I'm trying to support cross-origin resource sharing (CORS) calls on my API written using Google Cloud Endpoints Framework v2 in Python, but I am not able to do it.
According to the documentation, CORS is enabled by default, but I can't make any calls from a different origin using Javascript, I get this:
XMLHttpRequest cannot load https://myapp.appspot.com/_ah/api/apiname/v1/events. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://fiddle.jshell.net' is therefore not allowed access. The response had HTTP status code 500.
I've tried adding response.headers like this SO question does, but it's not working either.
Does anyone know how I can enable CORS in my API?
Thanks!
The SO link you posted mentions that the CORS headers need to be sent by the server.
You have to send the http header: "Access-Control-Allow-Origin" with value of "*" or "your client domain".
You can either send this header from the Extensible Serviceble Proxy (ESP) which is part of the Google Cloud Endpoint, or you can send the http header from your server side api script.
I would recommend sending the header from the webserver, since the ESP may cache the api responses.
Related
I needed to use the StackOverflow API to retrieve some data from the site. Actually, when I tried the first time to use the API I got an exception due to CORS policy.
Access to fetch at 'https://stackoverflow.com/users/myID/reputation'
from origin 'http://localhost:3000' has been blocked by CORS policy:
No 'Access-Control-Allow-Origin' header is present on the requested
resource. If an opaque response serves your needs, set the request's
mode to 'no-cors' to fetch the resource with CORS disabled.
I understand that the reason why my request was blocked was that the header was not in the response. However, does not StackExchange API attach in the response header Access-Control-Allow-Origin? I'm doing something wrong in how I'm invoking the request?
does not StackExchange API attach in the response header Access-Control-Allow-Origin? I'm doing something wrong in how I'm invoking the request?
The Stack Exchange API permits client-side requests, but the page you're requesting is not the Stack Exchange API - it's just a plain Stack Exchange page, not the API endpoint designed for such things, so it doesn't have the required header.
If you want to use the API properly, go through the documentation here and choose the endpoint you need. For an example using my user ID, one might use the following code:
fetch('https://api.stackexchange.com/2.2/users/9515207/reputation?site=stackoverflow')
.then(res => res.json())
.then(console.log);
api.stackexchange.com has the proper headers: access-control-allow-origin: *, which allows for client-side scripts to request it.
since this request is for a trial project, can I implement a proxy using a free-tier of some platform? I see a lot of suggestions for Heroku but I'm not very familiar with that platform
For the more general case of a server that doesn't set the required headers, if you wanted to use one of their responses client-side, you would have to bounce the request off a relay server. You could either make your own app on Heroku (a good free option), or use something like https://cors-anywhere.herokuapp.com/
I'm a n00b trying to learn React. I'm building a website that uses Etsy's APIs. Registered an app there and everything. They have a page that talks about CORS and proxying here: https://www.etsy.com/developers/documentation/getting_started/jsonp
So for example, I'm trying to do a fetch on a store's listings:
fetch('https://openapi.etsy.com/v2/shops/[shopId]/listings/active?api_key=[apiKey]')
But that violates the browser's CORS policy. No problem, says the documentation on Etsy. You can always use their proxy: beta-api.etsy.com. So I add that to my package.json file:
"proxy": "https://beta-api.etsy.com/"
And then I change my fetch line:
fetch('/v2/shops/[shopId]/listings/active?api_key=[apiKey]')
But CORS is still being violated in the browser.
Access to fetch at 'https://www.etsy.com/shop/beta-api/v2/shops/[shopId]/listings/active?api_key=[apiKey]' (redirected from 'http://localhost:3000/v2/shops/[shopId]/listings/active?api_key=[apiKey]') from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
I don't want an opaque response, either, so doing "no-cors" really doesn't help. Does anyone have any recommendations on how I can at least get a local website up and running?
You are getting that error because your server has set Access-Control-Allow-Origin to restrict cross-domain traffic. You are sending your request from your localhost so that is considered cross-domain.
If you are able to change your server settings to set Access-Control-Allow-Origin: * then you can make those requests without a CORS error but I don't suggest doing this.
The best solution would probably be a proxy server. You can use cors-anywhere heroku app to easily do this.
Excerpt from Medium Article on this issue
The cors-anywhere server is a proxy that adds CORS headers to a
request. A proxy acts as an intermediary between a client and server.
In this case, the cors-anywhere proxy server operates in between the
frontend web app making the request, and the server that responds with
data.
Similar to the Allow-control-allow-origin plugin, it adds the
more open Access-Control-Allow-Origin: * header to the response.
Say your frontend is trying to make a GET request to:
https://joke-api-strict-cors.appspot.com/jokes/random
But this api does not have a Access-Control-Allow-Origin value
in place that permits the web application domain to access it.
So instead, send your GET request to:
https://cors-anywhere.herokuapp.com/https://joke-api-strict-cors.appspot.com/jokes/random
The proxy server receives the
https://joke-api-strict-cors.appspot.com/jokes/random
from the url above. Then it makes the request to get that server’s
response. And finally, the proxy applies the Access-Control-Allow-
Origin: * to that original response.
I have react app what I already deployed to the GitHub Pages.
But now I have a problem: what I am requesting auth status to server and didn`t get any response. What is the problem?
I have this error in console about my requests
has been blocked by CORS policy:
Response to preflight request doesn't pass access control check:
No 'Access-Control-Allow-Origin' header is present on the requested resource
GitHub pages supports CORS since 2015, so you can follow "Fix CORS Error| React Tutorial" which points to:
"Run Chrome browser without CORS" (not recommended, just for testing)
axios/axios issue 853
That last issue mentions:
cURL does not enforce CORS rules. Those rules are enforced by browsers for security purposes.
When you mention that you added the relevant header, I assume you mean you added those headers to the request.
Actually, the header is expected in the response headers from the server, indicating that the resource is allowed to be accessed by other websites directly.
FYI, CORS - Cross Origin Resource Sharing. Since your API does not support it, you have two options -
Use a proxy server on the same domain as your webpage to access 4chan's API or,
Use a proxy server on any other domain, but modify the response to include the necessary headers.
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.
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.