Why use strtolower to verify $_SERVER['HTTP_X_REQUESTED_WITH']? - php

It's extremely common to see code like this for checking XHR:
if (
isset($_SERVER['HTTP_X_REQUESTED_WITH']) &&
strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest'
) {
// ajax happened
}
Why is strtolower always used here instead of just comparing to XMLHttpRequest? Is it just paranoia or is there a real reason?

HTTP headers in the request are always included by the client. A client can be a shell script, a browser or an Ajax call fired by Javascript or a Javascript framework.
The "j" in Ajax stands for Javascript, but the HTTP request of thus can be created with any other script or program.
From Common non-standard request headers:
X-Requested-With: mainly used to identify Ajax requests. Most JavaScript frameworks send this header with value of XMLHttpRequest XMLHttpRequest.
All headers starting with X-are non standard headers, which means there is no official document defining their values.
From https://www.rfc-editor.org/rfc/rfc6648:
Historically, designers and implementers of application protocols
have often distinguished between standardized and unstandardized
parameters by prefixing the names of unstandardized parameters with
the string "X-" or similar constructs.
The HTTP protocol is not fixed or static, there are just standards you should follow.
You can even create your own HTTP request and put individual headers in, for example:
X-Requested-With: MySuperCURLScript
X-MyOwnHeader: Cool!
To answer your question, if one client sends the header X-Requested-With: XMLHttpRequest, the other sends X-Requested-With: xmlHttpRequest, you can simply lowercase 'em all and be sure not to miss different notations. Simple as that!
Security aspect: The headers and its contents are only information, not something you should 100% rely on. If you have a deep look into CURL, or Google results for "send http header with php", you'll quickly find out that any information can be sent and faked easily. HTTP headers have often been abused to hack servers, by sending manipulated cookies (- a cookie is a header, simple as that: Cookie: ...), manipulated file information (upload a fake gif which is an exe file and so on), manipulating session data, POST / request data.

Related

Callback function

So in JavaScript, I used to be able to have an http request initiate a callback when AJAX sent a response back to some data I sent to the server, successfully being a callback function. I'm now experimenting with the OAuth2 gem for Ruby, and I'm finding callbacks to not be the same;
I have a web server and facebook app set up, and I have a small php script that writes the current URL (including the auth code, for example) to a file, no problem. All the settings in the facebook app are set up, and if I put this in the URL in the browser:
http://graph.facebook.com/oauth/authorize?client_id=[my_client_id]&redirect_uri=http://localhost/oauth/callback/index.php
It redirects successfully to that script, which then writes the authorization code to a file which I can then use to get the access token. Problem is that I can only do this process manually; using the Net::HTTP.get(URI(address)) command in ruby doesn't seem to initiate the php script.
Ayone have any ideas?
I have no idea why you posted your history with javascript ajax requests, as it has no bearing on your ruby script, which by the way doesn't even use a callback method/function. Using a callback function just means you are calling some function and passing it another function as an argument. When I started programming, the term callback function was very confusing to me, and in my opinion the term should be dropped from the lingo.
As for your ruby script, you need to use something like Firebug to look at the request headers that are being sent by your browser to the server when you manually enter the url in your browser. If you use those same headers in your ruby script, then it should work, e.g.:
req['header1'] = 'hello'
req['header2'] = '10'
or:
headers = {
'header1' => 'hello',
'header2' => '10',
...
}
req = Net::HTTP::Get.new(uri.request_uri, headers)
http = Net::HTTP.new(uri.host, uri.port)
resp = http.request(req)
It's possible that you have a cookie set in your browser, which your browser automatically adds to the request headers when it sends the request to the server. Your browser probably adds thousands of headers to the request--many of which will have no bearing on your problem. If you have the patience, you can try to figure out which header is causing your ruby script's request to malfunction.
Another option is to use the mechanize gem, which will automatically handle cookies and redirects for requests sent by ruby scripts:
http://docs.seattlerb.org/mechanize/GUIDE_rdoc.html
(Read the section Let's Fetch a Page; Don't use the line require 'rubygems' if you are using ruby 1.9+).

How to receive a file via HTTP PUT with PHP

This is something that has been bugging me for a while.. I'm building of a RESTful API that has to receive files on some occasions.
When using HTTP POST, we can read data from $_POST and files from $_FILES.
When using HTTP GET, we can read data from $_GET and files from $_FILES.
However, when using HTTP PUT, AFAIK the only way to read data is to use the php://input stream.
All good and well, untill I want to send a file over HTTP PUT. Now the php://input stream doesn't work as expected anymore, since it has a file in there as well.
Here's how I currently read data on a PUT request:
(which works great as long as there are no files posted)
$handle = fopen('php://input', 'r');
$rawData = '';
while ($chunk = fread($handle, 1024)) {
$rawData .= $chunk;
}
parse_str($rawData, $data);
When I then output rawData, it shows
-----ZENDHTTPCLIENT-44cf242ea3173cfa0b97f80c68608c4c
Content-Disposition: form-data; name="image_01"; filename="lorem-ipsum.png"
Content-Type: image/png; charset=binary
�PNG
���...etc etc...
���,
-----ZENDHTTPCLIENT-8e4c65a6678d3ef287a07eb1da6a5380
Content-Disposition: form-data; name="testkey"
testvalue
-----ZENDHTTPCLIENT-8e4c65a6678d3ef287a07eb1da6a5380
Content-Disposition: form-data; name="otherkey"
othervalue
Does anyone know how to properly receive files over HTTP PUT, or how to parse files out of the php://input stream?
===== UPDATE #1 =====
I have tried only the above method, don't really have a clue as to what I can do else.
I have gotten no errors using this method, besides that I don't get the desired result of the posted data and files.
===== UPDATE #2 =====
I'm sending this test request using Zend_Http_Client, as follows:
(haven't had any problems with Zend_Http_Client so far)
$client = new Zend_Http_Client();
$client->setConfig(array(
'strict' => false,
'maxredirects' => 0,
'timeout' => 30)
);
$client->setUri( 'http://...' );
$client->setMethod(Zend_Http_Client::PUT);
$client->setFileUpload( dirname(__FILE__) . '/files/lorem-ipsum.png', 'image_01');
$client->setParameterPost(array('testkey' => 'testvalue', 'otherkey' => 'othervalue');
$client->setHeaders(array(
'api_key' => '...',
'identity' => '...',
'credential' => '...'
));
===== SOLUTION =====
Turns out I made some wrong assumptions, mainly that HTTP PUT would be similar to HTTP POST. As you can read below, DaveRandom explained to me that HTTP PUT is not meant for transferring multiple files on the same request.
I have now moved the transferring of formdata from the body to url querystring. The body now holds the contents of a single file.
For more information, read DaveRandom's answer. It's epic.
The data you show does not depict a valid PUT request body (well, it could, but I highly doubt it). What it shows is a multipart/form-data request body - the MIME type used when uploading files via HTTP POST through an HTML form.
PUT requests should exactly compliment the response to a GET request - they send you the file contents in the message body, and nothing else.
Essentially what I'm saying is that it is not your code to receive the file that is wrong, it is the code that is making the request - the client code is incorrect, not the code you show here (although the parse_str() call is a pointless exercise).
If you explain what the client is (a browser, script on other server, etc) then I can help you take this further. As it is, the appropriate request method for the request body that you depict is POST, not PUT.
Let's take a step back from the problem, and look at the HTTP protocol in general - specifically the client request side - hopefully this will help you understand how all of this is supposed to work. First, a little history (if you're not interested in this, feel free to skip this section).
History
HTTP was originally designed as a mechanism for retrieving HTML documents from remote servers. At first it effectively supported only the GET method, whereby the client would request a document by name and the server would return it to the client. The first public specification for HTTP, labelled as HTTP 0.9, appeared in 1991 - and if you're interested, you can read it here.
The HTTP 1.0 specification (formalised in 1996 with RFC 1945) expanded the capabilities of the protocol considerably, adding the HEAD and POST methods. It was not backwards compatible with HTTP 0.9, due to a change in the format of the response - a response code was added, as well as the ability to include metadata for the returned document in the form of MIME format headers - key/value data pairs. HTTP 1.0 also abstracted the protocol from HTML, allowing for the transfer of files and data in other formats.
HTTP 1.1, the form of the protocol that is almost exclusively in use today is built on top of HTTP 1.0 and was designed to be backwards compatible with HTTP 1.0 implementations. It was standardised in 1999 with RFC 2616. If you are a developer working with HTTP, get to know this document - it is your bible. Understanding it fully will give you a considerable advantage over your peers who do not.
Get to the point already
HTTP works on a request-response architecture - the client sends a request message to the server, the server returns a response message to the client.
A request message includes a METHOD, a URI and optionally, a number of HEADERS. The request METHOD is what this question relates to, so it is what I will cover in the most depth here - but first it is important to understand exactly what we mean when we talk about the request URI.
The URI is the location on the server of the resource we are requesting. In general, this consists of a path component, and optionally a query string. There are circumstances where other components may be present as well, but for the purposes of simplicity we shall ignore them for now.
Let's imagine you type http://server.domain.tld/path/to/document.ext?key=value into the address bar of your browser. The browser dismantles this string, and determines that it needs to connect to an HTTP server at server.domain.tld, and ask for the document at /path/to/document.ext?key=value.
The generated HTTP 1.1 request will look (at a minimum) like this:
GET /path/to/document.ext?key=value HTTP/1.1
Host: server.domain.tld
The first part of the request is the word GET - this is the request METHOD. The next part is the path to the file we are requesting - this is the request URI. At the end of this first line is an identifier indicating the protocol version in use. On the following line you can see a header in MIME format, called Host. HTTP 1.1 mandates that the Host: header be included with every request. This is the only header of which this is true.
The request URI is broken into two parts - everything to the left of the question mark ? is the path, everything to the right of it is the query string.
Request Methods
RFC 2616 (HTTP/1.1) defines 8 request methods.
OPTIONS
The OPTIONS method is rarely used. It is intended as a mechanism for determining what kind of functionality the server supports before attempting to consume a service the server may provide.
Off the top of my head, the only place in fairly common usage that I can think of where this is used is when opening documents in Microsoft office directly over HTTP from Internet Explorer - Office will send an OPTIONS request to the server to determine if it supports the PUT method for the specific URI, and if it does it will open the document in a way that allows the user to save their changes to the document directly back to the remote server. This functionality is tightly integrated within these specific Microsoft applications.
GET
This is by far and away the most common method in every day usage. Every time you load a regular document in your web browser it will be a GET request.
The GET method requests that the server return a specific document. The only data that should be transmitted to the server is information that the server requires to determine which document should be returned. This can include information that the server can use to dynamically generate the document, which is sent in the form of headers and/or query string in the request URI. While we're on the subject - Cookies are sent in the request headers.
HEAD
This method is identical to the GET method, with one difference - the server will not return the requested document, if will only return the headers that would be included in the response. This is useful for determining, for example, if a particular document exists without having to transfer and process the entire document.
POST
This is the second most commonly used method, and arguably the most complex. POST method requests are almost exclusively used to invoke some actions on the server that may change its state.
A POST request, unlike GET and HEAD, can (and usually does) include some data in the body of the request message. This data can be in any format, but most commonly it is a query string (in the same format as it would appear in the request URI) or a multipart message that can communicate key/value pairs along with file attachments.
Many HTML forms use the POST method. In order to upload files from a browser, you would need to use the POST method for your form.
The POST method is semantically incompatible with RESTful APIs because it is not idempotent. That is to say, a second identical POST request may result in a further change to the state of the server. This contradicts the "stateless" constraint of REST.
PUT
This directly complements GET. Where a GET requests indicates that the server should return the document at the location specified by the request URI in the response body, the PUT method indicates that the server should store the data in the request body at the location specified by the request URI.
DELETE
This indicates that the server should destroy the document at the location indicated by the request URI. Very few internet facing HTTP server implementations will perform any action when they receive a DELETE request, for fairly obvious reasons.
TRACE
This provides an application-layer level mechanism to allow clients to inspect the request it has sent as it looks by the time it reaches the destination server. This is mostly useful for determining the effect that any proxy servers between the client and the destination server may be having on the request message.
CONNECT
HTTP 1.1 reserves the name for a CONNECT method, but does not define its usage, or even its purpose. Some proxy server implementations have since used the CONNECT method to facilitate HTTP tunnelling.
I've never tried using PUT (GET POST and FILES were sufficient for my needs) but this example is from the php docs so it might help you (http://php.net/manual/en/features.file-upload.put-method.php):
<?php
/* PUT data comes in on the stdin stream */
$putdata = fopen("php://input", "r");
/* Open a file for writing */
$fp = fopen("myputfile.ext", "w");
/* Read the data 1 KB at a time
and write to the file */
while ($data = fread($putdata, 1024))
fwrite($fp, $data);
/* Close the streams */
fclose($fp);
fclose($putdata);
?>
Here is the solution that I found to be the most useful.
$put = array();
parse_str(file_get_contents('php://input'), $put);
$put will be an array, just like you are used to seeing in $_POST, except now you can follow true REST HTTP protocol.
Use POST and include an X- header to indicate the actual method (PUT in this case). Usually this is how one works around a firewall which does not allow methods other than GET and POST. Simply declare PHP buggy (since it refuses to handle multipart PUT payloads, it IS buggy), and treat it as you would an outdated/draconian firewall.
The opinions as to what PUT means in relation to GET are just that, opinions. The HTTP makes no such requirement. It simply states 'equivalent' .. it is up to the designer to determine what 'equivalent' means. If your design can accept a multi-file upload PUT and produce an 'equivalent' representation for a subsequent GET for the same resource, that's just fine and dandy, both technically and philosophically, with the HTTP specifications.
Just follow what it says in the DOC:
<?php
/* PUT data comes in on the stdin stream */
$putdata = fopen("php://input", "r");
/* Open a file for writing */
$fp = fopen("myputfile.ext", "w");
/* Read the data 1 KB at a time
and write to the file */
while ($data = fread($putdata, 1024))
fwrite($fp, $data);
/* Close the streams */
fclose($fp);
fclose($putdata);
?>
This should read the whole file that is on the PUT stream and save it locally, then you could do what you want with it.

Cross-domain AJAX request error on HTTP 200

I'm writing a very basic Facebook app, but I'm encountering an issue with cross-domain AJAX requests (using jQuery).
I've written a proxy page to make requests to the graph via cURL that I'm calling via AJAX. I can visit the page in the browser and see it has the correct output, but requesting the page via always causes jQuery to fire the error handler callback.
So I have two files:
Proxy, which does the cURL request
<?php
//Do some cURL requests, manipulate some data
//return it as JSON
print json_encode($data);
?>
The facebook canvas, which contains this AJAX call
$.getJSON("http://myDomain.com/proxy.php?get=stuff",
function(JSON)
{
alert("success");
})
.error(function(err)
{
alert("err");
});
Inspecting the call with Firebug shows it returns with HTTP code 200 OK, but the error handler is always fired, and no content is returned. This happens whether I set Content-Type: application/json or not.
I have written JSON-returning APIs in PHP before using AJAX and never had this trouble.
What could be causing the request to always trigger the error handler?
Recently I experienced the same issue and my problem was the fact that there was a domain difference between the webpage and the API, due to the SSL.
The web page got a HTTP address (http://myDomain.com) and the content I was requesting with JQuery was on the same domain but HTTPS protocol (https://myDomain.com). The browser (Chrome in this case) considered that the domains were differents (the first one with HTTP, the second one with HTTPS), just because of the protocol, and because the request response type was "application/json", the browser did not allowed it.
Basically, the request worked fine, but your browser did not allowed the response content.
I had to add a "Access-Control-Allow-Origin" header to make it work. If you're in the same case, have a look there: https://developer.mozilla.org/en/http_access_control.
I hope that'll help you, I got a headache myself.

is it possible to send referer information with php?

is it possible to send referer information with php?
If you are, for example, fetching the contents of a URL in PHP using cURL, you can send any additional headers you want, including a referrer header.
You can not force the users browser to send a referrer header by any means, especially not with a server side language.
It's not possible to get the client browser to send a different Referer header.
However, it is theory possible for you to do this when conducting an HTTP request from PHP (either using cURL or native URL wrappers), but including a custom request header in this request.
Yes, when trying to load a page, just write the Referer header to the output stream.
Referer is a 'request' header meaning sent by the client i.e. browser. From server side i.e. using PHP you can only control 'response' headers.
If you are planning to make HTTP requests with PHP, that is different of course.
Edit: ..and requests made from the server to the other servers is a pretty common scenario actually. It seems like you should be able to set the headers you want while creating the HttpRequest:
$options = array(headers => $header_array,
httpauth => $credentials);
$r = new HttpRequest($url, HTTP_METH_POST, $options);
Or you can use the addHeaders method:
$r->addHeaders(array('Referer' => 'http://example.com'));

emulating LiveHTTPheaders server side

Is it possible to 'translate' headers from this firefox extension into server side script?
edit:
I'm trying to SEND headers, not retrieve them. I performed some actions in browser and i want them to be automatically repeated (with few changes) by server-side script.
You can use PHP's header() function to send headers to the user's browser.
If you're making HTTP requests to other sites from your server, use cURL's curl_setopt function to set the CURLOPT_HTTPHEADER option - you can provide an array of headers to pass along with your request.
Consider print_r(apache_request_headers());
PHP Manual: apache_request_headers()
Here is an example and its source code.
Use the cURL functions for your request and use curl_setopt:
curl_setopt(CURLOPT_HTTPHEADER, array('Referer: http://www.example.com/'));

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