insert_id() . “&y=$a”;

mail($e, ‘Registration Confirmation’, ‘$body’, ‘From: derekbanas@verizon.net’);

echo ‘<br /><br /><h1>Thank you for registering! A confirmation email has been sent to your address. Please click on the link in that email in order to activate your account.</h1>’;

exit();

} else {

echo ‘<p><font color=”red” size=”+1″>You could not be registered due to a system error. We apologize for any inconvenience.</font></p>’;

}

} else {

echo ‘<p><font color=”red” size=”+1″>That email address has already been registered. If you have forgotten your password, use the link to have your password sent to you.</font></p>’;

}

mysql_close();
}

<h1>Register</h1>

<p><b>First Name:</b> <input type=”text” name=”first_name” size=”15″ maxlength=”15″ value=”<?php if (isset($_POST[‘first_name’])) echo $_POST[‘first_name’]; ?>” /></p>

<p><b>Email Address:</b> <input type=”text” name=”email” size=”40″ maxlength=”40″ value=”<?php if (isset($_POST[’email’])) echo $_POST[’email’]; ?>” /> </p>

<p><b>Street:</b> <input type=”text” name=”street” size=”40″ maxlength=”40″ value=”<?php if (isset($_POST[‘street’])) echo $_POST[‘street’]; ?>” /> </p>

<p><b>State:</b> <input type=”text” name=”state” size=”2″ maxlength=”2″ value=”<?php if (isset($_POST[‘state’])) echo $_POST[‘state’]; ?>” /> <small>Use only the two letter initials</small></p>

<p><b>Phone:</b> <input type=”text” name=”work_phone” size=”20″ maxlength=”20″ value=”<?php if (isset($_POST[‘work_phone’])) echo $_POST[‘work_phone’]; ?>” /> </p>

<p><b>Password:</b> <input type=”password” name=”password1″ size=”20″ maxlength=”20″ /> <small>Use only letters and numbers. Must be between 4 and 20 characters long.</small></p>

<p><b>Confirm Password:</b> <input type=”password” name=”password2″ size=”20″ maxlength=”20″ /></p>

</fieldset>

</form>

MySQL Connect Code

<?php
// Define these as constants so that they can’t be changed
DEFINE (‘DBUSER’, ‘mysqladm’);
DEFINE (‘DBPW’, ‘password’);
DEFINE (‘DBHOST’, ‘localhost’);
DEFINE (‘DBNAME’, ‘hamdb’);

if ($dbc = mysql_connect (DBHOST, DBUSER, DBPW)) {

if (!mysql_select_db (DBNAME)) { // If it can’t select the database.

// Handle the error.

trigger_error(“Could not select the database!<br />MySQL Error: ” . mysql_error());

exit();

} // End of mysql_select_db IF.

} else {

// Print a message to the user, and kill the script.

trigger_error(“Could not connect to MySQL!<br />MySQL Error: ” . mysql_error());

exit();

}

// A function that strips harmful data.
function escape_data ($data) {

// Check for mysql_real_escape_string() support.
// This function escapes characters that could be used for sql injection
if (function_exists(‘mysql_real_escape_string’)) {
global $dbc; // Need the connection.
$data = mysql_real_escape_string (trim($data), $dbc);
$data = strip_tags($data);
} else {
$data = mysql_escape_string (trim($data));
$data = strip_tags($data);
}

// Return the escaped value.
return $data;

} // End of function.

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