Php – How to validate captcha in registration form

captchaPHP

I'm trying to create a registration form with a captcha, using this tutorial, but I don't know how to validate the captcha, can you help me?

<?php

include ('php/mysql_prisijungimas.php');


if (isset($_POST['formsubmitted'])) {
    $error = array();//Declare An Array to store any error message  
    if (empty($_POST['name'])) {//if no name has been supplied 
        $error[] = 'Please Enter a name ';//add to array "error"
    } else {
        $name = $_POST['name'];//else assign it a variable
    }

    if (empty($_POST['e-mail'])) {
        $error[] = 'Please Enter your Email ';
    } else {


        if (preg_match("/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/", $_POST['e-mail'])) {
           //regular expression for email validation
            $Email = $_POST['e-mail'];
        } else {
             $error[] = 'Your EMail Address is invalid  ';
        }


    }


    if (empty($_POST['Password'])) {
        $error[] = 'Please Enter Your Password ';
    } else {
        $Password = $_POST['Password'];
    }


    if (empty($error)) //send to Database if there's no error '

    { // If everything's OK...

        // Make sure the email address is available:
        $query_verify_email = "SELECT * FROM members  WHERE Email ='$Email'";
        $result_verify_email = mysqli_query($dbc, $query_verify_email);
        if (!$result_verify_email) {//if the Query Failed ,similar to if($result_verify_email==false)
            echo ' Database Error Occured ';
        }

        if (mysqli_num_rows($result_verify_email) == 0) { // IF no previous user is using this email .


            // Create a unique  activation code:
            $activation = md5(uniqid(rand(), true));


            $query_insert_user = "INSERT INTO `members` ( `Username`, `Email`, `Password`, `Activation`) VALUES ( '$name', '$Email', '$Password', '$activation')";


            $result_insert_user = mysqli_query($dbc, $query_insert_user);
            if (!$result_insert_user) {
                echo 'Query Failed ';
            }

            if (md5($_POST['norobot']) == $_SESSION['randomnr2'])   { 
        // here you  place code to be executed if the captcha test passes
            echo "Hey great , it appears you are not a robot";
    }   else {  
        // here you  place code to be executed if the captcha test fails
            echo "you're a very naughty robot!";
    }

            if (mysqli_affected_rows($dbc) == 1) { //If the Insert Query was successfull.


                // Send the email:
                $message = " To activate your account, please click on this link:\n\n";
                $message .= WEBSITE_URL . '/activate.php?email=' . urlencode($Email) . "&key=$activation";
                mail($Email, 'Registration Confirmation', $message, 'From: test@gmail.com');

                // Flush the buffered output.


                // Finish the page:
                echo '<div class="success">Thank you for
registering! A confirmation email
has been sent to '.$Email.' Please click on the Activation Link to Activate your account </div>';


            } else { // If it did not run OK.
                echo '<div class="errormsgbox">You could not be registered due to a system
error. We apologize for any
inconvenience.</div>';
            }

        } else { // The email address is not available.
            echo '<div class="errormsgbox" >That email
address has already been registered.
</div>';
        }

    } else {//If the "error" array contains error msg , display them



echo '<div class="errormsgbox"> <ol>';
        foreach ($error as $key => $values) {

            echo '  <li>'.$values.'</li>';



        }
        echo '</ol></div>';

    }

    mysqli_close($dbc);//Close the DB Connection

} // End of the main Submit conditional.



?>


<head>
    <meta charset="UTF-8">

    <!-- Remove this line if you use the .htaccess -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

    <meta name="viewport" content="width=device-width">

    <meta name="description" content="test.">
    <meta name="author" content="test">

    <title>test</title>


    <link href='http://fonts.googleapis.com/css?family=Open+Sans:400italic,400,700' rel='stylesheet' type='text/css'>
    <link rel="stylesheet" href="css/stilius.css">

</head>
<body>

<div class="container">

<hr>
<div class="home-page main">
    <section class="grid-wrap" >
        <header class="grid col-full">

<div class="right">
<form align="center" action="registracija.php" method="post" class="registration_form">
  <fieldset>
    <legend>Registracijos forma </legend>


    <div class="elements">
      <label for="name">Slapyvardis :</label>
      <input type="text" id="name" name="name" size="25" />
    </div>
    <div class="elements">
      <label for="e-mail">El. pa&#353;tas :</label>
      <input type="text" id="e-mail" name="e-mail" size="25" />
    </div>
    <div class="elements">
      <label for="Password">slapta&#382;odis:</label>
      <input type="password" id="Password" name="Password" size="25" />


      <img src="captcha_code_file.php?rand=<?php echo rand(); ?>"
id="captchaimg" >
<label for="message">Enter the code above here :</label>
<input id="6_letters_code" name="6_letters_code" type="text">



    </div>
    <div class="submit">
     <input type="hidden" name="formsubmitted" value="TRUE" />
      <input type="submit" value="Registruotis!" />
    </div>
  </fieldset>
</form>
</div>

</body>
</html>

Best Answer

Captcha is just any string created using image library.Process as below:

1- create random or dictionary word string 2- store it anywhere [session in your case before displaying your registration form 3- compare session value to user submit value

Your code :

if (md5($_POST['norobot']) == $_SESSION['randomnr2'])
{
    echo 'You passed captcha test';
}

$_SESSION['randomnr2'] is random string created and stored in session.before storing it is md5 encrypted.

Correctly setting up the connection

Note that when using PDO to access a MySQL database real prepared statements are not used by default. To fix this you have to disable the emulation of prepared statements. An example of creating a connection using PDO is:

$dbConnection = new PDO('mysql:dbname=dbtest;host=127.0.0.1;charset=utf8', 'user', 'password');

$dbConnection->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$dbConnection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

In the above example the error mode isn't strictly necessary, but it is advised to add it. This way the script will not stop with a Fatal Error when something goes wrong. And it gives the developer the chance to catch any error(s) which are thrown as PDOExceptions.

What is mandatory, however, is the first setAttribute() line, which tells PDO to disable emulated prepared statements and use real prepared statements. This makes sure the statement and the values aren't parsed by PHP before sending it to the MySQL server (giving a possible attacker no chance to inject malicious SQL).

Although you can set the charset in the options of the constructor, it's important to note that 'older' versions of PHP (before 5.3.6) silently ignored the charset parameter in the DSN.

Explanation

The SQL statement you pass to prepare is parsed and compiled by the database server. By specifying parameters (either a ? or a named parameter like :name in the example above) you tell the database engine where you want to filter on. Then when you call execute, the prepared statement is combined with the parameter values you specify.

The important thing here is that the parameter values are combined with the compiled statement, not an SQL string. SQL injection works by tricking the script into including malicious strings when it creates SQL to send to the database. So by sending the actual SQL separately from the parameters, you limit the risk of ending up with something you didn't intend.

Any parameters you send when using a prepared statement will just be treated as strings (although the database engine may do some optimization so parameters may end up as numbers too, of course). In the example above, if the $name variable contains 'Sarah'; DELETE FROM employees the result would simply be a search for the string "'Sarah'; DELETE FROM employees", and you will not end up with an empty table.

Another benefit of using prepared statements is that if you execute the same statement many times in the same session it will only be parsed and compiled once, giving you some speed gains.

Oh, and since you asked about how to do it for an insert, here's an example (using PDO):

$preparedStatement = $db->prepare('INSERT INTO table (column) VALUES (:column)');

$preparedStatement->execute([ 'column' => $unsafeValue ]);

Can prepared statements be used for dynamic queries?

While you can still use prepared statements for the query parameters, the structure of the dynamic query itself cannot be parametrized and certain query features cannot be parametrized.

For these specific scenarios, the best thing to do is use a whitelist filter that restricts the possible values.

// Value whitelist
// $dir can only be 'DESC', otherwise it will be 'ASC'
if (empty($dir) || $dir !== 'DESC') {
   $dir = 'ASC';
}

Best Answer

Related Solutions

Practical non-image based CAPTCHA approaches

Php – How to prevent SQL injection in PHP

Correctly setting up the connection

Explanation

Can prepared statements be used for dynamic queries?

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