What is the correct way to log out of HTTP authentication protected folder?
There are workarounds that can achieve this, but they are potentially dangerous because they can be buggy or don't work in certain situations / browsers. That is why I am looking for correct and clean solution.
Mu. No correct way exists, not even one that's consistent across browsers.
This is a problem that comes from the HTTP specification (section 15.6):
Existing HTTP clients and user agents typically retain authentication information indefinitely. HTTP/1.1. does not provide a method for a server to direct clients to discard these cached credentials.
On the other hand, section 10.4.2 says:
If the request already included Authorization credentials, then the 401 response indicates that authorization has been refused for those credentials. If the 401 response contains the same challenge as the prior response, and the user agent has already attempted authentication at least once, then the user SHOULD be presented the entity that was given in the response, since that entity might include relevant diagnostic information.
In other words, you may be able to show the login box again (as @Karsten says), but the browser doesn't have to honor your request - so don't depend on this (mis)feature too much.
Method that works nicely in Safari. Also works in Firefox and Opera, but with a warning.
Location: http://logout@yourserver.example.com/
This tells browser to open URL with new username, overriding previous one.
The simple answer is that you can't reliably log out of http-authentication.
The long answer:
Http-auth (like the rest of the HTTP spec) is meant to be stateless. So being "logged in" or "logged out" isn't really a concept that makes sense. The better way to see it is to ask, for each HTTP request (and remember a page load is usually multiple requests), "are you allowed to do what you're requesting?". The server sees each request as new and unrelated to any previous requests.
Browsers have chosen to remember the credentials you tell them on the first 401, and re-send them without the user's explicit permission on subsequent requests. This is an attempt at giving the user the "logged in/logged out" model they expect, but it's purely a kludge. It's the browser that's simulating this persistence of state. The web server is completely unaware of it.
So "logging out", in the context of http-auth is purely a simulation provided by the browser, and so outside the authority of the server.
Yes, there are kludges. But they break RESTful-ness (if that's of value to you) and they are unreliable.
If you absolutely require a logged-in/logged-out model for your site authentication, the best bet is a tracking cookie, with the persistence of state stored on the server in some manner (mysql, sqlite, flatfile, etc). This will require all requests to be evaluated, for instance, with PHP.
Workaround
You can do this using Javascript:
<html><head>
<script type="text/javascript">
function logout() {
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest();
}
// code for IE
else if (window.ActiveXObject) {
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
if (window.ActiveXObject) {
// IE clear HTTP Authentication
document.execCommand("ClearAuthenticationCache");
window.location.href='/where/to/redirect';
} else {
xmlhttp.open("GET", '/path/that/will/return/200/OK', true, "logout", "logout");
xmlhttp.send("");
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {window.location.href='/where/to/redirect';}
}
}
return false;
}
</script>
</head>
<body>
<a href="#" onclick="logout();">Log out</a>
</body>
</html>
What is done above is:
for IE - just clear auth cache and redirect somewhere
for other browsers - send an XMLHttpRequest behind the scenes with 'logout' login name and password. We need to send it to some path that will return 200 OK to that request (i.e. it shouldn't require HTTP authentication).
Replace '/where/to/redirect' with some path to redirect to after logging out and replace '/path/that/will/return/200/OK' with some path on your site that will return 200 OK.
Workaround (not a clean, nice (or even working! see comments) solution):
Disable his credentials one time.
You can move your HTTP authentication logic to PHP by sending the appropriate headers (if not logged in):
Header('WWW-Authenticate: Basic realm="protected area"');
Header('HTTP/1.0 401 Unauthorized');
And parsing the input with:
$_SERVER['PHP_AUTH_USER'] // httpauth-user
$_SERVER['PHP_AUTH_PW'] // httpauth-password
So disabling his credentials one time should be trivial.
Let’s say I have a HTTP Basic Auth realm named “Password protected”, and Bob is logged in. To log out I make 2 AJAX requests:
WWW-Authenticate: Basic realm="Password protected"At this point browser forgot Bob’s credentials.
My solution to the problem is the following. You can find the function http_digest_parse , $realm and $users in the second example of this page: http://php.net/manual/en/features.http-auth.php.
session_start();
function LogOut() {
session_destroy();
session_unset($_SESSION['session_id']);
session_unset($_SESSION['logged']);
header("Location: /", TRUE, 301);
}
function Login(){
global $realm;
if (empty($_SESSION['session_id'])) {
session_regenerate_id();
$_SESSION['session_id'] = session_id();
}
if (!IsAuthenticated()) {
header('HTTP/1.1 401 Unauthorized');
header('WWW-Authenticate: Digest realm="'.$realm.
'",qop="auth",nonce="'.$_SESSION['session_id'].'",opaque="'.md5($realm).'"');
$_SESSION['logged'] = False;
die('Access denied.');
}
$_SESSION['logged'] = True;
}
function IsAuthenticated(){
global $realm;
global $users;
if (empty($_SERVER['PHP_AUTH_DIGEST']))
return False;
// check PHP_AUTH_DIGEST
if (!($data = http_digest_parse($_SERVER['PHP_AUTH_DIGEST'])) ||
!isset($users[$data['username']]))
return False;// invalid username
$A1 = md5($data['username'] . ':' . $realm . ':' . $users[$data['username']]);
$A2 = md5($_SERVER['REQUEST_METHOD'].':'.$data['uri']);
// Give session id instead of data['nonce']
$valid_response = md5($A1.':'.$_SESSION['session_id'].':'.$data['nc'].':'.$data['cnonce'].':'.$data['qop'].':'.$A2);
if ($data['response'] != $valid_response)
return False;
return True;
}
The only effective way I've found to wipe out the PHP_AUTH_DIGEST or PHP_AUTH_USER AND PHP_AUTH_PW credentials is to call the header HTTP/1.1 401 Unauthorized.
function clear_admin_access(){
header('HTTP/1.1 401 Unauthorized');
die('Admin access turned off');
}
Typically, once a browser has asked the user for credentials and supplied them to a particular web site, it will continue to do so without further prompting. Unlike the various ways you can clear cookies on the client side, I don't know of a similar way to ask the browser to forget its supplied authentication credentials.
This might be not the solution that was looked for but i solved it like this. i have 2 scripts for the logout process.
logout.php
<?php
header("Location: http://.@domain.com/log.php");
?>
log.php
<?php
header("location: https://google.com");
?>
This way i dont get a warning and my session is terminated
Trac - by default - uses HTTP Authentication as well. Logout does not work and can not be fixed:
- This is an issue with the HTTP authentication scheme itself, and there's nothing we can do in Trac to fix it properly.
- There is currently no workaround (JavaScript or other) that works with all major browsers.
From: http://trac.edgewall.org/ticket/791#comment:103
Looks like that there is no working answer to the question, that issue has been reported seven years ago and it makes perfect sense: HTTP is stateless. Either a request is done with authentication credentials or not. But that's a matter of the client sending the request, not the server receiving it. The server can only say if a request URI needs authorization or not.
I needed to reset .htaccess authorization so I used this:
<?php
if (!isset($_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;
}
?>
Found it here : http://php.net/manual/en/features.http-auth.php
Go figure.
A number of solutions reside on that page and it even notes at the bottom: Lynx, doesn't clear the auth like other browsers ;)
I tested it out on my installed browsers and once closed, each browser seems like it consistently requires reauth on reentry.
Maybe I'm missing the point.
The most reliable way I've found to end HTTP Authentication is to close the browser and all browser windows. You can close a browser window using Javascript but I don't think you can close all browser windows.
AFAIK, there's no clean way to implement a "logout" function when using htaccess (i.e. HTTP-based) authentication.
This is because such authentication uses the HTTP error code '401' to tell the browser that credentials are required, at which point the browser prompts the user for the details. From then on, until the browser is closed, it will always send the credentials without further prompting.
The best solution I found so far is (it is sort of pseudo-code, the $isLoggedIn is pseudo variable for http auth):
At the time of "logout" just store some info to the session saying that user is actually logged out.
function logout()
{
//$isLoggedIn = false; //This does not work (point of this question)
$_SESSION['logout'] = true;
}
In the place where I check for authentication I expand the condition:
function isLoggedIn()
{
return $isLoggedIn && !$_SESSION['logout'];
}
Session is somewhat linked to the state of http authentication so user stays logged out as long as he keeps the browser open and as long as http authentication persists in the browser.
There's a lot of great - complex - answers here. In my particular case i found a clean and simple fix for the logout. I have yet to test in Edge. On my page that I have logged in to, I have placed a logout link similar to this:
<a href="https://MyDomainHere.net/logout.html">logout</a>
And in the head of that logout.html page (which is also protected by the .htaccess) I have a page refresh similar to this:
<meta http-equiv="Refresh" content="0; url=https://logout:logout@MyDomainHere.net/" />
Where you would leave the words "logout" in place to clear the username and password cached for the site.
I will admit that if multiple pages needed to be able to be directly logged in to from the beginning, each of those points of entry would need their own corresponding logout.html page. Otherwise you could centralize the logout by introducing an additional gatekeeper step into the process before the actual login prompt, requiring entry of a phrase to reach a destination of login.
I have summarised my solution in an article (https://www.hattonwebsolutions.co.uk/articles/how_to_logout_of_http_sessions) however I have used an ajax call and 2x htaccess files (as suggested in this question: How to logout of an HTTP authentication (htaccess) that works in Google Chrome?).
In short - you:
This avoids having a secondary popup in the logout folder requesting another username (which would confuse users). My article uses Jquery but it should be possible to avoid this.
While the others are correct in saying that its impossible to logout from basic http authentication there are ways to implement authentication which behave similarly. One obvious appeoach is to use auth_memcookie. If you really want to implement Basic HTTP authentication (i.e. use the browser dialogs for logging in trather than an HTTP form) using this - just set the authentication to a seperate .htaccess protected directory containing a PHP script which redirects back where te user came after createing the memcache session.
I achieved this with sending a 401 header. This works fine. With PHP
header('HTTP/1.0 401 Unauthorized');
