Survey Security

[MDCode]

I am making a survey feature for my website.  Nothing is wrong with the current security (that I know of :s)  I was actually wondering what I could do to improve the security.  Sorry for the lack of organization I have no code editor on this computer.

 

submit_survey.php

<?php			
require('check/ip_check.php');			
if($id == "1"){
if($ip_check != "0") {
echo "<p>Error: You have already taken this survey.<br>";
echo "<a href='../index.php'>Back</a></p>";
die;
}
else {
if($_POST['agree'] == "Yes") {
}
else if($_POST['agree'] == "No") {
}
else {
echo "<p>Error: Please select an answer for question 1<br>";
echo "<a href='../survey.php?id=1'>Back</a></p>";
die;
}
if($_POST['placement'] == "") {
echo "<p>Error: Please enter text for question 2<br>";
echo "<a href='../survey.php?id=1'>Back</a></p>";
die;
}
if($_POST['different_location'] == "Yes") {
if($_POST['location'] == ""){
echo "<p>Error: It seems you selected yes for question 3.  Please enter text for question 4.<br>";
echo "<a href='../survey.php?id=1'>Back</a></p>";
die;
}
}
else if($_POST['different_location'] == "No") {
}
else {
echo "<p>Error: Please select an answer for question 3<br>";
echo "<a href='../survey.php?id=1'>Back</a></p>";
die;
}
include('add_survey1.php');
}
}
else {
echo "Error: Invalid survey id";
}

?>

 

Both ip_check.php (One for selecting survey, other for if a user were to make their own form and submit)

<?php
session_start();

require('../config.php');

$ip = $_SERVER['REMOTE_ADDR'];

include('connection.php');

$getid = mysql_real_escape_string($_GET['id']);

$sql ="SELECT * FROM Survey_Responses WHERE `ip` = '$ip' AND `id` = '$getid'";

$result = @mysql_query($sql, $connection) or die(mysql_error());

$ip_check = mysql_num_rows($result);
?>

 

add_survey1.php

<?php
session_start();

require('../config.php');
include('connection.php');

$ip = $_SERVER['REMOTE_ADDR'];

$question1 = htmlentities($_POST['agree'], ENT_QUOTES);
$question1 = mysql_real_escape_string($question1);

$question2 = htmlentities($_POST['placement'], ENT_QUOTES);
$question2 = mysql_real_escape_string($question2);

$question3 = htmlentities($_POST['different_location'], ENT_QUOTES);
$question3 = mysql_real_escape_string($question3);

$question4 = htmlentities($_POST['location'], ENT_QUOTES);
$question4 = mysql_real_escape_string($question4);

$question5 = htmlentities($_POST['other_locations'], ENT_QUOTES);
$question5 = mysql_real_escape_string($question5);

$sql ="INSERT INTO Survey_Responses VALUES('1', '$question1', '$question2', '$question3', '$question4', '$question5', '$ip')";

$result = @mysql_query($sql, $connection) or die(mysql_error());

echo "Thank you for taking our survey.  Your answers have been successfully recorded.";

?>

 

Any help would be appreciated

[maxudaskin]

An IP does not necessarily mean a computer. There can be many computers to an IP. What if the user is using a public computer (many responses, few IPs).

 

Register the survey with an email. This allows you a reply-to address, as well as a way to weed out multiple survey submits. What ever system you use, unless you require a fingerprint scan, there is always the risk of multiple submissions.

[Mahngiel]

unless you require a fingerprint scan

 

I have 10 fingers.

 

@OP: Cookies, sessions, emails, it's nigh impossible to keep out people who want to fake a submission.  Best thing you can do is determine what method will slow down the most amount of fakers.  Email address submissions (useful, because you can build a mailing list to drive return visits - you just need to weed out fake emails), user registration, captcha, ip time-outs, etc. Just bear in mind, even in the real world statistics have margins of error.

[ignace]

unless you require a fingerprint scan

 

I have 10 fingers.

 

Require a DNA sample

[scootstah]

Remove the @ in front of mysql_query(). Suppressing errors isn't a good thing to do, and mysql_query() doesn't output anything if a query fails.

 

Also, remove the or die(mysql_error())'s when you go to production. In production you should be logging the errors, not displaying them to the public - especially SQL errors. All the user has to know is that something went wrong. Maybe send a "500 - Internal Server Error" header or something.