Response to preflight request doesn’t pass access control check

Response to preflight request doesn’t pass access control check

I’m getting this error using ngResource to call a REST API on Amazon Web Services:

XMLHttpRequest cannot load
http://server.apiurl.com:8000/s/login?login=facebook. 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.
Error 405

Service:
socialMarkt.factory(‘loginService’, [‘$resource’, function($resource){
var apiAddress = “http://server.apiurl.com:8000/s/login/”;
return $resource(apiAddress, { login:”facebook”, access_token: “@access_token” ,facebook_id: “@facebook_id” }, {
getUser: {method:’POST’}
});
}]);

Controller:
[…]
loginService.getUser(JSON.stringify(fbObj)),
function(data){
console.log(data);
},
function(result) {
console.error(‘Error’, result.status);
}
[…]

I’m using Chrome, and I dont know what else to do in order to fix this problem. I’ve even configured the server to accept headers from origin localhost.

Solutions/Answers:

Solution 1:

You are running into CORS issues.

There are several ways to fix/workaround this.

  1. Turn off CORS. For example: how to turn off cors in chrome
  2. Use a plugin for your browser
  3. Use a proxy such as nginx. example of how to set up

More verbosely, you are trying to access api.serverurl.com from localhost. This is the exact definition of cross domain request.

By either turning it off just to get your work done (OK, put poor security for you if you visit other sites and just kicks the can down the road) you can use a proxy which makes your browser think all requests come from local host when really you have local server that then calls the remote server.

so api.serverurl.com might become localhost:8000/api and your local nginx or other proxy will send to the correct destination.


Now by popular demand, 100% more CORS info….same great taste!


And for the downvoters…. bypassing CORS is exactly what is shown for those simply learning the front end.
https://codecraft.tv/courses/angular/http/http-with-promises/

Solution 2:

My “API Server” is an PHP Application so to solve this problem I found the below solution to work:

Place the lines in index.php

header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');

Solution 3:

In AspNetCore web api, this issue got fixed by adding “Microsoft.AspNetCore.Cors” (ver 1.1.1) and adding the below changes on Startup.cs.

public void ConfigureServices(IServiceCollection services)
{ 
    services.AddCors(options =>
    {
          options.AddPolicy("AllowAllHeaders",
                builder =>
            {
                    builder.AllowAnyOrigin()
                           .AllowAnyHeader()
                           .AllowAnyMethod();
                });
    });
    .
    .
    .
}

and

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{


    // Shows UseCors with named policy.
    app.UseCors("AllowAllHeaders");
    .
    .
    .
}

and putting [EnableCors("AllowAllHeaders")] on the controller.

Solution 4:

JavaScript XMLHttpRequest and Fetch follow the same-origin policy. So,
a web application using XMLHttpRequest or Fetch could only make HTTP
requests to its own domain.

Source: https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS

You have to send the Access-Control-Allow-Origin: * HTTP header from your server side.

If you are using Apache as your HTTP server then you can add it to your Apache configuration file like this:

<IfModule mod_headers.c>
    Header set Access-Control-Allow-Origin "*"
</IfModule>

Mod_headers is enabled by default in Apache, however, you may want to ensure it’s enabled by running:

 a2enmod headers

Solution 5:

There are some caveats when it comes to CORS. First, it does not allow wildcards * but don’t hold me on this one I’ve read it somewhere and I can’t find the article now.

If you are making requests from a different domain you need to add the allow origin headers.

Access-Control-Allow-Origin: www.other.com

If you are making requests that affect server resources like POST/PUT/PATCH, and if the mime type is different than the following application/x-www-form-urlencoded, multipart/form-data, or text/plain the browser will automatically make a pre-flight OPTIONS request to check with the server if it would allow it.

So your API/server needs to handle these OPTIONS requests accordingly, you need to respond with the appropriate access control headers and the http response status code needs to be 200.

The headers should be something like this, adjust them for your needs:

Access-Control-Allow-Methods: GET, POST, PUT, PATCH, POST, DELETE, OPTIONS
Access-Control-Allow-Headers: Content-Type
Access-Control-Max-Age: 86400

The max-age header is important, in my case, it wouldn’t work without it, I guess the browser needs the info for how long the “access rights” are valid.

In addition, if you are making e.g. a POST request with application/json mime from a different domain you also need to add the previously mentioned allow origin header, so it would look like this:


Access-Control-Allow-Origin: www.other.com
Access-Control-Allow-Methods: GET, POST, PUT, PATCH, POST, DELETE, OPTIONS
Access-Control-Allow-Headers: Content-Type
Access-Control-Max-Age: 86400

When the pre-flight succeeds and gets all the needed info your actual request will be made.

Generally speaking, whatever Access-Control headers are requested in the initial or pre-flight request, should be given in the response in order for it to work.

There is a good example in the MDN docs here on this link, and you should also check out this SO post

Solution 6:

If you’re writing a chrome-extension

You have to add in the manifest.json the permissions for your domain(s).

"permissions": [
   "http://example.com/*",
   "https://example.com/*"
]