I'm trying to use a SOAP-webservice from javascript.
Both the server and client are in the same LAN and i control both.
when i try to send a request i get:
XMLHttpRequest cannot load .
Origin is not allowed by Access-Control-Allow-Origin.
this is probably because of cross-origin-scripting?
I would like to fix this on the server side.
that means: adding extra headers on outgoing messages:
Access-Control-Allow-Origin: *
how can I add these response headers?
I'm using Netbeans to manage the web service in Glassfish
There is a hint in the error message. The server running on a different host needs to return the Access-contol-allow-origin header and possibly also Access-control-include-credential.
Note that this only works in newer browsers, so if there are older browsers in your network, you may need to lookk at something like proxying or using eadyXDM.
Btw, use "cross origin" instead of cross site scripting". Cross site scripting is a vulnerability, and using this term makes the question a bit confusing.
Related
I have a web method that I want to call from my C# app and was provided with a Javascript example, showing how to call the method. I have established that running the Javascript from my desktop runs into CORS problems - i was able to run the sample when I put the javascript on the server and ran it from the same folder as the web method.
Will my C# app run into the same CORS issue? or will it be ok because only the browsers have the built in CORS security?
--Edit--
I've been using System.Net.Http.HttpClient and http://restsharp.org/
Am I correct in assuming that these two objects are wrappers around a web browser? and that they will have issues with CORS?
I really don't want to have to write Sockets code.
Due to security reasons browsers restrict cross-origin HTTP requests initiated from within scripts on the browser. For example, XMLHttpRequest follows the same-origin policy. That means a web application using XMLHttpRequest could only make HTTP requests to its own domain. This prevents application from being vulnerable to CSRF attacks. However, there are cases when applications need to access resources from different domain. This is when CORS comes into play to allow cross-domain requests.
Having said all that, your C# app should be able to call the WEB API without any CORS issues as long as it's a socket to socket communication (not via browser).
Some where in deep recess of my mind I remember browser related cors will always be blocked unless noted or changed like for example if you're in chrome and have the cors extension allow browser cors control, but on the server side, their is nothing preventing servers from interacting with one another.
but it depends on what is allowed on the headers
I'll try to produce some documentation that confirms that.
https://spring.io/understanding/CORS
The request includes an Origin header that indicates the origin of the client code.
The server will consider the request's Origin and either allow or disallow the request. If the server allows the request, then it will respond with the requested resource and an Access-Control-Allow-Origin header in the response. This header will indicate to the client which client origins will be allowed to access the resource. Assuming that the Access-Control-Allow-Origin header matches the request's Origin, the browser will allow the request.
On the other hand, if Access-Control-Allow-Origin is missing in the response or if it doesn't match the request's Origin, the browser will disallow the request.
webui-aria2 is a tool that allows controlling aria2 (powerful download tool) through rpc methods from a browser.
Using http://ziahamza.github.io/webui-aria2/, one can control aria2, provided the application is launched with the --enable-rpc option. aria2 basically starts an HTTP server listening on localhost:6800.
Great but I am surprised that the browser (both webkit and gecko) allows a page hosted on github.io to make requests to localhost. How come it does? Isn’t this a serious vulnerability?
Requests to localhost from github.io will be treated like any other cross origin request.
JavaScript embedded on the site can't read the data across origins unless either:
Explicit permission is given with CORS or
A hack such as JSONP is used
Presumably the server uses one of those techniques.
I'd like to use WebSockets for inter-process communication for my application (Daemon<->WebGUI and Daemon<->FatClient, etc.). During testing, I tried connecting to my locally running web socket server (ws://localhost:1234) via the JavaScript WebSocket client on websocket.org (http://www.websocket.org/echo.html).
My question now is:
Why is this possible? Is there no cross-origin policy implemented in the browsers (here: FF29 on Linux)?
I am asking because if websocket.org was evil, it could try to communicate with my local WS server and redirect every message it receives from localhost to any other server:
Local WebSocket Server Browser Evil Web Server
at ws://localhost:1234 at http://evil.tld
| | |
| |------[GET /]--------->|
| |<-----[HTML+EvilJS]----|
|<------[connect ws://..]----| |
|<----[some communication]-->| |
| |----[evil forward]---->|
| | |
I have not tested the entire use case, but the connect to ws://localhost from the JS delivered by websocket.org definitely works.
To address the "Why?" part, the reason why browsers don't enforce the Same Origin Policy (of which CORS is a relaxation) for WebSockets as opposed to AJAX calls, is because WebSockets were introduced after the value of cross-origin requests was established, and because they're not subject to SOP to begin with, the historical reason for the CORS client-side checks doesn't apply.
For AJAX, in the days of a blanket Single Origin Policy, servers never expected an authenticated browser to send a request from a different domain1, and so didn't need to ensure the request was coming from a trusted location2, just check the session cookie. Later relaxations like CORS had to have client-side checks to avoid exposing existing applications to abuse by violating this assumption (effectively doing a CSRF attack).
If the Web were being invented today, knowing what we know now, neither SOP nor CORS would be required for AJAX and it's possible that all the validation would be left to the server.
WebSockets, being a newer technology, are designed to support cross-domain scenarios from the get go. Anyone writing server logic should be aware of the possibility of cross-origin requests and perform the necessary validation, without the need for heavy-handed browser-side precautions à la CORS.
1 This is a simplification. Cross-origin GET requests for resources (including <img>, <link> and <script> tags) and form submission POST requests were always permitted as a fundamental feature of the Web. Nowadays, cross-origin AJAX calls whose requests have the same properties are also permitted and known as simple cross-origin requests. However, accessing the returned data from such requests in code is not allowed unless explicitly permitted by the server's CORS headers. Also, it is these "simple" POST requests that are the primary reason why anti-CSRF tokens are necessary for servers to protect themselves from malicious websites.
2 In fact, a secure way to check the request source wasn't even available since the Referer header can be spoofed e.g. using an open redirect vulnerability. This also shows how poorly CSRF vulnerabilities were understood back then.
oberstet answered the question. Thank you! Unfortunately I can't mark it as "correct" because it was a comment. The browser sends the "origin" header which can be checked by the application.
In Java [1]:
#Override
public void onOpen(WebSocket clientSocket, ClientHandshake handshake) {
String clientOrigin = handshake.getFieldValue("origin");
if (clientOrigin == null || !clientOrigin.equals(WEBSOCKET_ALLOWED_ORIGIN_HEADER)) {
logger.log(Level.WARNING, "Client did not sent correct origin header: " + clientOrigin);
clientSocket.close();
return;
}
// ...
}
[1] using https://github.com/TooTallNate/Java-WebSocket
WebSockets can cross domain communication, and they are not limited by the SOP (Same Origin Policy).
The same security issue you described can happen without WebSockets.
The evil JS can:
Create a script/image tag with a URL to evil.tld and put data in the query string.
Create a form tag, put the data in the fields, and invoke the "submit" action of the form, doing an HTTP POST, that can be cross domain. AJAX is limited by the SOP, but normal HTTP POST is not. Check the XSRF web security issue.
If something injects javascript in your page, or you get malicious javascript, your security is already broken.
I'm building a nodejs server and I need to access more services using ajax from another domain, so how can I break the cross-domain restriction in nodejs code?
Note: Frameworks like ExpressJS is not an acceptable solution
Generally speaking, when there is a cross domain restriction in effect you have two possible options to take.
Determine if the remote party you're trying to talk to supports CORS. Have them allow your domain on their end in the HTTP headers. Sometimes this is not possible.
Setup a reverse HTTP proxy that allows you to communicate to the remote party but goes through your web server first so you bypass the cross domain origin security issue. Node-http-proxy is a possible solution if you're already using Node.js
CORS is generally only supported in more recent browsers, so if you have a requirement to support old stuff that might not be suitable.
Note in jQuery from linked resource.
$.support.cors
boolean will be set to true if the browser supports CORS
I am developing applications using Angular and the client side is 100% JS. I am about to replace an old application made using ExtJS but I will not change the server-side. Only the client-side be re-coded from scratch.
I would like to work on this project from anywhere and any machine but I need to be able to perform cross-domain AJAX queries with the original server (server-side is ASP.NET MVC with IIS and I don't want to install Windows + everything on all the computers I use). Is there a way to do this easily?
Thanks for your ideas!
PS: JsonP is not a solution for me.
Couple of things:
At the end of the day you have to enable CORS in your server.
You can use a CORS proxy https://github.com/gr2m/CORS-Proxy for development. This proxy will actually change the request header of X-Origin which browsers even can but "won't" because of policy. So you will be able to make Cross Origin Requests.
If neither JSONP nor CORS are availble to you as options then you will have to take help of server side scripting.
You can create a method in your server side code and get the response from desired cross domain url and return the response to your javascript function.
You can use CORS (Cross Origin Resource Sharing)