Post by Stuart DallasPost by Stuart DallasOops, sent this message from the wrong email address, so the list rejected it.
Subject: Re: [PHP] Basic Auth
Date: 27 August 2013 16:36:27 BST
Post by Stuart DallasPost by Stuart DallasPost by Jim GinerPost by Stuart DallasIt's not really confusing so long as you understand how PHP works. Each request is brand new - nothing is retained from previous requests. The two variable you're changing are set by PHP when the request comes in from the browser. The fact you changed them in a previous request is irrelevant because 1) that change was not communicated to the browser in any way, and 2) PHP doesn't retain any data between requests [1].
If you've been coding assuming that changes you make to global variables are retained between requests you must have been having some pretty frustrating times!
-Stuart
Not really - this is the first time I've had something not work as expected.
I've been playing with dynamite since I was 4 - hey, it must be a safe, proper thing to do!
Just because nothing has blown up in your face yet doesn't mean it won't, and I'm concerned that you might not actually see how important it is to make sure you're using the tool correctly.
-Stuart
This may very well be the first time with this problem because I haven't tried anything like this before.
header("WWW-Authenticate: Basic realm=$realm");
header('HTTP/1.0 401 Unauthorized');
echo "<h3>You have entered invalid credentials<br>";
echo "Click <a href='$return_url'> here </a> to return to the menu.";
exit();
when it doesn't detect the PHP_AUTH_USER or it is an invalid value.
So - to effect a signoff, what does one do? You said to use an invalid value, but what do I do with that? How do I ignore the 401? Now I'm getting the signin dialog and I'm stuck.
You don't need to do anything on the server-side. You simply need a JS function that sends a request to a URL that requires basic auth, with an Authenticate header that contains an invalid username and password. Then, when your server responds with a 401 Authentication required (which it should already do for an invalid request) you can set location.href to whatever URL you want the logged out user to see.
If you don't know how to make a request from Javascript -- commonly known as an AJAX request -- then google for it. I'd recommend the jquery library if you want a very easy way to do it.
-Stuart
I am familiar with an ajax request (xmlhttprequest) and I have a function ready to call a script to effect this signoff. I just don't know what to put in that php script I'm calling. From what you just wrote I'm guessing that my headers as shown previously may be close - I"m confused about your mention of "contains an invalid username...". As you can see from my sample I don't include such a thing.
For the last time: YOU DO NOT NEED TO MAKE ANY CHANGES SERVER-SIDE.
From the Javascript, request any URL that requires authentication - it doesn't matter. When you make the AJAX request, pass an Authentication header that contains an invalid username and password. If you don't know what I mean by that, please google how HTTP Basic Auth works.
-Stuart
It's not the basic auth that I'm having the issue with - it's the 'header' thing and understanding what a 401 is doing and how I'm to ignore it. Never had to play with these things before and this part is all new. Let's face it - I'm an applications guy, not a systems guy. All this talk of headers and such is greek to me.
HTTP headers are as important for application guys as they are for systems guys. I appreciate that this may be new to you, but it's pretty basic knowledge about how HTTP works.
1) Browser hits page.
2) The PHP script knows this page requires HTTP Auth, checks the PHP_AUTH_[USER|PW] variables but doesn't find anything, so it responds with an HTTP status of 401 Unauthorised.
3) The browser gets the 401 response and displays the login box.
4) User enters username and password.
5) Browser sends the request again, but this time with an Authorization header containing the username and password. It also caches the username and password for use with future requests.
6) PHP populates the PHP_AUTH_[USER|PW] variables with the username and password in the Authorization header.
7) The PHP script checks those variables as per step 2, finds them, checks they're correct, and then shows the user the page with a 200 OK HTTP response (the default with PHP).
8) Every subsequent request the browser sends to that domain will now include the Authorization header, so the server will never respond with a 401 status again until the browser session ends (i.e. the browser is closed).
So, we do it with Javascript. Send a request using AJAX to any URL that requires authentication, setting our own Authorization header with an invalid username and password. PHP will see that the username and password are incorrect and will respond with a 401 status as per step 2 above, but step 3 will not happen because AJAX requests don't reach the browser's default response handlers (i.e. 401 == display login box).
When our Javascript gets the response it simply redirects the user to a page telling them they've successfully logged out, or whatever you want them to see. The only reason this works is that the browser has now cached the bogus username and password you sent in the AJAX request, so if/when the user then hits another page that requires authentication they will get the login box because those cached details are not valid.
To send the Authorization header with XMLHttpRequest there are username and password parameters to the open method: https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest.
Hopefully this makes more sense now.
-Stuart
--
Stuart Dallas
3ft9 Ltd
http://3ft9.com/
Eureka!!!
Thanks to your wonderful explanation - much of which I kinda knew, just
not in such detail - I have a working solution which I will show. From
your latest missive I gleaned that I needed to have a script on my
server that had the authenticate header included as well as my xml js
function opening the connection with a user and pswd value (bogus as
they were).
For those reading along:
My php script that is called from JS via xml/ajax:
<?
//
// BasicAuth_Signoff.php
// A script used by an xml request to enforce a basic auth signoff
//
header("WWW-Authenticate: Basic realm=My Bowling League Data");
header('HTTP/1.0 401 Unauthorized');
echo "true";
exit();
Note: the realm has to match the one used when the user signed in!
My JS xml call:
var myreq = new XMLHttpRequest();
url="http://jimginer.net/bowling_dir/BasicAuth_Signoff.php";
urlmeth = "GET";
myreq.open(urlmeth, url, true,"x","x");
(just the essentials of making the call here)
In my mind I see it like this:
The php script expects authentication to occur because of the first
header, and responds with the 401 because of the 2nd. The JS code calls
the php script and provides the responses to the authentication request
in the open statement.
Any ideas on improving this would be appreciated, but as it stands
above, it's working almost exactly as I wish. The only drawback right
now is that the user only has to hit enter to the first request for a
following signin and he is prompted with a second signin dialog showing
the last valid credentials, making the signoff not that effective.
(Note: both the userid and pswd parms MUST be provided in the XML open
call or IE defaults the next attempt to signon to the last working set
of credentials, making the signoff even more fruitless.) Any tips on
this will also be appreciated.
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