HTTP authentication with PHP

December 30, 2012 2079 views 1 comments

It is possible to use the header() function to send an “Authentication Required” message to the client browser causing it to pop up a Username/Password input window. Once the user has filled in a username and a password, the URL containing the PHP script will be called again with the predefined variables PHP_AUTH_USER, PHP_AUTH_PW, and AUTH_TYPE set to the user name, password and authentication type respectively. These predefined variables are found in the $_SERVER and $HTTP_SERVER_VARS arrays. Both “Basic” and “Digest” (since PHP 5.1.0) authentication methods are supported. See the header() function for more information.

Note: PHP Version Note
Superglobals, such as $_SERVER, became available in PHP » 4.1.0.
An example script fragment which would force client authentication on a page is as follows:

Example #1 Basic HTTP Authentication example
<?php
if (!isset($_SERVER['PHP_AUTH_USER'])) {
header(‘WWW-Authenticate: Basic
realm=”My Realm”‘);
header(‘HTTP/1.0 401 Unauthorized’);
echo ‘Text to send if user hits Cancel button’;
exit;
} else {
echo “<p>Hello {$_SERVER['PHP_AUTH_USER']}
.</p>”;
echo “<p>You entered {$_SERVER['PHP_AUTH_PW']} as your password.</p>”;
}
?>

Example #2 Digest HTTP Authentication example
This example shows you how to implement a simple Digest HTTP authentication script.

<?php
$realm = ‘Restricted area’;
//user => password
$users = array(‘admin’ => ‘mypass’, ‘guest’ => ‘guest’);
if(empty($_SERVER['PHP_AUTH_DIGEST']))
{
header(‘HTTP/1.1 401 Unauthorized’);
header(‘WWW-Authenticate: Digest realm=”‘. $realm. ‘”,qop=”auth”,nonce=”‘. uniqid() .’”,opaque=”‘. md5($realm) .’”‘);
die(‘Text to send if user hits Cancel button’);
}
// analyze the PHP_AUTH_DIGEST variable
if (!($data = http_digest_parse($_SERVER['PHP_AUTH_DIGEST'])) || !isset($users[$data['username']]))
die(‘Wrong Credentials!’);
// generate the valid response
$A1 = md5($data['username'] . ‘:’ . $realm . ‘:’ . $users[$data['username']]);
$A2 = md5($_SERVER['REQUEST_METHOD'].’:’. $data['uri']);
$valid_response = md5($A1. ‘:’ . $data['nonce'] .’:’. $data['nc'] .’:’. $data['cnonce'] .’:’. $data['qop'] .’:’. $A2);
if ($data['response'] != $valid_response)
die(‘Wrong Credentials!’);
// ok, valid username & password
echo ‘You are logged in as: ‘ . $data['username'];
// function to parse the http auth header
function http_digest_parse($txt)
{
// protect against missing data
$needed_parts = array(‘nonce’=>1,’nc’=>1, ‘cnonce’=>1, ‘qop’=>1, ‘username’=>1, ‘uri’=>1, ‘response’=>1);
$data = array();
$keys = implode(‘|’, array_keys($needed_parts));
preg_match_all(‘@(‘ . $keys . ‘)=(?:([\'"])([^\2]+?)\2|([^\s,]+))@’, $txt, $matches, PREG_SET_ORDER);
foreach ($matches as $m) {
$data[$m[1]] = $m[3] ? $m[3] : $m[4];
unset($needed_parts[$m[1]]);
}
return $needed_parts ? false : $data;
}
?>

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