I have a backend Flask app running on localhost:3000 and a React front-end app running on localhost:5000. In my backend app I am using Flask's 'Response.set_cookie' to set a cookie:
resp = make_response({}, 200)
resp.set_cookie('my_cookie_name', 'my_val', max_age=604800, domain='127.0.0.1', samesite='Lax', secure=None, httponly=None)
I am also allowing cross-origin for all responses in my flask app as follows:
# Child class of Flask to override some features
class TailoredFlask(Flask):
# Override make_response
def make_response(self, rv):
# Call default version from partent
resp = super().make_response(rv)
# Add CORS header to every response
resp.headers["Access-Control-Allow-Origin"] = "*"
resp.headers["Access-Control-Allow-Methods"] = "GET,POST,OPTIONS,HEAD"
resp.headers["Access-Control-Allow-Headers"] = "Origin, X-Requested-With, Content-Type, Accept, Authorization"
return resp
My client accesses my flask cookie endpoint with a call to fetch.
In the Chrome dev tools I can see that the cookie is sent with the HTTP response from my backend. It is visible when on the Network->Cookies tab when I select the request to my backend. However, if I go to the Application tab in the dev tools, my cookie is not there.
It seems like chrome is silently discarding my cookie. I have seen several simiar issues here on SO but none of them seem to explain what is going on or provide a solution to my issue.
I'm also confused about the cookie options. There is a 'domain' option which I've read is to allow cross domain operation for the cookie. However, everything is running on localhost so I feel that I shouldn't need this unless the port is causing issues. However, I have also read that the port should not be included in the cookie 'domain' field.
If anyone can help to explain this to me I would greatly appreciate it because I'm just going round in circles with this stuff.
One more thing to note: I am pointing the browser at 'localhost', but the API call to my backend and the cookie domain both use '127.0.0.1', since I've read elsewhere that the 'domain' field must have at least two dots in it. (I don't have a choice in the browser URL since I am using AWS cognito login UI to redirect to my app after login. Cognito allows http for 'localhost', but only allows https for '127.0.0.1' so I have to use 'localhost' for development.) Could the missmatch between the browser url and cookie domain be causing this issue? Or is there something else that I'm missing?
Ok, so I think I now understand what's going on here, although I don't think there's a fix for my specific problem. As described in this thread browsers (including Chrome) will not allow a domian of 'localhost' within a cookie (I just wish there was a message in the console or something to indicate why the cookie is not being saved, rather than a silent fail!)
There are various suggestions for workarounds, such as using '.app.localhost' to access the application. Unfortunately this is not an option for me as I am redirecting to my front-end app from AWS Cognito, and the only domain that is supported with HTTP (rather than HTTPS) is 'localhost'. Variants such as '.app.localhost' or '127.0.0.1' are not allowed.
There were some features I wanted from apollo-server and spent some time refactoring my code to it (was previously using express-graphql). The only problem now is a "CORS" problem between my web app (using apollo-client) for authenticated requests. I recall having this problem as well back in version 1.x, and spent a lot of time wrestling with it, but my previous solution does not work in 2.x and would greatly appreciate some help for anyone who has managed to get this to work.
my webapp is hosted on localhost:8081
my server is hosted on localhost:4000
Following their code verbatim from here, I have the following:
Client code
const client = new ApolloClient({
link: createHttpLink({
uri: 'http://localhost:4000/graphql',
credentials: 'include'
})
})
Server code
// Initializing express app code
var app = ....
// Using cors
app.use(cors({
credentials: true,
origin: 'http://localhost:8081',
}));
// Apollo Server create and apply middleware
var apolloServer = new ApolloServer({ ... });
apolloServer.applyMiddleware({ app })
When the client queries the backend via. apollo-client, I get the following error in Chrome:
Yet in my server code, I am explicitly setting the origin. When I inspect the network request in console, I get a contradictory story as well as Access-Control-Allow-Origin explicitly is set to http://localhost:8081
I don't encounter this problem when using Insomnia to query my backend server and get the expected results. Does anyone have any experience setting up apollo on client and server on localhost and successfully authenticating?
I'm actually just dumb. I was looking at the wrong response, sideshowbarker was onto it, apollo-server-v2 automatically overrides CORS and sets the Access-Control-Allow-Origin header to * by default. Even if your express app specifies CORS and you apply that as a middleware to the apollo-server, this setting will be overridden for GraphQL routes. If anyone faces this problem, hopefully this'll save some time:
https://github.com/apollographql/apollo-server/issues/1142
You can now specify CORS explicitly for apollo-server in its applyMiddleware method:
https://www.apollographql.com/docs/apollo-server/api/apollo-server.html#Parameters-2
I am working on an app using Vue js.
According to my setting I need to pass to a variable to my URL when setting change.
<!-- language: lang-js -->
$.get('http://172.16.1.157:8002/firstcolumn/' + c1v + '/' + c1b, function (data) {
// some code...
});
But when my app hit on URL, it shows the following message.
Failed to load http://172.16.1.157:8002/firstcolumn/2017-03-01/2017-10-26: Redirect from 'http://172.16.1.157:8002/firstcolumn/2017-03-01/2017-10-26' to 'http://172.16.1.157:8002/firstcolumn/2017-03-01/2017-10-26/' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access.
In addition to what awd mentioned about getting the person responsible for the server to reconfigure (an impractical solution for local development) I use a change-origin chrome plugin like this:
Moesif Orign & CORS Changer (use to be free but now wants a work email address >_>)
Allow CORS: Access-Control-Allow-Origin
You can make your local dev server (ex: localhost:8080) to appear to be coming from 172.16.1.157:8002 or any other domain.
In case the 2nd plugin link breaks in the future or the plugin writer decides to capitalize off the fame of this thread, open your browser's
plugin marketplace and search "allow cors", there's going to be a
bunch of them.
Thanks all, I solved by this extension on chrome.
Allow CORS: Access-Control-Allow-Origin
If you have control over your server, you can use PHP:
<?PHP
header('Access-Control-Allow-Origin: *');
?>
Ask the person maintaining the server at http://172.16.1.157:8002/ to add your hostname to Access-Control-Allow-Origin hosts, the server should return a header similar to the following with the response-
Access-Control-Allow-Origin: yourhostname:port
Using npm:
To allow cross-origin requests install 'cors':
npm i cors
Add this in the server-side:
let cors = require("cors");
app.use(cors());
When you have this problem with Chrome, you don't need an Extension.
Start Chrome from the Console:
chrome.exe --user-data-dir="C:/Chrome dev session" --disable-web-security
Maybe you have to close all Tabs in Chrome and restart it.
I will assume that you're a front-end developer only and that you don't have access to the backend of the application (regarding the tags of the question).
Short answer on how to properly solve this in your case? You can't, you'll need somebody else.
What is this about?
You need to understand that CORS is a security thing, it's not just here to annoy you just for fun.
It's purpose is to mainly prevent the usage of a (malicious) HTTP call from a non-whitelisted frontend to your backend with some critical mutation.
You could give a look to this YouTube video or any other one really, but I recommend a visual video because text-based explanation can be quite hard to understand.
You also need to understand that if you use Postman or any other tool to try your API call, you will not get the CORS issue. The reason being that those tools are not Web frontends but rather some server-based tools.
Hence, don't be surprised if something is working there but not in your Vue app, the context is different.
Now, how to solve this?
Depending of the framework used by your backend team, the syntax may be quite different but overall, you'll need to tell them to provide something like Access-Control-Allow-Origin: http://localhost:3000 (or any other port you'll be using).
PS: Using Access-Control-Allow-Origin: * would be quite risky because it would allow anybody to access it, hence why a stricter rule is recommended.
If you're using a service, like an API to send SMS, payment, some Google console or something else really, you'll need to allow your localhost in the dashboard of the service. Ask for credentials to your manager or Tech Lead.
If you have access to the backend, you could it yourself as shown here (ExpressJS in this example): https://flaviocopes.com/cors/
How to hack it in a dirty way?
If you're in a damn hurry and want to get something really dirty, you could use a lot of various hacks a listed in the other answers, here's a quick list:
use any extension who is able to create a middleware and forward the request to the backend (it will work because it's not directly coming from your frontend)
force your browser to disable CORS, not sure how this would actually solve the issue
use a proxy, if you're using Nuxt2, #nuxtjs/proxy is a popular one but any kind of proxy (even a real backend will do the job)
any other hack related somehow to the 3 listed above...
At the end, solving the CORS issue can be done quite fast and easily. You only need to communicate with your team or find something on your side (if you have access to the backend/admin dashboard of some service).
I heavily do recommend trying get it right from the beginning because it's related to security and that it may be forgotten down the road...
The approved answer to this question is not valid.
You need to set headers on your server-side code
app.use((req,res,next)=>{
res.setHeader('Access-Control-Allow-Origin','*');
res.setHeader('Access-Control-Allow-Methods','GET,POST,PUT,PATCH,DELETE');
res.setHeader('Access-Control-Allow-Methods','Content-Type','Authorization');
next();
})
You can also try a chrome extension to add these headers automatically.
Hello If I understood it right you are doing an XMLHttpRequest to a different domain than your page is on. So the browser is blocking it as it usually allows a request in the same origin for security reasons. You need to do something different when you want to do a cross-domain request. A tutorial about how to achieve that is Using CORS.
When you are using 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.
To add the CORS authorization to the header using Apache, simply add the following line inside either the <Directory>, <Location>, <Files> or <VirtualHost> sections of your server config (usually located in a *.conf file, such as httpd.conf or apache.conf), or within a .htaccess file:
Header set Access-Control-Allow-Origin "*"
And then restart apache.
Altering headers requires the use of mod_headers. Mod_headers is enabled by default in Apache, however, you may want to ensure it's enabled.
I had the same problem in my Vue.js and SpringBoot projects. If somebody work with spring you can add this code:
#Bean
public FilterRegistrationBean simpleCorsFilter() {
UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
CorsConfiguration config = new CorsConfiguration();
config.setAllowCredentials(true);
// *** URL below needs to match the Vue client URL and port ***
config.setAllowedOrigins(Collections.singletonList("http://localhost:8080"));
config.setAllowedMethods(Collections.singletonList("*"));
config.setAllowedHeaders(Collections.singletonList("*"));
source.registerCorsConfiguration("/**", config);
FilterRegistrationBean bean = new FilterRegistrationBean<>(new CorsFilter(source));
bean.setOrder(Ordered.HIGHEST_PRECEDENCE);
return bean;
}
I found solution in this article Build a Simple CRUD App with Spring Boot and Vue.js
You are making a request to external domain 172.16.1.157:8002/ from your local development server that is why it is giving cross origin exception.
Either you have to allow headers Access-Control-Allow-Origin:* in both frontend and backend or alternatively use this extension cors header toggle - chrome extension unless you host backend and frontend on the same domain.
Try running this command in your terminal and then test it again.
curl -H "origin: originHost" -v "RequestedResource"
Eg:
If my originHost equals https://localhost:8081/ and my RequestedResource equals https://example.com/
My command would be as below:
curl -H "origin: https://localhost:8081/" -v "https://example.com/"
If you can notice the following line then it should work for you.
< access-control-allow-origin: *
Hope this helps.
Do specify #CrossOrigin(origins = "http://localhost:8081")
in Controller class.
You can solve this temporarily by using the Firefox add-on, CORS Everywhere. Just open Firefox, press Ctrl+Shift+A , search the add-on and add it!
You won't believe this,
Make sure to add "." at the end of the "url"
I got a similar error with this code:
fetch(https://itunes.apple.com/search?term=jack+johnson)
.then( response => {
return response.json();
})
.then(data => {
console.log(data.results);
}).catch(error => console.log('Request failed:', error))
The error I got:
Access to fetch at 'https://itunes.apple.com/search?term=jack+johnson'
from origin 'http://127.0.0.1:5500' 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.
But I realized after a lot of research that the problem was that I did not copy the
right URL address from the iTunes API documentation.
It should have been
https://itunes.apple.com/search?term=jack+johnson.
not
https://itunes.apple.com/search?term=jack+johnson
Notice the dot at the end
There is a huge explanation about why the dot is important quoting issues about DNS and character encoding but the truth is you probably do not care. Try adding the dot it might work for you too.
When I added the "." everything worked like a charm.
I hope it works for you too.
install:
npm i cors
Then include cors():
app.get("/list",cors(),(req,res) =>{
});
In addition to the Berke Kaan Cetinkaya's answer.
If you have control over your server, you can do the following in ExpressJs:
app.use(function(req, res, next) {
// update to match the domain you will make the request from
res.header("Access-Control-Allow-Origin", "YOUR-DOMAIN.TLD");
res.header("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
next();
});
https://enable-cors.org/server_expressjs.html
I tried this code,and that works for me.You can see the documentation in this link
var io = require("socket.io")(http, {
cors: {
origin: "*",
methods: ["GET", "POST"]
}
})
The reason that I came across this error was that I hadn't updated the path for different environments.
you have to customize security for your browser or allow permission through customizing security. (it is impractical for your local testing)
to know more about please go through the link.
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
These errors may be caused due to follow reasons, ensure the following steps are followed. To connect the local host with the local virtual machine(host). Here, I'am connecting http://localhost:3001/ to the http://abc.test Steps to be followed:
1.We have to allow CORS, placing Access-Control-Allow-Origin: in header of request
may not work. Install a google extension which enables a CORS request.*
2.Make sure the credentials you provide in the request are valid.
3.Make sure the vagrant has been provisioned. Try vagrant up --provision this make the localhost connect to db of the homestead.
Try changing the content type of the header. header:{ 'Content-Type' : 'application/x-www-form-urlencoded; charset=UTF-8;application/json' }
this point is very important.
Another solution to this problem in a specific scenario :
If
AWS APIGW is your backend with authentication enabled and
authentication fails,
your browser may end up complaining about CORS even if CORS is enabled in APIGW. You also need to enable CORS for 4XX as follows
API:YourAPI > Resources > /YourResource > Actions > Enable CORS > Gateway Responses for yourAPI check Default 4XX
Authentication will still fail but it won't look like CORS is the root cause
$.get('https://172.16.1.157:8002/firstcolumn/' + c1v + '/' + c1b, function (data) {
// some code...
});
Just put "https" .
I am building a website using NodeJS, and I deploy it to Heroku. But when I open the website, something went wrong. Here is the problem:
Code:
In the main source file of my web:
app.get('/', (req, res) => {
var data = {
rootURL: `${req.protocol}://${req.get('Host')}`,
};
res.render('home.html', data);
});
Then, in home.html, I include the following script:
<script type="text/javascript">
$.getJSON('{{rootURL}}'+'/about', {}, function(data){
// Code here is deleted for now.
}).fail(function(evt) {
// Code here is deleted for now.
});
</script>
Here I use hbs template, so {{rootURL}} is equal to the 'rootURL' property within the 'data' object rendered along with the 'home.html' page.
The '/about' is one of the APIs I designed for my web. It basically sends back something about the website itself and this information is wrapped in JSON.
Then, here comes the problem. The code works fine locally, and works well when I send HTTP request instead of HTTPS to Heroku. But if I send HTTPS request to Heroku, I'll get 'Mixed Content' Errors:
Errors I get in Chrome Console.
I then switched to 'Elements' tab in the developers tool, and I saw this:
The schema is HTTP, not HTTPS!
I'm very confused here. I just grab the 'protocol' property within the 'req' object, and fill in the template with it. So, I'm assuming if I enter '[my-website-name].herokuapp.com' with 'https' schema in my Chrome Browser, my nodeJS app deployed on Heroku should get 'https' for req.protocol. But Apparently it's not the case. What is wrong here?
I assume you don't actually have an SSL certificate? Heroku will be providing the HTTPS, but it will then translate it to normal HTTP internally when it hits your express endpoint, which is why it sees req.protocol as HTTP.
Is there any point in even providing the URL to getJSON? Why not just send it $.getJSON('/about', callback) and let the browser handle that?
Also, you haven't hidden your URL in that first image you uploaded, if that's what you were intending.
Heroku router is doing SSL termination, so no matter if you connect via http or https, you get http on your side. Original protocol is however set in X-Forward-Proto header. You need use this value.
I am trying to build a quick demo site that I do not have control over the server I am trying to connect to. Here is the code that I am using to build it with AngularJS. I am running the file through a simple Python HTTP Server and viewing it at localhost:8000.
var retrieveAppliances = function () {
console.log('Attempting to retrieve appliance list.');
var requestUrl = '****';
$http({
method: 'GET',
url: requestUrl,
})
.then(function (response) {
console.log(response);
});
};
retrieveAppliances();
I have read multiple places to try switching the method to JSONP but doing so resulted in a parsing error.
While I have considered trying to build a server.js file and running NodeJS with it, I am unsuccessful in learning the basics of making an AJAX request and proxying that to my app.js.
I will greatly appreciate any help that someone may be able to give me, with clear and easy to follow steps.
If you're running an Ajax call to a different origin (e.g. different host, port or protocol) and the server at that origin does not have support for cross origin requests, then you cannot fix that from your client. There is nothing you can do from the client.
If the server supported JSONP, you could use that, but that also requires specific server support.
The only solutions from a browser web page are:
CORS support on the target server.
JSONP (also requires support on the target server).
Set up your own server that you do have access to (either on your existing page domain or with CORS) and then have that server get the file/data for you and proxy it back to you. You can either write your own proxy or deploy a pre-built proxy.
Find some existing third party proxy service that you can use.
If you're interested in making your own node.js proxy, you can see a simple example here: How to create a simple http proxy in node.js?.