CORS error with Javascript but not with Python/PHP

CORS error with Javascript but not with Python/PHP - javascript

I'm writing a small script to access an external API for work. I originally did this in Python and everything worked fine.
I was then asked to try and do it in Javascript. Now, I'm no programmer really, but I do know (or believe) that Javascript is largely for client-side, whereas PHP or Python are really for server-side operations. When I wrote the script in Python I had no problems, but in Javascript I get a
Response to preflight request doesn't pass access control check: No
'Access-Control-Allow-Origin' header is present on the requested
resource.
error. From what I've read about CORS here and similar questions on Stack, that makes sense, but I don't really understand why I don't get a similar error in Python or PHP...
I'm fairly new to this so I'm probably missing a number of things, but I'd really appreciate any insight anyone can give me. If I've left out any important info, please let me know.

From Mozilla's documentation:
For security reasons, browsers restrict cross-origin HTTP requests initiated from within scripts. For example, 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.
Since Javascript in the browser uses XMLHttpRequest and fetch to make HTTP requests, they're subject to CORS policy enforcement.
More information on the reasons for CORS:
CORS is intended to allow resource hosts (any service that makes its data available via HTTP) to restrict which websites may access that data.
Example: You are hosting a website that shows traffic data and you are using AJAX requests on your website. If SOP and CORS were not there, any other website could show your traffic data by simply AJAXing to your endpoints; anyone could easily "steal" your data and thus your users and your money.
The external API you're using likely implemented a CORS policy intentionally. For example, if the API requires an application-level secret key for authentication, a CORS policy would discourage the use of that key in a public environment (namely the browser). Alternatively, the API may have a list of acceptable domain names for CORS that doesn't include the domain you're currently using.
Those are just a few examples; there could be any number of reasons for an API to implement CORS headers.

Related

Why can you load a local Javascript file and not a local JSON or XML file? [duplicate]

tl;dr; About the Same Origin Policy
I have a Grunt process which initiates an instance of express.js server. This was working absolutely fine up until just now when it started serving a blank page with the following appearing in the error log in the developer's console in Chrome (latest version):
XMLHttpRequest cannot load https://www.example.com/
No 'Access-Control-Allow-Origin' header is present on the requested
resource. Origin 'http://localhost:4300' is therefore not allowed access.
What is stopping me from accessing the page?

tl;dr — When you want to read data, (mostly) using client-side JS, from a different server you need the server with the data to grant explicit permission to the code that wants the data.
There's a summary at the end and headings in the answer to make it easier to find the relevant parts. Reading everything is recommended though as it provides useful background for understanding the why that makes seeing how the how applies in different circumstances easier.
About the Same Origin Policy
This is the Same Origin Policy. It is a security feature implemented by browsers.
Your particular case is showing how it is implemented for XMLHttpRequest (and you'll get identical results if you were to use fetch), but it also applies to other things (such as images loaded onto a <canvas> or documents loaded into an <iframe>), just with slightly different implementations.
The standard scenario that demonstrates the need for the SOP can be demonstrated with three characters:
Alice is a person with a web browser
Bob runs a website (https://www.example.com/ in your example)
Mallory runs a website (http://localhost:4300 in your example)
Alice is logged into Bob's site and has some confidential data there. Perhaps it is a company intranet (accessible only to browsers on the LAN), or her online banking (accessible only with a cookie you get after entering a username and password).
Alice visits Mallory's website which has some JavaScript that causes Alice's browser to make an HTTP request to Bob's website (from her IP address with her cookies, etc). This could be as simple as using XMLHttpRequest and reading the responseText.
The browser's Same Origin Policy prevents that JavaScript from reading the data returned by Bob's website (which Bob and Alice don't want Mallory to access). (Note that you can, for example, display an image using an <img> element across origins because the content of the image is not exposed to JavaScript (or Mallory) … unless you throw canvas into the mix in which case you will generate a same-origin violation error).
Why the Same Origin Policy applies when you don't think it should
For any given URL it is possible that the SOP is not needed. A couple of common scenarios where this is the case are:
Alice, Bob, and Mallory are the same person.
Bob is providing entirely public information
… but the browser has no way of knowing if either of the above is true, so trust is not automatic and the SOP is applied. Permission has to be granted explicitly before the browser will give the data it has received from Bob to some other website.
Why the Same Origin Policy applies to JavaScript in a web page but little else
Outside the web page
Browser extensions*, the Network tab in browser developer tools, and applications like Postman are installed software. They aren't passing data from one website to the JavaScript belonging to a different website just because you visited that different website. Installing software usually takes a more conscious choice.
There isn't a third party (Mallory) who is considered a risk.
* Browser extensions do need to be written carefully to avoid cross-origin issues. See the Chrome documentation for example.
Inside the webpage
Most of the time, there isn't a great deal of information leakage when just showing something on a webpage.
If you use an <img> element to load an image, then it gets shown on the page, but very little information is exposed to Mallory. JavaScript can't read the image (unless you use a crossOrigin attribute to explicitly enable request permission with CORS) and then copy it to her server.
That said, some information does leak so, to quote Domenic Denicola (of Google):
The web's fundamental security model is the same origin policy. We
have several legacy exceptions to that rule from before that security
model was in place, with script tags being one of the most egregious
and most dangerous. (See the various "JSONP" attacks.)
Many years ago, perhaps with the introduction of XHR or web fonts (I
can't recall precisely), we drew a line in the sand, and said no new
web platform features would break the same origin policy. The existing
features need to be grandfathered in and subject to carefully-honed
and oft-exploited exceptions, for the sake of not breaking the web,
but we certainly can't add any more holes to our security policy.
This is why you need CORS permission to load fonts across origins.
Why you can display data on the page without reading it with JS
There are a number of circumstances where Mallory's site can cause a browser to fetch data from a third party and display it (e.g. by adding an <img> element to display an image). It isn't possible for Mallory's JavaScript to read the data in that resource though, only Alice's browser and Bob's server can do that, so it is still secure.
CORS
The Access-Control-Allow-Origin HTTP response header referred to in the error message is part of the CORS standard which allows Bob to explicitly grant permission to Mallory's site to access the data via Alice's browser.
A basic implementation would just include:
Access-Control-Allow-Origin: *
… in the response headers to permit any website to read the data.
Access-Control-Allow-Origin: http://example.com
… would allow only a specific site to access it, and Bob can dynamically generate that based on the Origin request header to permit multiple, but not all, sites to access it.
The specifics of how Bob sets that response header depend on Bob's HTTP server and/or server-side programming language. Users of Node.js/Express.js should use the well-documented CORS middleware. Users of other platforms should take a look at this collection of guides for various common configurations that might help.
NB: Some requests are complex and send a preflight OPTIONS request that the server will have to respond to before the browser will send the GET/POST/PUT/Whatever request that the JS wants to make. Implementations of CORS that only add Access-Control-Allow-Origin to specific URLs often get tripped up by this.
Obviously granting permission via CORS is something Bob would only do only if either:
The data was not private or
Mallory was trusted
How do I add these headers?
It depends on your server-side environment.
If you can, use a library designed to handle CORS as they will present you with simple options instead of having to deal with everything manually.
Enable-Cors.org has a list of documentation for specific platforms and frameworks that you might find useful.
But I'm not Bob!
There is no standard mechanism for Mallory to add this header because it has to come from Bob's website, which she does not control.
If Bob is running a public API then there might be a mechanism to turn on CORS (perhaps by formatting the request in a certain way, or a config option after logging into a Developer Portal site for Bob's site). This will have to be a mechanism implemented by Bob though. Mallory could read the documentation on Bob's site to see if something is available, or she could talk to Bob and ask him to implement CORS.
Error messages which mention "Response for preflight"
Some cross-origin requests are preflighted.
This happens when (roughly speaking) you try to make a cross-origin request that:
Includes credentials like cookies
Couldn't be generated with a regular HTML form (e.g. has custom headers or a Content-Type that you couldn't use in a form's enctype).
If you are correctly doing something that needs a preflight
In these cases then the rest of this answer still applies but you also need to make sure that the server can listen for the preflight request (which will be OPTIONS (and not GET, POST, or whatever you were trying to send) and respond to it with the right Access-Control-Allow-Origin header but also Access-Control-Allow-Methods and Access-Control-Allow-Headers to allow your specific HTTP methods or headers.
If you are triggering a preflight by mistake
Sometimes people make mistakes when trying to construct Ajax requests, and sometimes these trigger the need for a preflight. If the API is designed to allow cross-origin requests but doesn't require anything that would need a preflight, then this can break access.
Common mistakes that trigger this include:
trying to put Access-Control-Allow-Origin and other CORS response headers on the request. These don't belong on the request, don't do anything helpful (what would be the point of a permissions system where you could grant yourself permission?), and must appear only on the response.
trying to put a Content-Type: application/json header on a GET request that has no request body the content of which to describe (typically when the author confuses Content-Type and Accept).
In either of these cases, removing the extra request header will often be enough to avoid the need for a preflight (which will solve the problem when communicating with APIs that support simple requests but not preflighted requests).
Opaque responses (no-cors mode)
Sometimes you need to make an HTTP request, but you don't need to read the response. e.g. if you are posting a log message to the server for recording.
If you are using the fetch API (rather than XMLHttpRequest), then you can configure it to not try to use CORS.
Note that this won't let you do anything that you require CORS to do. You will not be able to read the response. You will not be able to make a request that requires a preflight.
It will let you make a simple request, not see the response, and not fill the Developer Console with error messages.
How to do it is explained by the Chrome error message given when you make a request using fetch and don't get permission to view the response with CORS:
Access to fetch at 'https://example.com/' from origin 'https://example.net' 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.
Thus:
fetch("http://example.com", { mode: "no-cors" });
Alternatives to CORS
JSONP
Bob could also provide the data using a hack like JSONP which is how people did cross-origin Ajax before CORS came along.
It works by presenting the data in the form of a JavaScript program that injects the data into Mallory's page.
It requires that Mallory trust Bob not to provide malicious code.
Note the common theme: The site providing the data has to tell the browser that it is OK for a third-party site to access the data it is sending to the browser.
Since JSONP works by appending a <script> element to load the data in the form of a JavaScript program that calls a function already in the page, attempting to use the JSONP technique on a URL that returns JSON will fail — typically with a CORB error — because JSON is not JavaScript.
Move the two resources to a single Origin
If the HTML document the JS runs in and the URL being requested are on the same origin (sharing the same scheme, hostname, and port) then the Same Origin Policy grants permission by default. CORS is not needed.
A Proxy
Mallory could use server-side code to fetch the data (which she could then pass from her server to Alice's browser through HTTP as usual).
It will either:
add CORS headers
convert the response to JSONP
exist on the same origin as the HTML document
That server-side code could be written & hosted by a third party (such as CORS Anywhere). Note the privacy implications of this: The third party can monitor who proxies what across their servers.
Bob wouldn't need to grant any permissions for that to happen.
There are no security implications here since that is just between Mallory and Bob. There is no way for Bob to think that Mallory is Alice and to provide Mallory with data that should be kept confidential between Alice and Bob.
Consequently, Mallory can only use this technique to read public data.
Do note, however, that taking content from someone else's website and displaying it on your own might be a violation of copyright and open you up to legal action.
Writing something other than a web app
As noted in the section "Why the Same Origin Policy only applies to JavaScript in a web page", you can avoid the SOP by not writing JavaScript in a webpage.
That doesn't mean you can't continue to use JavaScript and HTML, but you could distribute it using some other mechanism, such as Node-WebKit or PhoneGap.
Browser extensions
It is possible for a browser extension to inject the CORS headers in the response before the Same Origin Policy is applied.
These can be useful for development but are not practical for a production site (asking every user of your site to install a browser extension that disables a security feature of their browser is unreasonable).
They also tend to work only with simple requests (failing when handling preflight OPTIONS requests).
Having a proper development environment with a local development server
is usually a better approach.
Other security risks
Note that SOP / CORS do not mitigate XSS, CSRF, or SQL Injection attacks which need to be handled independently.
Summary
There is nothing you can do in your client-side code that will enable CORS access to someone else's server.
If you control the server the request is being made to: Add CORS permissions to it.
If you are friendly with the person who controls it: Get them to add CORS permissions to it.
If it is a public service:
Read their API documentation to see what they say about accessing it with client-side JavaScript:
They might tell you to use specific URLs
They might support JSONP
They might not support cross-origin access from client-side code at all (this might be a deliberate decision on security grounds, especially if you have to pass a personalized API Key in each request).
Make sure you aren't triggering a preflight request you don't need. The API might grant permission for simple requests but not preflighted requests.
If none of the above apply: Get the browser to talk to your server instead, and then have your server fetch the data from the other server and pass it on. (There are also third-party hosted services that attach CORS headers to publically accessible resources that you could use).

Target server must allowed cross-origin request. In order to allow it through express, simply handle http options request :
app.options('/url...', function(req, res, next){
res.header('Access-Control-Allow-Origin', "*");
res.header('Access-Control-Allow-Methods', 'POST');
res.header("Access-Control-Allow-Headers", "accept, content-type");
res.header("Access-Control-Max-Age", "1728000");
return res.sendStatus(200);
});

As this isn't mentioned in the accepted answer.
This is not the case for this exact question, but might help others that search for that problem
This is something you can do in your client-code to prevent CORS errors in some cases.
You can make use of Simple Requests.
In order to perform a 'Simple Requests' the request needs to meet several conditions. E.g. only allowing POST, GET and HEAD method, as well as only allowing some given Headers (you can find all conditions here).
If your client code does not explicit set affected Headers (e.g. "Accept") with a fix value in the request it might occur that some clients do set these Headers automatically with some "non-standard" values causing the server to not accept it as Simple Request - which will give you a CORS error.

This is happening because of the CORS error. CORS stands for Cross Origin Resource Sharing. In simple words, this error occurs when we try to access a domain/resource from another domain.
Read More about it here: CORS error with jquery
To fix this, if you have access to the other domain, you will have to allow Access-Control-Allow-Origin in the server. This can be added in the headers. You can enable this for all the requests/domains or a specific domain.
How to get a cross-origin resource sharing (CORS) post request working
These links may help

This CORS issue wasn't further elaborated (for other causes).
I'm having this issue currently under different reason.
My front end is returning 'Access-Control-Allow-Origin' header error as well.
Just that I've pointed the wrong URL so this header wasn't reflected properly (in which i kept presume it did). localhost (front end) -> call to non secured http (supposed to be https), make sure the API end point from front end is pointing to the correct protocol.

I got the same error in Chrome console.
My problem was, I was trying to go to the site using http:// instead of https://. So there was nothing to fix, just had to go to the same site using https.

This bug cost me 2 days. I checked my Server log, the Preflight Option request/response between browser Chrome/Edge and Server was ok. The main reason is that GET/POST/PUT/DELETE server response for XHTMLRequest must also have the following header:
access-control-allow-origin: origin
"origin" is in the request header (Browser will add it to request for you). for example:
Origin: http://localhost:4221
you can add response header like the following to accept for all:
access-control-allow-origin: *
or response header for a specific request like:
access-control-allow-origin: http://localhost:4221
The message in browsers is not clear to understand: "...The requested resource"
note that:
CORS works well for localhost. different port means different Domain.
if you get error message, check the CORS config on the server side.

In most housing services just add in the .htaccess on the target server folder this:
Header set Access-Control-Allow-Origin 'https://your.site.folder'

I had the same issue. In my case i fixed it by adding addition parameter of timestamp to my URL. Even this was not required by the server I was accessing.
Example yoururl.com/yourdocument?timestamp=1234567
Note: I used epos timestamp

"Get" request with appending headers transform to "Options" request. So Cors policy problems occur. You have to implement "Options" request to your server. Cors Policy about server side and you need to allow Cors Policy on your server side. For Nodejs server:details
app.use(cors)
For Java to integrate with Angular:details
#CrossOrigin(origins = "http://localhost:4200")

You should enable CORS to get it working.

Webscraping with pure browser JS possible? [duplicate]

tl;dr; About the Same Origin Policy
I have a Grunt process which initiates an instance of express.js server. This was working absolutely fine up until just now when it started serving a blank page with the following appearing in the error log in the developer's console in Chrome (latest version):
XMLHttpRequest cannot load https://www.example.com/
No 'Access-Control-Allow-Origin' header is present on the requested
resource. Origin 'http://localhost:4300' is therefore not allowed access.
What is stopping me from accessing the page?

Target server must allowed cross-origin request. In order to allow it through express, simply handle http options request :
app.options('/url...', function(req, res, next){
res.header('Access-Control-Allow-Origin', "*");
res.header('Access-Control-Allow-Methods', 'POST');
res.header("Access-Control-Allow-Headers", "accept, content-type");
res.header("Access-Control-Max-Age", "1728000");
return res.sendStatus(200);
});

As this isn't mentioned in the accepted answer.
This is not the case for this exact question, but might help others that search for that problem
This is something you can do in your client-code to prevent CORS errors in some cases.
You can make use of Simple Requests.
In order to perform a 'Simple Requests' the request needs to meet several conditions. E.g. only allowing POST, GET and HEAD method, as well as only allowing some given Headers (you can find all conditions here).
If your client code does not explicit set affected Headers (e.g. "Accept") with a fix value in the request it might occur that some clients do set these Headers automatically with some "non-standard" values causing the server to not accept it as Simple Request - which will give you a CORS error.

This is happening because of the CORS error. CORS stands for Cross Origin Resource Sharing. In simple words, this error occurs when we try to access a domain/resource from another domain.
Read More about it here: CORS error with jquery
To fix this, if you have access to the other domain, you will have to allow Access-Control-Allow-Origin in the server. This can be added in the headers. You can enable this for all the requests/domains or a specific domain.
How to get a cross-origin resource sharing (CORS) post request working
These links may help

This CORS issue wasn't further elaborated (for other causes).
I'm having this issue currently under different reason.
My front end is returning 'Access-Control-Allow-Origin' header error as well.
Just that I've pointed the wrong URL so this header wasn't reflected properly (in which i kept presume it did). localhost (front end) -> call to non secured http (supposed to be https), make sure the API end point from front end is pointing to the correct protocol.

I got the same error in Chrome console.
My problem was, I was trying to go to the site using http:// instead of https://. So there was nothing to fix, just had to go to the same site using https.

This bug cost me 2 days. I checked my Server log, the Preflight Option request/response between browser Chrome/Edge and Server was ok. The main reason is that GET/POST/PUT/DELETE server response for XHTMLRequest must also have the following header:
access-control-allow-origin: origin
"origin" is in the request header (Browser will add it to request for you). for example:
Origin: http://localhost:4221
you can add response header like the following to accept for all:
access-control-allow-origin: *
or response header for a specific request like:
access-control-allow-origin: http://localhost:4221
The message in browsers is not clear to understand: "...The requested resource"
note that:
CORS works well for localhost. different port means different Domain.
if you get error message, check the CORS config on the server side.

In most housing services just add in the .htaccess on the target server folder this:
Header set Access-Control-Allow-Origin 'https://your.site.folder'

I had the same issue. In my case i fixed it by adding addition parameter of timestamp to my URL. Even this was not required by the server I was accessing.
Example yoururl.com/yourdocument?timestamp=1234567
Note: I used epos timestamp

"Get" request with appending headers transform to "Options" request. So Cors policy problems occur. You have to implement "Options" request to your server. Cors Policy about server side and you need to allow Cors Policy on your server side. For Nodejs server:details
app.use(cors)
For Java to integrate with Angular:details
#CrossOrigin(origins = "http://localhost:4200")

You should enable CORS to get it working.

Does Cross-origin resource sharing affect all clients that connect to a web method?

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.

Is there a way around Access-Control-Allow-Origin?

I'm using an API from JIRA to get some information on bugs. Here's an example of the JQuery I'm using to get it:
var endpoint = 'https://jira.cyanogenmod.org/rest/api/latest/issue/CYAN-2631';
$.get(endpoint, function(data) {
do_stuff(data, data['fields']['project']['self']);
});
And, I'm getting the ever-terrible Access-Control-Allow-Origin error. It looks like this:
XMLHttpRequest cannot load
https://jira.cyanogenmod.org/rest/api/latest/issue/CYAN-2631.
No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'http://127.0.0.1:8000' is therefore not allowed access.
I'd really like to use this API if possible. Following the directions on this question didn't help. I got another error,
GET https://jira.cyanogenmod.org/rest/api/latest/issue/CYAN-2631callback=jQuery172039181585889309645_1431307158851?_=1431307165515
Seems to be a Jquery error, so I don't think that's the right approach. Maybe the server doesn't allow for jsonp.
Anyway, does anyone have a way around this or can I just not use this particular API? Thanks

There is no way to enable cross origin requests entirely from the browser without external code. If there was, it would entirely defeat the purpose of the security protections in the first place.
When using a browser, it is the server that decides if it wants to support cross origin requests or not and what domains it wants to support requests from. You cannot bypass it in the client.
The choices are:
Server enables CORs access from your domain or all domains.
Server supports JSONP allowing you to use it to work-around the cross origin access.
You create your own server proxy where you make a request from the browser to your own server (which would either be same origin or have CORS enabled), then your own server gets the data from the other site and returns it back to the browser. Servers are not limited by the same origin limitations as this is a security feature built into browsers only.
You find some third party proxy service that you can use to serve the same purpose as option #3.
FYI, a Google search turned up this article about enabling CORS on the API: https://answers.atlassian.com/questions/69356/cross-origin-resource-sharing-with-jira-rest-api-and-javascript. I don't understand enough about the service to quite follow the article, but maybe it points you in a helpful direction.

H-i, short answer is "yes".
The medium answer is "enable CORS on your application SERVER"
The long answer is here: http://enable-cors.org/
At some point you'll encounter the concept of a "pre-flight request", and you'll probably get confused.
That's because it's confusing, stupid, and poorly engineered. Just keep on going.
The easiest way to enable CORS is at your webserver (nginx or apache), although, you can enable it in the application itself.
The http://enable-cors.org/ site lists configurations for a variety of web servers and application stacks.
Good luck!

Ajax Cross domain request to non-controlled domain

I have been seeing lot of questions and answers here, but something really not answered my questions
How do I make a cross domain request to a http://otherdomain.com?login.php?username="test"&pass="pass"
I would like to state that, this domain is not controlled by us and it will return normal HTTP response if you actually make a HTTP POST request to the above URL.
So based on the HTTP Response [HTML], I would like to evaluate successful or failure login.
Since it's an internal application, if it's not possible in normal scenario, we can configure internal system browsers to achieve the same [last option].
Can anyone post a link to tutorial/working example?
Note: I don't have control over otherdomain application. It doesn't return a JSON formatted data. The request must be originated from Clients browser, not allowed any proxy due to application dependance on IP address.

See Ways to circumvent the same-origin policy. None of them will meet your requirements.
Preventing Mallory's site from using Alice's site with Bob's credentials (such as his IP address) is the point of the Same Origin Policy. There is no way around this for a web application.
Since it's an internal application
If it is an internal application, then you could look at using a browser extension to access the data. They have less restrictive security policies as they have to be explicitly installed.

Develop Reference

JavaScript is the programming language of the Web.