PHP: Check if URL redirects? - php

Question

I have implemented a function that runs on each page that I want to restrict from non-logged in users. The function automatically redirects the visitor to the login page in the case of he or she is not logged in.
I would like to make a PHP function that is run from a exernal server and iterates through a number of set URLs (array with URLs that is for each protected site) to see if they are redirected or not. Thereby I could easily make sure if protection is up and running on every page.
How could this be done?
Thanks.

Answer 1

$urls = array(
'http://www.apple.com/imac',
'http://www.google.com/'
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
foreach($urls as $url) {
curl_setopt($ch, CURLOPT_URL, $url);
$out = curl_exec($ch);
// line endings is the wonkiest piece of this whole thing
$out = str_replace("\r", "", $out);
// only look at the headers
$headers_end = strpos($out, "\n\n");
if( $headers_end !== false ) {
$out = substr($out, 0, $headers_end);
}
$headers = explode("\n", $out);
foreach($headers as $header) {
if( substr($header, 0, 10) == "Location: " ) {
$target = substr($header, 10);
echo "[$url] redirects to [$target]<br>";
continue 2;
}
}
echo "[$url] does not redirect<br>";
}

Answer 2

I use curl and only take headers, after I compare my url and url from header curl:
$url="http://google.com";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_TIMEOUT, '60'); // in seconds
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_NOBODY, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$res = curl_exec($ch);
if(curl_getinfo($ch)['url'] == $url){
echo "not redirect";
}else {
echo "redirect";
}

Answer 3

You could always try adding:
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
since 302 means it moved, allow the curl call to follow it and return whatever the moved url returns.

Answer 4

Getting the headers with get_headers() and checking if Location is set is much simpler.
$urls = [
"https://example-1.com",
"https://example-2.com"
];
foreach ($urls as $key => $url) {
$is_redirect = does_url_redirect($url) ? 'yes' : 'no';
echo $url . ' is redirected: ' . $is_redirect . PHP_EOL;
}
function does_url_redirect($url){
$headers = get_headers($url, 1);
if (!empty($headers['Location'])) {
return true;
} else {
return false;
}
}

Answer 5

I'm not sure whether this really makes sense as a security check.
If you are worried about files getting called directly without your "is the user logged in?" checks being run, you could do what many big PHP projects do: In the central include file (where the security check is being done) define a constant BOOTSTRAP_LOADED or whatever, and in every file, check for whether that constant is set.
Testing is great and security testing is even better, but I'm not sure what kind of flaw you are looking to uncover with this? To me, this idea feels like a waste of time that will not bring any real additional security.
Just make sure your script die() s after the header("Location:...") redirect. That is essential to stop additional content from being displayed after the header command (a missing die() wouldn't be caught by your idea by the way, as the redirect header would still be issued...)
If you really want to do this, you could also use a tool like wget and feed it a list of URLs. Have it fetch the results into a directory, and check (e.g. by looking at the file sizes that should be identical) whether every page contains the login dialog. Just to add another option...

Answer 6

Do you want to check the HTTP code to see if it's a redirect?
$params = array('http' => array(
'method' => 'HEAD',
'ignore_errors' => true
));
$context = stream_context_create($params);
foreach(array('http://google.com', 'http://stackoverflow.com') as $url) {
$fp = fopen($url, 'rb', false, $context);
$result = stream_get_contents($fp);
if ($result === false) {
throw new Exception("Could not read data from {$url}");
} else if (! strstr($http_response_header[0], '301')) {
// Do something here
}
}

Answer 7

I hope it will help you:
function checkRedirect($url)
{
$headers = get_headers($url);
if ($headers) {
if (isset($headers[0])) {
if ($headers[0] == 'HTTP/1.1 302 Found') {
//this is the URL where it's redirecting
return str_replace("Location: ", "", $headers[9]);
}
}
}
return false;
}
$isRedirect = checkRedirect($url);
if(!$isRedirect )
{
echo "URL Not Redirected";
}else{
echo "URL Redirected to: ".$isRedirect;
}

Answer 8

You can use session,if the session array is not set ,the url redirected to a login page.
.

Answer 9

I modified Adam Backstrom answer and implemented chiborg suggestion. (Download only HEAD). It have one thing more: It will check if redirection is in a page of the same server or is out. Example: terra.com.br redirects to terra.com.br/portal. PHP will considerate it like redirect, and it is correct. But i only wanted to list that url that redirect to another URL. My English is not good, so, if someone found something really difficult to understand and can edit this, you're welcome.
function RedirectURL() {
$urls = array('http://www.terra.com.br/','http://www.areiaebrita.com.br/');
foreach ($urls as $url) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
// chiborg suggestion
curl_setopt($ch, CURLOPT_NOBODY, true);
// ================================
// READ URL
// ================================
curl_setopt($ch, CURLOPT_URL, $url);
$out = curl_exec($ch);
// line endings is the wonkiest piece of this whole thing
$out = str_replace("\r", "", $out);
echo $out;
$headers = explode("\n", $out);
foreach($headers as $header) {
if(substr(strtolower($header), 0, 9) == "location:") {
// read URL to check if redirect to somepage on the server or another one.
// terra.com.br redirect to terra.com.br/portal. it is valid.
// but areiaebrita.com.br redirect to bwnet.com.br, and this is invalid.
// what we want is to check if the address continues being terra.com.br or changes. if changes, prints on page.
// if contains http, we will check if changes url or not.
// some servers, to redirect to a folder available on it, redirect only citting the folder. Example: net11.com.br redirect only to /heiden
// only execute if have http on location
if ( strpos(strtolower($header), "http") !== false) {
$address = explode("/", $header);
print_r($address);
// $address['0'] = http
// $address['1'] =
// $address['2'] = www.terra.com.br
// $address['3'] = portal
echo "url (address from array) = " . $url . "<br>";
echo "address[2] = " . $address['2'] . "<br><br>";
// url: terra.com.br
// address['2'] = www.terra.com.br
// check if string terra.com.br is still available in www.terra.com.br. It indicates that server did not redirect to some page away from here.
if(strpos(strtolower($address['2']), strtolower($url)) !== false) {
echo "URL NOT REDIRECT";
} else {
// not the same. (areiaebrita)
echo "SORRY, URL REDIRECT WAS FOUND: " . $url;
}
}
}
}
}
}

Answer 10

function unshorten_url($url){
$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_URL, $url);
$out = curl_exec($ch);
$real_url = $url;//default.. (if no redirect)
if (preg_match("/location: (.*)/i", $out, $redirect))
$real_url = $redirect[1];
if (strstr($real_url, "bit.ly"))//the redirect is another shortened url
$real_url = unshorten_url($real_url);
return $real_url;
}

Answer 11

I have just made a function that checks if a URL exists or not
$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
function url_exists($url, $ch) {
curl_setopt($ch, CURLOPT_URL, $url);
$out = curl_exec($ch);
// line endings is the wonkiest piece of this whole thing
$out = str_replace("\r", "", $out);
// only look at the headers
$headers_end = strpos($out, "\n\n");
if( $headers_end !== false ) {
$out = substr($out, 0, $headers_end);
}
//echo $out."====<br>";
$headers = explode("\n", $out);
//echo "<pre>";
//print_r($headers);
foreach($headers as $header) {
//echo $header."---<br>";
if( strpos($header, 'HTTP/1.1 200 OK') !== false ) {
return true;
break;
}
}
}
Now I have used an array of URLs to check if a URL exists as following:
$my_url_array = array('http://howtocode.pk/result', 'http://google.com/jobssss', 'https://howtocode.pk/javascript-tutorial/', 'https://www.google.com/');
for($j = 0; $j < count($my_url_array); $j++){
if(url_exists($my_url_array[$j], $ch)){
echo 'This URL "'.$my_url_array[$j].'" exists. <br>';
}
}

Answer 12

I can't understand your question.
You have an array with URLs and you want to know if user is from one of the listed URLs?
If I'm right in understanding your quest:
$urls = array('http://url1.com','http://url2.ru','http://url3.org');
if(in_array($_SERVER['HTTP_REFERER'],$urls))
{
echo 'FROM ARRAY';
} else {
echo 'NOT FROM ARR';
}