I have an AngularJs website and when I am trying to post data then when I am opening my website without using www then I am getting
Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource
Otherwise, I am not getting any error.
I tried to search and found that I should implement CORS on my backend which is in NodeJs but can anyone please tell me how can I only implement CORS Headers such that for both www and without, it would work but for any other domain trying to access my API must result in preflight error.
I am trying to do this because I read here which-security-risks-do-cors-imply that allowing all domains can increase security overhead for my website which I do not want.
Thanks.
I'm afraid this is not something you can tweak just in your client-side code. In order for cross-origin requests to work, you need to set an http response header: it's the server, who serves the resource, who will need the change, not the client side code from angularJs.
I believe that you should update your question stating what your server side language is and how are you handling http requests in the server side. As far as I know, just adding a header like:
Access-Control-Allow-Origin: http://client.domain.com
In your responses will do the trick. Where client.domain.com is the domain of your client, angularJs application.
Related
Forgive me for the obvious error I am obviously committing...
I understand CORS, how and why it's used. But I'm missing the blindingly obvious in this instance.
I'm trying to access a publicly available API that should work fine (I've been assured)
If I hit the endpoint in Chrome, or in Postman, all works fine: wonderful JSON is returned.
When I try to do the same using axios from within my create-react-app's componentDidMount, I get a CORS error, specifically
Access to XMLHttpRequest at 'http://some-interesting-url/sub-url?blabla=blip&foo=bar' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
What is it I'm failing to grasp? Is there anything I can do from my end? (I have no control over the server)
The Postman app is not a browser so it isn't bound by the rules of CORS. In a browser too, trying to access a URL directly doesn't trigger Cross-Origin-Request-Sharing policies. CORS, by definition will only affects the 'cross-origin' requests made from background JS code of a web-page, to another web-page or API not hosted on same domain name.
Based on the error posted, the API in question is not sending Access-Control-Allow-Origin header. If it's possible to get the API changed, that you should get the header added to response (with value '*', or your domain name). However if that's not possible, then you'd need to route the request through a web-server that you own and include this header there. This kind of does work like a proxy, albeit for a specialized use-case.
If you already have some server side application running, you can simply add another end point to your application. A call to this new end point should trigger the 'Public API' call, and send the response back to client. Since the server side program (eg PHP/Python/NodeJS) would never be a browser, they will not face the CORS issues. If your original web-page is also loaded from same web-server, then the response header can be skipped.
when trying to $.ajax to fetch some content from other websites in my website, I got the error.
Failed to load https://www.pinterest.com/: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8100' is therefore not allowed access.
I knew if the target website didn't allow localhost:8100 to fetch the data, I cannot fetch it in the client side on the web.
However, I found that mobile app (not mobile browser, but android/ios application) does not have the issue, they can simply get the website content by their default mobile built-in HTTP get function.
Do i want to ask why mobile will not encounter CORS issue (mobile can fetch the webcontent simply by the built-in http get function)?
thanks.
CORS is enforced by the browser to fulfill the security standard they have to meet. It does not affect requests made programmatically from any language, like a curl call on bash.
This is how CORS works, based on Wikipedia:
The browser sends the OPTIONS request with an Origin HTTP header. The value of this header is the domain that served the parent page. When a page from http://www.example.com attempts to access a user's data in service.example.com, the following request header would be sent to service.example.com: Origin: http://www.example.com.
The server at service.example.com may respond with:
An Access-Control-Allow-Origin (ACAO) header in its response indicating which origin sites are allowed. For example Access-Control-Allow-Origin: http://www.example.com
An error page if the server does not allow the cross-origin request
An Access-Control-Allow-Origin (ACAO) header with a wildcard that allows all domains: Access-Control-Allow-Origin: *
The way CORS works means it is optional. Browsers enforce it to prevent Javascript AJAX calls to perform malicious calls. But other types of consumers built by hand don't need to enforce CORS.
Think in this example:
You are the owner of somesite.com
Users authenticate to your site using the traditional cookie method
User logins into anothersite.com, built by an attacker. This site has the following code:
<script>fetch('http://somesite.com/posts/1', { method: 'DELETE' });</script>
... effectively performing a request to your site and doing bad things.
Happily, the browser will perform a preflight request when it sees a cross-domain request, and if your site does not respond saying that requests coming from anothersite.com are OK, you will be covered by default from a potential attack
This is why CORS only makes sense in the context of a browser. Javascript you send to the browser can not (at least easily) circumvent CORS because the only API that allows you to perform requests from the browser is written in stone. Additionally, there are no local storage or cookies outside of the browser.
Corolarium: Enforcing CORS is a deliberate action from the requester, or whoever is making the requests for you, not the sender. Javascript APIs in browsers enforce it. Other languages don't have the need for the reasons explained.
When running on a device, your files are served over the file:// protocol, not http://, and your origin will therefore not exist. That's why the request from the native device does not trigger CORS.
I'm trying to fetch the list of official images from docker hub using v2 api. If I try to do curl or use postman, I get the response correctly, but when I try to fetch the list using angularjs service, I get the following error
XMLHttpRequest cannot load https://hub.docker.com/v2/repositories/library/?page=8&page_size=15. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://run.plnkr.co' is therefore not allowed access.
Can someone suggest solution for this. How can I enable cors for this?
CORS could be enabled on the server side, and this is not your case. What you could do is :
1) use a proxy, for instance NGNIX, and make Sure that all request Made to localhost/whatever are redirected to hub.docker.com . This way you can "cheat" Cross-origin block
2) if you need a temporary and dirty solution you could more simply install chrome/safari plugins to bypass CORS security check
There is only one way to bypass CORS is send request through a cors proxy like http://crossorigin.me
It's an opensource project and you can build your own proxy server by download the full source code from here: https://github.com/technoboy10/crossorigin.me
Reason behind the issue :
As per my understanding you are doing an AJAX call to a different domain than your page is on. So, the browser is blocking it for security reasons as it usually allows a request in the same origin.A tutorial about how to achieve that is using CORS.
When you are using curl or postman they are not restricted by this policy. Quoted from Cross-Origin XMLHttpRequest:
Regular web pages can use the XMLHttpRequest object to send and receive data from remote servers, but they're limited by the same origin policy. Extensions aren't so limited. An extension can talk to remote servers outside of its origin, as long as it first requests cross-origin permissions.
Why can I make a REST API request from a browser/Postman/ even Node.js (http.get method), but not from Angular resource?
The snippet of the error message is:
XMLHttpRequest cannot load http://example-of-external-api-site.com
Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'http://localhost' is therefore not allowed access.
Before asking this, I tried to look at the definition of CORS. And from my understanding, I can understand why it disallow the request I make from Angular's resource since it is coming from a different domain. But, isn't my browser/Postman/Node.js app are from a different domain as well?
Please help me answering this, I can't really understand why..
When a request is made from the browser when accessing a url directly, you are requesting the content of a url without the use of XMLHttpRequest.
There are two scenarios for $http.get():
When accessing a uri that is NOT the same domain that is hosting your AngularJS content, via an ajax call utilizing XMLHttpRequest from within the rendered content of your browser, you must provide a CORs header that matches the whitelisting on the target server. This is due to browser security restrictions to prevent nasty, malicious attacks such as Cross Site Scripting.
When accessing a uri that IS the same domain as that which is hosting your AngularJS content (typically done via relative paths: /Api/1 instead of http://domain.com/api/1), CORs whitelisting is not required, since both the origin and the target domain are the same.
Finally, when invoking a url from node, you are making a server to server concurrent call which does not have the same security restrictions since it is not executing within your browser.
I'm using nginx on the remote server, and with no support for the OPTIONS method I've been terribly stuck. Both the server and angular refuse to talk to each other.
I just want to make a simple $http.post() request. Is there a way to configure the service to ONLY send the POST request, and not do any preflighting with OPTIONS?
This is not something AngularJS does, but something your browser does according to the Cross-Origin Resource Sharing standard. See also this answer on a related issue.
However, if you make it so that the AngularJS application is served from the same domain as your resource (different subdomains will affect cross-origin), then the browser will not send the OPTIONS request as the resource is no longer from a cross-origin server.
Example:
www.example.com requests resource on api.example.com will trigger OPTIONS request
www.example.com requests resource from www.example.com/api will not trigger OPTIONS request
If CORS is Unavoidable
You could change the header of the request to text/plain and then parse your response manually acording to answers in this link below
How to skip the OPTIONS preflight request in AngularJS