The CURL User Agent

Question

So how can I check using codeigniter if the client is curl, and then return something different for it?

Answer 1

You can fake the user-agent when using cURL, so it's pointless depending on the user-agent sent when you KNOW it's a cURL request.

For example: I recently wrote an app which gets the pagerank of a url from google. Now Google doesn't like this, so it allows only a certain user agent to access its pagerank servers. Solution? Spoof the user-agent using cURL and Google will be none the wiser.

Moral of the story: cURL user agents are JUST NOT reliable.

If you still want to do this, then you should be able to get the passed user agent just like normal

$userAgent=$_SERVER['HTTP_USER_AGENT'];

EDIT A quick test proved this:

dumpx.php:

<?php

    $url="http://localhost/dump.php";

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL,$url);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
    if($_GET['u']==y) {  
    curl_setopt($ch, CURLOPT_USERAGENT, "booyah!");
    }
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);

    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 2);
    curl_setopt($ch, CURLOPT_TIMEOUT, 60);
    //curl_setopt($ch, CURLOPT_CUSTOMREQUEST,'GET');
    curl_setopt ($ch, CURLOPT_HEADER, 0);
    $exec=curl_exec ($ch);
?>

dump.php:

<?php
    var_dump($_SERVER);
?>

Case 1: http://localhost/dumpx.php?u=y

 'HTTP_USER_AGENT' => string 'booyah!' (length=7)

Case 2: http://localhost/dumpx.php?u=n

No $_SERVER['HTTP_USER_AGENT']

This proves that there is no default user agent for curl: it will just not pass it in the request header